Citrix XenServer ® 7.0 Administrator's Guide 7 0 Administrators

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Citrix XenServer ® 7.0 Administrator's Guide

Published October 2017
1.0 Edition

Citrix XenServer ® 7.0 Administrator's Guide
Copyright © 2016 Citrix Systems. Inc. All Rights Reserved.
Version: 7.0
Citrix, Inc.
851 West Cypress Creek Road
Fort Lauderdale, FL 33309
United States of America
Disclaimers
This document is furnished "AS IS." Citrix, Inc. disclaims all warranties regarding the contents of this document,
including, but not limited to, implied warranties of merchantability and fitness for any particular purpose. This
document may contain technical or other inaccuracies or typographical errors. Citrix, Inc. reserves the right to
revise the information in this document at any time without notice. This document and the software described
in this document constitute confidential information of Citrix, Inc. and its licensors, and are furnished under a
license from Citrix, Inc.
Citrix Systems, Inc., the Citrix logo, Citrix XenServer and Citrix XenCenter, are trademarks of Citrix Systems, Inc.
and/or one or more of its subsidiaries, and may be registered in the United States Patent and Trademark Office
and in other countries. All other trademarks and registered trademarks are property of their respective owners.
Trademarks
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XenServer ®
XenCenter ®

Contents
1. Document Overview ...................................................................................... 1
1.1. Introducing XenServer .................................................................................................. 1
1.1.1. Benefits of Using XenServer ............................................................................... 1
1.1.2. Administering XenServer .................................................................................... 2
1.2. XenServer Documentation ............................................................................................ 2

2. Managing Users ............................................................................................. 3
2.1. Authenticating Users With Active Directory (AD) ............................................................ 3
2.1.1. Configuring Active Directory Authentication ........................................................ 4
2.1.2. User Authentication ........................................................................................... 6
2.1.3. Removing Access for a User ............................................................................... 7
2.1.4. Leaving an AD Domain ....................................................................................... 8
2.2. Role Based Access Control ............................................................................................ 8
2.2.1. Roles ................................................................................................................. 9
2.2.2. Definitions of RBAC Roles and Permissions ........................................................ 10
2.2.3. Using RBAC with the CLI .................................................................................. 16
2.2.3.1. To List All the Available Defined Roles in XenServer ................................. 16
2.2.3.2. To Display a List of Current Subjects: ...................................................... 16
2.2.3.3. To Add a Subject to RBAC ...................................................................... 17
2.2.3.4. To Assign an RBAC Role to a Created subject .......................................... 17
2.2.3.5. To Change a Subject's RBAC Role: .......................................................... 17
2.2.4. Auditing ........................................................................................................... 18
2.2.4.1. Audit Log xe CLI Commands .................................................................. 18
2.2.4.2. To Obtain All Audit Records From the Pool ............................................. 18
2.2.4.3. To Obtain Audit Records of the Pool Since a Precise Millisecond
Timestamp ........................................................................................................ 18
2.2.4.4. To Obtain Audit Records of the Pool Since a Precise Minute
Timestamp ........................................................................................................ 18
2.2.5. How Does XenServer Compute the Roles for the Session? .................................. 18

3. XenServer Hosts and Resource Pools .......................................................... 20
3.1. Hosts and Resource Pools Overview ............................................................................ 20
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3.2. Requirements for Creating Resource Pools ................................................................... 20
3.3. Creating a Resource Pool ............................................................................................ 21
3.4. Creating Heterogeneous Resource Pools ...................................................................... 22
3.5. Adding Shared Storage ................................................................................................ 22
3.6. Removing a XenServer Host from a Resource Pool ........................................................ 23
3.7. Preparing a Pool of XenServer Hosts for Maintenance .................................................. 23
3.8. Export Resource Pool Data .......................................................................................... 24
3.8.1. To Export Resource Data .................................................................................. 25
3.9. High Availability .......................................................................................................... 26
3.9.1. HA Overview ................................................................................................... 26
3.9.1.1. Overcommitting .................................................................................... 27
3.9.1.2. Overcommitment Warning .................................................................... 27
3.9.1.3. Host Fencing ......................................................................................... 27
3.9.2. Configuration Requirements ............................................................................. 27
3.9.3. Restart configuration settings ........................................................................... 28
3.9.3.1. Start order ............................................................................................ 29
3.10. Enabling HA on your XenServer Pool ......................................................................... 29
3.10.1. Enabling HA Using the CLI .............................................................................. 29
3.10.2. Removing HA Protection from a VM using the CLI ............................................ 30
3.10.3. Recovering an Unreachable Host .................................................................... 30
3.10.4. Shutting Down a host When HA is Enabled ..................................................... 30
3.10.5. Shutting Down a VM When it is Protected by HA ............................................. 31
3.11. Host Power On ......................................................................................................... 31
3.11.1. Powering on Hosts Remotely .......................................................................... 31
3.11.2. Using the CLI to Manage Host Power On ......................................................... 31
3.11.2.1. To Enable Host Power On Using the CLI ................................................ 31
3.11.2.2. To Turn on Hosts Remotely Using the CLI .............................................. 32
3.11.3. Configuring a Custom Script for XenServer's Host Power On Feature ................. 32
3.11.3.1. Key/Value Pairs ................................................................................... 32
3.11.3.1.1. host.power_on_mode ............................................................... 32
3.11.3.1.2. host.power_on_config .............................................................. 32

3.11.3.2. Sample Script ...................................................................................... 33
3.12. Communicating with XenServer Hosts and Resource Pools .......................................... 33

4. Networking ................................................................................................... 34
4.1. Networking Support .................................................................................................... 34
4.2. vSwitch Networks ....................................................................................................... 34
4.3. XenServer Networking Overview ................................................................................. 35
4.3.1. Network Objects .............................................................................................. 36
4.3.2. Networks ......................................................................................................... 36
4.3.3. VLANs ............................................................................................................. 36
4.3.3.1. Using VLANs with Management Interfaces ............................................. 36
4.3.3.2. Using VLANs with Virtual Machines ........................................................ 36
4.3.3.3. Using VLANs with Dedicated Storage NICs .............................................. 36
4.3.3.4. Combining Management Interfaces and Guest VLANs on a Single Host
NIC ................................................................................................................... 37
4.3.4. Jumbo frames .................................................................................................. 37
4.3.5. NIC Bonds ....................................................................................................... 37
4.3.5.1. Active-Active Bonding ............................................................................ 39
4.3.5.2. Active-Passive Bonding .......................................................................... 40
4.3.5.3. LACP Link Aggregation Control Protocol Bonding ..................................... 41
4.3.5.4. Switch Configuration ............................................................................. 43
4.3.5.4.1. Switch Configuration for LACP Bonds ........................................... 44
4.3.6. Initial Networking Configuration after Setup ...................................................... 44
4.3.7. Changing Networking Configuration .................................................................. 45
4.3.7.1. Modifying the Network Object ............................................................... 45
4.3.8. Changing the Up Delay for Bonds ..................................................................... 45
4.4. Managing Networking Configuration ........................................................................... 46
4.4.1. Cross-Server Private Networks .......................................................................... 46
4.4.2. Creating Networks in a Standalone Server ......................................................... 47
4.4.3. Creating Networks in Resource Pools ................................................................ 47
4.4.4. Creating VLANs ................................................................................................ 47
4.4.5. Creating NIC Bonds on a Standalone Host ......................................................... 48

4.4.5.1. Creating a NIC Bond .............................................................................. 48
4.4.5.2. Controlling the MAC Address of the Bond .............................................. 48
4.4.5.3. Reverting NIC Bonds .............................................................................. 49
4.4.6. Creating NIC Bonds in Resource Pools ............................................................... 49
4.4.6.1. Adding NIC Bonds to New Resource Pools .............................................. 49
4.4.6.2. Adding NIC Bonds to an Existing Pool ..................................................... 50
4.4.7. Configuring a Dedicated Storage NIC ................................................................. 50
4.4.8. Using SR-IOV Enabled NICs ............................................................................... 51
4.4.9. Controlling the Rate of Outgoing Data (QoS) ..................................................... 52
4.4.10. Changing Networking Configuration Options ................................................... 53
4.4.10.1. Hostname ........................................................................................... 53
4.4.10.2. DNS Servers ........................................................................................ 53
4.4.10.3. Changing IP Address Configuration for a Standalone Host ...................... 53
4.4.10.4. Changing IP Address Configuration in Resource Pools ............................ 53
4.4.10.5. Management Interface ........................................................................ 54
4.4.10.6. Disabling Management Access ............................................................. 55
4.4.10.7. Adding a New Physical NIC .................................................................. 55
4.4.10.8. Using Switch Port Locking .................................................................... 55
4.4.10.8.1. Requirements ........................................................................... 55
4.4.10.8.2. Notes ....................................................................................... 55
4.4.10.8.3. Implementation Notes .............................................................. 56
4.4.10.8.4. Examples .................................................................................. 56
4.4.10.8.5. How Switch-port Locking Works ................................................ 57
4.4.10.8.6. VIF Locking-Mode States ........................................................... 57
4.4.10.8.7. Configuring Switch Port Locking ................................................ 58
4.4.10.8.8. Preventing a Virtual Machine from Sending or Receiving Traffic
from a Specific Network ............................................................................ 59
4.4.10.8.9. Removing a VIF's Restriction to an IP Address ............................. 60
4.4.10.8.10. Simplifying VIF Locking Mode Configuration in the Cloud ........... 60
4.4.10.8.11. Using Network Settings for VIF Traffic Filtering ......................... 61
4.5. Networking Troubleshooting ....................................................................................... 61
4.5.1. Diagnosing Network Corruption ........................................................................ 61

4.5.2. Emergency Network Reset ............................................................................... 62
4.5.2.1. Verifying the Network Reset .................................................................. 62
4.5.2.2. Using the CLI for Network Reset ............................................................ 62
4.5.2.2.1. Pool Master Command Line Examples ......................................... 64
4.5.2.2.2. Pool Member Command Line Examples ....................................... 64

5. Storage ......................................................................................................... 66
5.1. Storage Overview ....................................................................................................... 66
5.1.1. Storage Repositories (SRs) ................................................................................ 66
5.1.2. Virtual Disk Image (VDI) ................................................................................... 66
5.1.3. Physical Block Devices (PBDs) ........................................................................... 66
5.1.4. Virtual Block Devices (VBDs) ............................................................................. 67
5.1.5. Summary of Storage objects ............................................................................. 67
5.1.6. Virtual Disk Data Formats ................................................................................. 67
5.1.6.1. VDI Types ............................................................................................. 67
5.1.6.2. Creating a Raw Virtual Disk Using the xe CLI ........................................... 67
5.1.6.3. Converting Between VDI Formats ........................................................... 68
5.1.6.4. VHD-based VDIs .................................................................................... 68
5.2. Storage Repository Formats ........................................................................................ 69
5.2.1. Local LVM ........................................................................................................ 69
5.2.1.1. LVM Performance Considerations ........................................................... 69
5.2.1.2. Creating a Local LVM SR (lvm) ................................................................ 70
5.2.2. Local EXT3 ....................................................................................................... 70
5.2.2.1. Creating a Local EXT3 SR (ext) ................................................................ 70
5.2.3. udev ................................................................................................................ 70
5.2.4. ISO .................................................................................................................. 71
5.2.5. Software iSCSI Support ..................................................................................... 71
5.2.5.1. XenServer Host iSCSI configuration ......................................................... 71
5.2.6. Software FCoE Storage ..................................................................................... 72
5.2.6.1. Creating a Software FCoE SR .................................................................. 72
5.2.7. Hardware Host Bus Adapters (HBAs) ................................................................. 72
5.2.7.1. Sample QLogic iSCSI HBA setup ............................................................. 72

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5.2.7.2. Removing HBA-based SAS, FC or iSCSI Device Entries .............................. 73
5.2.8. Shared LVM Storage ......................................................................................... 73
5.2.8.1. Creating a Shared LVM Over iSCSI SR Using the Software iSCSI Initiator
(lvmoiscsi) ......................................................................................................... 73
5.2.8.2. Creating a Shared LVM over Fibre Channel / Fibre Channel over
Ethernet / iSCSI HBA or SAS SR (lvmohba) .......................................................... 74
5.2.9. NFS and SMB ................................................................................................... 76
5.2.9.1. Creating a Shared NFS SR (NFS) ............................................................. 76
5.2.9.2. Creating a Shared SMB SR (SMB) ........................................................... 77
5.2.10. LVM over Hardware HBA ................................................................................ 78
5.3. Storage Configuration ................................................................................................. 78
5.3.1. Creating Storage Repositories ........................................................................... 78
5.3.2. Probing an SR .................................................................................................. 79
5.4. Storage Multipathing .................................................................................................. 81
5.5. XenServer and IntelliCache .......................................................................................... 82
5.5.1. IntelliCache Deployment .................................................................................. 82
5.5.1.1. Enabling on Host Installation ................................................................. 83
5.5.1.2. Converting an Existing Host to Use Thin Provisioning ............................... 83
5.5.1.3. VM Boot Behavior ................................................................................. 84
5.5.1.3.1. VM Caching Behavior Settings ..................................................... 84
5.5.1.4. Implementation Details and Troubleshooting .......................................... 84
5.6. Storage Read Caching ................................................................................................. 85
5.6.1. Enabling and Disabling ..................................................................................... 85
5.6.2. Limitations ....................................................................................................... 86
5.6.3. Comparison with IntelliCache ........................................................................... 86
5.6.4. To Set the Read Cache Size .............................................................................. 86
5.6.4.1. How to View the Current dom0 Memory Allocation ................................ 86
5.6.4.2. XenCenter Display Notes ....................................................................... 87
5.7. Managing Storage Repositories ................................................................................... 87
5.7.1. Removing SRs .................................................................................................. 87
5.7.2. Introducing an SR ............................................................................................ 88
5.7.3. Live LUN Expansion .......................................................................................... 88

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5.7.4. Live VDI Migration ........................................................................................... 89
5.7.4.1. Limitations and Caveats ......................................................................... 89
5.7.4.2. To Move Virtual Disks using XenCenter ................................................... 89
5.7.5. Cold VDI Migration between SRs (Offline Migration) .......................................... 89
5.7.5.1. Copying All of a VMs VDIs to a Different SR ............................................ 89
5.7.5.2. Copying Individual VDIs to a Different SR ................................................ 89
5.7.6. Converting Local Fibre Channel SRs to Shared SRs ............................................. 90
5.7.7. Reclaiming Space for Block-Based Storage on the Backing Array Using Discard ..... 90
5.7.8. Automatically Reclaiming Space When Deleting Snapshots ................................. 91
5.7.8.1. Reclaiming Space Using the Off Line Coalesce Tool .................................. 91
5.7.9. Adjusting the Disk IO Scheduler ........................................................................ 92
5.7.10. Virtual Disk QoS Settings ................................................................................ 92

6. Configuring VM Memory ............................................................................. 94
6.1. What is Dynamic Memory Control (DMC)? .................................................................. 94
6.1.1. The Concept of Dynamic Range ........................................................................ 94
6.1.2. The Concept of Static Range ............................................................................. 94
6.1.3. DMC Behavior ................................................................................................. 95
6.1.4. How Does DMC Work? ..................................................................................... 95
6.1.5. Memory Constraints ........................................................................................ 95
6.2. xe CLI Commands ....................................................................................................... 96
6.2.1. Display the Static Memory Properties of a VM .................................................. 96
6.2.2. Display the Dynamic Memory Properties of a VM .............................................. 96
6.2.3. Updating Memory Properties ........................................................................... 97
6.2.4. Update Individual Memory Properties .............................................................. 97
6.3. Upgrade Issues ........................................................................................................... 98

7. XenServer Memory Usage ........................................................................... 99
7.1. Control Domain Memory ............................................................................................ 99
7.1.1. Changing the Amount of Memory Allocated to the Control Domain .................... 99
7.1.2. How Much Memory is Available to VMs .......................................................... 100

8. Disaster Recovery and Backup ................................................................... 101

8.1. Understanding XenServer DR ..................................................................................... 101
8.2. DR Infrastructure Requirements ................................................................................ 101
8.3. Deployment Considerations ....................................................................................... 103
8.3.1. Steps to Take Before a Disaster ....................................................................... 103
8.3.2. Steps to Take After a Disaster ......................................................................... 103
8.3.3. Steps to Take After a Recovery ....................................................................... 103
8.4. Enabling Disaster Recovery in XenCenter ................................................................... 103
8.5. Recovering VMs and vApps in the Event of Disaster (Failover) ..................................... 104
8.6. Restoring VMs and vApps to the Primary Site After Disaster (Failback) ......................... 105
8.7. Test Failover ............................................................................................................. 105
8.8. vApps ....................................................................................................................... 107
8.8.1. Using the Manage vApps dialog box in XenCenter ............................................ 107
8.9. Backing Up and Restoring XenServer Hosts and VMs .................................................. 107
8.9.1. Backing up Virtual Machine metadata ............................................................. 109
8.9.1.1. Backing up single host installations ...................................................... 109
8.9.1.2. Backing up pooled installations ............................................................ 109
8.9.2. Backing up XenServer hosts ............................................................................ 110
8.9.3. Backing up VMs ............................................................................................. 111
8.10. VM Snapshots ......................................................................................................... 111
8.10.1. Regular Snapshots ........................................................................................ 111
8.10.2. Quiesced Snapshots ..................................................................................... 111
8.10.3. Snapshots with memory ............................................................................... 112
8.10.4. Creating a VM Snapshot ............................................................................... 112
8.10.5. Creating a snapshot with memory ................................................................ 112
8.10.6. To list all of the snapshots on a XenServer pool ............................................. 113
8.10.7. To list the snapshots on a particular VM ........................................................ 113
8.10.8. Restoring a VM to its previous state .............................................................. 114
8.10.8.1. Deleting a snapshot ........................................................................... 114
8.10.9. Snapshot Templates ..................................................................................... 115
8.10.9.1. Creating a template from a snapshot .................................................. 115
8.10.9.2. Exporting a snapshot to a template .................................................... 115

8.10.9.3. Advanced Notes for Quiesced Snapshots ............................................ 116
8.11. Coping with machine failures .................................................................................. 116
8.11.1. Member failures .......................................................................................... 116
8.11.2. Master failures ............................................................................................. 117
8.11.3. Pool failures ................................................................................................. 118
8.11.4. Coping with Failure due to Configuration Errors ............................................. 118
8.11.5. Physical Machine failure ............................................................................... 118

9. Monitoring and Managing XenServer ........................................................ 120
9.1. Monitoring XenServer Performance ........................................................................... 120
9.1.1. Available Host Metrics .................................................................................... 120
9.1.2. Available VM Metrics ..................................................................................... 123
9.1.3. Analyzing and Visualizing Metrics in XenCenter ............................................... 125
9.1.3.1. Configuring Performance Graphs .......................................................... 125
9.1.3.1.1. Configuring the Graph Type ...................................................... 126
9.1.4. Configuring Metrics ........................................................................................ 126
9.1.5. Using RRDs .................................................................................................... 127
9.1.5.1. Analysing RRDs using HTTP .................................................................. 128
9.1.5.2. Analysing RRDs using rrd2csv ............................................................... 128
9.2. Alerts ....................................................................................................................... 128
9.2.1. Using XenCenter to View Alerts ...................................................................... 128
9.2.1.1. XenCenter Performance Alerts ............................................................. 128
9.2.1.1.1. To Configure Performance Alerts ............................................... 129
9.2.1.2. XenCenter Alerts ................................................................................. 130
9.2.1.3. XenCenter Software Update Alerts ....................................................... 131
9.2.2. Configuring Performance Alerts Using the xe CLI .............................................. 131
9.2.2.1. Generic Example Configuration ............................................................ 133
9.3. Configuring Email Alerts ............................................................................................ 133
9.3.1. Enabling Email Alerts Using XenCenter ............................................................ 134
9.3.2. Enabling Email Alerts using the xe CLI ............................................................. 134
9.3.2.1. Sending Email Alerts Through Authenticated SMTP Servers .................... 134
9.3.2.1.1. Additional Configuration Options ............................................... 134

9.4. Custom Fields and Tags ............................................................................................. 135
9.5. Custom Searches ...................................................................................................... 135
9.6. Determining throughput of physical bus adapters ....................................................... 136

10. Troubleshooting ....................................................................................... 137
10.1. Support .................................................................................................................. 137
10.2. Health Check .......................................................................................................... 137
10.3. XenServer host logs ................................................................................................ 138
10.3.1. Sending host log messages to a central server ............................................... 138
10.4. XenCenter logs ........................................................................................................ 138
10.5. Troubleshooting connections between XenCenter and the XenServer host ................. 138

A. Command Line Interface ........................................................................... 140
A.1. Basic xe Syntax ......................................................................................................... 140
A.2. Special Characters and Syntax ................................................................................... 141
A.3. Command Types ....................................................................................................... 141
A.3.1. Parameter Types ............................................................................................ 142
A.3.2. Low-level Parameter Commands .................................................................... 143
A.3.3. Low-level List Commands ............................................................................... 143
A.4. xe Command Reference ............................................................................................ 144
A.4.1. Appliance Commands .................................................................................... 144
A.4.1.1. Appliance Parameters .......................................................................... 144
A.4.1.2. appliance-assert-can-be-recovered ....................................................... 144
A.4.1.3. appliance-create ................................................................................. 144
A.4.1.4. appliance-destroy ................................................................................ 145
A.4.1.5. appliance-recover ................................................................................ 145
A.4.1.6. appliance-shutdown ............................................................................ 145
A.4.1.7. appliance-start .................................................................................... 145
A.4.2. Audit Commands ........................................................................................... 145
A.4.2.1. audit-log-get parameters ..................................................................... 145
A.4.2.2. audit-log-get ....................................................................................... 145
A.4.3. Bonding Commands ....................................................................................... 146
A.4.3.1. Bond Parameters ................................................................................ 146
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A.4.3.2. bond-create ........................................................................................ 146
A.4.3.3. bond-destroy ...................................................................................... 146
A.4.4. CD Commands ............................................................................................... 146
A.4.4.1. CD Parameters .................................................................................... 146
A.4.4.2. cd-list ................................................................................................. 147
A.4.5. Console Commands ....................................................................................... 148
A.4.5.1. Console Parameters ............................................................................ 148
A.4.6. Disaster Recovery (DR) Commands ................................................................. 148
A.4.6.1. drtask-create ...................................................................................... 148
A.4.6.2. drtask-destroy ..................................................................................... 149
A.4.6.3. vm-assert-can-be-recovered ................................................................ 149
A.4.6.4. appliance-assert-can-be-recovered ....................................................... 149
A.4.6.5. appliance-recover ................................................................................ 149
A.4.6.6. vm-recover ......................................................................................... 149
A.4.6.7. sr-enable-database-replication ............................................................. 149
A.4.6.8. sr-disable-database-replication ............................................................ 149
A.4.6.9. Example Usage ................................................................................... 149
A.4.7. Event Commands ........................................................................................... 150
A.4.7.1. Event Classes ...................................................................................... 150
A.4.7.2. event-wait .......................................................................................... 150
A.4.8. GPU Commands ............................................................................................ 151
A.4.8.1. Physical GPU (pGPU) Parameters ......................................................... 151
A.4.8.2. pGPU Operations ................................................................................ 152
A.4.8.2.1. pgpu-param-set ........................................................................ 152
A.4.8.2.2. pgpu-param-get-uuid ................................................................ 152
A.4.8.2.3. pgpu-param-set-uuid ................................................................ 152
A.4.8.2.4. pgpu-param-add-uuid ............................................................... 152
A.4.8.3. GPU Group Parameters ....................................................................... 152
A.4.8.3.1. GPU Group Operations ............................................................. 153
A.4.8.4. Virtual GPU Parameters ....................................................................... 153
A.4.8.5. Virtual GPU Type Parameters ............................................................... 154

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A.4.8.6. Virtual GPU Operations ....................................................................... 155
A.4.8.6.1. vgpu-create .............................................................................. 155
A.4.8.6.2. vgpu-destroy ............................................................................ 155
A.4.8.6.3. Disabling VNC for VMs with virtual GPU .................................... 155
A.4.9. Host Commands ............................................................................................ 155
A.4.9.1. Host Selectors ..................................................................................... 155
A.4.9.2. Host Parameters ................................................................................. 156
A.4.9.3. host-backup ........................................................................................ 159
A.4.9.4. host-bugreport-upload ........................................................................ 159
A.4.9.5. host-crashdump-destroy ...................................................................... 159
A.4.9.6. host-crashdump-upload ....................................................................... 159
A.4.9.7. host-disable ........................................................................................ 159
A.4.9.8. host-dmesg ......................................................................................... 159
A.4.9.9. host-emergency-management-reconfigure ........................................... 160
A.4.9.10. host-enable ....................................................................................... 160
A.4.9.11. host-evacuate ................................................................................... 160
A.4.9.12. host-forget ........................................................................................ 160
A.4.9.13. host-get-system-status ....................................................................... 160
A.4.9.14. host-get-system-status-capabilities ..................................................... 161
A.4.9.15. host-is-in-emergency-mode ............................................................... 162
A.4.9.16. host-apply-edition ............................................................................. 162
A.4.9.17. host-license-add ................................................................................ 162
A.4.9.18. host-license-view .............................................................................. 162
A.4.9.19. host-logs-download ........................................................................... 162
A.4.9.20. host-management-disable ................................................................. 162
A.4.9.21. host-management-reconfigure ........................................................... 163
A.4.9.22. host-power-on .................................................................................. 163
A.4.9.23. host-get-cpu-features ........................................................................ 163
A.4.9.24. host-set-cpu-features ........................................................................ 163
A.4.9.25. host-set-power-on ............................................................................. 163
A.4.9.26. host-reboot ....................................................................................... 164

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A.4.9.27. host-restore ...................................................................................... 164
A.4.9.28. host-set-hostname-live ...................................................................... 164
A.4.9.29. host-shutdown .................................................................................. 164
A.4.9.30. host-syslog-reconfigure ...................................................................... 165
A.4.9.31. host-data-source-list .......................................................................... 165
A.4.9.32. host-data-source-record .................................................................... 165
A.4.9.33. host-data-source-forget ..................................................................... 165
A.4.9.34. host-data-source-query ..................................................................... 166
A.4.10. Message Commands .................................................................................... 166
A.4.10.1. Message Parameters ......................................................................... 166
A.4.10.2. message-create ................................................................................. 166
A.4.10.3. message-destroy ............................................................................... 166
A.4.10.4. message-list ...................................................................................... 166
A.4.11. Network Commands .................................................................................... 167
A.4.11.1. Network Parameters .......................................................................... 167
A.4.11.2. network-create ................................................................................. 168
A.4.11.3. network-destroy ................................................................................ 168
A.4.12. Patch (Update) Commands ........................................................................... 168
A.4.12.1. Patch Parameters .............................................................................. 168
A.4.12.2. patch-apply ....................................................................................... 169
A.4.12.3. patch-pool-clean ............................................................................... 169
A.4.12.4. patch-pool-apply ............................................................................... 169
A.4.12.5. patch-precheck ................................................................................. 169
A.4.12.6. patch-upload ..................................................................................... 169
A.4.13. PBD Commands ........................................................................................... 169
A.4.13.1. PBD Parameters ................................................................................ 169
A.4.13.2. pbd-create ........................................................................................ 170
A.4.13.3. pbd-destroy ...................................................................................... 170
A.4.13.4. pbd-plug ........................................................................................... 170
A.4.13.5. pbd-unplug ....................................................................................... 170
A.4.14. PIF Commands ............................................................................................. 170

A.4.14.1. PIF Parameters .................................................................................. 171
A.4.14.2. pif-forget .......................................................................................... 173
A.4.14.3. pif-introduce ..................................................................................... 173
A.4.14.4. pif-plug ............................................................................................. 173
A.4.14.5. pif-reconfigure-ip .............................................................................. 173
A.4.14.6. pif-scan ............................................................................................. 174
A.4.14.7. pif-unplug ......................................................................................... 174
A.4.15. Pool Commands ........................................................................................... 174
A.4.15.1. Pool Parameters ................................................................................ 174
A.4.15.2. pool-designate-new-master ............................................................... 175
A.4.15.3. pool-dump-database ......................................................................... 175
A.4.15.4. pool-eject ......................................................................................... 176
A.4.15.5. pool-emergency-reset-master ............................................................ 176
A.4.15.6. pool-emergency-transition-to-master ................................................. 176
A.4.15.7. pool-ha-enable .................................................................................. 176
A.4.15.8. pool-ha-disable ................................................................................. 176
A.4.15.9. pool-join ........................................................................................... 176
A.4.15.10. pool-recover-slaves .......................................................................... 176
A.4.15.11. pool-restore-database ...................................................................... 176
A.4.15.12. pool-sync-database .......................................................................... 177
A.4.16. Storage Manager Commands ........................................................................ 177
A.4.16.1. SM Parameters ................................................................................. 177
A.4.17. SR Commands .............................................................................................. 177
A.4.17.1. SR Parameters ................................................................................... 178
A.4.17.2. sr-create ........................................................................................... 179
A.4.17.3. sr-destroy ......................................................................................... 179
A.4.17.4. sr-enable-database-replication ........................................................... 179
A.4.17.5. sr-disable-database-replication .......................................................... 179
A.4.17.6. sr-forget ............................................................................................ 179
A.4.17.7. sr-introduce ...................................................................................... 179
A.4.17.8. sr-probe ............................................................................................ 180

xvi

A.4.17.9. sr-scan .............................................................................................. 180
A.4.18. Task Commands ........................................................................................... 180
A.4.18.1. Task Parameters ................................................................................ 180
A.4.18.2. task-cancel ........................................................................................ 181
A.4.19. Template Commands .................................................................................... 181
A.4.19.1. VM Template Parameters .................................................................. 182
A.4.19.2. template-export ................................................................................ 188
A.4.20. Update Commands ...................................................................................... 188
A.4.20.1. update-upload .................................................................................. 188
A.4.21. User Commands .......................................................................................... 188
A.4.21.1. user-password-change ....................................................................... 188
A.4.22. VBD Commands ........................................................................................... 188
A.4.22.1. VBD Parameters ................................................................................ 188
A.4.22.2. vbd-create ........................................................................................ 190
A.4.22.3. vbd-destroy ....................................................................................... 190
A.4.22.4. vbd-eject .......................................................................................... 190
A.4.22.5. vbd-insert ......................................................................................... 190
A.4.22.6. vbd-plug ........................................................................................... 191
A.4.22.7. vbd-unplug ....................................................................................... 191
A.4.23. VDI Commands ............................................................................................ 191
A.4.23.1. VDI Parameters ................................................................................. 191
A.4.23.2. vdi-clone ........................................................................................... 192
A.4.23.3. vdi-copy ............................................................................................ 193
A.4.23.4. vdi-create ......................................................................................... 193
A.4.23.5. vdi-destroy ........................................................................................ 193
A.4.23.6. vdi-forget .......................................................................................... 193
A.4.23.7. vdi-import ......................................................................................... 193
A.4.23.8. vdi-introduce .................................................................................... 194
A.4.23.9. vdi-pool-migrate ................................................................................ 194
A.4.23.10. vdi-resize ........................................................................................ 194
A.4.23.11. vdi-snapshot ................................................................................... 194

xvii

A.4.23.12. vdi-unlock ....................................................................................... 194
A.4.24. VIF Commands ............................................................................................. 195
A.4.24.1. VIF Parameters .................................................................................. 195
A.4.24.2. vif-create .......................................................................................... 196
A.4.24.3. vif-destroy ........................................................................................ 197
A.4.24.4. vif-plug ............................................................................................. 197
A.4.24.5. vif-unplug ......................................................................................... 197
A.4.24.6. vif-configure-ipv4 .............................................................................. 197
A.4.24.7. vif-configure-ipv6 .............................................................................. 197
A.4.25. VLAN Commands ......................................................................................... 197
A.4.25.1. vlan-create ........................................................................................ 197
A.4.25.2. pool-vlan-create ................................................................................ 197
A.4.25.3. vlan-destroy ...................................................................................... 198
A.4.26. VM Commands ............................................................................................ 198
A.4.26.1. VM Selectors ..................................................................................... 198
A.4.26.2. VM Parameters ................................................................................. 198
A.4.26.3. vm-assert-can-be-recovered ............................................................... 204
A.4.26.4. vm-cd-add ........................................................................................ 205
A.4.26.5. vm-cd-eject ....................................................................................... 205
A.4.26.6. vm-cd-insert ...................................................................................... 205
A.4.26.7. vm-cd-list .......................................................................................... 205
A.4.26.8. vm-cd-remove ................................................................................... 205
A.4.26.9. vm-clone ........................................................................................... 206
A.4.26.10. vm-compute-maximum-memory ...................................................... 206
A.4.26.11. vm-copy .......................................................................................... 206
A.4.26.12. vm-crashdump-list ........................................................................... 206
A.4.26.13. vm-data-source-list .......................................................................... 207
A.4.26.14. vm-data-source-record .................................................................... 207
A.4.26.15. vm-data-source-forget ..................................................................... 207
A.4.26.16. vm-data-source-query ..................................................................... 207
A.4.26.17. vm-destroy ...................................................................................... 208

xviii

A.4.26.18. vm-disk-add .................................................................................... 208
A.4.26.19. vm-disk-list ..................................................................................... 208
A.4.26.20. vm-disk-remove .............................................................................. 208
A.4.26.21. vm-export ....................................................................................... 208
A.4.26.22. vm-import ....................................................................................... 209
A.4.26.23. vm-install ........................................................................................ 209
A.4.26.24. vm-memory-shadow-multiplier-set .................................................. 209
A.4.26.25. vm-migrate ..................................................................................... 210
A.4.26.26. vm-reboot ....................................................................................... 211
A.4.26.27. vm-recover ...................................................................................... 211
A.4.26.28. vm-reset-powerstate ....................................................................... 211
A.4.26.29. vm-resume ...................................................................................... 211
A.4.26.30. vm-shutdown .................................................................................. 211
A.4.26.31. vm-start .......................................................................................... 212
A.4.26.32. vm-suspend .................................................................................... 212
A.4.26.33. vm-uninstall .................................................................................... 212
A.4.26.34. vm-vcpu-hotplug ............................................................................. 212
A.4.26.35. vm-vif-list ........................................................................................ 212

xix

Chapter 1. Document Overview
This document is a system administrator's guide for XenServer, the complete server virtualization platform from
Citrix. It contains procedures to guide you through configuring a XenServer deployment. In particular, it focuses on
setting up storage, networking and resource pools, and how to administer XenServer hosts using the xe command
line interface.
This document covers the following topics:
•

Managing Users with Active Directory and Role Based Access Control

•

Creating Resource Pools and setting up High Availability

•

Configuring and Managing Storage Repositories

•

Configuring Virtual Machine Memory using Dynamic Memory Control

•

Setting Control Domain Memory on a XenServer host

•

Configuring Networking

•

Recovering Virtual Machines using Disaster Recovery and Backing Up Data

•

Monitoring XenServer Performance Metrics and Configuring Alerts

•

Troubleshooting XenServer

•

Using the XenServer xe command line interface

1.1. Introducing XenServer
XenServer is the complete server virtualization platform from Citrix. The XenServer package contains all you need
to create and manage a deployment of virtual x86 computers running on Xen, the open-source paravirtualizing
hypervisor with near-native performance. XenServer is optimized for both Windows and Linux virtual servers.
XenServer runs directly on server hardware without requiring an underlying operating system, which results in
an efficient and scalable system. XenServer works by abstracting elements from the physical machine (such as
hard drives, resources and ports) and allocating them to the virtual machines running on it.
A virtual machine (VM) is a computer composed entirely of software that can run its own operating system and
applications as if it were a physical computer. A VM behaves exactly like a physical computer and contains its own
virtual (software-based) CPU, RAM, hard disk and network interface card (NIC).
XenServer lets you create VMs, take VM disk snapshots and manage VM workloads. For a comprehensive list of
major XenServer features, visit www.citrix.com/xenserver.

1.1.1. Benefits of Using XenServer
Using XenServer reduces costs by:
•

Consolidating multiple VMs onto physical servers

•

Reducing the number of separate disk images that need to be managed

•

Allowing for easy integration with existing networking and storage infrastructures

Using XenServer increases flexibility by:
•

Allowing you to schedule zero downtime maintenance by using XenMotion to live migrate VMs between
XenServer hosts

•

Increasing availability of VMs by using High Availability to configure policies that restart VMs on another
XenServer host if one fails

•

Increasing portability of VM images, as one VM image will work on a range of deployment infrastructures
1

1.1.2. Administering XenServer
There are two methods by which to administer XenServer: XenCenter and the XenServer Command-Line Interface
(CLI).
XenCenter is a graphical, Windows-based user interface. XenCenter allows you to manage XenServer hosts, pools
and shared storage, and to deploy, manage and monitor VMs from your Windows desktop machine.
The XenCenter on-line Help is a useful resource for getting started with XenCenter and for context-sensitive
assistance.
The XenServer Command-line Interface (CLI) allows you to administer XenServer using the Linux-based xe
commands.

1.2. XenServer Documentation
XenServer documentation shipped with this release includes:
•

XenServer Release Notes cover new features in XenServer 7.0 and any advisories and known issues that affect
this release.

•

XenServer Quick Start Guide provides an introduction for new users to the XenServer environment and
components. This guide steps through the installation and configuration essentials to get XenServer and the
XenCenter management console up and running quickly. After installation, it demonstrates how to create
a Windows VM, VM template and pool of XenServer hosts. It introduces basic administrative tasks and
advanced features, such as shared storage, VM snapshots and XenMotion live migration.

•

XenServer Installation Guide steps through the installation, configuration and initial operation of XenServer
and the XenCenter management console.

•

XenServer Virtual Machine User's Guide describes how to install Windows and Linux VMs within a XenServer
environment. This guide explains how to create new VMs from installation media, from VM templates
included in the XenServer package and from existing physical machines (P2V). It explains how to import disk
images and how to import and export appliances.

•

XenServer Administrator's Guide gives an in-depth description of the tasks involved in configuring a XenServer
deployment, including setting up storage, networking and pools. It describes how to administer XenServer
using the xe Command Line Interface.

•

vSwitch Controller User's Guide is a comprehensive user guide to the vSwitch Controller for XenServer.

•

Supplemental Packs and the DDK introduces the XenServer Driver Development Kit, which can be used to
modify and extend the functionality of XenServer.

•

XenServer Software Development Kit Guide presents an overview of the XenServer SDK. It includes code
samples that demonstrate how to write applications that interface with XenServer hosts.

•

XenAPI Specification is a reference guide for programmers to the XenServer API.

For additional resources, visit the Citrix Knowledge Center.

Chapter 2. Managing Users
Defining users, groups, roles and permissions allows you to control who has access to your XenServer hosts and
pools and what actions they can perform.
When you first install XenServer, a user account is added to XenServer automatically. This account is the local
super user (LSU), or root, which is authenticated locally by the XenServer computer.
The LSU, or root, is a special user account intended for system administration and has all rights or permissions.
In XenServer, the LSU is the default account at installation. The LSU is only authenticated by XenServer and does
not require any external authentication service. If an external authentication service fails, the LSU can still log in
and manage the system. The LSU can always access the XenServer physical server through SSH.
You can create additional users by adding the Active Directory accounts through either XenCenter's Users tab or
the xe CLI. If your environment does not use Active Directory, you are limited to the LSU account.
Note:
When you create new users, XenServer does not assign newly created user accounts RBAC
roles automatically. As a result, these accounts do not have any access to the XenServer pool
until you assign them a role.
These permissions are granted through roles, as discussed in Section 2.1, “Authenticating Users With Active
Directory (AD)”.

2.1. Authenticating Users With Active Directory (AD)
If you want to have multiple user accounts on a server or a pool, you must use Active Directory user accounts for
authentication. This lets XenServer users log in to a pool using their Windows domain credentials.
The only way you can configure varying levels of access for specific users is by enabling Active Directory
authentication, adding user accounts, and assign roles to those accounts.
Active Directory users can use the xe CLI (passing appropriate -u and -pw arguments) and also connect to the
host using XenCenter. Authentication is done on a per-resource pool basis.
Access is controlled by the use of subjects. A subject in XenServer maps to an entity on your directory server
(either a user or a group). When external authentication is enabled, the credentials used to create a session are
first checked against the local root credentials (in case your directory server is unavailable) and then against the
subject list. To permit access, you must create a subject entry for the person or group you wish to grant access
to. This can be done using XenCenter or the xe CLI.
If you are familiar with XenCenter, note that the XenServer CLI uses slightly different terminology to refer to Active
Directory and user account features:

XenCenter Term

XenServer CLI Term

Users

Subjects

Add users

Add subjects

Understanding Active Directory Authentication in the XenServer Environment
Even though XenServer is Linux-based, XenServer lets you use Active Directory accounts for XenServer user
accounts. To do so, it passes Active Directory credentials to the Active Directory domain controller.
When added to XenServer, Active Directory users and groups become XenServer subjects, generally referred to
as simply users in XenCenter. When a subject is registered with XenServer, users/groups are authenticated with
Active Directory on login and do not need to qualify their user name with a domain name.
Note:
By default, if you did not qualify the user name (for example, enter either mydomain\myuser
or myser@mydomain.com), XenCenter always attempts to log users in to Active Directory
authentication servers using the domain to which it is currently joined. The exception to this
is the LSU account, which XenCenter always authenticates locally (that is, on the XenServer)
first.
The external authentication process works as follows:
1. The credentials supplied when connecting to a server are passed to the Active Directory domain controller
for authentication.
2. The domain controller checks the credentials. If they are invalid, the authentication fails immediately.
3. If the credentials are valid, the Active Directory controller is queried to get the subject identifier and group
membership associated with the credentials.
4. If the subject identifier matches the one stored in the XenServer, the authentication is completed successfully.
When you join a domain, you enable Active Directory authentication for the pool. However, when a pool is joined
to a domain, only users in that domain (or a domain with which it has trust relationships) can connect to the pool.
Note:
Manually updating the DNS configuration of a DHCP-configured network PIF is unsupported
and might cause Active Directory integration, and consequently user authentication, to fail
or stop working.

2.1.1. Configuring Active Directory Authentication
XenServer supports use of Active Directory servers using Windows 2003 or later.
Active Directory authentication for a XenServer host requires that the same DNS servers are used for both the
Active Directory server (configured to allow for interoperability) and the XenServer host. In some configurations,
the active directory server may provide the DNS itself. This can be achieved either using DHCP to provide the
IP address and a list of DNS servers to the XenServer host, or by setting values in the PIF objects or using the
installer if a manual static configuration is used.
Citrix recommends enabling DHCP to broadcast host names. In particular, the host names localhost or linux
should not be assigned to hosts.
Warning:
XenServer hostnames should be unique throughout the XenServer deployment.
4

Note the following:
•

XenServer labels its AD entry on the AD database using its hostname. Therefore, if two XenServer hosts have
the same hostname and are joined to the same AD domain, the second XenServer will overwrite the AD entry
of the first XenServer, regardless of if they are in the same or in different pools, causing the AD authentication
on the first XenServer to stop working.
It is possible to use the same hostname in two XenServer hosts, as long as they join different AD domains.

•

The XenServer hosts can be in different time-zones, as it is the UTC time that is compared. To ensure
synchronization is correct, you may choose to use the same NTP servers for your XenServer pool and the
Active Directory server.

•

Mixed-authentication pools are not supported (that is, you cannot have a pool where some servers in the
pool are configured to use Active Directory and some are not).

•

The XenServer Active Directory integration uses the Kerberos protocol to communicate with the Active
Directory servers. Consequently, XenServer does not support communicating with Active Directory servers
that do not utilize Kerberos.

•

For external authentication using Active Directory to be successful, it is important that the clocks on your
XenServer hosts are synchronized with those on your Active Directory server. When XenServer joins the Active
Directory domain, this will be checked and authentication will fail if there is too much skew between the
servers.
Warning:
Host names must consist solely of no more than 63 alphanumeric characters, and must not
be purely numeric.

Once you have Active Directory authentication enabled, if you subsequently add a server to that pool, you are
prompted to configure Active Directory on the server joining the pool. When you are prompted for credentials
on the joining server, enter Active Directory credentials with sufficient privileges to add servers to that domain.
Active Directory integration
Make sure that the following firewall ports are open for outbound traffic in order for XenServer to access the
domain controllers.
Port

Protocol

Use

UDP/TCP

DNS

UDP/TCP

Kerberos 5

123

UDP

NTP

137

UDP

NetBIOS Name Service

139

TCP

NetBIOS Session (SMB)

389

UDP/TCP

LDAP

445

TCP

SMB over TCP

464

UDP/TCP

Machine password changes

3268

TCP

Global Catalog Search

Note:
To view the firewall rules on a Linux computer using iptables, run the following command:
iptables - nL.

Note:
XenServer uses PowerBroker Identity Services (PBIS) to authenticate the AD user in the AD
server, and to encrypt communications with the AD server.
How does XenServer manage the machine account password for AD integration?
Similarly to Windows client machines, PBIS automatically updates the machine account password, renewing it
once every 30 days, or as specified in the machine account password renewal policy in the AD server.

Enabling external authentication on a pool
•

External authentication using Active Directory can be configured using either XenCenter or the CLI using the
command below.
xe pool-enable-external-auth auth-type=AD \
service-name= \
config:user= \
config:pass=

The user specified needs to have Add/remove computer objects or workstations privileges,
which is the default for domain administrators.
Note:
If you are not using DHCP on the network used by Active Directory and your XenServer hosts,
use you can use these two approaches to setup your DNS:
1. Set up your domain DNS suffix search order for resolving non-FQDNs:
xe pif-param-set uuid= \
“other-config:domain=suffix1.com suffix2.com suffix3.com”

2. Configure the DNS server to use on your XenServer hosts:
xe pif-reconfigure-ip mode=static dns= ip= \
gateway= netmask= uuid=

3. Manually set the management interface to use a PIF that is on the same network as your
DNS server:
xe host-management-reconfigure pif-uuid=

Note:
External authentication is a per-host property. However, Citrix advises that you enable and
disable this on a per-pool basis – in this case XenServer will deal with any failures that occur
when enabling authentication on a particular host and perform any roll-back of changes that
may be required, ensuring that a consistent configuration is used across the pool. Use the
host-param-list command to inspect properties of a host and to determine the status of
external authentication by checking the values of the relevant fields.

Disabling external authentication
•

Use XenCenter to disable Active Directory authentication, or the following xe command:
xe pool-disable-external-auth

2.1.2. User Authentication
To allow a user access to your XenServer host, you must add a subject for that user or a group that they are in.
(Transitive group memberships are also checked in the normal way, for example: adding a subject for group A,
where group A contains group B and user 1 is a member of group B would permit access to user 1.) If
you wish to manage user permissions in Active Directory, you could create a single group that you then add and

remove users to/from; alternatively, you can add and remove individual users from XenServer, or a combination
of users and groups as your would be appropriate for your authentication requirements. The subject list can be
managed from XenCenter or using the CLI as described below.
When authenticating a user, the credentials are first checked against the local root account, allowing you to
recover a system whose AD server has failed. If the credentials (i.e. username then password) do not match/
authenticate, then an authentication request is made to the AD server – if this is successful the user's information
will be retrieved and validated against the local subject list, otherwise access will be denied. Validation against the
subject list will succeed if the user or a group in the transitive group membership of the user is in the subject list.
Note:
When using Active Directory groups to grant access for Pool Administrator users who will
require host ssh access, the number of users in the Active Directory group must not exceed
500.

Allowing a user access to XenServer using the CLI
•

To add an AD subject to XenServer:
xe subject-add subject-name=

The entity name should be the name of the user or group to which you want to grant access. You may
optionally include the domain of the entity (for example, '' as opposed to '') although
the behavior will be the same unless disambiguation is required.

Using the CLI to Revoke User Access
1.

Find the user's subject identifier. This is the user or the group containing the user (removing a group would
remove access to all users in that group, providing they are not also specified in the subject list). To do this
use the subject list command:
xe subject-list

This returns a list of all users.
You may wish to apply a filter to the list, for example to find the subject identifier for a user named user1
in the testad domain, you could use the following command:
xe subject-list other-config:subject-name=''

Remove the user using the subject-remove command, passing in the subject identifier you learned in the
previous step:
xe subject-remove subject-uuid=

You may wish to terminate any current session this user has already authenticated. See Terminating all
authenticated sessions using xe and Terminating individual user sessions using xe for more information about
terminating sessions. If you do not terminate sessions the users whose permissions have been revoked may
be able to continue to access the system until they log out.

Listing subjects with access
•

To identify the list of users and groups with permission to access your XenServer host or pool, use the
following command:
xe subject-list

2.1.3. Removing Access for a User
Once a user is authenticated, they will have access to the server until they end their session, or another user
terminates their session. Removing a user from the subject list, or removing them from a group that is in the
7

subject list, will not automatically revoke any already-authenticated sessions that the user has; this means that
they may be able to continue to access the pool using XenCenter or other API sessions that they have already
created. In order to terminate these sessions forcefully, XenCenter and the CLI provide facilities to terminate
individual sessions, or all currently active sessions. See the XenCenter help for more information on procedures
using XenCenter, or below for procedures using the CLI.

Terminating all authenticated sessions using xe
•

Execute the following CLI command:
xe session-subject-identifier-logout-all

Terminating individual user sessions using xe
1.

Determine the subject identifier whose session you wish to log out. Use either the session-subjectidentifier-list or subject-list xe commands to find this (the first shows users who have sessions, the second
shows all users but can be filtered, for example, using a command like xe subject-list other-config:subjectname=xendt\\user1 – depending on your shell you may need a double-backslash as shown).

Use the session-subject-logout command, passing the subject identifier you have determined in the
previous step as a parameter, for example:
xe session-subject-identifier-logout subject-identifier=

2.1.4. Leaving an AD Domain
Warning:
When you leave the domain (that is, disable Active Directory authentication and disconnect
a pool or server from its domain), any users who authenticated to the pool or server with
Active Directory credentials are disconnected.
Use XenCenter to leave an AD domain. See the XenCenter help for more information. Alternately run the pooldisable-external-auth command, specifying the pool uuid if required.
Note:
Leaving the domain will not cause the host objects to be removed from the AD database. See
this knowledge base article for more information about this and how to remove the disabled
host entries.

2.2. Role Based Access Control
XenServer's Role Based Access Control (RBAC) allows you to assign users, roles, and permissions to control who
has access to your XenServer and what actions they can perform. The XenServer RBAC system maps a user
(or a group of users) to defined roles (a named set of permissions), which in turn have associated XenServer
permissions (the ability to perform certain operations).
As users are not assigned permissions directly, but acquire them through their assigned role, management of
individual user permissions becomes a matter of simply assigning the user to the appropriate role; this simplifies
common operations. XenServer maintains a list of authorized users and their roles.
RBAC allows you to easily restrict which operations different groups of users can perform- thus reducing the
probability of an accident by an inexperienced user.
To facilitate compliance and auditing, RBAC also provides an Audit Log feature.

RBAC depends on Active Directory for authentication services. Specifically, XenServer keeps a list of authorized
users based on Active Directory user and group accounts. As a result, you must join the pool to the domain and
add Active Directory accounts before you can assign roles.
The local super user (LSU), or root, is a special user account used for system administration and has all rights or
permissions. In XenServer, the local super user is the default account at installation. The LSU is authenticated via
XenServer and not external authentication service, so if the external authentication service fails, the LSU can still
log in and manage the system. The LSU can always access the XenServer physical host via SSH.

RBAC process
This is the standard process for implementing RBAC and assigning a user or group a role:
1. Join the domain. See Enabling external authentication on a pool
2. Add an Active Directory user or group to the pool. This becomes a subject. See Section 2.2.3.3, “To Add a
Subject to RBAC”.
3. Assign (or modify) the subject's RBAC role. See Section 2.2.3.4, “To Assign an RBAC Role to a Created subject”.

2.2.1. Roles
XenServer is shipped with the following six, pre-established roles:
•

Pool Administrator (Pool Admin) – the same as being the local root. Can perform all operations.
Note:
The local super user (root) will always have the "Pool Admin" role. The Pool Admin role has
the same permissions as the local root.

•

Pool Operator (Pool Operator) – can do everything apart from adding/removing users and modifying their
roles. This role is focused mainly on host and pool management (i.e. creating storage, making pools, managing
the hosts etc.)

•

Virtual Machine Power Administrator (VM Power Admin) – creates and manages Virtual Machines. This role
is focused on provisioning VMs for use by a VM operator.

•

Virtual Machine Administrator (VM Admin) – similar to a VM Power Admin, but cannot migrate VMs or
perform snapshots.

•

Virtual Machine Operator (VM Operator) – similar to VM Admin, but cannot create/destroy VMs – but can
perform start/stop lifecycle operations.

•

Read-only (Read Only) – can view resource pool and performance data.
Note:
You cannot add, remove or modify roles in this version of XenServer.
Warning:
9

You can not assign the role of pool-admin to an AD group which has more than 500 members,
if you want users of the AD group to have SSH access.
For a summary of the permissions available for each role and more detailed information on the operations
available for each permission, see Section 2.2.2, “Definitions of RBAC Roles and Permissions”.
All XenServer users need to be allocated to an appropriate role. By default, all new users will be allocated to the
Pool Administrator role. It is possible for a user to be assigned to multiple roles; in that scenario, the user will
have the union of all the permissions of all their assigned roles.

A user's role can be changed in two ways:
1. Modify the subject -> role mapping (this requires the assign/modify role permission, only available to a Pool
Administrator.)
2. Modify the user's containing group membership in Active Directory.

2.2.2. Definitions of RBAC Roles and Permissions
The following table summarizes which permissions are available for each role. For details on the operations
available for each permission, see Definitions of permissions.

Table 2.1. Permissions available for each role
Role permissions

Pool
Admin

Pool
Operator

Assign/modify roles

Server backup/restore

Import/export
OVF/OVA
packages and disk images

Set cores per socket

Convert virtual machines using
XenServer Conversion Manager

Switch-port locking

Log out active user connections

Create and dismiss alerts

Cancel task of any user

Pool management

Storage XenMotion

VM advanced operations

VM create/destroy operations

VM change CD media

VM Power
Admin

VM
Admin

VM
Operator

Read
Only

Role permissions

Pool
Admin

Pool
Operator

VM Power
Admin

VM
Admin

VM
Operator

Read
Only

VM change power state

View VM consoles

XenCenter view management
operations

Cancel own tasks

Read audit logs

Connect to pool and read all pool
metadata

Configure virtual GPU

View virtual GPU configuration

Access the config drive (CoreOS
VMs only)

Container management

Health Check configuration

View Health Check results and
settings

Definitions of Permissions
The following table provides additional details about permissions:

Table 2.2. Definitions of permissions
Permission

Allows Assignee To

Rationale/Comments

Assign/modify roles

•

Add/remove users

•

Add/remove roles from users

•

Enable and disable Active
Directory integration (being
joined to the domain)

This permission lets the user grant
himself or herself any permission
or perform any task.

•

Server console access through
ssh

•

Server console access through
XenCenter

•

Back up and restore servers

•

Back up and restore pool
metadata

Server backup/restore VM create/
destroy operations

Warning: This role lets the
user disable the Active Directory
integration and all subjects added
from Active Directory.
Warning: With access to a root
shell, the assignee could arbitrarily
reconfigure the entire system,
including RBAC.
The ability to restore a backup
lets the assignee revert RBAC
configuration changes.

Permission

Allows Assignee To

Rationale/Comments

Import/export OVF/OVA packages
and disk images

•

Import OVF and OVA packages

•

Import disk images

•

Export VMs
packages

Set cores-per-socket

•

Set the number of cores per
socket for the VM's virtual
CPUs

This permission enables the user to
specify the topology for the VM's
virtual CPUs.

Convert VMs using XenServer
Conversion Manager

•

Convert VMware
XenServer VMs

This permission lets the user
convert workloads from VMware
to XenServer by copying batches
of VMware VMs to XenServer
environment.

Switch-port locking

•

Control traffic on a network

Log out active user connections

•

Ability to disconnect logged in
users

OVF/OVA

VMs

Create/dismiss alerts

This permission lets the user to
block all traffic on a network
by default, or define specific IP
addresses from which a VM is
allowed to send traffic.

Warning: A user with this
permission can dismiss alerts for
the entire pool.
Note: The ability to view alerts is
part of the Connect to Pool and
read all pool metadata permission.

Cancel task of any user

•

Cancel any user's running task

This permission lets the user
request XenServer cancel an inprogress task initiated by any user.

Permission

Allows Assignee To

Rationale/Comments

Pool management

•

Set pool properties (naming,
default SRs)

•

Enable, disable, and configure
HA

This permission includes all the
actions required to maintain a
pool.

•

Set per-VM
priorities

•

Configure DR and perform
DR failover, failback and test
failover operations

•

Enable, disable, and configure
Workload Balancing (WLB)

•

Add and remove server from
pool

•

Emergency
master

•

Emergency master address

•

Emergency recover slaves

•

Designate new master

•

Manage pool
certificates

•

Patching

•

Set server properties

•

Configure server logging

•

Enable and disable servers

•

Shut down, reboot,
power-on servers

•

Restart toolstack

•

System status reports

•

Apply license

•

Live migration of all other VMs
on a server to another server,
due to either Maintenance
Mode, or HA

•

Configure server management
interface
and
secondary
interfaces

•

Disable server management

•

Delete crashdumps

•

Add, edit,
networks

•

Add, edit, and remove PBDs/
PIFs/VLANs/Bonds/SRs

•

Add, remove, and retrieve
secrets

restart

transition

and

server

and

remove

Note: If the management interface
is not functioning, no logins can
authenticate except local root
logins.

Permission

Allows Assignee To

Storage XenMotion

•

Migrate VMs from one host to
another host

•

Move Virtual Disk (VDIs) from
one SR to another SR

•

Adjust VM memory (through
Dynamic Memory Control)

•

Create a VM snapshot with
memory, take VM snapshots,
and roll-back VMs

•

Migrate VMs

•

Start VMs, including specifying
physical server

•

Resume VMs

•

Install or delete

•

Clone/copy VMs

•

Add, remove, and configure
virtual disk/CD devices

•

Add, remove, and configure
virtual network devices

•

Import/export XVA files

•

VM configuration change

•

Eject current CD

•

Insert new CD

•

Start
VMs
placement)

•

Shut down VMs

•

Reboot VMs

•

Suspend VMs

•

Resume VMs
placement)

•

See and interact with VM
consoles

This permission does not let the
user view server consoles.

•

Create and modify global
XenCenter folders

•

Create and modify global
XenCenter custom fields

Folders, custom fields, and
searches are shared between all
users accessing the pool

•

Create and modify global
XenCenter searches

•

Lets a user cancel their own
tasks

VM advanced operations

VM create/destroy operations

VM change CD media

VM change power state

View VM consoles
XenCenter
operations

view

Cancel own tasks

management

Rationale/Comments

This permission provides the
assignee with enough privileges to
start a VM on a different server
if they are not satisfied with the
server XenServer selected.

Server backup/restore VM create/
destroy operations

Import/export OVF/OVA packages;
import disk images
(automatic

This permission does not include
start_on, resume_on, and migrate,
which are part of the VM advanced
operations permission.

(automatic

Permission

Allows Assignee To

Read audit log

•

Download the XenServer audit
log

Connect to pool and read all pool
metadata

•

View pool metadata

•

View historical performance
data

•

View logged in users

•

View users and roles

•

View messages

•

Specify a pool-wide placement
policy

•

Assign a virtual GPU to a VM

•

Remove a virtual GPU from a
VM

•

Modify allowed virtual GPU
types

•

Create, destroy, or assign a
GPU group

View virtual GPU configuration

•

View GPUs, GPU placement
policies, and virtual GPU
assignments

Access the config drive (CoreOS
VMs only)

•

Access the config driver of the
VM

•

Modify
the
parameters

•

Start

•

Stop

•

Pause

•

Resume

•

Access information about the
container

•

Enable Health Check

•

Disable Health Check

•

Update Health Check settings

•

Manually upload a server
status report

•

View the results of a Health
Check upload

•

View Health Check enrollment
settings

Configure virtual GPU

Container management

Health Check configuration

View Health Check results and
settings

Rationale/Comments

cloud-config

Note:
In some cases, a Read Only user cannot move a resource into a folder in XenCenter, even after
receiving an elevation prompt and supplying the credentials of a more privileged user. In this
case, log on to XenCenter as the more privileged user and retry the action.

2.2.3. Using RBAC with the CLI
2.2.3.1. To List All the Available Defined Roles in XenServer
•

Run the command: xe role-list
This command returns a list of the currently defined roles, for example:

uuid( RO): 0165f154-ba3e-034e-6b27-5d271af109ba
name ( RO): pool-admin
description ( RO): The Pool Administrator role has full access to all
features and settings, including accessing Dom0 and managing subjects,
roles and external authentication
uuid ( RO): b9ce9791-0604-50cd-0649-09b3284c7dfd
name ( RO): pool-operator
description ( RO): The Pool Operator role manages host- and pool-wide resources,
including setting up storage, creating resource pools and managing patches, and
high availability (HA).
uuid( RO): 7955168d-7bec-10ed-105f-c6a7e6e63249
name ( RO): vm-power-admin
description ( RO): The VM Power Administrator role has full access to VM and
template management and can choose where to start VMs and use the dynamic memory
control and VM snapshot features
uuid ( RO): aaa00ab5-7340-bfbc-0d1b-7cf342639a6e
name ( RO): vm-admin
description ( RO): The VM Administrator role can manage VMs and templates
uuid ( RO): fb8d4ff9-310c-a959-0613-54101535d3d5
name ( RO): vm-operator
description ( RO): The VM Operator role can use VMs and interact with VM consoles
uuid ( RO): 7233b8e3-eacb-d7da-2c95-f2e581cdbf4e
name ( RO): read-only
description ( RO): The Read-Only role can log in with basic read-only access

Note:
This list of roles is static; it is not possible to add, remove, or modify roles.

2.2.3.2. To Display a List of Current Subjects:
•

Run the command xe subject-list

This will return a list of XenServer users, their uuid, and the roles they are associated with:

uuid ( RO): bb6dd239-1fa9-a06b-a497-3be28b8dca44
subject-identifier ( RO): S-1-5-21-1539997073-1618981536-2562117463-2244
other-config (MRO): subject-name: example01\user_vm_admin; subject-upn: \
user_vm_admin@XENDT.NET; subject-uid: 1823475908; subject-gid: 1823474177; \
subject-sid: S-1-5-21-1539997073-1618981536-2562117463-2244; subject-gecos: \
user_vm_admin; subject-displayname: user_vm_admin; subject-is-group: false; \
subject-account-disabled: false; subject-account-expired: false; \
subject-account-locked: false;subject-password-expired: false
roles (SRO): vm-admin
uuid ( RO): 4fe89a50-6a1a-d9dd-afb9-b554cd00c01a
subject-identifier ( RO): S-1-5-21-1539997073-1618981536-2562117463-2245
other-config (MRO): subject-name: example02\user_vm_op; subject-upn: \
user_vm_op@XENDT.NET; subject-uid: 1823475909; subject-gid: 1823474177; \
subject-sid: S-1-5-21-1539997073-1618981536-2562117463-2245; \
subject-gecos: user_vm_op; subject-displayname: user_vm_op; \
subject-is-group: false; subject-account-disabled: false; \
subject-account-expired: false; subject-account-locked: \
false; subject-password-expired: false
roles (SRO): vm-operator
uuid ( RO): 8a63fbf0-9ef4-4fef-b4a5-b42984c27267
subject-identifier ( RO): S-1-5-21-1539997073-1618981536-2562117463-2242
other-config (MRO): subject-name: example03\user_pool_op; \
subject-upn: user_pool_op@XENDT.NET; subject-uid: 1823475906; \
subject-gid: 1823474177; subject-s id:
S-1-5-21-1539997073-1618981536-2562117463-2242; \
subject-gecos: user_pool_op; subject-displayname: user_pool_op; \
subject-is-group: false; subject-account-disabled: false; \
subject-account-expired: false; subject-account-locked: \
false; subject-password-expired: false
roles (SRO): pool-operator

2.2.3.3. To Add a Subject to RBAC
In order to enable existing AD users to use RBAC, you will need to create a subject instance within XenServer,
either for the AD user directly, or for one of their containing groups:
1. Run the command xe subject-add subject-name=
This adds a new subject instance.

2.2.3.4. To Assign an RBAC Role to a Created subject
Once you have added a subject, you can assign it to an RBAC role. You can refer to the role by either its uuid
or name:
1. Run the command:
xe subject-role-add uuid= role-uuid=
or
xe subject-role-add uuid= role-name=
For example, the following command adds a subject with the uuid b9b3d03b-3d10-79d3-8ed7a782c5ea13b4 to the Pool Administrator role:
xe subject-role-add uuid=b9b3d03b-3d10-79d3-8ed7-a782c5ea13b4 role-name=pool-admin

2.2.3.5. To Change a Subject's RBAC Role:
To change a user's role it is necessary to remove them from their existing role, and add them to a new role:
17

1. Run the commands:
xe subject-role-remove uuid= role-name= \

xe subject-role-add uuid= role-name= \

To ensure that the new role takes effect, the user should be logged out and logged back in again (this requires
the "Logout Active User Connections" permission - available to a Pool Administrator or Pool Operator).
Warning:
Once you have added or removed a pool-admin subject, there can be a delay of a few seconds
for ssh sessions associated to this subject to be accepted by all hosts of the pool.

2.2.4. Auditing
The RBAC audit log will record any operation taken by a logged-in user.
•

the message will explicitly record the Subject ID and user name associated with the session that invoked the
operation.

•

if an operation is invoked for which the subject does not have authorization, this will be logged.

•

if the operation succeeded then this is recorded; if the operation failed then the error code is logged.

2.2.4.1. Audit Log xe CLI Commands
xe audit-log-get [since=] filename=
This command downloads to a file all the available records of the RBAC audit file in the pool. If the optional
parameter 'since' is present, then it only downloads the records from that specific point in time.

2.2.4.2. To Obtain All Audit Records From the Pool
Run the following command:
xe audit-log-get filename=/tmp/auditlog-pool-actions.out

2.2.4.3. To Obtain Audit Records of the Pool Since a Precise Millisecond Timestamp
Run the following command:
xe audit-log-get since=2009-09-24T17:56:20.530Z \
filename=/tmp/auditlog-pool-actions.out

2.2.4.4. To Obtain Audit Records of the Pool Since a Precise Minute Timestamp
Run the following command:
xe audit-log-get since=2009-09-24T17:56Z \
filename=/tmp/auditlog-pool-actions.out

2.2.5. How Does XenServer Compute the Roles for the Session?
1. The subject is authenticated via the Active Directory server to verify which containing groups the subject may
also belong to.
2. XenServer then verifies which roles have been assigned both to the subject, and to its containing groups.
3. As subjects can be members of multiple Active Directory groups, they will inherit all of the permissions of the
associated roles.
18

In this illustration, since Subject 2 (Group 2) is the Pool Operator and User 1 is a member
of Group 2, when Subject 3 (User 1) tries to log in, he or she inherits both Subject 3
(VM Operator) and Group 2 (Pool Operator) roles. Since the Pool Operator role is
higher, the resulting role for Subject 3 (User 1) is Pool Operator and not VM Operator.

Chapter 3. XenServer Hosts and Resource
Pools
This chapter describes how resource pools can be created through a series of examples using the xe command
line interface (CLI). A simple NFS-based shared storage configuration is presented and a number of simple VM
management examples are discussed. Procedures for dealing with physical node failures are also described.

3.1. Hosts and Resource Pools Overview
A resource pool comprises multiple XenServer host installations, bound together into a single managed entity
which can host Virtual Machines. When combined with shared storage, a resource pool enables VMs to be started
on any XenServer host which has sufficient memory and then dynamically moved between XenServer hosts while
running with minimal downtime (XenMotion). If an individual XenServer host suffers a hardware failure, then the
administrator can restart the failed VMs on another XenServer host in the same resource pool. If high availability
(HA) is enabled on the resource pool, VMs will automatically be moved if their host fails. Up to 16 hosts are
supported per resource pool, although this restriction is not enforced.
A pool always has at least one physical node, known as the master. Only the master node exposes an
administration interface (used by XenCenter and the XenServer Command Line Interface, known as the xe CLI);
the master forwards commands to individual members as necessary.
Note:
If the pool's master fails, master re-election will only take place if High Availability is enabled.

3.2. Requirements for Creating Resource Pools
A resource pool is a homogeneous (or heterogeneous with restrictions, see Section 3.4, “Creating Heterogeneous
Resource Pools”) aggregate of one or more XenServer hosts, up to a maximum of 16. The definition of
homogeneous is:
•

the CPUs on the server joining the pool are the same (in terms of vendor, model, and features) as the CPUs
on servers already in the pool.

•

the server joining the pool is running the same version of XenServer software, at the same patch level, as
servers already in the pool

The software will enforce additional constraints when joining a server to a pool – in particular:
•

it is not a member of an existing resource pool

•

it has no shared storage configured

•

there are no running or suspended VMs on the XenServer host which is joining

•

there are no active operations on the VMs in progress, such as one shutting down

You must also check that the clock of the host joining the pool is synchronized to the same time as the pool
master (for example, by using NTP), that its management interface is not bonded (you can configure this once
the host has successfully joined the pool), and that its management IP address is static (either configured on the
host itself or by using an appropriate configuration on your DHCP server).
XenServer hosts in resource pools may contain different numbers of physical network interfaces and have local
storage repositories of varying size. In practice, it is often difficult to obtain multiple servers with the exact same
CPUs, and so minor variations are permitted. If you are sure that it is acceptable in your environment for hosts
with varying CPUs to be part of the same resource pool, then the pool joining operation can be forced by passing
a --force parameter.
20

Note:
The requirement for a XenServer host to have a static IP address to be part of a resource pool
also applies to servers providing shared NFS or iSCSI storage for the pool.
Although not a strict technical requirement for creating a resource pool, the advantages of pools (for example,
the ability to dynamically choose on which XenServer host to run a VM and to dynamically move a VM between
XenServer hosts) are only available if the pool has one or more shared storage repositories. If possible, postpone
creating a pool of XenServer hosts until shared storage is available. Once shared storage has been added, Citrix
recommends that you move existing VMs whose disks are in local storage into shared storage. This can be done
using the xe vm-copy command or using XenCenter.

3.3. Creating a Resource Pool
Resource pools can be created using either the XenCenter management console or the CLI. When you join a new
host to a resource pool, the joining host synchronizes its local database with the pool-wide one, and inherits
some settings from the pool:
•

VM, local, and remote storage configuration is added to the pool-wide database. All of these will still be tied
to the joining host in the pool unless you explicitly take action to make the resources shared after the join
has completed.

•

The joining host inherits existing shared storage repositories in the pool and appropriate PBD records are
created so that the new host can access existing shared storage automatically.

•

Networking information is partially inherited to the joining host: the structural details of NICs, VLANs and
bonded interfaces are all inherited, but policy information is not. This policy information, which must be reconfigured, includes:
•

the IP addresses of management NICs, which are preserved from the original configuration

•

the location of the management interface, which remains the same as the original configuration. For
example, if the other pool hosts have their management interfaces on a bonded interface, then the joining
host must be explicitly migrated to the bond once it has joined.

•

Dedicated storage NICs, which must be re-assigned to the joining host from XenCenter or the CLI, and
the PBDs re-plugged to route the traffic accordingly. This is because IP addresses are not assigned as
part of the pool join operation, and the storage NIC is not useful without this configured correctly. See
Section 4.4.7, “Configuring a Dedicated Storage NIC” for details on how to dedicate a storage NIC from
the CLI.

To join XenServer hosts host1 and host2 into a resource pool using the CLI
1.

Open a console on XenServer host host2.

Command XenServer host host2 to join the pool on XenServer host host1 by issuing the command:
xe pool-join master-address= master-username= \
master-password=

The master-address must be set to the fully-qualified domain name of XenServer host host1 and the
password must be the administrator password set when XenServer host host1 was installed.

Naming a resource pool
•

XenServer hosts belong to an unnamed pool by default. To create your first resource pool, rename the
existing nameless pool. Use tab-complete to find the pool_uuid:
xe pool-param-set name-label=<"New Pool"> uuid=

3.4. Creating Heterogeneous Resource Pools
XenServer simplifies expanding deployments over time by allowing disparate host hardware to be joined into
a resource pool, known as heterogeneous resource pools. Heterogeneous resource pools are made possible by
leveraging technologies in Intel (FlexMigration) and AMD (Extended Migration) CPUs that provide CPU "masking"
or "leveling". These features allow a CPU to be configured to appear as providing a different make, model, or
functionality than it actually does. This enables you to create pools of hosts with disparate CPUs but still safely
support live migrations.
Note:
The CPUs of XenServer hosts joining a heterogeneous pool must be of the same vendor (that
is, AMD, Intel) as the CPUs on hosts already in the pool, though the specific type, (family,
model and stepping numbers) need not be.
XenServer 7.0 simplifies the support of heterogeneous pools. In previous versions of XenServer, a new pool
member with a feature set different to that of the pool had to be CPU masked by users before it was allowed
to join the pool. Hosts can now be added to existing resource pools, irrespective of the underlying CPU type (as
long as the CPU is from the same vendor family). The pool feature set is dynamically calculated every time:
•

a new host joins the pool

•

a pool member leaves the pool

•

a pool member reconnects following a reboot

Any change in the pool feature set does not affect VMs that are currently running in the pool. A Running VM
will continue to use the feature set which was applied when it was started. This feature set is fixed at boot and
persists across migrate, suspend, and resume operations. In scenarios where a pool level drops when a lesscapable host joins the pool, a running VM can be migrated to any host in the pool, except the newly added
host. When you attempt to move or migrate a VM to a different host within or across pools, XenServer performs
migration checks to compare the VM's feature set against the feature set of the destination host. If the feature
sets are found to be compatible, the VM will be allowed to migrate. This enables the VM to move freely within
and across pools, regardless of the CPU features the VM is using. If you use Workload Balancing (WLB) to choose
an optimal destination host to migrate your VM, a host with incompatible feature set will not be recommended
as the destination host.

3.5. Adding Shared Storage
For a complete list of supported shared storage types, see the Storage chapter. This section demonstrates how
shared storage (represented as a storage repository) can be created on an existing NFS server.

Adding NFS shared storage to a resource pool using the CLI
1.

Open a console on any XenServer host in the pool.

Create the storage repository on by issuing the command
xe sr-create content-type=user type=nfs name-label=<"Example SR"> shared=true \
device-config:server= \
device-config:serverpath=

The device-config:server refers to the hostname of the NFS server and deviceconfig:serverpath refers to the path on the NFS server. Since shared is set to true, the shared
storage will be automatically connected to every XenServer host in the pool and any XenServer hosts that
subsequently join will also be connected to the storage. The Universally Unique Identifier (UUID) of the
created storage repository will be printed on the screen.
3.

Find the UUID of the pool by the command
xe pool-list

Set the shared storage as the pool-wide default with the command
22

xe pool-param-set uuid= default-SR=

Since the shared storage has been set as the pool-wide default, all future VMs will have their disks created
on shared storage by default. See Chapter 5, Storage for information about creating other types of shared
storage.

3.6. Removing a XenServer Host from a Resource Pool
Note:
Before removing a XenServer host from a pool, ensure that you shut down all the VMs running
on that host. Otherwise, you may see a warning stating that the host cannot be removed.
When a XenServer host is removed (ejected) from a pool, the machine is rebooted, reinitialized, and left in a state
equivalent to that after a fresh installation. It is important not to eject a XenServer host from a pool if there is
important data on the local disks.

To remove a host from a resource pool using the CLI
1.

Open a console on any host in the pool.

Find the UUID of the host by running the command
xe host-list

Eject the required host from the pool:
xe pool-eject host-uuid=

The XenServer host will be ejected and left in a freshly-installed state.
Warning:
Do not eject a host from a resource pool if it contains important data stored on its local
disks. All of the data will be erased upon ejection from the pool. If you wish to preserve this
data, copy the VM to shared storage on the pool first using XenCenter, or the xe vm-copy
CLI command.
When a XenServer host containing locally stored VMs is ejected from a pool, those VMs will still be present in the
pool database and visible to the other XenServer hosts. They will not start until the virtual disks associated with
them have been changed to point at shared storage which can be seen by other XenServer hosts in the pool, or
simply removed. It is for this reason that you are strongly advised to move any local storage to shared storage
upon joining a pool, so that individual XenServer hosts can be ejected (or physically fail) without loss of data.

3.7. Preparing a Pool of XenServer Hosts for Maintenance
Before performing maintenance operations on a XenServer host that is part of a resource pool, you should disable
it (which prevents any VMs from being started on it), then migrate its VMs to another XenServer host in the pool.
This can most readily be accomplished by placing the XenServer host into Maintenance mode using XenCenter.
See the XenCenter Help for details.
Note:
Placing the master host into maintenance mode will result in the loss of the last 24hrs of RRD
updates for offline VMs. This is because the backup synchronization occurs every 24hrs.
Warning:
Citrix highly recommends rebooting all XenServers prior to installing an update and then
verifying their configuration. This is because some configuration changes only take effect
when a XenServer is rebooted, so the reboot may uncover configuration problems that would
cause the update to fail.

To prepare a XenServer host in a pool for maintenance operations using the CLI
1.

Run the command
xe host-disable uuid=
xe host-evacuate uuid=

This will disable the XenServer host and then migrate any running VMs to other XenServer hosts in the pool.
2.

Perform the desired maintenance operation.

Once the maintenance operation is completed, enable the XenServer host:
xe host-enable

Restart any halted VMs and/or resume any suspended VMs.

3.8. Export Resource Pool Data
Note:
Export Resource Pool Data is available for XenServer Enterprise Edition customers, or those
who have access to XenServer through their XenApp/XenDesktop entitlement. To learn more
about XenServer editions, and to find out how to upgrade, visit the Citrix website here. For
detailed information on Licensing - refer to XenServer 7.0 Licensing FAQ.
The Export Resource Data option allows you to generate a resource data report for your pool and export the
report into a .xls or .csv file. This report provides detailed information about various resources in the pool such
as, servers, networks, storage, virtual machines, VDIs, and GPUs. This feature enables administrators to track,
plan, and assign resources based on various workloads such as CPU, storage, and Network.
The following table provides a list of resources and various types of resource data included in the report:
Resource

Resource Data

Server

•

Name

•

Pool Master

•

UUID

•

Address

•

CPU Usage

•

Network (avg/max KBs)

•

Used Memory

•

Storage

•

Uptime

•

Description

•

Name

•

Link Status

•

MAC

•

MTU

•

VLAN

•

Type

•

Location

Networks

Resource

Resource Data

VDI

•

Name

•

Type

•

UUID

•

Size

•

Storage

•

Description

•

Name

•

Type

•

UUID

•

Size

•

Location

•

Description

•

Name

•

Power State

•

Running on

•

Address

•

MAC

•

NIC

•

Operating System

•

Storage

•

Used Memory

•

CPU Usage

•

UUID

•

Uptime

•

Template

•

Description

Storage

VMs

GPU

Note: Information about GPUs will be available only if
there are GPUs attached to your XenServer host.
•

Name

•

Servers

•

PCI Bus Path

•

UUID

•

Power Usage

•

Temperature

•

Used Memory

•

Computer Utilization

3.8.1. To Export Resource Data
1. In the XenCenter Navigation pane, click Infrastructure and then click on the pool
25

2. Click the Pool menu and then select Export Resource Data.
3. Browse to a location where you would like to save report and then click Save.

3.9. High Availability
3.9.1. HA Overview
HA is a set of automatic features designed to plan for, and safely recover from, issues which take down XenServer
hosts or make them unreachable. For example physically disrupted networking or host hardware failures.
Note:
HA is designed to be used in conjunction with storage multipathing and network bonding to
create a system which is resilient to, and can recover from hardware faults. HA should always
be used with multipathed storage and bonded networking.
Firstly, HA ensures that in the event of a host becoming unreachable or unstable, VMs which were known to be
running on that host are shut down and able to be restarted elsewhere. This avoids the scenario where VMs are
started (manually or automatically) on a new host and at some point later, the original host is able to recover.
This scenario could lead two instances of the same VM running on different hosts, and a corresponding high
probability of VM disk corruption and data loss.
Secondly, HA recovers administrative control of a pool in the event that the pool master becomes unreachable
or unstable. HA ensures that administrative control is restored automatically without any manual intervention.
Optionally, HA can also automate the process of restarting VMs on hosts which are known to be in a good state
without manual intervention. These VMs can be scheduled for restart in groups to allow time to start services.
This allows infrastructure VMs to started before their dependent VMs (For example, a DHCP server before its
dependent SQL server).

Warning:
HA is designed to be used in conjunction with multipathed storage and bonded networking,
and this should be configured before attempting to set up HA. Customers who do not set
up multipathed networking and storage, may see unexpected host reboot behaviour (Self
Fencing) in the event of infrastructure instability. For more information see CTX134880 Designing XenServer Network Configurations and CTX134881 - Configuring iSCSI Multipathing
Support for XenServer

3.9.1.1. Overcommitting
A pool is overcommitted if the VMs that are currently running could not be restarted elsewhere following a userdefined number of host failures.
This would happen if there was not enough free memory across the pool to run those VMs following failure.
However there are also more subtle changes which can make HA guarantees unsustainable: changes to Virtual
Block Devices (VBDs) and networks can affect which VMs may be restarted on which hosts. Currently it is not
possible for XenServer to check all actions before they occur and determine if they will cause violation of HA
demands. However an asynchronous notification is sent if HA becomes unsustainable.
XenServer dynamically maintains a failover plan which details what to do if a set of hosts in a pool fail at any given
time. An important concept to understand is the host failures to tolerate value, which is defined as part of HA
configuration. This determines the number of failures that is allowed without any loss of service. For example, if
a resource pool consisted of 16 hosts, and the tolerated failures is set to 3, the pool calculates a failover plan that
allows for any 3 hosts to fail and still be able to restart VMs on other hosts. If a plan cannot be found, then the
pool is considered to be overcommitted. The plan is dynamically recalculated based on VM lifecycle operations
and movement. Alerts are sent (either through XenCenter or e-mail) if changes (for example the addition on new
VMs to the pool) cause your pool to become overcommitted.

3.9.1.2. Overcommitment Warning
If you attempt to start or resume a VM and that action causes the pool to be overcommitted, a warning alert is
raised. This warning is displayed in XenCenter and is also available as a message instance through the Xen API.
The message may also be sent to an email address if configured. You will then be allowed to cancel the operation,
or proceed anyway. Proceeding causes the pool to become overcommitted. The amount of memory used by VMs
of different priorities is displayed at the pool and host levels.

3.9.1.3. Host Fencing
If a server failure occurs such as the loss of network connectivity or a problem with the control stack
is encountered, the XenServer host self-fences to ensure that the VMs are not running on two servers
simultaneously. When a fence action is taken, the server immediately and abruptly restarts, causing all VMs
running on it to be stopped. The other servers will detect that the VMs are no longer running and the VMs will
be restarted according to the restart priorities assign to them. The fenced server will enter a reboot sequence,
and when it has restarted it will try to re-join the resource pool.

3.9.2. Configuration Requirements
Note:
Citrix recommends that you enable HA only in pools that contain at least 3 XenServer hosts.
For details on how the HA feature behaves when the heartbeat is lost between two hosts in
a pool, see the Citrix Knowledge Base article CTX129721.
To use the HA feature, you need:
•

Shared storage, including at least one iSCSI, NFS or Fibre Channel LUN of size 356MB or greater- the heartbeat
SR. The HA mechanism creates two volumes on the heartbeat SR:
27

4MB heartbeat volume
Used for heartbeating.
256MB metadata volume
Stores pool master metadata to be used in the case of master failover.
Note:
For maximum reliability, Citrix strongly recommends that you use a dedicated NFS or iSCSI
storage repository as your HA heartbeat disk, which must not be used for any other purpose.
If you are using a NetApp or EqualLogic SR, manually provision an NFS or iSCSI LUN on the array to use as
the heartbeat SR.
•

A XenServer pool (this feature provides high availability at the server level within a single resource pool).

•

Static IP addresses for all hosts.
Warning:
Should the IP address of a server change while HA is enabled, HA will assume that the host's
network has failed, and will probably fence the host and leave it in an unbootable state. To
remedy this situation, disable HA using the host-emergency-ha-disable command, reset the
pool master using pool-emergency-reset-master, and then re-enable HA.

For a VM to be protected by the HA feature, it must be agile. This means that:
•

it must have its virtual disks on shared storage (any type of shared storage may be used; the iSCSI, NFS or
Fibre Channel LUN is only required for the storage heartbeat and can be used for virtual disk storage if you
prefer, but this is not necessary)

•

it must not have a connection to a local DVD drive configured

•

it should have its virtual network interfaces on pool-wide networks.

Citrix strongly recommends the use of a bonded management interface on the servers in the pool if HA is enabled,
and multipathed storage for the heartbeat SR.
If you create VLANs and bonded interfaces from the CLI, then they may not be plugged in and active despite
being created. In this situation, a VM can appear to be not agile, and cannot be protected by HA. If this occurs,
use the CLI pif-plug command to bring the VLAN and bond PIFs up so that the VM can become agile. You can
also determine precisely why a VM is not agile by using the xe diagnostic-vm-status CLI command to analyze its
placement constraints, and take remedial action if required.

3.9.3. Restart configuration settings
Virtual machines can be considered protected, best-effort or unprotected by HA. The value of ha-restartpriority defines whether a VM is treated as protected, best-effort, or unprotected. The restart behavior for
VMs in each of these categories is different.

Protected

Restart behavior

harestartpriority
value

HA guarantees to restart a protected VM that goes offline or whose host goes
offline, provided the pool is not overcommitted and the VM is agile.

restart

If a protected VM cannot be restarted at the time of a server failure (for
example, if the pool was overcommitted when the failure occurred), further
attempts to start this VM are made when extra capacity becomes available in
a pool, which might now succeed.

Restart behavior

harestartpriority
value

Best-effort

If the host where a best-effort VM is running goes offline, HA attempts to
restart the best-effort VM on another host only after all protected VMs have
been successfully restarted. HA makes only one attempt to restart a best-effort
VM and if this attempt fails no further restart is attempted.

besteffort

Unprotected

If an unprotected VM or the host it runs on is stopped, HA does not attempt
to restart the VM.

Value is an
empty string

Note:
HA never stops or migrates a running VM to free resources for a protected or best-effort VM
to be restarted.
If the pool experiences server failures and enters a state where the number of tolerable failures drops to zero, the
protected VMs are no longer guaranteed to be restarted. If this condition is reached, a system alert is generated.
In this case, if an additional failure occurs, all VMs that have a restart priority set behave according to the besteffort behavior.

3.9.3.1. Start order
The start order is the order in which XenServer HA attempts to restart protected VMs if a failure occurs. The start
order is determined by the values of the order property for each of the protected VMs.
The order property of a VM is used by HA and also by other features that start and shutdown VMs. Any VM can
have the order property set, not just those marked as protected for HA. However, HA uses the order property
for protected VMs only.
The value of the order property is an integer. The default value is 0, which is the highest priority. Protected VMs
with an order value of 0 are restarted first by HA. The higher the value of the order property, the later in the
sequence the VM is restarted.
You can set the value of the order property of a VM by using the command-line interface:
xe vm-param-set uuid= order=

Or in XenCenter, in the Start Options panel for a VM, set Start order to the required value.

3.10. Enabling HA on your XenServer Pool
HA can be enabled on a pool using either XenCenter or the command-line interface. In either case, you will
specify a set of priorities that determine which VMs should be given highest restart priority when a pool is
overcommitted.
Warning:
When HA is enabled, some operations that would compromise the plan for restarting VMs
may be disabled, such as removing a server from a pool. To perform these operations, HA can
be temporarily disabled, or alternately, VMs protected by HA made unprotected.

3.10.1. Enabling HA Using the CLI
1.

Verify that you have a compatible Storage Repository (SR) attached to your pool. iSCSI, NFS or Fibre Channel
are compatible SR types. Please refer to Section 5.3, “Storage Configuration” for details on how to configure
such a storage repository using the CLI.

For each VM you wish to protect, set a restart priority and start order. You can do this as follows:
29

xe vm-param-set uuid= ha-restart-priority=restart order=<1>

Enable HA on the pool, and optionally, specify a timeout:
xe pool-ha-enable heartbeat-sr-uuids= ha-config:timeout=

Timeout is the period during which networking or storage is not accessible by the hosts in your pool. If you
do not specify a timeout when you enable HA, XenServer will use the default 30 seconds timeout. If any
XenServer host is unable to access networking or storage within the timeout period, it will self-fence and
restart.
4.

Run the pool-ha-compute-max-host-failures-to-tolerate command. This command returns the maximum
number of hosts that can fail before there are insufficient resources to run all the protected VMs in the pool.
xe pool-ha-compute-max-host-failures-to-tolerate

The number of failures to tolerate determines when an alert is sent: the system will recompute a failover
plan as the state of the pool changes and with this computation the system identifies the capacity of the pool
and how many more failures are possible without loss of the liveness guarantee for protected VMs. A system
alert is generated when this computed value falls below the specified value for ha-host-failuresto-tolerate.
5.

Specify the number of failures to tolerate parameter. This should be less than or equal to the computed
value:
xe pool-param-set ha-host-failures-to-tolerate=<2> uuid=

3.10.2. Removing HA Protection from a VM using the CLI
To disable HA features for a VM, use the xe vm-param-set command to set the ha-restart-priority
parameter to be an empty string. This does not clear the start order settings. You can enable HA for a VM again
by setting the ha-restart-priority parameter to restart or best-effort as appropriate.

3.10.3. Recovering an Unreachable Host
If for some reason a host cannot access the HA statefile, it is possible that a host may become unreachable.
To recover your XenServer installation it may be necessary to disable HA using the host-emergency-ha-disable
command:
xe host-emergency-ha-disable --force

If the host was the pool master, then it should start up as normal with HA disabled. Slaves should reconnect and
automatically disable HA. If the host was a Pool slave and cannot contact the master, then it may be necessary to
force the host to reboot as a pool master (xe pool-emergency-transition-to-master) or to tell it where the new
master is (xe pool-emergency-reset-master):
xe pool-emergency-transition-to-master uuid=
xe pool-emergency-reset-master master-address=

When all hosts have successfully restarted, re-enable HA:
xe pool-ha-enable heartbeat-sr-uuid=

3.10.4. Shutting Down a host When HA is Enabled
When HA is enabled special care needs to be taken when shutting down or rebooting a host to prevent the HA
mechanism from assuming that the host has failed. To shutdown a host cleanly in an HA-enabled environment,
first disable the host, then evacuate the host and finally shutdown the host using either XenCenter or the
CLI. To shutdown a host in an HA-enabled environment on the command line:
xe host-disable host=
xe host-evacuate uuid=
xe host-shutdown host=

3.10.5. Shutting Down a VM When it is Protected by HA
When a VM is protected under a HA plan and set to restart automatically, it cannot be shut down while this
protection is active. To shut down a VM, first disable its HA protection and then execute the CLI command.
XenCenter offers you a dialog box to automate disabling the protection if you click on the Shutdown button of
a protected VM.
Note:
If you shut down a VM from within the guest, and the VM is protected, it is automatically
restarted under the HA failure conditions. This helps ensure that operator error (or an errant
program that mistakenly shuts down the VM) does not result in a protected VM being left
shut down accidentally. If you want to shut this VM down, disable its HA protection first.

3.11. Host Power On
3.11.1. Powering on Hosts Remotely
You can use the XenServer Host Power On feature to turn a server on and off remotely, either from XenCenter
or by using the CLI.
To enable host power, the host must have one of the following power-control solutions:
•

Wake On LAN enabled network card.

•

Dell Remote Access Cards (DRAC). To use XenServer with DRAC, you must install the Dell supplemental pack
to get DRAC support. DRAC support requires installing RACADM command-line utility on the server with
the remote access controller and enable DRAC and its interface. RACADM is often included in the DRAC
management software. For more information, see Dell’s DRAC documentation.

•

Hewlett-Packard Integrated Lights-Out (iLO). To use XenServer with iLO, you must enable iLO on the host
and connect interface to the network. For more information, see HP’s iLO documentation.

•

A custom script based on the XenAPI that enables you to turn the power on and off through XenServer. For
more information, see Section 3.11.3, “Configuring a Custom Script for XenServer's Host Power On Feature”.

Using the Host Power On feature requires two tasks:
1. Ensuring the hosts in the pool support controlling the power remotely (that is, they have Wake-on-LAN
functionality, a DRAC or iLO card, or you created custom script).
2. Enabling the Host Power On functionality using the CLI or XenCenter.

3.11.2. Using the CLI to Manage Host Power On
You can manage the Host Power On feature using either the CLI or XenCenter. This topic provides information
about managing it with the CLI.
Host Power On is enabled at the host level (that is, on each XenServer).
After you enable Host Power On, you can turn hosts on using either the CLI or XenCenter.

3.11.2.1. To Enable Host Power On Using the CLI
1. Run the command:
xe host-set-power-on host=\
power-on-mode=("" , "wake-on-lan",
"iLO", "DRAC","custom")
power-on-config:key=value

For iLO and DRAC the keys are power_on_ip, power_on_user, power_on_password_secret. Use
power_on_password_secret to specify the password if you are using the secret feature.
31

3.11.2.2. To Turn on Hosts Remotely Using the CLI
1. Run the command:
xe host-power-on host=

3.11.3. Configuring a Custom Script for XenServer's Host Power On Feature
If your servers' remote-power solution uses a protocol that is not supported by default (such as Wake-On-Ring
or Intel Active Management Technology), you can create a custom Linux Python script to turn on your XenServer
computers remotely. However, you can also can create custom scripts for iLO, DRAC, and Wake-On-LAN remotepower solutions.
This topic provides information about configuring a custom script for Host Power On using the key/value pairs
associated with the XenServer API call host.power_on.
When you create a custom script, run it from the command line each time you want to control power remotely
on XenServer. Alternatively, you can specify it in XenCenter and use the XenCenter UI features to interact with it.
The XenServer API is documented in the document, the [Citrix XenServer Management API], which is available
from the Citrix Web site.
Warning:
Do not modify the scripts provided by default in the /etc/xapi.d/plugins/ directory.
You can include new scripts in this directory, but you should never modify the scripts
contained in that directory after installation.

3.11.3.1. Key/Value Pairs
To use Host Power On, you must configure the host.power_on_mode and host.power_on_config keys. Their
values are provided below.
There is also an API call that lets you set these fields all at once:
void host.set_host_power_on_mode(string mode, Dictionary config)

3.11.3.1.1. host.power_on_mode
•

Definition: This contains key/value pairs to specify the type of remote-power solution (for example, Dell
DRAC).

•

Possible values:

•

An empty string, representing power-control disabled

•

"iLO". Lets you specify HP iLO.

•

"DRAC". Lets you specify Dell DRAC. To use DRAC, you must have already installed the Dell supplemental
pack.

•

"wake-on-lan". Lets you specify Wake on LAN.

•

Any other name (used to specify a custom power-on script). This option is used to specify a custom script
for power management.

Type: string

3.11.3.1.2. host.power_on_config
•

Definition: This contains key/value pairs for mode configuration. Provides additional information for iLO and
DRAC.

•

Possible values:
32

•

•
•

If you configured iLO or DRAC as the type of remote-power solution, you must also specify one of the
following keys:
•

"power_on_ip". This is the IP address you specified configured to communicate with the powercontrol card. Alternatively, you can enter the domain name for the network interface where iLO or
DRAC is configured.

•

"power_on_user". This is the iLO or DRAC user name that is associated with the management
processor, which you may or may not have changed from its factory default settings.

•

"power_on_password_secret". Specifies using the secrets feature to secure your password.

To use the secrets feature to store your password, specify the key "power_on_password_secret".

Type: Map (string,string)

3.11.3.2. Sample Script
This sample script imports the XenServer API, defines itself as a custom script, and then passes parameters
specific to the host you want to control remotely. You must define the parameters session, remote_host,
and power_on_config in all custom scripts.
The result is only displayed when the script is unsuccessful.
import XenAPI
def custom(session,remote_host,
power_on_config):
result="Power On Not Successful"
for key in power_on_config.keys():
result=result+"
key="+key+"
value="+power_on_config[key]
return result

Note:
After creation, save the script in the /etc/xapi.d/plugins with a .py extension.

3.12. Communicating with XenServer Hosts and Resource Pools
XenServer 7.0 uses TLS protocols to encrypt XenAPI traffic. This means any communication between XenServer
and XenAPI clients (or appliances) will now use TLS 1.2 protocol by default. However, if the XenAPI client or the
appliance does not communicate using TLS 1.2, earlier protocols may be used for communication.
XenServer uses the following ciphersuites:
•

TLS_RSA_WITH_AES_128_CBC_SHA256

•

TLS_RSA_WITH_AES_256_CBC_SHA

•

TLS_RSA_WITH_AES_128_CBC_SHA

•

TLS_RSA_WITH_RC4_128_SHA

•

TLS_RSA_WITH_RC4_128_MD5

•

TLS_RSA_WITH_3DES_EDE_CBC_SHA

XenServer also enables you to configure your host or resource pool to allow communication through TLS 1.2
only. This option allows communication between XenServer and XenAPI clients (or appliances) using the TLS 1.2
protocol. The TLS 1.2 only option uses ciphersuite TLS_RSA_WITH_AES_128_CBC_SHA256.
Warning:
Do not choose the TLS 1.2 only option before you ensure that all XenAPI clients and appliances
that communicate with the XenServer pool are compatible with TLS 1.2.

Chapter 4. Networking
This chapter provides an overview of XenServer networking, including networks, VLANs, and NIC bonds. It also
discusses how to manage your networking configuration and troubleshoot it.
Important:
The XenServer default network stack is the vSwitch; however, you can use the Linux network
stack if desired by using the instructions in Section 4.2, “vSwitch Networks”.
If you are already familiar with XenServer networking concepts, you may want to skip ahead to one of the
following sections:
•

To create networks for standalone XenServer hosts, see Section 4.4.2, “Creating Networks in a Standalone
Server”.

•

To create private networks across XenServer hosts, see Section 4.4.1, “Cross-Server Private Networks”

•

To create networks for XenServer hosts that are configured in a resource pool, see Section 4.4.3, “Creating
Networks in Resource Pools”.

•

To create VLANs for XenServer hosts, either standalone or part of a resource pool, see Section 4.4.4, “Creating
VLANs”.

•

To create bonds for standalone XenServer hosts, see Section 4.4.5, “Creating NIC Bonds on a Standalone
Host”.

•

To create bonds for XenServer hosts that are configured in a resource pool, see Section 4.4.6, “Creating NIC
Bonds in Resource Pools”.

For additional information about networking and network design, see Designing XenServer Network
Configurations in the Citrix Knowledge Center.
For consistency with XenCenter terminology changes in this release, this chapter now uses the term management
interface to refer to the IP-enabled NIC that carries the management traffic. In the last release, this chapter used
the term primary management interface for this purpose. Likewise, this chapter now uses the term secondary
interface to refer to an IP-enabled NIC configured for storage traffic.

4.1. Networking Support
XenServer supports up to 16 physical network interfaces (or up to 8 bonded network interfaces) per XenServer
host and up to 7 virtual network interfaces per VM.
Note:
XenServer provides automated configuration and management of NICs using the xe command
line interface (CLI). Unlike previous XenServer versions, the host networking configuration
files should not be edited directly in most cases; where a CLI command is available, do not
edit the underlying files.

4.2. vSwitch Networks
When used with a controller appliance, vSwitch networks support open flow and provide extra functionality,
such as Access Control Lists (ACL). The controller appliance for the XenServer vSwitch is known as the vSwitch
Controller: it lets you monitor your networks through a graphical user interface. The vSwitch Controller:
•

Supports fine-grained security policies to control the flow of traffic sent to and from a VM.

•

Provides detailed visibility into the behavior and performance of all traffic sent in the virtual network
environment.
34

A vSwitch greatly simplifies IT administration in virtualized networking environments—all VM configuration and
statistics remain bound to the VM even if it migrates from one physical host in the resource pool to another. See
the XenServer vSwitch Controller User Guide for more details.
To determine what networking stack is currently configured, run the following command:
xe host-list params=software-version

In the command output, look for network_backend. If the vSwitch is configured as the network stack, the
output displays:
network_backend: openvswitch

If the Linux bridge is configured as the network stack, the output displays:
network_backend: bridge

Note:
To revert to the Linux network stack, run the following command:
xe-switch-network-backend bridge

Reboot your host after running this command.
Warning:
The Linux network stack is not open-flow enabled, does not support Cross Server Private
Networks, and cannot be managed by the XenServer vSwitch Controller.

4.3. XenServer Networking Overview
This section describes the general concepts of networking in the XenServer environment.
During XenServer installation, one network is created for each physical network interface card (NIC). When you
add a server to a resource pool, these default networks are merged so that all physical NICs with the same device
name are attached to the same network.
Typically, you would only add a new network if you wanted to create an internal network, set up a new VLAN
using an existing NIC, or create a NIC bond.
You can configure four different types of networks in XenServer:
•

External networks have an association with a physical network interface and provide a bridge between a
virtual machine and the physical network interface connected to the network, enabling a virtual machine to
connect to resources available through the server's physical network interface card.

•

Bonded networks create a bond between two NICs to create a single, high-performing channel between the
virtual machine and the network.

•

Single-Server Private networks have no association to a physical network interface and can be used to provide
connectivity between the virtual machines on a given host, with no connection to the outside world.

•

Cross-Server Private networks extend the single server private network concept to allow VMs on different
hosts to communicate with each other by using the vSwitch.
Note:
Some networking options have different behaviors when used with standalone XenServer
hosts compared to resource pools. This chapter contains sections on general information that
applies to both standalone hosts and pools, followed by specific information and procedures
for each.

4.3.1. Network Objects
This chapter uses three types of server-side software objects to represent networking entities. These objects are:
•

A PIF, which represents a physical NIC on a XenServer host. PIF objects have a name and description, a globally
unique UUID, the parameters of the NIC that they represent, and the network and server they are connected
to.

•

A VIF, which represents a virtual NIC on a virtual machine. VIF objects have a name and description, a globally
unique UUID, and the network and VM they are connected to.

•

A network, which is a virtual Ethernet switch on a XenServer host. Network objects have a name and
description, a globally unique UUID, and the collection of VIFs and PIFs connected to them.

Both XenCenter and the xe CLI allow configuration of networking options, control over which NIC is used for
management operations, and creation of advanced networking features such as virtual local area networks
(VLANs) and NIC bonds.

4.3.2. Networks
Each XenServer host has one or more networks, which are virtual Ethernet switches. Networks that are not
associated with a PIF are considered internal and can be used to provide connectivity only between VMs on a
given XenServer host, with no connection to the outside world. Networks associated with a PIF are considered
external and provide a bridge between VIFs and the PIF connected to the network, enabling connectivity to
resources available through the PIF's NIC.

4.3.3. VLANs
Virtual Local Area Networks (VLANs), as defined by the IEEE 802.1Q standard, allow a single physical network to
support multiple logical networks. XenServer hosts can work with VLANs in multiple ways.
Note:
All supported VLAN configurations are equally applicable to pools and standalone hosts, and
bonded and non-bonded configurations.

4.3.3.1. Using VLANs with Management Interfaces
Switch ports configured to perform 802.1Q VLAN tagging/untagging, commonly referred to as ports with a native
VLAN or as access mode ports, can be used with management interfaces to place management traffic on a desired
VLAN. In this case the XenServer host is unaware of any VLAN configuration.
Management interfaces cannot be assigned to a XenServer VLAN via a trunk port.

4.3.3.2. Using VLANs with Virtual Machines
Switch ports configured as 802.1Q VLAN trunk ports can be used in combination with the XenServer VLAN features
to connect guest virtual network interfaces (VIFs) to specific VLANs. In this case, the XenServer host performs the
VLAN tagging/untagging functions for the guest, which is unaware of any VLAN configuration.
XenServer VLANs are represented by additional PIF objects representing VLAN interfaces corresponding to a
specified VLAN tag. XenServer networks can then be connected to the PIF representing the physical NIC to see
all traffic on the NIC, or to a PIF representing a VLAN to see only the traffic with the specified VLAN tag.
For procedures on how to create VLANs for XenServer hosts, either standalone or part of a resource pool, see
Section 4.4.4, “Creating VLANs”.

4.3.3.3. Using VLANs with Dedicated Storage NICs
Dedicated storage NICs (also known as IP-enabled NICs or simply management interfaces) can be configured to
use native VLAN / access mode ports as described above for management interfaces, or with trunk ports and
XenServer VLANs as described above for virtual machines. To configure dedicated storage NICs, see Section 4.4.7,
“Configuring a Dedicated Storage NIC”.
36

4.3.3.4. Combining Management Interfaces and Guest VLANs on a Single Host NIC
A single switch port can be configured with both trunk and native VLANs, allowing one host NIC to be used for a
management interface (on the native VLAN) and for connecting guest VIFs to specific VLAN IDs.

4.3.4. Jumbo frames
Jumbo frames can be used to optimize the performance of storage traffic. Jumbo frames are Ethernet frames
containing more than 1500 bytes of payload. Jumbo frames are typically used to achieve better throughput,
reducing the load on system bus memory, and reducing the CPU overhead.
Note:
XenServer supports jumbo frames only when using vSwitch as the network stack on all hosts
in the pool.
Requirements for using jumbo frames
Customers should note the following when using jumbo frames:
•

Jumbo frames are configured at a pool level

•

vSwitch must be configured as the network backend on all hosts in the pool

•

Every device on the subnet must be configured to use jumbo frames

•

It is recommended that customers only enable jumbo frames on a dedicated storage network

•

Enabling jumbo frames on the Management network is not a supported configuration

•

Jumbo frames are not supported for use on VMs

In order to use jumbo frames, customers should set the Maximum Transmission Unit (MTU) to a value between
1500 and 9216. This can be done either by using XenCenter or the xe CLI. For more information about configuring
networks with jumbo frames, see Designing XenServer Network Configurations in the Citrix Knowledge Center.

4.3.5. NIC Bonds
NIC bonds, sometimes also known as NIC teaming, improve XenServer host resiliency and/or bandwidth by
enabling administrators to configure two or more NICs together so they logically function as one network card.
All bonded NICs share the same MAC address.
If one NIC in the bond fails, the host's network traffic is automatically redirected through the second NIC.
XenServer supports up to eight bonded networks.
XenServer provides support for active-active, active-passive, and LACP bonding modes. The number of NICs
supported and the bonding mode supported varies according to network stack:
•

LACP bonding is only available for the vSwitch whereas active-active and active-passive are available for both
the vSwitch and Linux bridge.

•

When the vSwitch is the network stack, you can bond either two, three, or four NICs.

•

When the Linux bridge is the network stack, you can only bond two NICs.

In the illustration that follows, the management interface is on a bonded pair of NICs. XenServer will use this
bond for management traffic.

This illustration shows a host with a management interface on a bond and two
pairs of NICs bonded for guest traffic. Excluding the management interface bond,
XenServer uses the other two NIC bonds and the two non-bonded NICs for VM traffic.
All bonding modes support failover; however, not all modes allow all links to be active for all traffic types.
XenServer supports bonding the following types of NICs together:
•

NICs (non-management). You can bond NICs that XenServer is using solely for VM traffic. Bonding these NICs
not only provides resiliency, but doing so also balances the traffic from multiple VMs between the NICs.

•

Management interfaces. You can bond a management interface to another NIC so that the second NIC
provides failover for management traffic. Although configuring a LACP link aggregation bond provides load
balancing for management traffic, active-active NIC bonding does not.

•

Secondary interfaces. You can bond NICs that you have configured as secondary interfaces (for example,
for storage). However, for most iSCSI software initiator storage, Citrix recommends configuring multipathing
instead of NIC bonding as described in the Designing XenServer Network Configurations.
Through out this section, the term IP-based storage traffic is used to refer to iSCSI and NFS traffic collectively.

You can create a bond if a VIF is already using one of the interfaces that will be bonded: the VM traffic will be
automatically migrated to the new bonded interface.
In XenServer, the NIC bond is represented by an additional PIF. XenServer NIC bonds completely subsume the
underlying physical devices (PIFs).
Note:
Creating a bond that contains only one NIC is not supported.
Key points about IP addressing
Bonded NICs will either have one IP address or no IP addresses, as follows:
•

•

Management and storage networks.
•

If you bond a management interface or secondary interface, a single IP address is assigned to the
bond. That is, each NIC does not have its own IP address; XenServer treats the two NICs as one logical
connection.

•

When bonds are used for non-VM traffic (to connect to shared network storage or XenCenter for
management), you must configure an IP address for the bond. However, if you have already assigned an
IP address to one of the NICs (that is, created a management interface or secondary interface), that IP
address is assigned to the entire bond automatically.

•

If you bond a management interface or secondary interface to a NIC without an IP address, as of XenServer
6.0, the bond assumes the IP address of the respective interface automatically.

VM networks. When bonded NICs are used for VM (guest) traffic, you do not need to configure an IP address
for the bond. This is because the bond operates at Layer 2 of the OSI model, the data link layer, and no IP
addressing is used at this layer. IP addresses for virtual machines are associated with VIFs.

Bonding types
XenServer provides three different types of bonds, all of which can be configured using either the CLI or
XenCenter:
•

Active/Active mode, with VM traffic balanced between the bonded NICs. See Section 4.3.5.1, “Active-Active
Bonding”.

•

Active/Passive mode, where only one NIC actively carries traffic. See Section 4.3.5.2, “Active-Passive
Bonding”.

•

LACP Link Aggregation, in which active and stand-by NICs are negotiated between the switch and the server.
See Section 4.3.5.3, “ LACP Link Aggregation Control Protocol Bonding”.
38

Note:
Bonding is set up with an Up Delay of 31000ms and a Down Delay of 200ms. The seemingly
long Up Delay is deliberate because of the time some switches take to actually enable the
port. Without a delay, when a link comes back after failing, the bond could rebalance traffic
onto it before the switch is ready to pass traffic. If you want to move both connections to a
different switch, move one, then wait 31 seconds for it to be used again before moving the
other. For information about changing the delay, see Section 4.3.8, “Changing the Up Delay
for Bonds”.
Bond Status
XenServer provides status for bonds in the event logs for each host. If one or more links in a bond fails or is
restored, it is noted in the event log. Likewise, you can query the status of a bond's links by using the linksup parameter as shown in the following example:
xe bond-param-get uuid= param-name=links-up

XenServer checks the status of links in bonds approximately every 5 seconds. Consequently, if additional links in
the bond fail in the five-second window, the failure is not logged until the next status check.
Bonding event logs appear in the XenCenter Logs tab. For users not running XenCenter, event logs also appear
in /var/log/xensource.log on each host.

4.3.5.1. Active-Active Bonding
Active-active is an active/active configuration for guest traffic: both NICs can route VM traffic simultaneously.
When bonds are used for management traffic, only one NIC in the bond can route traffic: the other NIC remains
unused and provides fail-over support. Active-active mode is the default bonding mode when either the Linux
bridge or vSwitch network stack is enabled.
When active-active bonding is used with the Linux bridge, you can only bond two NICs. When using the vSwitch
as the network stack, you can bond either two, three, or four NICs in active-active mode. However, in activeactive mode, bonding three or four NICs is generally only beneficial for VM traffic, as shown in the illustration
that follows.

This illustration shows how bonding four NICs may only benefit guest traffic. In the top picture of a
management network, NIC 2 is active but NICs 1, 3, and 4 are passive. For the VM traffic, all four NICs in the
bond are active; however, this assumes a minimum of four VMs. For the storage traffic, only NIC 11 is active.
39

XenServer can only send traffic over two or more NICs when there is more than one MAC address associated with
the bond. XenServer can use the virtual MAC addresses in the VIF to send traffic across multiple links. Specifically:
•

VM traffic. Provided you enable bonding on NICs carrying only VM (guest) traffic, all links are active and NIC
bonding can balance spread VM traffic across NICs. An individual VIF's traffic is never split between NICs.

•

Management or storage traffic. Only one of the links (NICs) in the bond is active and the other NICs remain
unused unless traffic fails over to them. Configuring a management interface or secondary interface on a
bonded network provides resilience.

•

Mixed traffic. If the bonded NIC carries a mixture of IP-based storage traffic and guest traffic, only the guest
and control domain traffic are load balanced. The control domain is essentially a virtual machine so it uses
a NIC like the other guests. XenServer balances the control domain's traffic the same way as it balances VM
traffic.

Traffic Balancing
XenServer balances the traffic between NICs by using the source MAC address of the packet. Because, for
management traffic, only one source MAC address is present, active-active mode can only use one NIC and traffic
is not balanced. Traffic balancing is based on two factors:
•

The virtual machine and its associated VIF sending or receiving the traffic

•

The quantity of data (in kilobytes) being sent.

XenServer evaluates the quantity of data (in kilobytes) each NIC is sending and receiving. If the quantity of data
sent across one NIC exceeds the quantity of data sent across the other NIC, XenServer rebalances which VIFs use
which NICs. The VIF's entire load is transferred; one VIF's load is never split between two NICs.
While active-active NIC bonding can provide load balancing for traffic from multiple VMs, it cannot provide a
single VM with the throughput of two NICs. Any given VIF only uses one of the links in a bond at a time. As
XenServer periodically rebalances traffic, VIFs are not permanently assigned to a specific NIC in the bond.
Active-active mode is sometimes referred to as Source Load Balancing (SLB) bonding as XenServer uses SLB to
share load across bonded network interfaces. SLB is derived from the open-source Adaptive Load Balancing (ALB)
mode and reuses the ALB capability to dynamically re-balance load across NICs.
When rebalancing, the number of bytes going over each slave (interface) is tracked over a given period. When
a packet to be sent contains a new source MAC address, it is assigned to the slave interface with the lowest
utilisation. Traffic is re-balanced at regular intervals.
Each MAC address has a corresponding load and XenServer can shift entire loads between NICs depending on
the quantity of data a VM sends and receives. For active-active traffic, all the traffic from one VM can be sent
on only one NIC.
Note:
Active-active bonding does not require switch support for EtherChannel or 802.3ad (LACP).

4.3.5.2. Active-Passive Bonding
An active-passive bond routes traffic over only one of the NICs, so traffic fails over to the other NIC in the bond if
the active NIC loses network connectivity. Active-passive bonds route traffic over the active NIC: only if the active
NIC fails is traffic shifted to the passive NIC.
Active-passive bonding is available in the Linux bridge and the vSwitch network stack. When used with the Linux
bridge, you can bond two NICs together. When used with the vSwitch, you can only bond two, three, or four NICs
together. However, regardless of the traffic type, when you bond NICs together in active-passive mode, only one
link is active and there is no load balancing between links.
The illustration that follows shows two bonded NICs configured in active-passive mode.

This illustration shows two NICs bonded in active-passive mode. NIC 1 is active. The bond includes
a NIC for failover that is connected to a second switch. This NIC will be used only if NIC 1 fails.
Since active-active mode is the default bonding configuration in XenServer, if you are configuring bonds using the
CLI, you must specify a parameter for the active-passive mode or the bond is created as active-active. However,
you do not need to configure active-passive mode just because a network is carrying management traffic or
storage traffic.
Active-passive can be a good choice for resiliency since it offers several benefits. With active-passive bonds,
traffic does not move around between NICs. Likewise, active-passive bonding lets you configure two switches
for redundancy but does not require stacking. (If the management switch dies, stacked switches can be a single
point of failure.)
Active-passive mode does not require switch support for EtherChannel or 802.3ad (LACP).
Consider configuring active-passive mode in situations when you do not need load balancing or when you only
intend to send traffic on one NIC.
Important:
After you have created VIFs or your pool is in production, be extremely careful about making
changes to bonds or creating new bonds.

4.3.5.3. LACP Link Aggregation Control Protocol Bonding
LACP Link Aggregation Control Protocol is a type of bonding that bundles a group of ports together and treats
it like a single logical channel. LACP bonding provides failover and can increase the total amount of bandwidth
available.
Unlike other bonding modes, LACP bonding requires configuring both sides of the links: creating a bond on the
host and, on the switch, creating a Link Aggregation Group (LAG) for each bond, as described in Section 4.3.5.4.1,
“Switch Configuration for LACP Bonds”. To use LACP bonding, you must configure the vSwitch as the network
stack. Also, your switches must support the IEEE 802.3ad standard.
The following table compares active-active SLB bonding and LACP bonding:

Active-active SLB Bonding

Benefits

Considerations

•

Can be used with any switch
on the XenServer Hardware
Compatibility List.

•

Optimal
load
balancing
requires at least one NIC per
VIF.

•

Does not require switches that
support stacking.

•

Supports four NICs.

Storage or management traffic
cannot be split on multiple
NICs.

•

Load balancing occurs only if
multiple MAC addresses are
present.

LACP bonding

Benefits

Considerations

•

All links can be active
regardless of traffic type.

•

Switches must support the
IEEE 802.3ad standard.

•

Traffic balancing does not
depend on source MAC
addresses, so all traffic types
can be balanced.

•

Requires
configuration.

•

Supported
vSwitch.

•

Requires a single switch or
stacked switch.

switch-side

only

for

the

Traffic Balancing
XenServer supports two LACP bonding hashing types —the term hashing refers to the way in the NICs and the
switch distribute the traffic— (1) load balancing based on IP and port of source and destination addresses and
(2) load balancing based on source MAC address.
Depending on the hashing type and traffic pattern, LACP bonding can potentially distribute traffic more evenly
than active-active NIC bonding.
Note:
You configure settings for outgoing and incoming traffic separately on the host and the switch:
the configuration does not have to match on both sides.
Load balancing based on IP and port of source and destination addresses.
This hashing type is the default LACP bonding hashing algorithm. Traffic coming from one guest can be distributed
over two links provided that there is a variation in the source or destination IP or port numbers.
If one virtual machine is running several applications, which use different IP or port numbers, this hashing type
distributes traffic over several links giving the guest the possibility of using the aggregate throughput. This hashing
type lets one guest use the whole throughput of multiple NICs.
Likewise, as shown in the illustration that follows, this hashing type can distribute the traffic of two different
applications on a virtual machine to two different NICs.

This illustration shows how, if you use LACP bonding and enable LACP with load
balancing based on IP and port of source and destination as the hashing type, the
traffic coming from two different applications on VM1 can be distributed to two NICs.
Configuring LACP bonding based on IP and port of source and destination address is beneficial when you want
to balance the traffic of two different applications on the same VM (for example, when only one virtual machine
is configured to use a bond of three NICs).

This illustration shows how, if you use LACP bonding and enable LACP with load
balancing based on IP and port of source and destination as the hashing type, XenServer
can send the traffic of each application in the virtual machine through one of the
three NICs in the bond even though the number of NICs exceeds the number of VIFs.
The balancing algorithm for this hashing type uses five factors to spread traffic across the NICs: the source IP
address, source port number, destination IP address, destination port number, and source MAC address.
Load balancing based on source MAC address.
This type of load balancing works well when there are multiple virtual machines on the same host. Traffic is
balanced based on the virtual MAC address of the VM from which the traffic originated. XenServer sends outgoing
traffic using the same algorithm as it does in the case of active-active bonding. Traffic coming from the same
guest is not split over multiple NICs. As a result, this hashing type is not suitable if there are fewer VIFs than NICs:
load balancing is not optimal because the traffic cannot be split across NICs.

This illustration shows how, if you use LACP bonding and enable LACP based on source MAC address as
the hashing type, if the number of NICs exceeds the number of VIFs, not all NICs will be used. Because
there are three NICs and only two VMs, only two NICs can be used at the same time and the maximum
bond throughput cannot be achieved. The packets from one VM cannot be split across multiple VMs.

4.3.5.4. Switch Configuration
Depending on your redundancy requirements, you can connect the NICs in the bond to either the same or
separate stacked switches. If you connect one of the NICs to a second, redundant switch and a NIC or switch fails,
traffic fails over to the other NIC. Adding a second switch prevents a single point-of-failure in your configuration
in the following ways:
•

When you connect one of the links in a bonded management interface to a second switch, if the switch fails,
the management network still remains online and the hosts can still communicate with each other.

•

If you connect a link (for any traffic type) to a second switch and the NIC or switch fails, the virtual machines
remain on the network since their traffic fails over to the other NIC/switch.

When you want to connect bonded NICs to multiple switches and you configured the LACP bonding mode, you
must use stacked switches. The term stacked switches refers to configuring multiple physical switches to function
as a single logical switch. You must join the switches together physically and through the switch-management
software so the switches function as a single logical switching unit, as per the switch manufacturer's guidelines.
43

Typically, switch stacking is only available through proprietary extensions and switch vendors may market this
functionality under different terms.
Note:
If you experience issues with active-active bonds, the use of stacked switches might be
necessary. Active-passive bonds do not require stacked switches.
The illustration that follows shows how the cables and network configuration for the bonded NICs have to match.

This illustration shows how two NICs in a bonded pair use the same network settings, as represented
by the networks in each host. The NICs in the bonds connect to different switches for redundancy.

4.3.5.4.1. Switch Configuration for LACP Bonds
While the specific details of switch configuration varies by manufacturer, there are a few key points to remember
when configuring switches for use with LACP bonds:
•

The switch must support LACP and the IEEE 802.3ad standard.

•

When you create the LAG group on the switch, you must create one LAG group for each LACP bond on the
host. This means if you have a five-host pool and you created a LACP bond on NICs 4 and 5 on each host,
you must create five LAG groups on the switch. One group for each set of ports corresponding with the NICs
on the host.
You may also need to add your VLAN ID to your LAG group.

•

XenServer LACP bonds require setting the Static Mode setting in the LAG group to be set to Disabled.

As previously mentioned in Section 4.3.5.4, “Switch Configuration”, stacking switches are required to connect
LACP bonds to multiple switches.

4.3.6. Initial Networking Configuration after Setup
The XenServer host networking configuration is specified during initial host installation. Options such as IP address
configuration (DHCP/static), the NIC used as the management interface, and hostname are set based on the
values provided during installation.
When a host has multiple NICs the configuration present after installation depends on which NIC is selected for
management operations during installation:
•

PIFs are created for each NIC in the host

•

the PIF of the NIC selected for use as the management interface is configured with the IP addressing options
specified during installation

•

a network is created for each PIF ("network 0", "network 1", etc.)

•

each network is connected to one PIF

•

the IP addressing options of all other PIFs are left unconfigured
44

When a XenServer host has a single NIC, the follow configuration is present after installation:
•

a single PIF is created corresponding to the host's single NIC

•

the PIF is configured with the IP addressing options specified during installation and to enable management
of the host

•

the PIF is set for use in host management operations

•

a single network, network 0, is created

•

network 0 is connected to the PIF to enable external connectivity to VMs

In both cases the resulting networking configuration allows connection to the XenServer host by XenCenter, the
xe CLI, and any other management software running on separate machines via the IP address of the management
interface. The configuration also provides external networking for VMs created on the host.
The PIF used for management operations is the only PIF ever configured with an IP address during XenServer
installation. External networking for VMs is achieved by bridging PIFs to VIFs using the network object which acts
as a virtual Ethernet switch.
The steps required for networking features such as VLANs, NIC bonds, and dedicating a NIC to storage traffic are
covered in the sections that follow.

4.3.7. Changing Networking Configuration
You can change your networking configuration by modifying the network object. To do so, you run a command
that affects either the network object or the VIF.

4.3.7.1. Modifying the Network Object
You can modify aspects of an network, such as the frame size (MTU), name-label, name-description, and other
values by using the xe network-param-set command and its associated parameters.
When you run the xe network-param-set command, the only required parameter is uuid.
Optional parameters include:
•

default_locking_mode. See Section 4.4.10.8.10, “Simplifying VIF Locking Mode Configuration in the Cloud”.

•

name-label

•

name-description

•

MTU

•

other-config:

If a value for a parameter is not given, the parameter is set to a null value. To set a (key,value) pair in a map
parameter, use the syntax 'map-param:key=value'.

4.3.8. Changing the Up Delay for Bonds
As described in Section 4.3.5, “NIC Bonds”, by default, bonding is set up with an Up Delay of 31000ms to prevent
traffic from being rebalanced onto a NIC after it fails. While seemingly long, the up delay is important for all
bonding modes and not just active-active.
However, if you understand the appropriate settings to select for your environment, you can change the up delay
for bonds by using the procedure that follows.

To change the up delay for bonds
1.

Set the up delay in milliseconds:
45

xe pif-param-set uuid=<> other-config:bond-updelay=<>

To make the change take effect, you must unplug and then replug the physical interface:
xe pif-unplug uuid=<>
xe pif-plug uuid=<>

4.4. Managing Networking Configuration
Some of the network configuration procedures in this section differ depending on whether you are configuring
a stand-alone server or a server that is part of a resource pool.

4.4.1. Cross-Server Private Networks
Previous versions of XenServer allowed you to create single-server private networks that allowed VMs running
on the same host to communicate with each other. The cross-server private network feature, which extends the
single-server private network concept to allow VMs on different hosts to communicate with each other. Crossserver private networks combine the same isolation properties of a single-server private network but with the
additional ability to span hosts across a resource pool. This combination enables use of VM agility features such
as XenMotion live migration for VMs with connections to cross-server private networks.
Cross-server private networks are completely isolated. VMs that are not connected to the private network cannot
sniff or inject traffic into the network, even when they are located on the same physical host with VIFs connected
to a network on the same underlying physical network device (PIF). VLANs provide similar functionality, though
unlike VLANs, cross-server private networks provide isolation without requiring configuration of a physical switch
fabric, through the use of the Generic Routing Encapsulation (GRE) IP tunnelling protocol.
Private networks provide the following benefits without requiring a physical switch:
•

the isolation properties of single-server private networks

•

the ability to span a resource pool, enabling VMs connected to a private network to live on multiple hosts
within the same pool

•

compatibility with features such as XenMotion

Cross-Server Private Networks must be created on a management interface or a secondary interface, as they
require an IP addressable NIC. Any IP-enabled NIC can be used as the underlying network transport. If you
choose to put cross-server private network traffic on a secondary interface, this secondary interface must be on
a separate subnet.
If any management or secondary interfaces are on the same subnet, traffic will be routed incorrectly.
Note:
To create a cross-server private network, the following conditions must be met:
•

All of the hosts in the pool must be using XenServer 6.0 or greater.

•

All of the hosts in the pool must be using the vSwitch for the networking stack.

•

The vSwitch Controller must be running and you must have added the pool to it.
(The pool must have a vSwitch Controller configured that handles the initialization and
configuration tasks required for the vSwitch connection.)

•

The cross-server private network must be created on a NIC configured as a management
interface. This can be the management interface or a secondary interface (IP-enabled PIF)
you configure specifically for this purpose, provided it is on a separate subnet.

For more information on configuring the vSwitch, see the XenServer vSwitch Controller User Guide. For UI-based
procedures for configuring private networks, see the XenCenter Help.

4.4.2. Creating Networks in a Standalone Server
Because external networks are created for each PIF during host installation, creating additional networks is
typically only required to:
•

use a private network

•

support advanced operations such as VLANs or NIC bonding

To add or remove networks using XenCenter, refer to the XenCenter online Help.

To add a new network using the CLI
1.

Open the XenServer host text console.

Create the network with the network-create command, which returns the UUID of the newly created
network:
xe network-create name-label=

At this point the network is not connected to a PIF and therefore is internal.

4.4.3. Creating Networks in Resource Pools
All XenServer hosts in a resource pool should have the same number of physical network interface cards (NICs),
although this requirement is not strictly enforced when a XenServer host is joined to a pool.
Having the same physical networking configuration for XenServer hosts within a pool is important because all
hosts in a pool share a common set of XenServer networks. PIFs on the individual hosts are connected to poolwide networks based on device name. For example, all XenServer hosts in a pool with an eth0 NIC will have a
corresponding PIF plugged into the pool-wide Network 0 network. The same will be true for hosts with eth1
NICs and Network 1, as well as other NICs present in at least one XenServer host in the pool.
If one XenServer host has a different number of NICs than other hosts in the pool, complications can arise because
not all pool networks will be valid for all pool hosts. For example, if hosts host1 and host2 are in the same pool
and host1 has four NICs while host2 only has two, only the networks connected to PIFs corresponding to eth0
and eth1 will be valid on host2. VMs on host1 with VIFs connected to networks corresponding to eth2 and eth3
will not be able to migrate to host host2.

4.4.4. Creating VLANs
For servers in a resource pool, you can use the pool-vlan-create command. This command creates the VLAN and
automatically creates and plugs in the required PIFs on the hosts in the pool. See Section A.4.25.2, “pool-vlancreate” for more information.

To connect a network to an external VLAN using the CLI
1.

Open the XenServer host console.

Create a new network for use with the VLAN. The UUID of the new network is returned:
xe network-create name-label=network5

Use the pif-list command to find the UUID of the PIF corresponding to the physical NIC supporting the desired
VLAN tag. The UUIDs and device names of all PIFs are returned, including any existing VLANs:
xe pif-list

Create a VLAN object specifying the desired physical PIF and VLAN tag on all VMs to be connected to the
new VLAN. A new PIF will be created and plugged into the specified network. The UUID of the new PIF object
is returned.
xe vlan-create network-uuid= pif-uuid= vlan=5

Attach VM VIFs to the new network. See Section 4.4.2, “Creating Networks in a Standalone Server” for more
details.

4.4.5. Creating NIC Bonds on a Standalone Host
Citrix recommends using XenCenter to create NIC bonds. For instructions, see the XenCenter help.
This section describes how to use the xe CLI to bond NIC interfaces on a XenServer host that is not in a pool.
See Section 4.4.6, “Creating NIC Bonds in Resource Pools” for details on using the xe CLI to create NIC bonds on
XenServer hosts that comprise a resource pool.

4.4.5.1. Creating a NIC Bond
When you bond a NIC, the bond absorbs the PIF/NIC currently in use as the management interface. From
XenServer 6.0 onwards, the management interface is automatically moved to the bond PIF.

To bond two or four NICs
1.

Use the network-create command to create a new network for use with the bonded NIC. The UUID of the
new network is returned:
xe network-create name-label=

Use the pif-list command to determine the UUIDs of the PIFs to use in the bond:
xe pif-list

Do one of the following:
•

To configure the bond in active-active mode (default), use the bond-create command to create the bond.
Using commas to separate the parameters, specify the newly created network UUID and the UUIDs of
the PIFs to be bonded:

xe bond-create network-uuid= pif-uuids=,,

Enter two UUIDs if you are bonding two NICs and four UUIDs if you are bonding four NICs. The UUID for
the bond is returned after running the command.
•

To configure the bond in active-passive or LACP bond mode, use the same syntax but add the optional
mode parameter and specify lacp or active-backup:

xe bond-create network-uuid= pif-uuids=,,
mode=

Note:
In previous releases, you specified the other-config:bond-mode to change the bond
mode. While this command still works, it may be not be supported in future releases and it
is not as efficient as the mode parameter. other-config:bond-mode requires running
pif-unplug and pif-plug to get the mode change to take effect.

4.4.5.2. Controlling the MAC Address of the Bond
When you bond the management interface, the PIF/NIC currently in use as the management interface is
subsumed by the bond. If the host uses DHCP, in most cases the bond's MAC address is the same as the PIF/NIC
currently in use, and the management interface's IP address can remain unchanged.
You can change the bond's MAC address so that it is different from the MAC address for the (current)
management-interface NIC. However, as the bond is enabled and the MAC/IP address in use changes, existing
network sessions to the host will be dropped.
You can control the MAC address for a bond in two ways:
48

•

An optional mac parameter can be specified in the bond-create command. You can use this parameter to set
the bond MAC address to any arbitrary address.

•

If the mac parameter is not specified, from XenServer 7.0 onwards, XenServer uses the MAC address of the
management interface if this is one of the interfaces in the bond. If the management interface is not part of
the bond, but another management interface is, the bond uses the MAC address (and also the IP address)
that management interface. If none of the NICs in the bond are management interfaces, the bond uses the
MAC of the first named NIC.

4.4.5.3. Reverting NIC Bonds
If reverting a XenServer host to a non-bonded configuration, be aware that the bond-destroy command
automatically configures the primary-slave as the interface to be used for the management interface.
Consequently, all VIFs will be moved to the management interface.
The term primary-slave refers to the PIF that the MAC and IP configuration was copied from when creating the
bond. When bonding two NICs, the primary slave is:
1. The management interface NIC (if the management interface is one of the bonded NICs).
2. Any other NIC with an IP address (if the management interface was not part of the bond).
3. The first named NIC. You can find out which one it is by running the following:
xe bond-list params=all

4.4.6. Creating NIC Bonds in Resource Pools
Whenever possible, create NIC bonds as part of initial resource pool creation prior to joining additional hosts
to the pool or creating VMs. Doing so allows the bond configuration to be automatically replicated to hosts as
they are joined to the pool and reduces the number of steps required. Adding a NIC bond to an existing pool
requires one of the following:
•

Using the CLI to configure the bonds on the master and then each member of the pool.

•

Using the CLI to configure the bonds on the master and then restarting each member of the pool so that it
inherits its settings from the pool master.

•

Using XenCenter to configure the bonds on the master. XenCenter automatically synchronizes the networking
settings on the member servers with the master, so you do not need to reboot the member servers.

For simplicity and to prevent misconfiguration, Citrix recommends using XenCenter to create NIC bonds. For
details, refer to the XenCenter Help.
This section describes using the xe CLI to create bonded NIC interfaces on XenServer hosts that comprise a
resource pool. See Section 4.4.5.1, “Creating a NIC Bond” for details on using the xe CLI to create NIC bonds on
a standalone XenServer host.
Warning:
Do not attempt to create network bonds while HA is enabled. The process of bond creation
will disturb the in-progress HA heartbeating and cause hosts to self-fence (shut themselves
down); subsequently they will likely fail to reboot properly and will need the host-emergencyha-disable command to recover.

4.4.6.1. Adding NIC Bonds to New Resource Pools
1.

Select the host you want to be the master. The master host belongs to an unnamed pool by default. To create
a resource pool with the CLI, rename the existing nameless pool:
xe pool-param-set name-label=<"New Pool"> uuid=

Create the NIC bond as described in Section 4.4.5.1, “Creating a NIC Bond”.
49

Open a console on a host that you want to join to the pool and run the command:
xe pool-join master-address= master-username=root master-password=

The network and bond information is automatically replicated to the new host. The management interface
is automatically moved from the host NIC where it was originally configured to the bonded PIF (that is, the
management interface is now absorbed into the bond so that the entire bond functions as the management
interface).
•

Use the host-list command to find the UUID of the host being configured:
xe host-list

4.4.6.2. Adding NIC Bonds to an Existing Pool
Warning:
Do not attempt to create network bonds while HA is enabled. The process of bond creation
disturbs the in-progress HA heartbeating and causes hosts to self-fence (shut themselves
down); subsequently they will likely fail to reboot properly and you will need to run the hostemergency-ha-disable command to recover them.
Note:
If you are not using XenCenter for NIC bonding, the quickest way to create pool-wide NIC
bonds is to create the bond on the master, and then restart the other pool members.
Alternatively, you can use the service xapi restart command. This causes the bond and VLAN
settings on the master to be inherited by each host. The management interface of each host
must, however, be manually reconfigured.
Follow the procedure in previous sections to create a NIC Bond, see Section 4.4.6.1, “Adding NIC Bonds to New
Resource Pools”.

4.4.7. Configuring a Dedicated Storage NIC
You can use either XenCenter or the xe CLI to assign a NIC an IP address and dedicate it to a specific function,
such as storage traffic. When you configure a NIC with an IP address, you do so by creating a secondary interface.
(The IP-enabled NIC XenServer used for management is known as the management interface.)
When you want to dedicate a secondary interface for a specific purpose, you must ensure the appropriate
network configuration is in place to ensure the NIC is used only for the desired traffic. For example, to dedicate
a NIC to storage traffic, the NIC, storage target, switch, and/or VLAN must be configured so that the target is
only accessible over the assigned NIC. If your physical and IP configuration do not limit the traffic that can be
sent across the storage NIC, it is possible to send other traffic, such as management traffic, across the secondary
interface.
When you create a new secondary interface for storage traffic, you must assign it an IP address that (a) is on the
same subnet as the storage controller, if applicable, and (b) is not on the same subnet as any other secondary
interfaces or the management interface.
When you are configuring secondary interfaces, each secondary interface must be on a separate subnet. For
example, if you want to configure two additional secondary interfaces for storage, you will require IP addresses
on three different subnets – one subnet for the management interface, one subnet for Secondary Interface 1,
and one subnet for Secondary Interface 2.
If you are using bonding for resiliency for your storage traffic, you may want to consider using LACP instead of
the Linux bridge bonding. To use LACP bonding, you must configure the vSwitch as your networking stack. For
more information, see Section 4.2, “vSwitch Networks”.
Note:
50

When selecting a NIC to configure as a secondary interface for use with iSCSI or NFS SRs,
ensure that the dedicated NIC uses a separate IP subnet that is not routable from the
management interface. If this is not enforced, then storage traffic may be directed over the
main management interface after a host reboot, due to the order in which network interfaces
are initialized.

To assign NIC functions using the xe CLI
1.

Ensure that the PIF is on a separate subnet, or routing is configured to suit your network topology in order
to force the desired traffic over the selected PIF.

Setup an IP configuration for the PIF, adding appropriate values for the mode parameter and if using static
IP addressing the IP, netmask, gateway, and DNS parameters:
xe pif-reconfigure-ip mode= uuid=

Set the PIF's disallow-unplug parameter to true:
xe pif-param-set disallow-unplug=true uuid=
xe pif-param-set other-config:management_purpose="Storage" uuid=

If you want to use a secondary interface for storage that can be routed from the management interface also
(bearing in mind that this configuration is not the best practice), you have two options:
•

After a host reboot, ensure that the secondary interface is correctly configured, and use the xe pbd-unplug
and xe pbd-plug commands to reinitialize the storage connections on the host. This restarts the storage
connection and routes it over the correct interface.

•

Alternatively, you can use xe pif-forget to remove the interface from the XenServer database and manually
configure it in the control domain. This is an advanced option and requires you to be familiar with how to
manually configure Linux networking.

4.4.8. Using SR-IOV Enabled NICs
Single Root I/O Virtualization (SR-IOV) is a PCI device virtualization technology that allows a single PCI device to
appear as multiple PCI devices on the physical PCI bus. The actual physical device is known as a Physical Function
(PF) while the others are known as Virtual Functions (VF). The purpose of this is for the hypervisor to directly
assign one or more of these VFs to a Virtual Machine (VM) using SR-IOV technology: the guest can then use the
VF as any other directly assigned PCI device.
Assigning one or more VFs to a VM allows the VM to directly exploit the hardware. When configured, each VM
behaves as though it is using the NIC directly, reducing processing overhead and improving performance.
Warning:
If your VM has an SR-IOV VF, functions that require VM mobility, for example, Live Migration,
Rolling Pool Upgrade, High Availability and Disaster Recovery, are not possible. This is because
the VM is directly tied to the physical SR-IOV enabled NIC VF. In addition, VM network traffic
sent via an SR-IOV VF bypasses the vSwitch, so it is not possible to create ACLs or view QoS.

Assigning a SR-IOV NIC VF to a VM
Note:
SR-IOV is supported only with SR-IOV enabled NICs listed on the XenServer Hardware
Compatibility List and only when used in conjunction with a Windows Server 2008 guest
operating system.
1.

Open a local command shell on your XenServer host.

Run the command lspci to display a list of the Virtual Functions (VF). For example:
51

07:10.0 Ethernet controller: Intel Corporation 82559 \
Ethernet Controller Virtual Function (rev 01)

In the example above, 07:10.0 is the bus:device.function address of the VF.
3.

Assign the required VF to the target VM by running the following commands:
xe vm-param-set other-config:pci=0/0000: uuid=

Start the VM, and install the appropriate VF driver for your specific hardware.
Note:
You can assign multiple VFs to a single VM, however the same VF cannot be shared across
multiple VMs.

4.4.9. Controlling the Rate of Outgoing Data (QoS)
To limit the amount of outgoing data a VM can send per second, you can set an optional Quality of Service (QoS)
value on VM virtual interfaces (VIFs). The setting lets you specify a maximum transmit rate for outgoing packets
in kilobytes per second.
The QoS value limits the rate of transmission from the VM. The QoS setting does not limit the amount of data
the VM can receive. If such a limit is desired, Citrix recommends limiting the rate of incoming packets higher up
in the network (for example, at the switch level).
Depending on networking stack configured in the pool, you can set the Quality of Service (QoS) value on VM
virtual interfaces (VIFs) in one of two places—either a) on the vSwitch Controller or b) in XenServer (using the
CLI or XenCenter)—as described in the following table:
Networking Stack

Configuration Methods Available

vSwitch

•

vSwitch Controller. This is the preferred method
of setting the maximum transmission rate on a VIF
when the vSwitch is the networking stack. When
using the vSwitch stack, the XenCenter QoS option
is not available.

•

xe commands. It is possible to set the QoS
transmit rate using the commands in the example
that follows. However, the preferred method is
through the vSwitch Controller UI, which provides
more finely grained control.

•

XenCenter. You can set the QoS transmit rate
limit value in the properties dialog for the virtual
interface.

•

xe commands. You can set the QoS transmit rate
using the CLI using the commands in the section
that follow.

Linux bridge

Important:
When the vSwitch is configured as the networking stack, it is possible to inadvertently
configure a QoS value on the vSwitch Controller and inside of the XenServer host. In this case,
XenServer limits the outgoing traffic using the lowest rate that you set.
Example of CLI command for QoS:
To limit a VIF to a maximum transmit rate of 100 kilobytes per second using the CLI, use the vif-param-set
command:

xe vif-param-set uuid= qos_algorithm_type=ratelimit
xe vif-param-set uuid= qos_algorithm_params:kbps=100

Note:
If you are using the vSwitch Controller, Citrix recommends setting the transmission rate limit
in the vSwitch Controller instead of this CLI command. For directions on setting the QoS rate
limit in the vSwitch Controller, see the vSwitch Controller User Guide.

4.4.10. Changing Networking Configuration Options
This section discusses how to change the networking configuration of a XenServer host. This includes:
•

changing the hostname (that is, the Domain Name System (DNS) name)

•

adding or removing DNS servers

•

changing IP addresses

•

changing which NIC is used as the management interface

•

adding a new physical NIC to the server

•

enabling ARP filtering (switch-port locking)

4.4.10.1. Hostname
The system hostname, also known as the domain or DNS name, is defined in the pool-wide database and modified
using the xe host-set-hostname-live CLI command as follows:
xe host-set-hostname-live host-uuid= host-name=

The underlying control domain hostname changes dynamically to reflect the new hostname.

4.4.10.2. DNS Servers
To add or remove DNS servers in the IP addressing configuration of a XenServer host, use the pif-reconfigure-ip
command. For example, for a PIF with a static IP:
pif-reconfigure-ip uuid= mode=static DNS=

4.4.10.3. Changing IP Address Configuration for a Standalone Host
Network interface configuration can be changed using the xe CLI. The underlying network configuration scripts
should not be modified directly.
To modify the IP address configuration of a PIF, use the pif-reconfigure-ip CLI command. See Section A.4.14.5,
“pif-reconfigure-ip” for details on the parameters of the pif-reconfigure-ip command.
Note:
See Section 4.4.10.4, “Changing IP Address Configuration in Resource Pools” for details on
changing host IP addresses in resource pools.

4.4.10.4. Changing IP Address Configuration in Resource Pools
XenServer hosts in resource pools have a single management IP address used for management and
communication to and from other hosts in the pool. The steps required to change the IP address of a host's
management interface are different for master and other hosts.
Note:
Caution should be used when changing the IP address of a server, and other networking
parameters. Depending upon the network topology and the change being made, connections
to network storage may be lost. If this happens the storage must be replugged using the
53

Repair Storage function in XenCenter, or the pbd-plug command using the CLI. For this
reason, it may be advisable to migrate VMs away from the server before changing its IP
configuration.

To change the IP address of a member host (not pool master)
1.

Use the pif-reconfigure-ip CLI command to set the IP address as desired. See Appendix A, Command Line
Interface for details on the parameters of the pif-reconfigure-ip command:
xe pif-reconfigure-ip uuid= mode=DHCP

Use the host-list CLI command to confirm that the member host has successfully reconnected to the master
host by checking that all the other XenServer hosts in the pool are visible:
xe host-list

Changing the IP address of the master XenServer host requires additional steps because each of the member
hosts uses the advertised IP address of the pool master for communication and will not know how to contact the
master when its IP address changes.
Whenever possible, use a dedicated IP address that is not likely to change for the lifetime of the pool for pool
masters.

To change the IP address of the pool master
1.

When the IP address of the pool master host is changed, all member hosts will enter into an emergency
mode when they fail to contact the master host.

On the master XenServer host, use the pool-recover-slaves command to force the master to contact each
of the member hosts and inform them of the new master IP address:
xe pool-recover-slaves

4.4.10.5. Management Interface
When XenServer is installed on a host with multiple NICs, one NIC is selected for use as the management interface.
The management interface is used for XenCenter connections to the host and for host-to-host communication.

To change the NIC used for the management interface
1.

Use the pif-list command to determine which PIF corresponds to the NIC to be used as the management
interface. The UUID of each PIF is returned.
xe pif-list

Use the pif-param-list command to verify the IP addressing configuration for the PIF that will be used for
the management interface. If necessary, use the pif-reconfigure-ip command to configure IP addressing for
the PIF to be used. See Appendix A, Command Line Interface for more detail on the options available for
the pif-reconfigure-ip command.
xe pif-param-list uuid=

Use the host-management-reconfigure CLI command to change the PIF used for the management interface.
If this host is part of a resource pool, this command must be issued on the member host console:
xe host-management-reconfigure pif-uuid=

Warning:
Putting the management interface on a VLAN network is not supported.
54

4.4.10.6. Disabling Management Access
To disable remote access to the management console entirely, use the host-management-disable CLI command.
Warning:
Once the management interface is disabled, you will have to log in on the physical host
console to perform management tasks and external interfaces such as XenCenter will no
longer work.

4.4.10.7. Adding a New Physical NIC
Install a new physical NIC on a XenServer host in the usual manner. Then, after restarting the server, run the xe
CLI command pif-scan to cause a new PIF object to be created for the new NIC.

4.4.10.8. Using Switch Port Locking
The XenServer switch-port locking feature lets you control traffic being sent from unknown, untrusted, or
potentially hostile VMs by limiting their ability to pretend they have a MAC or IP address that was not assigned to
them. You can use the port-locking commands in this feature to block all traffic on a network by default or define
specific IP addresses from which an individual VM is allowed to send traffic.
Switch-port locking is a feature designed for public cloud-service providers in environments concerned about
internal threats. This functionality may help public cloud-service providers who have a network architecture in
which each VM has a public, Internet-connected IP address. Because cloud tenants are always untrusted, it may
be desirable to use security measures, such as spoofing protection, to ensure tenants cannot attack other virtual
machines in the cloud.
Using switch-port locking lets you simplify your network configuration by enabling all of your tenants or guests
to use the same Layer 2 network.
One of the most important functions of the port-locking commands is they can restrict the traffic that an
untrusted guest can send, which, in turn, restricts the guest's ability to pretend it has a MAC or IP address it does
not actually possess. Specifically, you can use these commands to prevent a guest from:
•

Claiming an IP or MAC address other than the ones the XenServer administrator has specified it can use

•

Intercepting, spoofing, or disrupting the traffic of other VMs

4.4.10.8.1. Requirements
•

The XenServer switch-port locking feature is supported on the Linux bridge and vSwitch networking stacks.

•

When Role Based Access Control (RBAC) is enabled in your environment, the user configuring switch-port
locking must be logged in with an account that has at least a Pool Operator or Pool Admin role. When RBAC
is not enabled in your environment, the user must be logged in with the root account for the pool master.

•

When you run the switch-port locking commands, networks can be online or offline.

•

In Windows guests, the disconnected Network icon only appears when XenServer Tools are installed in the
guest.

4.4.10.8.2. Notes
Without any switch-port locking configurations, VIFs are set to "network_default" and Networks are set to
"unlocked."
Configuring switch-port locking is not supported when the vSwitch controller and other third-party controllers
are in use in the environment.
Switch port locking does not prevent cloud tenants from:
•

Performing an IP-level attack on another tenant/user. However, switch-port locking prevents them
performing the IP-level attack if they attempt to use the following means to do so and switch-port locking
55

is configured: a) impersonating another tenant in the cloud or user or b) initiating an intercept of traffic
intended for another user.
•

Exhausting network resources.

•

Receiving some traffic intended for other virtual machines through normal switch flooding behaviors (for
broadcast MAC addresses or unknown destination MAC addresses).

Likewise, switch-port locking does not restrict where a VM can send traffic to.

4.4.10.8.3. Implementation Notes
You can implement the switch-port locking functionality either by using the command line or the XenServer
API. However, in large environments, where automation is a primary concern, the most typical implementation
method might be by using the API.

4.4.10.8.4. Examples
This section provides examples of how switch-port locking can prevent certain types of attacks. In these examples,
VM-c is a virtual machine that a hostile tenant (Tenant C) is leasing and using for attacks. VM-a and VM-b are
virtual machines leased by non-attacking tenants.
Example 1: How Switch Port Locking Can Prevent ARP Spoofing Prevention
ARP spoofing refers to an attacker's attempts to associate his or her MAC address with the IP address for another
node, which could potentially result in the node's traffic being sent to the attacker instead. To achieve this goal
the attacker sends fake (spoofed) ARP messages to an Ethernet LAN.
Scenario:
Virtual Machine A (VM-a) wants to send IP traffic from VM-a to Virtual Machine B (VM-b) by addressing it to VMb's IP address. The owner of Virtual Machine C wants to use ARP spoofing to pretend his VM, VM-c, is actually
VM-b.
1. VM-c sends a speculative stream of ARP replies to VM-a. These ARP replies claim that the MAC address in
the reply (c_MAC) is associated with the IP address, b_IP
Result: Because the administrator enabled switch-port locking, these packets are all dropped because
enabling switch-port locking prevents impersonation.
2. VM-b sends an ARP reply to VM-a, claiming that the MAC address in the reply (b_MAC) is associated with
the IP address, b_IP.
Result: VM-a receives VM-b's ARP response.
Example 2: IP Spoofing Prevention
IP address spoofing is a process that conceals the identity of packets by creating Internet Protocol (IP) packets
with a forged source IP address.
Scenario:
Tenant C is attempting to perform a Denial of Service attack using his host, Host-C, on a remote system to disguise
his identity.
Attempt 1
Tenant C sets Host-C's IP address and MAC address to VM-a's IP and MAC addresses (a_IP and a_MAC). Tenant
C instructs Host-C to send IP traffic to a remote system.
Result: The Host-C packets are dropped. This is because the administrator enabled switch-port locking; the HostC packets are dropped because enabling switch-port locking prevents impersonation.
Attempt 2
56

Tenant C sets Host-C's IP address to VM-a's IP address (a_IP) and keeps his original c_MAC.
Tenant C instructs Host-C to send IP traffic to a remote system.
Result: The Host-C packets are dropped. This is because the administrator enabled switch-port locking, which
prevents impersonation.
Example 3: Web Hosting
Scenario:
Alice is an infrastructure administrator.
One of her tenants, Tenant B, is hosting multiple websites from his VM, VM-b. Each website needs a distinct IP
address hosted on the same virtual network interface (VIF).
Alice reconfigures Host-B's VIF to be locked to a single MAC but many IP addresses.

4.4.10.8.5. How Switch-port Locking Works
The switch-port locking feature lets you control packet filtering at one or more of two levels:
•

VIF level. Settings you configure on the VIF determine how packets are filtered. You can set the VIF to prevent
the VM from sending any traffic, restrict the VIF so it can only send traffic using its assigned IP address, or
allow the VM to send traffic to any IP address on the network connected to the VIF.

•

Network level. The XenServer network determines how packets are filtered. When a VIF’s locking mode is
set to network_default, it refers to the network-level locking setting to determine what traffic to allow.

Regardless of which networking stack you use, the feature operates the same way. However, as described in more
detail in the sections that follow, the Linux bridge does not fully support switch-port locking in IPv6.

4.4.10.8.6. VIF Locking-Mode States
The XenServer switch-port locking feature provides a locking mode that lets you configure VIFs in four different
states. These states only apply when the VIF is plugged into a running virtual machine.

This illustration shows how three different VIF locking mode states behave when the network locking
mode is set to unlocked and the VIF state is configured. In the first image, the VIF state is set to
default so no traffic from the VM is filtered. In the second image, the VIF does not send or receive
any packets because the locking mode is set to disabled. In the third image, the VIF state is set to
locked, so the VIF can only send packets if those packets contain the correct MAC and IP address.
•

Network_default. When the VIF's state is set to network_default, XenServer uses the network's
default-locking-mode parameter to determine if and how to filter packets travelling through the VIF.
The behavior varies according to if the associated network has the network default locking mode parameter
set to disabled or unlocked:
•

default-locking-mode=disabled, XenServer applies a filtering rule so that the VIF drops all
traffic.

•

default-locking-mode=unlocked, XenServer removes all the filtering rules associated with the VIF.
By default, the default locking mode parameter is set to unlocked.
57

For information about the default-locking-mode parameter, see Section A.4.11, “Network
Commands”.
The default locking mode of the network has no effect on attached VIFs whose locking state is anything other
than network_default.
Note:
You cannot change the default-locking-mode of a network that has active VIFs
attached to it.
•

Locked. XenServer applies filtering rules so that only traffic sent to or sent from the specified MAC and IP
addresses is allowed to be sent out through the VIF. In this mode, if no IP addresses are specified, then the
VM cannot send any traffic through that VIF (on that network).
To specify the IP addresses from which the VIF will accept traffic, use the IPv4 and/or IPv6 IP addresses
by using the ipv4_allowed or ipv6_allowed parameters. However, if you have the Linux bridge
configured, do not enter IPv6 addresses.
XenServer lets you enter IPv6 addresses when the Linux bridge is active; however, XenServer cannot filter
based on the IPv6 addresses entered. (The reason is the Linux bridge does not have modules to filter Neighbor
Discovery Protocol (NDP) packets, so complete protection cannot be implemented and guests would be
able to impersonate another guest by forging NDP packets.) As result, if you specify even one IPv6 address,
XenServer lets all IPv6 traffic pass through the VIF. If you do not specify any IPv6 addresses, XenServer will
not let any IPv6 traffic pass through to the VIF.

•

Unlocked. All network traffic can pass through the VIF. That is, no filters are applied to any traffic going to
or from the VIF.

•

Disabled. No traffic is allowed to pass through the VIF. (That is, XenServer applies a filtering rule so that the
VIF drops all traffic.)

4.4.10.8.7. Configuring Switch Port Locking
This section provides three different procedures:
•

Restrict VIFs to use a specific IP address

•

Add an IP address to an existing restricted list (for example, if you need to add an IP address to a VIF
while the VM is still running and connected to the network (for example, if you are taking a network offline
temporarily) )

•

Remove an IP address from an existing restricted list

If a VIF's locking-mode is set to locked, it can only use the addresses specified in the ipv4-allowed or
ipv6-allowed parameters.
Because, in some relatively rare cases, VIFs may have more than one IP address, it is possible to specify multiple
IP addresses for a VIF.
You can perform these procedures before or after the VIF is plugged in (or the VM is started).

To restrict VIFs to a specific IP address
1.

Change the default-locking mode to locked, if it is not using that mode already, by running the following
command:
xe vif-param-set uuid= locking-mode=locked

The vif-uuid represents the UUID of the VIF you want to allow to send traffic. To obtain the UUID, run
the xe vif-list command on the host. The vm-uuid indicates virtual machine for which the information is
displayed. The device ID indicates the device number of the VIF.

Run the vif-param-set command to specify the IP addresses from which the virtual machine can send traffic.
Do one or more of the following:
•

Specify one or more IPv4 IP addresses destinations. For example:
xe vif-param-set uuid= ipv4-allowed=

•

Specify one or more IPv6 IP addresses destinations. For example:
xe vif-param-set uuid= ipv6-allowed=

You can specify multiple IP addresses by separating them with a comma, as shown in the preceding example.

To restrict a VIF to an additional IP address
After performing the previous procedure to restrict a VIF to using a specific IP address, you can add one or more
IP addresses the VIF can use.
•

Run the vif-param-add command to add the IP addresses to the existing list. Do one or more of the following:
•

Specify the IPv4 IP address. For example:
xe vif-param-add uuid= ipv4-allowed=

•

Specify the IPv6 IP address. For example:
xe vif-param-add uuid= ipv6-allowed=

To remove an IP address from a VIF's list of IP addresses
If you restrict a VIF to use two or more IP addresses, you can remove one of those IP addresses from the list.
•

Run the vif-param-remove command to remove the IP addresses from the existing list. Do one or more of
the following:
•

Specify the IPv4 IP address to remove. For example:
xe vif-param-remove uuid= ipv4-allowed=

•

Specify the IPv6 IP address to remove. For example:
xe vif-param-remove uuid= ipv6-allowed=

4.4.10.8.8. Preventing a Virtual Machine from Sending or Receiving Traffic from a Specific Network
The following procedure prevents a virtual machine from communicating through a specific VIF. Since a VIF
connects to a specific XenServer network, you can use this procedure to prevent a virtual machine from sending
or receiving any traffic from a specific network. This provides a more granular level of control than disabling an
entire network.
If you use the CLI command, you do not need to unplug the VIF to set the VIF's locking mode; the command
changes the filtering rules while the VIF is running (live). In this case the network connection still appears to be
present; however, the VIF drops any packets the VM attempts to send.
Tip:
To find the UUID of a VIF, run the xe vif-list command on the host. The device ID indicates
the device number of the VIF.

To prevent a VIF from receiving traffic
•

Disable the VIF connected to the network from which you want to stop the VM from receiving traffic:
59

xe vif-param-set uuid= locking-mode=disabled

You can also disable the VIF in XenCenter by selecting the virtual network interface in the VM's Networking
tab and clicking Deactivate.

4.4.10.8.9. Removing a VIF's Restriction to an IP Address
To revert back to the default (original) locking mode state, use the following procedure. By default, when you
create a VIF, XenServer configures it so that it is not restricted to using a specific IP address.

To revert a VIF to an unlocked state
•

Change the VIF default-locking mode to unlocked, if it is not using that mode already, by running the
following command:
xe vif-param-set uuid= locking-mode=unlocked

4.4.10.8.10. Simplifying VIF Locking Mode Configuration in the Cloud
Rather than running the VIF locking mode commands for each VIF, you can ensure all VIFs are disabled by default.
To do so, you must modify the packet filtering at the network level, which causes the XenServer network to
determine how packets are filtered, as described in Section 4.4.10.8.5, “How Switch-port Locking Works”.
Specifically, a network's default-locking-mode setting determines how new VIFs with default settings
behave. Whenever a VIF's locking-mode is set to default, the VIF refers to the network-locking mode
(default-locking-mode) to determine if and how to filter packets travelling through the VIF:
•

Unlocked. When the network default-locking-mode parameter is set to unlocked, XenServer lets
the VM send traffic to any IP address on the network the VIF connects to.

•

Disabled. When the default-locking-mode parameter is set to disabled, XenServer applies a
filtering rule so that the VIF drops all traffic.

By default, the default-locking-mode for all networks created in XenCenter and using the CLI are set to
unlocked.
By setting the VIF's locking mode to its default (network_default), you can use this setting to create a basic
default configuration (at the network level) for all newly created VIFs that connect to a specific network.
This illustration shows how, when a VIF's locking-mode is set to its default setting (network_default),
the VIF uses the network default-locking-mode to determine its behavior.

This illustration shows how a VIF, when configured at its default setting (locking-mode=network_default),
checks to see the setting associated with the default-locking-mode. In this illustration, the
network is set to default-locking-mode=disabled so no traffic can pass through the VIF.
For example, since, by default, VIFs are created with their locking-mode set to network_default, if you
set a network's default-locking-mode=disabled any new VIFs for which you have not configured the
locking mode are disabled until you either (a) change the individual VIF's locking-mode parameter or (b)
explicitly set the VIF's locking-mode to unlocked (for example, if you trust a specific VM enough to not
want to filter its traffic at all).

To change a network's default locking mode setting
•

After creating the network, change the default-locking mode by running the following command:
xe network-param-set uuid= default-locking-mode=[unlocked|disabled]

Note:
To get the UUID for a network, run the xe network-list command. This command displays the
UUIDs for all the networks on the host on which you ran the command.

To check a network's default locking mode setting
•

Run one of the following commands:
xe network-param-get uuid= param-name=default-locking-mode

OR
xe network-list uuid= params=default-locking-mode

4.4.10.8.11. Using Network Settings for VIF Traffic Filtering
The following procedure instructs a VIF on a virtual machine to use the XenServer network defaultlocking-mode settings on the network itself to determine how to filter traffic.

To use network settings for VIF traffic filtering
1.

Change the VIF locking state to network_default, if it is not using that mode already, by running the
following command:
xe vif-param-set uuid= locking-mode=network_default

Change the default-locking mode to unlocked, if it is not using that mode already, by running the following
command:
xe network-param-set uuid= default-locking-mode=unlocked

4.5. Networking Troubleshooting
If you are having problems with configuring networking, first ensure that you have not directly modified any of
the control domain ifcfg-* files directly. These files are directly managed by the control domain host agent,
and changes will be overwritten.

4.5.1. Diagnosing Network Corruption
Some network card models require firmware upgrades from the vendor to work reliably under load, or when
certain optimizations are turned on. If you are seeing corrupted traffic to VMs, then you should first try to obtain
the latest recommended firmware from your vendor and apply a BIOS update.
If the problem still persists, then you can use the CLI to disable receive / transmit offload optimizations on the
physical interface.
Warning:
Disabling receive / transmit offload optimizations can result in a performance loss and / or
increased CPU usage.
First, determine the UUID of the physical interface. You can filter on the device field as follows:
xe pif-list device=eth0

Next, set the following parameter on the PIF to disable TX offload:
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xe pif-param-set uuid= other-config:ethtool-tx=off

Finally, re-plug the PIF or reboot the host for the change to take effect.

4.5.2. Emergency Network Reset
Incorrect networking settings can cause loss of network connectivity, and a XenServer host may become
inaccessible via XenCenter or remote SSH. Emergency Network Reset provides a simple mechanism to recover
and reset a host's networking.
This feature is available from the Command Line Interface (CLI) using the xe-reset-networking command
and within the Network and Management Interface section of xsconsole.
Incorrect settings which could cause a loss of network connectivity could include renaming network interfaces,
creating bonds or VLANs, or mistakes when changing the management interface (for example, entering the
wrong IP address). In addition, you may want to run this utility if a rolling pool upgrade, manual upgrade, hotfix
installation or driver installation causes a lack of network connectivity, or if a Pool master or host in a resource
pool is unable to contact with other hosts.
This utility should only be used in an emergency as it will remove the configuration for all PIFs, Bonds, VLANs
and tunnels associated with the host. Guest Networks and VIFs are preserved. As part of this utility, VMs will
be shutdown forcefully, where possible before running this command, VMs should be cleanly shutdown. Before
applying a reset, users can make changes to the management interface and specify which IP configuration, DHCP
or Static, should be used.
If the Pool Master requires a network reset, it must be carried out before a network reset of any other pool
members. It should then be followed a network reset on all remaining hosts in the pool to ensure that the pool's
networking configuration is homogeneous. This is a particularly important factor for XenMotion.
Note:
If the Pool Master's IP address (the management interface) changes, as a result of a network
reset or xe host-management-reconfigure, you must also apply the network reset
command to other hosts in the pool, so that they can reconnect to the Pool Master on its
new IP address. In this situation, the IP address of the Pool Master must be specified.
Network reset is NOT supported if High Availability (HA) is enabled. To reset network
configuration in this scenario, you must first manually disable HA, and then run the network
reset command.

4.5.2.1. Verifying the Network Reset
After specifying the configuration mode to be used after the network reset, xsconsole and the CLI will display
the settings which will be applied after host reboot. This offers a final chance to make any modifications before
applying the emergency network reset command. After reboot, the new network configuration can be verified
in XenCenter and xsconsole. In XenCenter, with the host selected, click the Networking tab, this displays the new
network configuration. In xsconsole, this information is displayed in the Network and Management Interface
section.
Note:
Emergency Network Reset should also be applied on other pool members to replicate bonds,
VLANs or tunnels from the Pool Master's new configuration.

4.5.2.2. Using the CLI for Network Reset
The following table shows the available optional parameters which can be used with the xe-reset-networking
command.
Warning:
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Users are responsible for ensuring the validity of parameters for the xe-reset-networking
command, check the parameters carefully. If invalid parameters are specified, network
connectivity and configuration will be lost. In this situation, Citrix advises customers to re-run
the command xe-reset-networking without using any parameters.
Resetting the networking configuration of a whole pool must begin on the Pool Master, and
should then be followed by network reset on all remaining hosts in the pool.

Parameter

Required/Optional

Description

-m, --master

Optional

IP address of the Pool Master's management interface. Defaults
to the last known Pool Master's IP address.

--device

Optional

Device name of the management interface. Defaults to the device
name specified during installation.

--mode=static

Optional

Enables the following four networking parameters for static IP
configuration for the management interface. If not specified,
networking will be configured using DHCP.

--ip

Required
mode=static

IP address for the host's management interface. Only valid if
mode=static.

--netmask

Required
mode=static

Netmask for the management interface. Only valid if
mode=static.

--gateway

Optional

Gateway for the management interface. Only valid if
mode=static.

--dns

Optional

DNS Server for the management interface. Only valid if
mode=static.

4.5.2.2.1. Pool Master Command Line Examples
Examples of commands that could be applied on a Pool Master:
To reset networking for DHCP configuration:
xe-reset-networking

To reset networking for Static IP configuration:
xe-reset-networking --mode= static --ip= \
--netmask= --gateway= \
--dns=

To reset networking for DHCP configuration if another interface became the management interface after initial
setup:
xe-reset-networking --device=

To reset networking for Static IP configuration if another interface became the management interface after
initial setup:
xe-reset-networking --device= --mode=static \
--ip= --netmask= \
--gateway= --dns=

4.5.2.2.2. Pool Member Command Line Examples
All previous examples also apply to pool members. Additionally the Pool Master's IP address can be specified
(which will be necessary if it has changed.)
To reset networking for DHCP configuration:
xe-reset-networking

To reset networking for DHCP if the Pool Master's IP address was modified:
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xe-reset-networking --master=

To reset networking for Static IP configuration, assuming the Pool Master's IP address didn't change:
xe-reset-networking --mode=static --ip= --netmask- \
--gateway= --dns=

To reset networking for DHCP configuration if the management interface and the Pool Master's IP address was
modified after initial setup:
xe-reset-networking --device= --master

Chapter 5. Storage
This chapter describes the way in which physical storage hardware is mapped to Virtual Machines (VMs), and
the software objects used by the XenServer host API to perform storage-related tasks. Detailed sections on each
of the supported storage types include procedures for creating storage for VMs using the CLI, with type-specific
device configuration options, generating snapshots for backup purposes and some best practices for managing
storage in XenServer host environments. Finally, the virtual disk QoS (quality of service) settings are described.

5.1. Storage Overview
This section explains what the XenServer storage objects are and how they are related to each other.

5.1.1. Storage Repositories (SRs)
A Storage Repository (SR) is a particular storage target, in which Virtual Machine (VM) Virtual Disk Images (VDIs)
are stored. A VDI is a storage abstraction which represent a virtual hard disk drive (HDD).
SRs are flexible, with built-in support for IDE, SATA, SCSI and SAS drives that are locally connected, and iSCSI, NFS,
SAS and Fibre Channel remotely connected. The SR and VDI abstractions allow for advanced storage features
such as Thin Provisioning, VDI snapshots, and fast cloning to be exposed on storage targets that support them.
For storage subsystems that do not inherently support advanced operations directly, a software stack is provided
based on Microsoft's Virtual Hard Disk (VHD) specification which implements these features.
SR commands provide operations for creating, destroying, resizing, cloning, connecting and discovering the
individual VDIs that they contain.
A storage repository is a persistent, on-disk data structure. For SR types that use an underlying block device, the
process of creating a new SR involves erasing any existing data on the specified storage target. Other storage
types such as NFS, create a new container on the storage array in parallel to existing SRs.
Each XenServer host can use multiple SRs and different SR types simultaneously. These SRs can be shared between
hosts or dedicated to particular hosts. Shared storage is pooled between multiple hosts within a defined resource
pool. A shared SR must be network accessible to each host. All hosts in a single resource pool must have at least
one shared SR in common.
CLI operations to manage storage repositories are described in Section A.4.17, “SR Commands”.

5.1.2. Virtual Disk Image (VDI)
Virtual Disk Images (VDI) are a storage abstraction which represent a virtual hard disk drive (HDD). VDIs are the
fundamental unit of virtualized storage in XenServer. VDIs are persistent, on-disk objects that exist independently
of XenServer hosts. CLI operations to manage VDIs are described in Section A.4.23, “VDI Commands”. The actual
on-disk representation of the data differs by SR type and is managed by a separate storage plug-in interface for
each SR, called the SM API.

5.1.3. Physical Block Devices (PBDs)
Physical Block Devices represent the interface between a physical server and an attached SR. PBDs are connector
objects that allow a given SR to be mapped to a XenServer host. PBDs store the device configuration fields that
are used to connect to and interact with a given storage target. For example, NFS device configuration includes
the IP address of the NFS server and the associated path that the XenServer host mounts. PBD objects manage
the run-time attachment of a given SR to a given XenServer host. CLI operations relating to PBDs are described
in Section A.4.13, “PBD Commands”.
66

5.1.4. Virtual Block Devices (VBDs)
Virtual Block Devices are connector objects (similar to the PBD described above) that allows mappings between
VDIs and VMs. In addition to providing a mechanism for attaching (also called plugging) a VDI into a VM, VBDs
allow for the fine-tuning of parameters regarding QoS (quality of service), statistics, and the bootability of a given
VDI. CLI operations relating to VBDs are described in Section A.4.22, “VBD Commands”.

5.1.5. Summary of Storage objects
The following image is a summary of how the storage objects presented so far are related:

Graphical overview of storage repositories and related objects

5.1.6. Virtual Disk Data Formats
In general, there are two types of mapping of physical storage to a VDI:
1. Logical Volume-based VHD on a LUN; The default XenServer blockdevice-based storage inserts a Logical
Volume manager on a disk, either a locally attached device (LVM type SR) or a SAN attached LUN over either
Fibre Channel (LVMoHBA type SR), iSCSI (LVMoISCSI type SR) or SAS (LVMoHBA type Sr). VDIs are represented
as volumes within the Volume manager and stored in VHD format to allow thin provisioning of reference
nodes on snapshot and clone.
2. File-based VHD on a filesystem; VM images are stored as thin-provisioned VHD format files on either a local
non-shared filesystem (EXT type SR) or a shared NFS target (NFS type SR)

5.1.6.1. VDI Types
In general, VHD format VDIs will be created. You can opt to use raw at the time you create the VDI; this can only
be done using the xe CLI. .
To check if a VDI was created with type=raw, check its sm-config map. The sr-param-list and vdi-param-list
xe commands can be used respectively for this purpose.

5.1.6.2. Creating a Raw Virtual Disk Using the xe CLI
1. Run the following command to create a VDI given the UUID of the SR you want to place the virtual disk in:
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xe vdi-create sr-uuid= type=user virtual-size= \
name-label= sm-config:type=raw

2. Attach the new virtual disk to a VM and use your normal disk tools within the VM to partition and format,
or otherwise make use of the new disk. You can use the vbd-create command to create a new VBD to map
the virtual disk into your VM.

5.1.6.3. Converting Between VDI Formats
It is not possible to do a direct conversion between the raw and VHD formats. Instead, you can create a new VDI
(either raw, as described above, or VHD) and then copy data into it from an existing volume. Citrix recommends
that you use the xe CLI to ensure that the new VDI has a virtual size at least as big as the VDI you are copying from
(by checking its virtual-size field, for example by using the vdi-param-list command). You can then attach this
new VDI to a VM and use your preferred tool within the VM (standard disk management tools in Windows, or the
dd command in Linux) to do a direct block-copy of the data. If the new volume is a VHD volume, it is important
to use a tool that can avoid writing empty sectors to the disk so that space is used optimally in the underlying
storage repository — in this case a file-based copy approach may be more suitable.

5.1.6.4. VHD-based VDIs
VHD files may be chained, allowing two VDIs to share common data. In cases where a VHD-backed VM is cloned,
the resulting VMs share the common on-disk data at the time of cloning. Each proceeds to make its own changes
in an isolated copy-on-write (CoW) version of the VDI. This feature allows VHD-based VMs to be quickly cloned
from templates, facilitating very fast provisioning and deployment of new VMs.
This leads to a situation where trees of chained VDIs are created over time as VMs and their associated VDIs get
cloned. When one of the VDIs in a chain is deleted, XenServer rationalizes the other VDIs in the chain to remove
unnecessary VDIs. This coalescing process runs asynchronously. The amount of disk space reclaimed and the time
taken to perform the process depends on the size of the VDI and the amount of shared data. Only one coalescing
process will ever be active for an SR. This process thread runs on the SR master host.
If you have critical VMs running on the master server of the pool and experience occasional slow IO due to this
process, you can take steps to mitigate against this:
•

Migrate the VM to a host other than the SR master

•

Set the disk IO priority to a higher level, and adjust the scheduler. See Section 5.7.10, “Virtual Disk QoS
Settings” for more information.

The VHD format used by LVM-based and File-based SR types in XenServer uses Thin Provisioning. The image file
is automatically extended in 2MB chunks as the VM writes data into the disk. For File-based VHD, this has the
considerable benefit that VM image files take up only as much space on the physical storage as required. With
LVM-based VHD the underlying logical volume container must be sized to the virtual size of the VDI, however
unused space on the underlying CoW instance disk is reclaimed when a snapshot or clone occurs. The difference
between the two behaviors can be characterized in the following way:
•

For LVM-based VHDs, the difference disk nodes within the chain consume only as much data as has been
written to disk but the leaf nodes (VDI clones) remain fully inflated to the virtual size of the disk. Snapshot
leaf nodes (VDI snapshots) remain deflated when not in use and can be attached Read-only to preserve the
deflated allocation. Snapshot nodes that are attached Read-Write will be fully inflated on attach, and deflated
on detach.

•

For file-based VHDs, all nodes consume only as much data as has been written, and the leaf node files grow
to accommodate data as it is actively written. If a 100GB VDI is allocated for a new VM and an OS is installed,
the VDI file will physically be only the size of the OS data that has been written to the disk, plus some minor
metadata overhead.

When cloning VMs based on a single VHD template, each child VM forms a chain where new changes are written
to the new VM, and old blocks are directly read from the parent template. If the new VM was converted into a

further template and more VMs cloned, then the resulting chain will result in degraded performance. XenServer
supports a maximum chain length of 30, but it is generally not recommended that you approach this limit without
good reason. If in doubt, "copy" the VM using XenCenter or use the vm-copy command, which resets the chain
length back to 0.

5.2. Storage Repository Formats
New storage repositories can be created in XenCenter using the New Storage Repository wizard. This wizard
guides you through the configuration steps. Alternatively use the CLI, and the sr-create command. This command
creates a new SR on the storage substrate (potentially destroying any existing data), and creates the SR API object
and a corresponding PBD record, enabling VMs to use the storage. On successful creation of the SR, the PBD
is automatically plugged. If the SR shared=true flag is set, a PBD record is created and plugged for every
XenServer in the resource pool.
If you are creating an SR for IP-based storage (iSCSI or NFS), you can configure one of the following as the storage
network: the NIC that handles the management traffic or a new NIC for the storage traffic. To assign an IP address
to a NIC, see Section 4.4.7, “Configuring a Dedicated Storage NIC”.
All XenServer SR types support VDI resize, fast cloning and snapshot. SRs based on the LVM SR type (local, iSCSI,
or HBA) provide thin provisioning for snapshot and hidden parent nodes. The other SR types support full thin
provisioning, including for virtual disks that are active.
Warning:
When VHD VDIs are not attached to a VM, for example in the case of a VDI snapshot, they
are stored as thinly-provisioned by default. When attempting to re-attach the VDI, customers
should ensure that there is sufficient disk-space available for the VDI to become thickly
provisioned. VDI clones are thickly-provisioned.
The maximum supported VDI sizes are:
Storage Repository Format

Maximum VDI size

EXT3

2TB

LVM

2TB

NFS

2TB

iSCSI

2TB

HBA

2TB

5.2.1. Local LVM
The Local LVM type presents disks within a locally-attached Volume Group.
By default, XenServer uses the local disk on the physical host on which it is installed. The Linux Logical Volume
Manager (LVM) is used to manage VM storage. A VDI is implemented in VHD format in an LVM logical volume
of the specified size.

5.2.1.1. LVM Performance Considerations
The snapshot and fast clone functionality provided in XenServer 5.5 and later for LVM-based SRs comes with an
inherent performance overhead. In cases where optimal performance is desired, XenServer supports creation
of VDIs in the raw format in addition to the default VHD format. The XenServer snapshot functionality is not
supported on raw VDIs.
69

Note:
Non-transportable snapshots using the default Windows VSS provider will work on any type
of VDI.
Warning:
Do not try to snapshot a VM that has type=raw disks attached. This could result in a
partial snapshot being created. In this situation, you can identify the orphan snapshot VDIs
by checking the snapshot-of field and then deleting them.

5.2.1.2. Creating a Local LVM SR (lvm)
An LVM SR is created bu default on host install.
Device-config parameters for lvm SRs are:
Parameter Name

Description

Required?

Device

device name on the local host to
use for the SR

Yes

To create a local lvm SR on /dev/sdb use the following command.
xe sr-create host-uuid= content-type=user \
name-label=<"Example Local LVM SR"> shared=false \
device-config:device=/dev/sdb type=lvm

5.2.2. Local EXT3
Using EXT3 enables Thin Provisioning on local storage. However, the default Storage Repository type is LVM as it
gives a consistent write performance and, prevents storage over-commit. Customers using EXT3 may see reduced
performance when carrying out VM lifecycle operations such as VM Create, suspend/resume and when initially
creating large files from within the VM.
Local disk EXT SRs must be configured using the XenServer CLI.

5.2.2.1. Creating a Local EXT3 SR (ext)
Device-config parameters for ext SRs:
Parameter Name

Description

Required?

Device

device name on the local host to
use for the SR

Yes

To create a local ext SR on /dev/sdb use the following command:
xe sr-create host-uuid= content-type=user \
name-label=<"Example Local EXT3 SR"> shared=false \
device-config:device=/dev/sdb type=ext

5.2.3. udev
The udev type represents devices plugged in using the udev device manager as VDIs.
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XenServer has two SRs of type udev that represent removable storage. One is for the CD or DVD disk in the
physical CD or DVD-ROM drive of the XenServer host. The other is for a USB device plugged into a USB port of
the XenServer host. VDIs that represent the media come and go as disks or USB sticks are inserted and removed.

5.2.4. ISO
The ISO type handles CD images stored as files in ISO format. This SR type is useful for creating shared ISO libraries.
For storage repositories that store a library of ISOs, the content-type parameter must be set to iso.
For example:
xe sr-create host-uuid= content-type=iso \
type=iso name-label=<"Example ISO SR"> \
device-config:location=

5.2.5. Software iSCSI Support
XenServer provides support for shared SRs on iSCSI LUNs. iSCSI is supported using the Open-iSCSI software iSCSI
initiator or by using a supported iSCSI Host Bus Adapter (HBA). The steps for using iSCSI HBAs are identical to
those for Fibre Channel HBAs, both of which are described in Section 5.2.8.2, “Creating a Shared LVM over Fibre
Channel / Fibre Channel over Ethernet / iSCSI HBA or SAS SR (lvmohba)”.
Shared iSCSI support using the software iSCSI initiator is implemented based on the Linux Volume Manager (LVM)
and provides the same performance benefits provided by LVM VDIs in the local disk case. Shared iSCSI SRs using
the software-based host initiator are capable of supporting VM agility using XenMotion: VMs can be started on
any XenServer host in a resource pool and migrated between them with no noticeable downtime.
iSCSI SRs use the entire LUN specified at creation time and may not span more than one LUN. CHAP support is
provided for client authentication, during both the data path initialization and the LUN discovery phases.
Note:
The block size of an iSCSI LUN must be 512 bytes.

5.2.5.1. XenServer Host iSCSI configuration
All iSCSI initiators and targets must have a unique name to ensure they can be uniquely identified on the network.
An initiator has an iSCSI initiator address, and a target has an iSCSI target address. Collectively these are called
iSCSI Qualified Names, or IQNs.
XenServer hosts support a single iSCSI initiator which is automatically created and configured with a random IQN
during host installation. The single initiator can be used to connect to multiple iSCSI targets concurrently.
iSCSI targets commonly provide access control using iSCSI initiator IQN lists, so all iSCSI targets/LUNs to be
accessed by a XenServer host must be configured to allow access by the host's initiator IQN. Similarly, targets/
LUNs to be used as shared iSCSI SRs must be configured to allow access by all host IQNs in the resource pool.
Note:
iSCSI targets that do not provide access control will typically default to restricting LUN access
to a single initiator to ensure data integrity. If an iSCSI LUN is intended for use as a shared
SR across multiple XenServer hosts in a resource pool, ensure that multi-initiator access is
enabled for the specified LUN.
The XenServer host IQN value can be adjusted using XenCenter, or using the CLI with the following command
when using the iSCSI software initiator:
xe host-param-set uuid= other-config:iscsi_iqn=

Warning:
It is imperative that every iSCSI target and initiator have a unique IQN. If a non-unique IQN
identifier is used, data corruption and/or denial of LUN access can occur.
Warning:
Do not change the XenServer host IQN with iSCSI SRs attached. Doing so can result in failures
connecting to new targets or existing SRs.

5.2.6. Software FCoE Storage
Software FCoE provides a standard framework to which hardware vendors can plug in their FCoE-capable NIC
and get the same benefits of a hardware-based FCoE. This eliminates the need for using expensive HBAs.
Before creating a new software FCoE storage, configuration required to expose a LUN to the host must be
completed manually, including configuring the FCoE fabric and allocating LUNs to your SAN's public world wide
name (PWWN). After completing this configuration, available LUN should be mounted to the host's CNA as a
SCSI device. The SCSI device can then be used to access the LUN as if it were a locally attached SCSI device. For
information about configuring the physical switch and the array to support FCoE, refer to the documentation
provided by the vendor.
Note:
Software FCoE can be used with Open vSwitch and Linux bridge as the network backend.

5.2.6.1. Creating a Software FCoE SR
Before creating a Software FCoE SR, customers must ensure there are FCoE-capable NICs attached to the host.
Device-config parameters for FCoE SRs are:
Parameter Name

Description

Required?

SCSIid

the SCSI bus ID of the destination
LUN

Yes

Run the following command to create a shared FCoE SR:
xe sr-create type=lvmofcoe \
name-label=<"FCoE SR"> shared=true device-config:SCSIid=

5.2.7. Hardware Host Bus Adapters (HBAs)
This section covers various operations required to manage SAS, Fibre Channel and iSCSI HBAs.

5.2.7.1. Sample QLogic iSCSI HBA setup
For full details on configuring QLogic Fibre Channel and iSCSI HBAs please refer to the QLogic website.
Once the HBA is physically installed into the XenServer host, use the following steps to configure the HBA:
1. Set the IP networking configuration for the HBA. This example assumes DHCP and HBA port 0. Specify the
appropriate values if using static IP addressing or a multi-port HBA.
72

/opt/QLogic_Corporation/SANsurferiCLI/iscli -ipdhcp 0

2. Add a persistent iSCSI target to port 0 of the HBA.
/opt/QLogic_Corporation/SANsurferiCLI/iscli -pa 0

3. Use the xe sr-probe command to force a rescan of the HBA controller and display available LUNs. See
Section 5.3.2, “Probing an SR” and Section 5.2.8.2, “Creating a Shared LVM over Fibre Channel / Fibre Channel
over Ethernet / iSCSI HBA or SAS SR (lvmohba)” for more details.

5.2.7.2. Removing HBA-based SAS, FC or iSCSI Device Entries
Note:
This step is not required. Citrix recommends that only power users perform this process if it
is necessary.
Each HBA-based LUN has a corresponding global device path entry under /dev/disk/by-scsibus in the
format -::: and a standard device path under /dev. To remove the device
entries for LUNs no longer in use as SRs use the following steps:
1. Use sr-forget or sr-destroy as appropriate to remove the SR from the XenServer host database. See
Section 5.7.1, “Removing SRs” for details.
2. Remove the zoning configuration within the SAN for the desired LUN to the desired host.
3. Use the sr-probe command to determine the ADAPTER, BUS, TARGET, and LUN values corresponding to the
LUN to be removed. See Section 5.3.2, “Probing an SR” for details.
4. Remove the device entries with the following command:
echo "1" > /sys/class/scsi_device/:::/device/delete

Warning:
Make absolutely sure you are certain which LUN you are removing. Accidentally removing
a LUN required for host operation, such as the boot or root device, will render the host
unusable.

5.2.8. Shared LVM Storage
The Shared LVM type represents disks as Logical Volumes within a Volume Group created on an iSCSI (FC or SAS)
LUN.
Note:
The block size of an iSCSI LUN must be 512 bytes.

5.2.8.1. Creating a Shared LVM Over iSCSI SR Using the Software iSCSI Initiator (lvmoiscsi)
Device-config parameters for lvmoiscsi SRs:
Parameter Name

Description

Required?

target

the IP address or hostname of the iSCSI filer that hosts the SR

yes

targetIQN

the IQN target address of iSCSI filer that hosts the SR

yes

SCSIid

the SCSI bus ID of the destination LUN

yes

Parameter Name

Description

Required?

chapuser

the username to be used for CHAP authentication

chappassword

the password to be used for CHAP authentication

port

the network port number on which to query the target

usediscoverynumber

the specific iSCSI record index to use

incoming_chapuser

the username that the iSCSI filter will use to authenticate against
the host

incoming_chappassword

the password that the iSCSI filter will use to authenticate against
the host

To create a shared lvmoiscsi SR on a specific LUN of an iSCSI target use the following command.
xe sr-create host-uuid= content-type=user \
name-label=<"Example shared LVM over iSCSI SR"> shared=true \
device-config:target= device-config:targetIQN= \
device-config:SCSIid= \
type=lvmoiscsi

5.2.8.2. Creating a Shared LVM over Fibre Channel / Fibre Channel over Ethernet / iSCSI HBA or
SAS SR (lvmohba)
SRs of type lvmohba can be created and managed using the xe CLI or XenCenter.
Device-config parameters for lvmohba SRs:
Parameter name

Description

Required?

SCSIid

Device SCSI ID

Yes

To create a shared lvmohba SR, perform the following steps on each host in the pool:
1. Zone in one or more LUNs to each XenServer host in the pool. This process is highly specific to the SAN
equipment in use. Please refer to your SAN documentation for details.
2. If necessary, use the HBA CLI included in the XenServer host to configure the HBA:
•

Emulex: /bin/sbin/ocmanager

•

QLogic FC: /opt/QLogic_Corporation/SANsurferCLI

•

QLogic iSCSI: /opt/QLogic_Corporation/SANsurferiCLI

See Section 5.2.7, “Hardware Host Bus Adapters (HBAs)” for an example of QLogic iSCSI HBA configuration.
For more information on Fibre Channel and iSCSI HBAs please refer to the Emulex and QLogic websites.
3. Use the sr-probe command to determine the global device path of the HBA LUN. sr-probe forces a re-scan
of HBAs installed in the system to detect any new LUNs that have been zoned to the host and returns a list
of properties for each LUN found. Specify the host-uuid parameter to ensure the probe occurs on the
desired host.
The global device path returned as the property will be common across all hosts in the pool and
therefore must be used as the value for the device-config:device parameter when creating the SR.
If multiple LUNs are present use the vendor, LUN size, LUN serial number, or the SCSI ID as included in the
property to identify the desired LUN.
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xe sr-probe type=lvmohba \
host-uuid=1212c7b3-f333-4a8d-a6fb-80c5b79b5b31
Error code: SR_BACKEND_FAILURE_90
Error parameters: , The request is missing the device parameter, \

/dev/disk/by-id/scsi-360a9800068666949673446387665336f

HITACHI

730157980002

80530636800

qla2xxx

Host4

qla2xxx

QLogic HBA Driver

4. On the master host of the pool create the SR, specifying the global device path returned in the
property from sr-probe. PBDs will be created and plugged for each host in the pool automatically.
xe sr-create host-uuid= \
content-type=user \
name-label=<"Example shared LVM over HBA SR"> shared=true \
device-config:SCSIid= type=lvmohba

Note:
You can use the XenCenter Repair Storage Repository function to retry the PBD creation
and plugging portions of the sr-create operation. This can be valuable in cases where the
LUN zoning was incorrect for one or more hosts in a pool when the SR was created. Correct

the zoning for the affected hosts and use the Repair Storage Repository function instead of
removing and re-creating the SR.

5.2.9. NFS and SMB
NFS and SMB SR types store disks as VHD files on a remote filesystem.
XenServer allows shares on NFS servers (that support NFSv4 or NFSv3), or shares on SMB servers (that support
SMB 3.0), over TCP/IP to be used immediately as a storage repository for virtual disks (VDIs). VDIs are stored in
the Microsoft VHD format only. Additionally, as these SRs can be shared, VDIs stored on shared SRs allow:
•

VMs to be started on any XenServer hosts in a resource pool

•

VM migrate between XenServer hosts in a resource pool using XenMotion (without noticeable downtime)
Important:
•

Support for SMB 3.0 is limited to the ability to connect to a share using the 3.0 protocol.
Additional features like Transparent Failover are dependent on feature availability in the
upstream Linux kernel and are not supported in XenServer 7.0.

•

For NFSv4, only the authentication type AUTH_SYS is supported in XenServer 7.0.

Note:
SMB storage is available for XenServer Enterprise edition customers, or those who have access
to XenServer through their XenApp/XenDesktop entitlement. To learn more about XenServer
editions, and to find out how to upgrade, visit the Citrix website here. For detailed information
on Licensing, refer to the XenServer 7.0 Licensing FAQ.
VDIs stored on file-based SRs are Thinly Provisioned. The image file is allocated as the VM writes data into the
disk. This has the considerable benefit that the VM image files take up only as much space on the storage as is
required. For example, if a 100GB VDI is allocated for a new VM and an OS is installed, the VDI file will only reflect
the size of the OS data that has been written to the disk rather than the entire 100GB.
VHD files may also be chained, allowing two VDIs to share common data. In cases where a file-based VM is cloned,
the resulting VMs will share the common on-disk data at the time of cloning. Each VM will proceed to make its
own changes in an isolated copy-on-write version of the VDI. This feature allows file-based VMs to be quickly
cloned from templates, facilitating very fast provisioning and deployment of new VMs.
Note:
The maximum supported length of VHD chains is 30.
XenServer's file-based SRs and VHD implementations assume that they have full control over the SR directory
on the file server. Administrators should not modify the contents of the SR directory, as this can risk corrupting
the contents of VDIs.
XenServer has been tuned for enterprise-class storage that use non-volatile RAM to provide fast
acknowledgments of write requests while maintaining a high degree of data protection from failure. XenServer
has been tested extensively against Network Appliance FAS2020 and FAS3210 storage, using Data OnTap 7.3 and
8.1
Warning:
As VDIs on file-based SRs are created as Thin Provisioned, administrators must ensure that
there is enough disk space on the file-based SRs for all required VDIs. XenServer hosts do not
enforce that the space required for VDIs on file-based SRs is actually present.

5.2.9.1. Creating a Shared NFS SR (NFS)
To create an NFS SR, you will need to provide the hostname or IP address of the NFS server. You can create the SR
on any valid destination path; use the sr-probe command to display a list of valid destination paths exported
by the server.
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In scenarios where XenServer is used with lower-end storage, it will cautiously wait for all writes to be
acknowledged before passing acknowledgments on to guest VMs. This will incur a noticeable performance cost,
and might be solved by setting the storage to present the SR mount point as an asynchronous mode export.
Asynchronous exports acknowledge writes that are not actually on disk, and so administrators should consider
the risks of failure carefully in these situations.
Note:
The NFS server must be configured to export the specified path to all XenServer hosts in the
pool, or the creation of the SR and the plugging of the PBD record will fail.
The XenServer NFS implementation uses TCP by default. If your situation allows, you can configure the
implementation to use UDP in scenarios where there may be a performance benefit. To do this, when creating
an SR, specify the device-config parameter useUDP=true.
Device-config parameters for NFS SRs:
Parameter Name

Description

Required?

server

IP address or hostname of the NFS
server

Yes

serverpath

path, including the NFS mount
point, to the NFS server that hosts
the SR

Yes

For example, to create a shared NFS SR on 192.168.1.10:/export1, use the following command:
xe sr-create content-type=user \
name-label=<"shared NFS SR"> shared=true \
device-config:server=192.168.1.10 device-config:serverpath=/export1 type=nfs \
nfsversion=<"3", "4">

To create a non-shared NFS SR, run the following command:
xe sr-create host-uuid= content-type=user \
name-label=<"Non-shared NFS SR"> \
device-config:server=192.168.1.10 device-config:serverpath=/export1 type=nfs \
nfsversion=<"3", "4">

5.2.9.2. Creating a Shared SMB SR (SMB)
To create an SMB SR, you will need to provide the hostname or IP address of the SMB server, the full path of the
exported share and appropriate credentials.
Note:
SMB SR has been tested against Network Appliance storage running OnTap 8.3 and Windows
Server 2012 R2.
Device-config parameters for SMB SRs:
Parameter Name

Description

Required?

server

Full path to share on server

Yes

username

User account with RW access to
share

Optional

password

Password for the user account

Optional

For example, to create a shared SMB SR on 192.168.1.10:/share1, use the following command:
77

xe sr-create content-type=user \
name-label=<"Example shared SMB SR"> shared=true \
device-config:server=//192.168.1.10/share1 \
device-config:username= device-config:password= type=smb

To create a non-shared SMB SR, run the following command:
xe sr-create host-uuid= content-type=user \
name-label=<"Non-shared SMB SR"> \
device-config:server=//192.168.1.10/share1 \
device-config:username= device-config:password= type=smb

5.2.10. LVM over Hardware HBA
The LVM over hardware HBA type represents disks as VHDs on Logical Volumes within a Volume Group created
on an HBA LUN providing, for example, hardware-based iSCSI or FC support.
XenServer hosts support Fibre Channel (FC) storage area networks (SANs) through Emulex or QLogic host bus
adapters (HBAs). All FC configuration required to expose a FC LUN to the host must be completed manually,
including storage devices, network devices, and the HBA within the XenServer host. Once all FC configuration is
complete the HBA will expose a SCSI device backed by the FC LUN to the host. The SCSI device can then be used
to access the FC LUN as if it were a locally attached SCSI device.
Use the sr-probe command to list the LUN-backed SCSI devices present on the host. This command forces a scan
for new LUN-backed SCSI devices. The path value returned by sr-probe for a LUN-backed SCSI device is consistent
across all hosts with access to the LUN, and therefore must be used when creating shared SRs accessible by all
hosts in a resource pool.
The same features apply to QLogic iSCSI HBAs.
See Section 5.3.1, “Creating Storage Repositories” for details on creating shared HBA-based FC and iSCSI SRs.
Note:
XenServer support for Fibre Channel does not support direct mapping of a LUN to a VM. HBAbased LUNs must be mapped to the host and specified for use in an SR. VDIs within the SR
are exposed to VMs as standard block devices.

5.3. Storage Configuration
This section covers creating storage repository types and making them available to a XenServer host. The
examples provided show how to do this using the CLI. See the XenCenter Help for details on using the New
Storage Repository wizard.

5.3.1. Creating Storage Repositories
This section explains how to create Storage Repositories (SRs) of different types and make them available to a
XenServer host. The examples provided cover creating SRs using the xe CLI. See the XenCenter help for details on
using the New Storage Repository wizard to add SRs using XenCenter.
Note:
Local SRs of type lvm and ext3 can only be created using the xe CLI. After creation all SR
types can be managed by either XenCenter or the xe CLI.
There are two basic steps involved in creating a new storage repository for use on a XenServer host using the CLI:
1. Probe the SR type to determine values for any required parameters.
2. Create the SR to initialize the SR object and associated PBD objects, plug the PBDs, and activate the SR.
These steps differ in detail depending on the type of SR being created. In all examples the sr-create command
returns the UUID of the created SR if successful.
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SRs can also be destroyed when no longer in use to free up the physical device, or forgotten to detach the SR
from one XenServer host and attach it to another. See Section 5.7.1, “Removing SRs” for details.

5.3.2. Probing an SR
The sr-probe command can be used in two ways:
1. To identify unknown parameters for use in creating a SR.
2. To return a list of existing SRs.
In both cases sr-probe works by specifying an SR type and one or more device-config parameters for that
SR type. When an incomplete set of parameters is supplied the sr-probe command returns an error message
indicating parameters are missing and the possible options for the missing parameters. When a complete set of
parameters is supplied a list of existing SRs is returned. All sr-probe output is returned as XML.
For example, a known iSCSI target can be probed by specifying its name or IP address, and the set of IQNs available
on the target will be returned:
xe sr-probe type=lvmoiscsi device-config:target=<192.168.1.10>
Error code: SR_BACKEND_FAILURE_96
Error parameters: , The request is missing or has an incorrect target IQN parameter, \

192.168.1.10

iqn.192.168.1.10:filer1

Probing the same target again and specifying both the name/IP address and desired IQN returns the set of SCSIids
(LUNs) available on the target/IQN.
xe sr-probe type=lvmoiscsi device-config:target=192.168.1.10
device-config:targetIQN=iqn.192.168.1.10:filer1

Error code: SR_BACKEND_FAILURE_107
Error parameters: , The SCSIid parameter is missing or incorrect, \

IET

42949672960

149455400000000000000000002000000b70200000f000000

Probing the same target and supplying all three parameters will return a list of SRs that exist on the LUN, if any.
xe sr-probe type=lvmoiscsi device-config:target=192.168.1.10 \
device-config:targetIQN=192.168.1.10:filer1 \
device-config:SCSIid=149455400000000000000000002000000b70200000f000000

3f6e1ebd-8687-0315-f9d3-b02ab3adc4a6

/dev/disk/by-id/scsi-149455400000000000000000002000000b70200000f000000

The following parameters can be probed for each SR type:
SR type

device-config
dependency

lvmoiscsi

Can
be
probed?

Required for sr-create?

target

Yes

chapuser

chappassword

targetIQN

Yes

SCSIid

Yes

lvmohba

SCSIid

Yes

NetApp

target

Yes

username

Yes

password

Yes

chapuser

chappassword

aggregate

No*

Yes

FlexVols

allocation

asis

server

Yes

serverpath

Yes

lvm

device

Yes

ext

device

Yes

EqualLogic

target

Yes

nfs

parameter,

order

SR type

device-config
dependency

parameter,

order

Can
be
probed?

Required for sr-create?

username

Yes

password

Yes

chapuser

chappassword

storagepool

No†

Yes

Aggregate probing is only possible at sr-create time. It needs to be done there so that the aggregate can be specified at the point that the
SR is created.
†
Storage pool probing is only possible at sr-create time. It needs to be done there so that the aggregate can be specified at the point that the
SR is created.

5.4. Storage Multipathing
Dynamic multipathing support is available for Fibre Channel and iSCSI storage backends. By default, XenServer
uses round-robin mode load balancing, so both routes have active traffic on them during normal operation.
You can enable multipathing in XenCenter or on the xe CLI. For additional information about multipathing, see
CTX134881—Configuring Multipathing for XenServer.
Before attempting to enable multipathing, verify that multiple targets are available on your
storage server. For example, an iSCSI storage backend queried for sendtargets on a given
portal should return multiple targets, as in the following example:
iscsiadm -m discovery --type sendtargets --portal 192.168.0.161
192.168.0.161:3260,1 iqn.strawberry:litchie
192.168.0.204:3260,2 iqn.strawberry:litchie

To enable storage multipathing using the xe CLI
1.

Unplug all PBDs on the host:
xe pbd-unplug uuid=

Set the host's other-config:multipathing parameter:
xe host-param-set other-config:multipathing=true uuid=host_uuid

Set the host's other-config:multipathhandle parameter to dmp:
xe host-param-set other-config:multipathhandle=dmp uuid=host_uuid

If there are existing SRs on the host running in single path mode but that have multiple paths:
•

Migrate or suspend any running guests with virtual disks in affected the SRs

•

Unplug and re-plug the PBD of any affected SRs to reconnect them using multipathing:
xe pbd-plug uuid=

To disable multipathing, first unplug your VBDs, set the host other-config:multipathing
parameter to false and then replug your PBDs as described above. Do not modify the otherconfig:multipathhandle parameter as this will be done automatically.
Multipath support in XenServer is based on the device-mapper multipathd components. Activation and
deactivation of multipath nodes is handled automatically by the Storage Manager API. Unlike the standard dmmultipath tools in Linux, device mapper nodes are not automatically created for all LUNs on the system, and
it is only when LUNs are actively used by the storage management layer that new device mapper nodes are
81

provisioned. Therefore, it is unnecessary to use any of the dm-multipath CLI tools to query or refresh DM
table nodes in XenServer. Should it be necessary to query the status of device-mapper tables manually, or list
active device mapper multipath nodes on the system, use the mpathutil utility:
•

mpathutil list

•

mpathutil status
Note:
Due to incompatibilities with the integrated multipath management architecture, the
standard dm-multipath CLI utility should not be used with XenServer. Please use the
mpathutil CLI tool for querying the status of nodes on the host.
Note:
Multipath support in EqualLogic arrays does not encompass Storage IO multipathing in the
traditional sense of the term. Multipathing must be handled at the network/NIC bond level.
Refer to the EqualLogic documentation for information about configuring network failover
for EqualLogic SRs/LVMoISCSI SRs.

5.5. XenServer and IntelliCache
Note:
This feature is only supported when using XenServer with XenDesktop.
Using XenServer with IntelliCache makes hosted Virtual Desktop Infrastructure deployments more cost-effective
by enabling you to use a combination of shared storage and local storage. It is of particular benefit when many
Virtual Machines (VMs) all share a common OS image. The load on the storage array is reduced and performance
is enhanced. In addition, network traffic to and from shared storage is reduced as the local storage caches the
master image from shared storage.
IntelliCache works by caching data from a VMs parent VDI in local storage on the VM host. This local cache is then
populated as data is read from the parent VDI. When many VMs share a common parent VDI (for example by all
being based on a particular master image), the data pulled into the cache by a read from one VM can be used by
another VM. This means that further access to the master image on shared storage is not required.
A thin provisioned, local SR is an IntelliCache prerequisite. Thin Provisioning is a way of optimizing the utilization
of available storage. This approach allows you to make more use of local storage instead of shared storage. It relies
on on-demand allocation of blocks of data instead of the traditional method of pre-allocating all of the blocks.
Important:
Thin Provisioning changes the default local storage type of the host from LVM to EXT3. Thin
Provisioning must be enabled in order for XenDesktop local caching to work properly.
Thin Provisioning allows the administrator to present more storage space to the VMs connecting to the Storage
Repository (SR) than is actually available on the SR. There are no space guarantees, and allocation of a LUN does
not claim any data blocks until the VM writes data.
Warning:
Thin provisioned SRs may run out of physical space, as the VMs within can grow to consume
disk capacity on demand. IntelliCache VMs handle this condition by automatically falling back
to shared storage if the local SR cache is full. It is not recommended to mix traditional virtual
machines and IntelliCache VMs on the same SR, as intellicache VMs may grow quickly in size.

5.5.1. IntelliCache Deployment
IntelliCache must be enabled either during host installation or be enabled manually on a running host using the
CLI.
82

Citrix recommends that you use a high performance local storage device to ensure the fastest possible data
transfer such as a Solid State Disk or a high performance RAID array. Both data throughput and storage capacity
should be considered when sizing local disks. The shared storage type, used to host the source Virtual Disk Image
(VDI), must be NFS or EXT based.

5.5.1.1. Enabling on Host Installation
To enable IntelliCache during host installation, on the Virtual Machine Storage screen, select Enable thin
provisioning (Optimized storage for XenDesktop). This selects the host's local SR to be the one to be used for
the local caching of VM VDIs.

5.5.1.2. Converting an Existing Host to Use Thin Provisioning
To destroy an existing LVM based local SR, and replace it with a thin provisioned EXT3 based SR, enter the following
commands.
Warning:
These commands will destroy your existing local SR, and VMs on the SR will be permanently
deleted.
localsr=`xe sr-list type=lvm host= params=uuid --minimal`
echo localsr=$localsr
pbd=`xe pbd-list sr-uuid=$localsr params=uuid --minimal`
echo pbd=$pbd
xe pbd-unplug uuid=$pbd
xe pbd-destroy uuid=$pbd
xe sr-forget uuid=$localsr
sed -i "s/'lvm'/'ext'/" /etc/firstboot.d/data/default-storage.conf
rm -f /etc/firstboot.d/state/10-prepare-storage
rm -f /etc/firstboot.d/state/15-set-default-storage
service firstboot start
xe sr-list type=ext

To enable local caching, enter the following commands:
xe host-disable host=
localsr=`xe sr-list type=ext host= params=uuid --minimal`
xe host-enable-local-storage-caching host= sr-uuid=$localsr
xe host-enable host=

5.5.1.3. VM Boot Behavior
There are two options for the behavior of a VM VDI when the VM is booted:
1. Shared Desktop Mode
On VM boot, the VDI is reverted to the state it was in at the previous boot. All changes while the VM is running
will be lost when the VM is next booted.
Select this option if you plan to deliver standardized desktops to which users cannot make permanent
changes.
2. Private Desktop Mode
On VM boot, the VDI is in the state it was left in at the last shutdown.
Select this option if you plan to allow users to make permanent changes to their desktops.

5.5.1.3.1. VM Caching Behavior Settings
The VDI flag allow-caching dictates the caching behavior:
5.5.1.3.1.1. Shared Desktop Mode

For shared desktops, the on-boot option is set to reset and the allow-caching flag is set to true, new VM data
is written only to local storage – there will be no writes to shared storage. This means that the load on shared
storage is significantly reduced. However the VM cannot be migrated between hosts.
5.5.1.3.1.2. Private Desktop Mode

For private desktops, the on-boot option is set to persist and the allow-caching flag is set to true, new VM
data is written to both local and shared storage. Reads of cached data do not require I/O traffic to shared storage
so the load on shared storage is somewhat reduced. VM Migration to another host is permitted and the local
cache on the new host is populated as data is read.

5.5.1.4. Implementation Details and Troubleshooting
Q:

Is IntelliCache compatible with XenMotion and High Availability?

You can use XenMotion and High Availability with IntelliCache when virtual desktops are in Private mode,
that is when on-boot=persist
Warning:
A VM cannot be migrated if any of its VDIs have caching behavior flags set to onboot=reset and allow-caching=true. Migration attempts for VMs with these
properties will fail.

Where does the local cache live on the local disk?

The cache lives in a Storage Repository (SR). Each host has a configuration parameter (called local-cachesr) indicating which (local) SR is to be used for the cache files. Typically this will be a EXT type SR. When
you run VMs with IntelliCache, you will see files inside the SR with names .vhdcache. This is
the cache file for the VDI with the given UUID. These files are not displayed in XenCenter – the only way of
seeing them is by logging into dom0 and listing the contents of /var/run/sr-mount/

How do I specify a particular SR for use as the cache?

The host object field local-cache-sr refers to a local SR. You can view its value by running the following
command:
xe sr-list params=local-cache-sr,uuid,name-label

This field is set either:
•

after host installation, if the "Enable thin provisioning" option was selected in the host installer

•

by executing xe
host-enable-local-storage-caching
host=
sruuid=. This command requires the specified host to be disabled, VMs must be shut down if this
command is used.

The first option uses the EXT type local SR and is created during host installation. The second option, uses
the SR that is specified on the command-line.
Warning:
These steps are only necessary for users who have configured more than one local SR.
Q:

When is the local cache deleted?

A VDI cache file is only deleted when the VDI itself is deleted. The cache is reset when a VDI is attached to
a VM (for example on VM start). If the host is offline when the VDI is deleted, the SR synchronisation that
runs on startup will garbage collect the cache file.
Note:
The cache file is not deleted from the host when a VM is migrated to a different host or shut
down.

5.6. Storage Read Caching
Note:
Storage Read Caching is available for XenServer Enterprise Edition customers or those who
have access to XenServer through their XenDesktop/XenApp entitlement. To learn more
about XenServer editions, and to find out how to upgrade, visit the Citrix website here. For
detailed information on Licensing - refer to XenServer 7.0 Licensing FAQ.
Read caching improves a VMs disk performance as, after the initial read from external disk, data is cached within
the host's free memory. It greatly improves performance in situations where many VMs are cloned off a single
base VM for example, in XenDesktop environment Machine Creation Service (MCS) environments, as it will
drastically reduce the number of blocks read from disk.
This performance improvement can be seen whenever data needs to be read from disk more than once, since
it gets cached in memory. This is most noticeable in the degradation of service that occurs during heavy I/O
situations. For example, when a significant number of end users boot up within a very narrow time frame (boot
storm), or when a significant number of VMs are scheduled to run malware scans at the same time (anti-virus
storms). Read caching is enabled by default if you have the appropriate licence type.

5.6.1. Enabling and Disabling
For file-based SRs, such as NFS and EXT3 SR types, read-caching is enabled by default. It is disabled for all other
SRs.
To disable read caching for a specific SR, enter:
xe sr-param-set uuid= other-config:o_direct=true

5.6.2. Limitations
•

Read caching is available only for NFS and EXT3 SRs. It is not available for other SR Types.

•

Read caching only applies to read-only VDIs and VDI parents; these exist where VMs are created from ‘Fast
Clone’ or snap-shotted disks. The greatest performance improvements will be seen when many VMs are
cloned from a single ‘golden’ image.

•

Performance improvements are dependent on the amount of free memory available in the host's Control
Domain (dom0). Increasing the amount of memory to dom0, will allow more memory to be allocated to the
read-cache. Refer to CTX134951 - How to Configure dom0 Memory in XenServer 6.1 and Later for information
on how to configure dom0 memory.

5.6.3. Comparison with IntelliCache
IntelliCache and memory based read caching are to some regards complementary. IntelliCache not only caches
on a different tier, but it also caches writes in addition to reads. The major difference is that IntelliCache works
by caching reads from the network onto a local disk, while in-memory read caching caches reads from either
network or disk into host memory. The advantage of in-memory read caching, is that memory is still an order
of magnitude faster than a solid-state disk (SSD), so performance in boot storms and other heavy I/O situations
should be improved.
It is possible for both read-caching and IntelliCache to be enabled simultaneously; in this case reads from the
network are cached by IntelliCache to a local disk, and reads from that local disk are cached in memory with
read caching.

5.6.4. To Set the Read Cache Size
The read cache performance can be optimized, by giving more memory to XenServer's control domain (dom0).
Important:
For optimization, the read cache size should be set on ALL hosts in the pool individually. Any
subsequent changes to the size of the read cache must also be set on all hosts in the pool.
On the XenServer host, open a local shell and log on as root.
To set the size of the read cache, run the following command:
/opt/xensource/libexec/xen-cmdline --set-xen dom0_mem=M,max:M

Both the initial and maximum values should be set to the same value, for example, to set dom0 memory to
2048MB:
/opt/xensource/libexec/xen-cmdline --set-xen dom0_mem=20480M,max:20480M

Important:
You must reboot all hosts after making any changes to the read cache size.

5.6.4.1. How to View the Current dom0 Memory Allocation
To view the current dom0 memory settings enter:
free -m

The output of free -m shows the current dom0 memory settings. The value may be less than expected due to
various overheads. The example table below shows the output from a host with dom0 set to 752MB

Mem

Total

Used

Free

Shared

Buffer

Cached

594

486

108

149

-/+ buffers/
cache
Swap

511

258

336

462

What Range of Values Can be Used?
As the XenServer 7.0 Control Domain (dom0) is 64-bit, large values can be used, for example 32768MB. Citrix
recommends that you do NOT set the initial value to be lower than 752MB, as doing so may cause the host to
fail to boot.

5.6.4.2. XenCenter Display Notes
Administrators should note that the entire host's memory can be considered to comprised of the Xen hypervisor,
dom0, VMs and free memory. While dom0 and VM memory is usually of a fixed size, the Xen hypervisor uses a
variable amount of memory. This is dependent on a number of factors including the number of VMs running on
the host at any time and how those VMs are configured. It is not possible to limit the amount of memory that
Xen uses, as it would then be possible for Xen to run out of memory, and could prevent new VMs from starting
even when the host had free memory.
To view the memory allocated to a host, in XenCenter select the host, and then click the Memory tab.
The XenServer field displays the sum of the memory allocated to dom0 and Xen memory. Therefore the amount
of memory displayed may be higher than specified by the administrator and its size will vary when starting and
stopping VMs, even when the administrator has set a fixed size for dom0.

5.7. Managing Storage Repositories
This section covers various operations required in the ongoing management of Storage Repositories (SRs),
including Live VDI Migration.

5.7.1. Removing SRs
A Storage Repository (SR) can be removed either temporarily or permanently.
•

Detach: breaks the association between the storage device and the pool or host, (PBD Unplug) and the SR (and
its VDIs) becomes inaccessible. The contents of the VDIs and the meta-information used by VMs to access
the VDIs are preserved. Detach can be used when you need to temporarily take a SR offline, for example, for
maintenance. A detached SR can subsequently be reattached.

•

Forget: preserves the contents of the SR on the physical disk, but the information used to connect VMs to
the VDIs it contains is permanently deleted (PBD and VBD Unplug). For example, allows you to re-attach the
SR, to another XenServer host, without removing any of the SR contents.

•

Destroy: deletes the contents of the SR from the physical disk.

In the case of Destroy or Forget, the PBD connected to the SR must be unplugged from the host.
1. Unplug the PBD to detach the SR from the corresponding XenServer host:
xe pbd-unplug uuid=

2. To destroy the SR - deletes the SR and corresponding PBD from the XenServer host database and deletes the
SR contents from the physical disk:
xe sr-destroy uuid=

3. To forget the SR - removes the SR and corresponding PBD from the XenServer host database but leaves the
actual SR contents intact on the physical media:
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xe sr-forget uuid=

Note:
It might take some time for the software object corresponding to the SR to be garbage
collected.

5.7.2. Introducing an SR
To reintroduce a previously forgotten SR, you will need to create a PBD, and manually plug the PBD to the
appropriate XenServer hosts to activate the SR.
The following example introduces a SR of type lvmoiscsi.
1. Probe the existing SR to determine its UUID:
xe sr-probe type=lvmoiscsi device-config:target=<192.168.1.10> \
device-config:targetIQN=<192.168.1.10:filer1> \
device-config:SCSIid=<149455400000000000000000002000000b70200000f000000>

2. Introduce the existing SR UUID returned from the sr-probe command. The UUID of the new SR is returned:
xe sr-introduce content-type=user name-label=<"Example Shared LVM over iSCSI SR">
shared=true uuid= type=lvmoiscsi

3. Create a PBD to accompany the SR. The UUID of the new PBD is returned:
xe pbd-create type=lvmoiscsi host-uuid= sr-uuid= \
device-config:target=<192.168.0.1> \
device-config:targetIQN=<192.168.1.10:filer1> \
device-config:SCSIid=<149455400000000000000000002000000b70200000f000000>

4. Plug the PBD to attach the SR:
xe pbd-plug uuid=

5. Verify the status of the PBD plug. If successful the currently-attached property will be true:
xe pbd-list sr-uuid=

Note:
Steps 3 through 5 must be performed for each host in the resource pool, and can also be
performed using the Repair Storage Repository function in XenCenter.

5.7.3. Live LUN Expansion
In order to fulfill capacity requirements, you may need to add capacity to the storage array to increase the size
of the LUN provisioned to the XenServer host. Live LUN Expansion allows to you to increase the size of the LUN
without any VM downtime.
After you have added more capacity to your storage array, enter,
xe sr-scan sr-uuid=

This command rescans the SR, and any extra capacity is added and made available.
This operation is also available in XenCenter; select the SR to resize, and then click Rescan. For more information,
press F1 to display the XenCenter Online Help.
Note:
In previous versions of XenServer explicit commands were required to resize the physical
volume group of iSCSI and HBA SRs. These commands are no longer required.

Warning:
It is not possible to shrink or truncate LUNs. Reducing the LUN size on the storage array may/
can lead to data loss.

5.7.4. Live VDI Migration
Live VDI migration allows the administrator to relocate the VMs Virtual Disk Image (VDI) without shutting down
the VM. This enables administrative operations such as:
•

Moving a VM from cheap local storage to fast, resilient, array-backed storage.

•

Moving a VM from a development to production environment.

•

Moving between tiers of storage when a VM is limited by storage capacity.

•

Performing storage array upgrades.

5.7.4.1. Limitations and Caveats
Live VDI Migration is subject to the following limitations and caveats
•

There must be sufficient disk space available on the target repository.

•

VDIs with more than one snapshot cannot be migrated.

5.7.4.2. To Move Virtual Disks using XenCenter
1. In the Resources pane, select the SR where the Virtual Disk is currently stored and then click the Storage tab.
2. In the Virtual Disks list, select the Virtual Disk that you would like to move, and then click Move.
3. In the Move Virtual Disk dialog box, select the target SR that you would like to move the VDI to.
Note:
Make sure that the SR has sufficient space for another virtual disk: the available space is
shown in the list of available SRs.
4. Click Move to move the virtual disk.
For xe cli reference, refer to Section A.4.23.9, “vdi-pool-migrate”.

5.7.5. Cold VDI Migration between SRs (Offline Migration)
VDIs associated with a VM can be copied from one SR to another to accommodate maintenance requirements
or tiered storage configurations. XenCenter provides the ability to copy a VM and all of its VDIs to the same or a
different SR, and a combination of XenCenter and the xe CLI can be used to copy individual VDIs.
For xe cli reference, refer to Section A.4.26.25, “vm-migrate”.

5.7.5.1. Copying All of a VMs VDIs to a Different SR
The XenCenter Copy VM function creates copies of all VDIs for a selected VM on the same or a different SR. The
source VM and VDIs are not affected by default. To move the VM to the selected SR rather than creating a copy,
select the Remove original VM option in the Copy Virtual Machine dialog box.
1. Shutdown the VM.
2. Within XenCenter select the VM and then select the VM > Copy VM menu option.
3. Select the desired target SR.

5.7.5.2. Copying Individual VDIs to a Different SR
A combination of the xe CLI and XenCenter can be used to copy individual VDIs between SRs.
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1. Shutdown the VM.
2. Use the xe CLI to identify the UUIDs of the VDIs to be moved. If the VM has a DVD drive its vdi-uuid will
be listed as and can be ignored.
xe vbd-list vm-uuid=

Note:
The vbd-list command displays both the VBD and VDI UUIDs. Be sure to record the VDI UUIDs
rather than the VBD UUIDs.
3. In XenCenter select the VM Storage tab. For each VDI to be moved, select the VDI and click the Detach button.
This step can also be done using the vbd-destroy command.
Note:
If you use the vbd-destroy command to detach the VDI UUIDs, be sure to first check if
the VBD has the parameter other-config:owner set to true. If so, set it to false.
Issuing the vbd-destroy command with other-config:owner=true will also destroy
the associated VDI.
4. Use the vdi-copy command to copy each of the VM VDIs to be moved to the desired SR.
xe vdi-copy uuid= sr-uuid=

5. Within XenCenter select the VM Storage tab. Click the Attach button and select the VDIs from the new SR.
This step can also be done use the vbd-create command.
6. To delete the original VDIs, within XenCenter select the Storage tab of the original SR. The original VDIs will
be listed with an empty value for the VM field and can be deleted with the Delete button.

5.7.6. Converting Local Fibre Channel SRs to Shared SRs
Use the xe CLI and the XenCenter Repair Storage Repository feature to convert a local FC SR to a shared FC SR:
1. Upgrade all hosts in the resource pool to XenServer 7.0.
2. Ensure all hosts in the pool have the SR's LUN zoned appropriately. See Section 5.3.2, “Probing an SR” for
details on using the sr-probe command to verify the LUN is present on each host.
3. Convert the SR to shared:
xe sr-param-set shared=true uuid=

4. Within XenCenter the SR is moved from the host level to the pool level, indicating that it is now shared. The
SR will be marked with a red exclamation mark to show that it is not currently plugged on all hosts in the pool.
5. Select the SR and then select the Storage > Repair Storage Repository menu option.
6. Click Repair to create and plug a PBD for each host in the pool.

5.7.7. Reclaiming Space for Block-Based Storage on the Backing Array Using Discard
Space reclamation allows you to free up unused blocks (for example, deleted VDIs in an SR) on a LUN that has
been thinly-provisioned by the storage array. Once released, the reclaimed space can then be reused by the array.
Note:
This functionality is only available on a subset of storage arrays. Please refer to the XenServer
Hardware Compatibility List and your storage vendor specific documentation to determine
if your array supports this functionality, and whether it needs a specific configuration for
operation.
To reclaim the space using XenCenter:
90

1. Select the Infrastructure view, and the click on the host or pool connected to the SR.
2. Click the Storage tab.
3. Select the SR from the list, and click Reclaim freed space.
4. To confirm the operation, click Yes.
5. Click Notifications and then Events to view the status of the operation.
For more information, in XenCenter press F1 to access the Online Help.
Note:
•

This is a XenCenter only operation.

•

The operation is only available for LVM-based SRs that are based on thinly-provisioned
LUNs on the array.

•

Local SSDs will also benefit from space reclamation.

•

It is not required for file-based SRs (such as NFS/Ext3); the Reclaim Freed Space button
is not available in XenCenter for these SR types.

•

Space Reclaim is an intensive operation and can lead to a degradation in storage array
performance. Therefore it should only be initiated when space reclamation is required on
the array. Citrix recommends that you schedule this work outside of peak array demand
hours.

5.7.8. Automatically Reclaiming Space When Deleting Snapshots
When deleting snapshots with XenServer 7.0, all allocated space allocated on LVM-based SRs is reclaimed
automatically and a VM reboot is not required; this is referred to as Online Coalescing.
Note:
Online Coalescing only applies to LVM-based SRs (LVM, LVMoISCSI, and LVMoHBA), it does
not apply to EXT or NFS SRs, whose behavior remains unchanged.
In certain cases, automated space reclamation may be unable to proceed, in these cases it is
advisable to use the Off-Line Coalesce tool:
•

Under conditions where a VM I/O throughput is considerable

•

In conditions where space is not being reclaimed after a period of time

Note:
Running the Off Line Coalesce tool will incur some downtime for the VM, due to the suspend/
resume operations performed.
Before running the tool, delete any snapshots and clones you no longer want; the script
will reclaim as much space as possible given the remaining snapshots/clones. If you want to
reclaim all space, delete all snapshots and clones.
All VM disks must be either on shared or local storage for a single host. VMs with disks in both
types of storage cannot be coalesced.

5.7.8.1. Reclaiming Space Using the Off Line Coalesce Tool
Note:
Online Coalescing only applies to LVM-based SRs (LVM, LVMoISCSI, and LVMoHBA), it does
not apply to EXT or NFS SRs, whose behavior remains unchanged.
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Using XenCenter, enable hidden objects (View menu -> Hidden objects). In the Resource pane, select the VM for
which you want to obtain the UUID. The UUID will displayed in the General tab.
In the Resource pane, select the resource pool master host (the first host in the list). The UUID will be displayed
in the General tab. If you are not using a resource pool, select the VM host.
1. Open a console on the host and run the following command:
xe host-call-plugin host-uuid= \
plugin=coalesce-leaf fn=leaf-coalesce args:vm_uuid=

For example, if the VM UUID is 9bad4022-2c2d-dee6-abf5-1b6195b1dad5 and the host UUID is b8722062de95-4d95-9baa-a5fe343898ea you would run this command:
xe host-call-plugin host-uuid=b8722062-de95-4d95-9baa-a5fe343898ea \
plugin=coalesce-leaf fn=leaf-coalesce args:vm_uuid=9bad4022-2c2d-dee6-abf5-1b6195b1dad5

2. This command suspends the VM (unless it is already powered down), initiates the space reclamation process,
and then resumes the VM.
Note:
Citrix recommends that, before executing the off-line coalesce tool, you shutdown or suspend
the VM manually (using either XenCenter or the XenServer CLI). If you execute the coalesce
tool on a VM that is running, the tool automatically suspends the VM, performs the required
VDI coalesce operation(s), and resumes the VM.
If the Virtual Disk Images (VDIs) to be coalesced are on shared storage, you must execute the
off-line coalesce tool on the pool master.
If the VDIs to be coalesced are on local storage, you must execute the off-line coalesce tool
on the server to which the local storage is attached.

5.7.9. Adjusting the Disk IO Scheduler
For general performance, the default disk scheduler noop is applied on all new SR types. The noop scheduler
provides the fairest performance for competing VMs accessing the same device. To apply disk QoS (see
Section 5.7.10, “Virtual Disk QoS Settings”) it is necessary to override the default setting and assign the cfq disk
scheduler to the SR. The corresponding PBD must be unplugged and re-plugged for the scheduler parameter to
take effect. The disk scheduler can be adjusted using the following command:
xe sr-param-set other-config:scheduler=noop|cfq|anticipatory|deadline \
uuid=

Note:
This will not effect EqualLogic, NetApp or NFS storage.

5.7.10. Virtual Disk QoS Settings
Virtual disks have an optional I/O priority Quality of Service (QoS) setting. This setting can be applied to existing
virtual disks using the xe CLI as described in this section.
In the shared SR case, where multiple hosts are accessing the same LUN, the QoS setting is applied to VBDs
accessing the LUN from the same host. QoS is not applied across hosts in the pool.
Before configuring any QoS parameters for a VBD, ensure that the disk scheduler for the SR has been set
appropriately. See Section 5.7.9, “Adjusting the Disk IO Scheduler” for details on how to adjust the scheduler. The
scheduler parameter must be set to cfq on the SR for which the QoS is desired.
Note:
92

Remember to set the scheduler to cfq on the SR, and to ensure that the PBD has been replugged in order for the scheduler change to take effect.
The first parameter is qos_algorithm_type. This parameter needs to be set to the value ionice, which is
the only type of QoS algorithm supported for virtual disks in this release.
The QoS parameters themselves are set with key/value pairs assigned to the qos_algorithm_param
parameter. For virtual disks, qos_algorithm_param takes a sched key, and depending on the value, also
requires a class key.
Possible values of qos_algorithm_param:sched are:
•

sched=rt or sched=real-time sets the QoS scheduling parameter to real time priority, which requires
a class parameter to set a value

•

sched=idle sets the QoS scheduling parameter to idle priority, which requires no class parameter to set
any value

•

sched= sets the QoS scheduling parameter to best effort priority, which requires a class
parameter to set a value

The possible values for class are:
•

One of the following keywords: highest, high, normal, low, lowest

•

an integer between 0 and 7, where 7 is the highest priority and 0 is the lowest, so that, for example, I/O
requests with a priority of 5, will be given priority over I/O requests with a priority of 2.

To enable the disk QoS settings, you also need to set the other-config:scheduler to cfq and replug
PBDs for the storage in question.
For example, the following CLI commands set the virtual disk's VBD to use real time priority 5:
xe
xe
xe
xe
xe

vbd-param-set uuid= qos_algorithm_type=ionice
vbd-param-set uuid= qos_algorithm_params:sched=rt
vbd-param-set uuid= qos_algorithm_params:class=5
sr-param-set uuid= other-config:scheduler=cfq
pbd-plug uuid=

Chapter 6. Configuring VM Memory
When a VM is first created, it is allocated a fixed amount of memory. To improve the utilisation of physical memory
in your XenServer environment, you can use Dynamic Memory Control (DMC), a memory management feature
that enables dynamic reallocation of memory between VMs.
XenCenter provides a graphical display of memory usage in its Memory tab. This is described in the XenCenter
Help.
Dynamic Memory Control (DMC) provides the following benefits:
•

Memory can be added or removed without restart thus providing a more seamless experience to the user.

•

When servers are full, DMC allows you to start more VMs on these servers, reducing the amount of memory
allocated to the running VMs proportionally.

6.1. What is Dynamic Memory Control (DMC)?
XenServer DMC works by automatically adjusting the memory of running VMs, keeping the amount of memory
allocated to each VM between specified minimum and maximum memory values, guaranteeing performance
and permitting greater density of VMs per server.
Without DMC, when a server is full, starting further VMs will fail with "out of memory" errors: to reduce the
existing VM memory allocation and make room for more VMs you must edit each VM's memory allocation and
then reboot the VM. With DMC enabled, even when the server is full, XenServer will attempt to reclaim memory
by automatically reducing the current memory allocation of running VMs within their defined memory ranges.

6.1.1. The Concept of Dynamic Range
For each VM the administrator can set a dynamic memory range – this is the range within which memory can
be added/removed from the VM without requiring a reboot. When a VM is running the administrator can adjust
the dynamic range. XenServer always guarantees to keep the amount of memory allocated to the VM within
the dynamic range; therefore adjusting it while the VM is running may cause XenServer to adjust the amount of
memory allocated to the VM. (The most extreme case is where the administrator sets the dynamic min/max to
the same value, thus forcing XenServer to ensure that this amount of memory is allocated to the VM.) If new
VMs are required to start on "full" servers, running VMs have their memory ‘squeezed’ to start new ones. The
required extra memory is obtained by squeezing the existing running VMs proportionally within their pre-defined
dynamic ranges
DMC allows you to configure dynamic minimum and maximum memory levels – creating a Dynamic Memory
Range (DMR) that the VM will operate in.
•

Dynamic Minimum Memory: A lower memory limit that you assign to the VM.

•

Dynamic Higher Limit: An upper memory limit that you assign to the VM.

For example, if the Dynamic Minimum Memory was set at 512 MB and the Dynamic Maximum Memory was set
at 1024 MB this would give the VM a Dynamic Memory Range (DMR) of 512 - 1024 MB, within which, it would
operate. With DMC, XenServer guarantees at all times to assign each VM memory within its specified DMR.

6.1.2. The Concept of Static Range
Many Operating Systems that XenServer supports do not fully ‘understand’ the notion of dynamically adding or
removing memory. As a result, XenServer must declare the maximum amount of memory that a VM will ever
be asked to consume at the time that it boots. (This allows the guest operating system to size its page tables
and other memory management structures accordingly.) This introduces the concept of a static memory range
within XenServer. The static memory range cannot be adjusted while the VM is running. For a particular boot,
the dynamic range is constrained such as to be always contained within this static range. Note that the static
94

minimum (the lower bound of the static range) is there to protect the administrator and is set to the lowest
amount of memory that the OS can run with on XenServer.
Note:
Citrix advises not to change the static minimum level as this is set at the supported level per
operating system – refer to the memory constraints table for more details.
By setting a static maximum level, higher than a dynamic max, means that in the future, if
you need to allocate more memory to a VM, you can do so without requiring a reboot.

6.1.3. DMC Behavior
Automatic VM squeezing
•

If DMC is not enabled, when hosts are full, new VM starts fail with ‘out of memory’ errors.

•

If DMC is enabled, even when hosts are full, XenServer will attempt to reclaim memory (by reducing the
memory allocation of running VMs within their defined dynamic ranges). In this way running VMs are
squeezed proportionally at the same distance between the dynamic minimum and dynamic maximum for
all VMs on the host

When DMC is enabled
•

When the host's memory is plentiful - All running VMs will receive their Dynamic Maximum Memory level

•

When the host's memory is scarce - All running VMs will receive their Dynamic Minimum Memory level.

When you are configuring DMC, remember that allocating only a small amount of memory to a VM can negatively
impact it. For example, allocating too little memory:
•

Using Dynamic Memory Control to reduce the amount of physical memory available to a VM may cause it to
boot slowly. Likewise, if you allocate too little memory to a VM, it may start extremely slowly.

•

Setting the dynamic memory minimum for a VM too low may result in poor performance or stability problems
when the VM is starting.

6.1.4. How Does DMC Work?
Using DMC, it is possible to operate a guest virtual machine in one of two modes:
1. Target Mode: The administrator specifies a memory target for the guest.XenServer adjusts the guest's
memory allocation to meet the target. Specifying a target is particularly useful in virtual server environments,
and in any situation where you know exactly how much memory you want a guest to use. XenServer will
adjust the guest's memory allocation to meet the target you specify.
2. Dynamic Range Mode: The administrator specifies a dynamic memory range for the guest; XenServer chooses
a target from within the range and adjusts the guest's memory allocation to meet the target. Specifying a
dynamic range is particularly useful in virtual desktop environments, and in any situation where you want
XenServer to repartition host memory dynamically in response to changing numbers of guests, or changing
host memory pressure. XenServer chooses a target from within the range and adjusts the guest's memory
allocation to meet the target.
Note:
It is possible to change between target mode and dynamic range mode at any time for any
running guest. Simply specify a new target, or a new dynamic range, and XenServer takes
care of the rest.

6.1.5. Memory Constraints
XenServer allows administrators to use all memory control operations with any guest operating system. However,
XenServer enforces the following memory property ordering constraint for all guests:
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0 ≤ memory-static-min ≤ memory-dynamic-min ≤ memory-dynamic-max ≤ memorystatic-max
XenServer allows administrators to change guest memory properties to any values that satisfy this constraint,
subject to validation checks. However, in addition to the above constraint, Citrix supports only certain guest
memory configurations for each supported operating system. The range of supported configurations depends on
the guest operating system in use. XenServer does not prevent administrators from configuring guests to exceed
the supported limit. However, customers are strongly advised to keep memory properties within the supported
limits to avoid performance or stability problems. Refer to the XenServer Virtual Machine User's Guide for detailed
guidelines on the minimum and maximum memory limits for each supported operating system.
Warning:
When configuring guest memory, Citrix advises NOT to exceed the maximum amount of
physical memory addressable by your operating system. Setting a memory maximum that
is greater than the operating system supported limit, may lead to stability problems within
your guest.
In addition, customers should also note that the dynamic minimum should be greater than or
equal to a quarter of the static maximum for all supported operating systems. Reducing the
lower limit below the dynamic minimum could also lead to stability problems. Administrators
are encouraged to calibrate the sizes of their VMs carefully, and make sure that their working
set of applications functions reliably at dynamic-minimum.

6.2. xe CLI Commands
6.2.1. Display the Static Memory Properties of a VM
1. Find the uuid of the required VM:
xe vm-list

2. Note the uuid, and then run the command param-name=memory-static
xe vm-param-get uuid= param-name=memory-static-{min,max}

For example, the following displays the static maximum memory properties for the VM with the uuid
beginning ec77:
xe vm-param-get uuid= \
ec77a893-bff2-aa5c-7ef2-9c3acf0f83c0 \
param-name=memory-static-max;
268435456

This shows that the static maximum memory for this VM is 268435456 bytes (256MB).

6.2.2. Display the Dynamic Memory Properties of a VM
To display the dynamic memory properties, follow the procedure as above but use the command paramname=memory-dynamic:
1. Find the uuid of the required VM:
xe vm-list

2. Note the uuid, and then run the command param-name=memory-dynamic:
xe vm-param-get uuid= param-name=memory-dynamic-{min,max}

For example, the following displays the dynamic maximum memory properties for the VM with uuid beginning
ec77
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xe vm-param-get uuid= \
ec77a893-bff2-aa5c-7ef2-9c3acf0f83c0 \
param-name=memory-dynamic-max;
134217728

This shows that the dynamic maximum memory for this VM is 134217728 bytes (128MB).

6.2.3. Updating Memory Properties
Warning:
It is essential that you use the correct ordering when setting the static/dynamic minimum/
maximum parameters. In addition you must not invalidate the following constraint:
0 ≤ memory-static-min ≤ memory-dynamic-min ≤ memory-dynamicmax ≤ memory-static-max
Update the static memory range of a virtual machine:
xe vm-memory-static-range-set uuid= min=max=

Update the dynamic memory range of a virtual machine:
xe vm-memory-dynamic-range-set \
uuid= min= \
max=

Specifying a target is particularly useful in virtual server environments, and in any situation where you know
exactly how much memory you want a guest to use. XenServer will adjust the guest's memory allocation to meet
the target you specify. For example:
xe vm-target-set target= vm=

Update all memory limits (static and dynamic) of a virtual machine:
xe vm-memory-limits-set \
uuid= \
static-min= \
dynamic-min= \
dynamic-max= static-max=

Note:
•

To allocate a specific amount memory to a VM that won't change, set the Dynamic
Maximum and Dynamic Minimum to the same value.

•

You cannot increase the dynamic memory of a VM beyond the static maximum.

•

To alter the static maximum of a VM – you must shut down the VM.

6.2.4. Update Individual Memory Properties
Warning:
Citrix advises not to change the static minimum level as this is set at the supported level per
operating system – refer to the memory constraints table for more details.
Update the dynamic memory properties of a VM.
1. Find the uuid of the required VM:
xe vm-list

2. Note the uuid, and then use the command memory-dynamic-{min,max}=
xe vm-param-set uuid=memory-dynamic-{min,max}=

The following example changes the dynamic maximum to 128MB:
xe vm-param-set uuid=ec77a893-bff2-aa5c-7ef2-9c3acf0f83c0 memory-dynamic-max=128MiB

6.3. Upgrade Issues
After upgrading from Citrix XenServer 5.5, XenServer sets all VMs memory so that the dynamic minimum is equal
to the dynamic maximum.

Chapter 7. XenServer Memory Usage
Two components contribute to the memory footprint of a XenServer host. Firstly, there is the memory consumed
by the Xen hypervisor itself; secondly there is the memory consumed by the Control Domain of the host. Also
known as 'Domain0', or 'dom0', the Control Domain is a secure, privileged Linux VM that runs the XenServer
management toolstack (xapi). Besides providing XenServer management functions, the Control Domain also runs
the driver stack that provides user created VM access to physical devices.

7.1. Control Domain Memory
The amount of memory allocated to the Control Domain is adjusted automatically and is based on the amount
of physical memory on the physical host:
Host Memory (GB)

Control Domain Memory Allocated (MB)

20 - 24

752

24 - 48

2048

48 - 64

3072

64 - 1024

4096

Note:
The amount of memory reported in the XenServer field in XenCenter may exceed these
values. This is because the amount reported includes the memory used by the Control Domain
(dom0), the Xen hypervisor itself, and the crash kernel. The amount of memory used by the
hypervisor will be larger for hosts with more memory.

7.1.1. Changing the Amount of Memory Allocated to the Control Domain
On hosts with smaller amounts of memory (for example, less than 16GB), you may wish to reduce the memory
allocated to the Control Domain to below the default of 752MB. However, Citrix recommends that you do not
reduce the dom0 memory below 400MB.
1. On the XenServer host, open a local shell and login as root.
2. Enter the following:
/opt/xensource/libexec/xen-cmdline --set-xen dom0_mem=M,max:M

Where represents the amount of memory, in megabytes, to be allocated to dom0.
3. Restart the XenServer host using XenCenter or the reboot command on the xs console.
When the host has rebooted, on the xs console, run the free command to verify the new memory settings.
Warning:
Increasing the amount of Control Domain memory will result in less memory being available
to VMs.
The amount of memory allocated to the Control Domain can be increased beyond the amount
shown above. However, this should only ever be carried out under the guidance of Citrix
Support.
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7.1.2. How Much Memory is Available to VMs
To find out how much host memory is actually available to be assigned to VMs, find the value of the memoryfree field of the host, and then enter the vm-compute-maximum-memory command to get the actual amount
of free memory that can be allocated to the VM, for example:
xe host-list uuid= params=memory-free
xe vm-compute-maximum-memory vm= total=

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Chapter 8. Disaster Recovery and Backup
The XenServer Disaster Recovery (DR) feature is designed to allow you to recover virtual machines (VMs) and
vApps from a catastrophic failure of hardware which disables or destroys a whole pool or site. For protection
against single server failures, see Section 3.9, “High Availability”
Note:
You must be logged in as root or have the role of Pool Operator or higher to use this feature.

8.1. Understanding XenServer DR
XenServer DR works by storing all the information needed to recover your business-critical VMs and vApps on
storage repositories (SRs) that are then replicated from your primary (production) environment to a backup
environment. When a protected pool at your primary site goes down, the VMs and vApps in that pool can be
recovered from the replicated storage and recreated on a secondary (DR) site, with minimal application or user
downtime.
In the event of a disaster, the Disaster Recovery wizard in XenCenter can be used to interrogate this storage and
import chosen VMs and vApps into a recovery pool. Once the VMs are running in the recovery pool, the recovery
pool metadata is also replicated to allow any changes to VM settings to be populated back to the primary pool,
should the primary pool be recovered. If the XenCenter wizard finds information for the same VM present in two
or more places (for example, storage from the primary site, storage from the disaster recovery site and also in
the pool that the data is to be imported into) then the wizard will ensure that only the most recent information
per Virtual Machine is used.
The Disaster Recovery feature can be used both with XenCenter and the xe CLI. See Section A.4.6, “Disaster
Recovery (DR) Commands” for details on these commands.
Tip:
You can also use the Disaster Recovery wizard to run test failovers for non-disruptive testing
of your disaster recovery system. In a test failover, all the steps are the same as for failover,
but the VMs and vApps are not started up after they have been recovered to the DR site,
and cleanup is performed when the test is finished to remove all VMs, vApps and storage
recreated on the DR site.
XenServer VMs consist of two components:
•

Virtual disks that are being used by the VM, stored on configured storage repositories (SRs) in the pool where
the VMs are located.

•

Metadata describing the VM environment. This is all the information needed to recreate the VM if the original
VM is unavailable or corrupted. Most metadata configuration data is written when the VM is created and is
updated only when you make changes to the VM configuration. For VMs in a pool, a copy of this metadata
is stored on every server in the pool.

In a DR environment, VMs are recreated on a secondary (DR) site from the pool metadata – configuration
information about all the VMs and vApps in the pool. The metadata for each VM includes its name, description
and Universal Unique Identifier (UUID), and its memory, virtual CPU and networking and storage configuration.
It also includes the VM startup options – start order, delay interval and HA restart priority – which are used when
restarting the VM in an HA or DR environment. For example, when recovering VMs during disaster recovery, the
VMs within a vApp will be restarted in the DR pool in the order specified in the VM metadata, and with the
specified delay intervals.

8.2. DR Infrastructure Requirements
To use XenServer DR, the appropriate DR infrastructure needs to be set up at both the primary and secondary
sites:
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•

The storage used for both the pool metadata and the virtual disks used by the VMs must be replicated from
your primary (production) environment to a backup environment. Storage replication, for example using
mirroring, is best handled by your storage solution, and will vary from device to device.

•

Once VMs and vApps have been recovered to a pool on your DR site and are up and running, the SRs
containing the DR pool metadata and virtual disks must also be replicated to allow the recovered VMs and
vApps to be restored back to the primary site (failed back) once the primary site is back online.

•

The hardware infrastructure at your DR site does not have to match the primary site, but the XenServer
environment must be at the same release and patch level, and sufficient resources should be configured in
the target pool to allow all the failed over VMs to be recreated and started.
Warning:
The Disaster Recovery wizard does not control any Storage Array functionality.
Users of the Disaster Recovery feature must ensure that the metadata storage is, in some
way replicated between the two sites. Some Storage Arrays contain “Mirroring” features to
achieve the replication automatically, if these features are used then it is essential that the
mirror functionality is disabled (“mirror is broken”) before Virtual Machines are restarted on
the recovery site.

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8.3. Deployment Considerations
Please review the following steps before enabling Disaster Recovery.

8.3.1. Steps to Take Before a Disaster
The following section describes the steps to take before disaster.
•

Configure your VMs and vApps.

•

Note how your VMs and vApps are mapped to SRs, and the SRs to LUNs. Take particular care with the naming
of the name_label and name_description fields. Recovering VMs and vApps from replicated storage
will be easier if your SRs are named in a way that captures how your VMs and vApps are mapped to SRs,
and the SRs to LUNs.

•

Arrange replication of the LUNs.

•

Enable pool metadata replication to one or more SRs on these LUNs.

8.3.2. Steps to Take After a Disaster
The following section describes the steps to take after a disaster has occurred.
•

Break any existing storage mirrors so that the recovery site has read/write access to the shared storage.

•

Ensure that the LUNs you wish to recover VM data from are not attached to any other pool, or corruption
may occur.

•

If you want to protect the recovery site from a disaster, you must enable pool metadata replication to one
or more SRs on the recovery site.

8.3.3. Steps to Take After a Recovery
The following section describes the steps to take after a successful recovery of data.
•

Re-synchronise any storage mirrors.

•

On the recovery site, shutdown down cleanly the VMs or vApps that you want to move back to the primary
site.

•

On the primary site, follow the same procedure as for the failover above, to failback selected VMs or vApps
to the primary

•

To protect the primary site against future disaster - you must re-enable pool metadata replication to one or
more SRs on the replicated LUNs.

8.4. Enabling Disaster Recovery in XenCenter
This section describes how to enable Disaster Recovery in XenCenter. Use the Configure DR dialog box to identify
storage repositories (SRs) where the metadata for a pool – configuration information about all the VMs and
vApps in the pool – will be stored. This metadata will be updated whenever you make changes to VM or vApp
configuration within the pool.
Note:
Disaster Recovery can only be enabled when using LVM over HBA or LVM over iSCSI. A small
amount of space will be required on this storage for a new LUN which will contain the pool
recovery information.
To do this:
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1. On the primary site, select the pool that you want to protect. From the Pool menu, point to Disaster Recovery,
and then click Configure.
2. Select up to 8 SRs where the pool metadata will be stored. A small amount of space will be required on this
storage for a new LUN which will contain the pool recovery information.
Note:
Information for all VMs in the pool is stored, VMs do not need to be independently selected
for protection.
3. Click OK. Your pool is now protected.

8.5. Recovering VMs and vApps in the Event of Disaster (Failover)
This section explains how to recover your VMs and vApps on the secondary (recovery) site.
1. In XenCenter select the secondary pool, and on the Pool menu, click Disaster Recovery and then Disaster
Recovery wizard.
The Disaster Recovery wizard displays three recovery options: Failover, Failback, and Test Failover. To recover
on to your secondary site, select Failover and then click Next.
Warning:
If you use Fibre Channel shared storage with LUN mirroring to replicate the data to the
secondary site, before you attempt to recover VMs, mirroring must be broken so that the
secondary site has Read/Write access.
2. Select the storage repositories (SRs) containing the pool metadata for the VMs and vApps that you want to
recover.
By default, the list on this wizard page shows all SRs that are currently attached within the pool. To scan for
more SRs, choose Find Storage Repositories and then select the storage type to scan for:
•

To scan for all the available Hardware HBA SRs, select Find Hardware HBA SRs.

•

To scan for software iSCSI SRs, select Find Software iSCSI SRs and then enter the target host, IQN and
LUN details in the dialog box.

When you have selected the required SRs in the wizard, click Next to continue.
3. Select the VMs and vApps that you wish to recover and choose the appropriate Power state after recovery
option to specify whether you want the wizard to start them up automatically as soon as they have been
recovered, or whether you prefer to wait and start them up manually yourself after failover is complete.
Click Next to progress to the next wizard page and begin failover prechecks.
4. The wizard performs a number of prechecks before starting failover, for example, to ensure that all the storage
required by the selected VMs and vApps is available. If any storage is missing at this point, you can click Attach
SR on this page to find and attach the relevant SR.
Resolve any issues on the prechecks page, and then click Failover to begin the recovery process.
5. A progress page is displayed showing whether recovery was successful for each VM and vApp. Failover may
take some time depending on the number of VMs and vApps you are recovering, as the metadata for the
VMs and vApps are exported from the replicated storage. The VMs and vApps are recreated in the primary
pool, the SRs containing the virtual disks are attached to the recreated VMs, and VMs are started, if specified.
6. When the failover is complete, click Next to see the summary report. Click Finish on the summary report
page to close the wizard.
Once the primary site is available again, and you want to return to running your VMs on that site, work through
the Disaster Recovery wizard again, but this time select the Failback option.
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8.6. Restoring VMs and vApps to the Primary Site After Disaster
(Failback)
This section explains how to restore VMs and vApps from replicated storage back to a pool on your primary
(production) site when the primary site comes back up after a disaster event. To failback VMs and vApps to your
primary site, use the Disaster Recovery wizard.
1. In XenCenter select the secondary pool, and on the Pool menu, click Disaster Recovery and then Disaster
Recovery wizard.
The Disaster Recovery wizard displays three recovery options: Failover, Failback, and Test Failover. To restore
VMs and vApps to your primary site, select Failback and then click Next.
Warning:
If you use Fibre Channel shared storage with LUN mirroring to replicate the data to the primary
site, before you attempt to restore VMs, mirroring must be broken so that the primary site
has Read/Write access.
2. Select the storage repositories (SRs) containing the pool metadata for the VMs and vApps that you want to
recover.
By default, the list on this wizard page shows all SRs that are currently attached within the pool. To scan for
more SRs, choose Find Storage Repositories and then select the storage type to scan for:
•

To scan for all the available Hardware HBA SRs, select Find Hardware HBA SRs.

•

To scan for software iSCSI SRs, select Find Software iSCSI SRs and then enter the target host, IQN and
LUN details in the dialog box.

When you have selected the required SRs in the wizard, click Next to continue.
3. Select the VMs and vApps that you wish to restore and choose the appropriate Power state after recovery
option to specify whether you want the wizard to start them up automatically as soon as they have been
recovered, or whether you prefer to wait and start them up manually yourself after failback is complete.
Click Next to progress to the next wizard page and begin failback prechecks.
4. The wizard performs a number of pre-checks before starting failback, for example, to ensure that all the
storage required by the selected VMs and vApps is available. If any storage is missing at this point, you can
click Attach SR on this page to find and attach the relevant SR.
Resolve any issues on the prechecks page, and then click Failback to begin the recovery process.
5. A progress page is displayed showing whether recovery was successful for each VM and vApp. Failback may
take some time depending on the number of VMs and vApps you are restoring, as the metadata for the VMs
and vApps are exported from the replicated storage. The VMs and vApps are recreated in the primary pool,
the SRs containing the virtual disks are attached to the recreated VMs, and VMs are started, if specified.
6. When the failback is complete, click Next to see the summary report. Click Finish on the summary report
page to close the wizard.

8.7. Test Failover
Failover testing is an essential component in disaster recovery planning. You can use the Disaster Recovery wizard
to perform non-disruptive testing of your disaster recovery system. During a test failover operation, all the steps
are the same as for failover, but instead of being started after they have been recovered to the DR site, the
VMs and vApps are placed in a paused state. At the end of a test failover operation, all VMs, vApps and storage
recreated on the DR site are automatically removed. After initial DR configuration, and after you make significant
configuration changes in a DR-enabled pool, we recommend that you verify that failover still works correctly by
performing a test failover.
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To perform a test failover of VMs and vApps to a secondary site
1.

In XenCenter select the secondary pool, and on the Pool menu, click Disaster Recovery to open the Disaster
Recovery Wizard.

Select Test Failover and then click Next.
Note:
If you use Fibre Channel shared storage with LUN mirroring to replicate the data to the
secondary site, before you attempt to recover data, mirroring must be broken so that the
secondary site has Read/Write access.

Select the storage repositories (SRs) containing the pool metadata for the VMs and vApps that you want
to recover.
By default, the list on this wizard page shows all SRs that are currently attached within the pool. To scan for
more SRs, choose Find Storage Repositories and then select the storage type to scan for:
•

To scan for all the available Hardware HBA SRs, select Find Hardware HBA SRs.

•

To scan for software iSCSI SRs, select Find Software iSCSI SRs and then enter the target host, IQN and
LUN details in the dialog box.
When you have selected the required SRs in the wizard, click Next to continue.

Select the VMs and vApps that you wish to recover then click Next to progress to the next wizard page and
begin failover prechecks.

Before beginning the test failover process, the wizard performs a number of pre-checks, for example, to
ensure that all the storage required by the selected VMs and vApps is available.
•

Check that storage is available If any storage is missing, you can click Attach SR on this page to find and
attach the relevant SR.

•

Check that HA is not enabled on the target DR pool. To avoid having the same VMs running on both the
primary and DR pools, HA must be disabled on the secondary pool to ensure that the recovered VMs
and vApps are not started up automatically by HA after recovery. To disable HA on the secondary pool,
you can simply click Disable HA on the this page. (If HA is disabled at this point, it will be enabled again
automatically at the end of the test failover process.)
Resolve any issues on the pre-checks page, and then click Failover to begin the test failover.

A progress page is displayed showing whether recovery was successful for each VM and vApp. Failover may
take some time depending on the number of VMs and vApps you are recovering, as the metadata for the
VMs and vApps are recovered from the replicated storage. The VMs and vApps are recreated in the DR pool,
the SRs containing the virtual disks are attached to the recreated VMs.
The recovered VMs are placed in a paused state: they will not be started up on the secondary site during
a test failover.

After you are satisfied that the test failover was performed successfully, click Next in the wizard to have the
wizard clean up on the DR site:
•

VMs and vApps that were recovered during the test failover will be removed.

•

Storage that was recovered during the test failover will be detached.

•

If HA on the DR pool was disabled at the prechecks stage to allow the test failover to take place, it will
be enabled again automatically.
The progress of the cleanup process is displayed in the wizard.

Click Finish to close the wizard.

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8.8. vApps
A vApp is logical group of one or more related Virtual Machines (VMs) which can be started up as a single
entity in the event of a disaster. When a vApp is started, the VMs contained within the vApp will start in a user
predefined order, to allow VMs which depend upon one another to be automatically sequenced. This means
that an administrator no longer has to manually sequence the startup of dependent VMs should a whole service
require restarting (for instance in the case of a software update). The VMs within the vApp do not have to reside
on one host and will be distributed within a pool using the normal rules. The vApp functionality is particularly
useful in the Disaster Recovery situation where an Administrator may choose to group all VMs which reside on
the same Storage Repository, or which relate to the same Service Level Agreement (SLA).

Creating vApps
To group VMs together in a vApp follow the procedure:
1.

Select the pool and, on the Pool menu, click Manage vApps. This displays the Manage vApps window.

Enter a name for the vApp, and optionally a description, and then click Next.
You can choose any name you like, but a descriptive name is usually best. Although it is advisable to avoid
having multiple vApps with the same name, it is not a requirement, and XenCenter does not enforce any
uniqueness constraints on vApp names. It is not necessary to use quotation marks for names that include
spaces.

Choose which VMs to include in the new vApp, and then click Next.
You can use the search box to list only VMs with names that include the specified string.

Specify the startup sequence for the VMs in the vApp, and then click Next.
Value

Description

Start Order

Specifies the order in which individual VMs will be started up within the vApp,
allowing certain VMs to be restarted before others. VMs with a start order
value of 0 (zero) will be started first, then VMs with a start order value of 1,
then VMs with a start order value of 2, and so on.

Attempt to start next VM
after

This is a delay interval that specifies how long to wait after starting the VM
before attempting to start the next group of VMs in the startup sequence,
that is, VMs with a lower start order.

On the final page of the wizard, you can review the vApp configuration. Click Previous to go back and modify
any settings, or Finish to create the new vApp and close the wizard.
Note:
A vApp can span multiple servers in a single pool, but cannot span across several pools.

8.8.1. Using the Manage vApps dialog box in XenCenter
XenCenter's Manage vApps dialog box allows you to create, delete and modify vApps, start and shutdown vApps,
and import and export vApps within the selected pool. When you select a vApp in the list, the VMs it contains
are listed in the details pane on the right. See the XenCenter online help for further details. Press F1 or click Help
to display the Help.

8.9. Backing Up and Restoring XenServer Hosts and VMs
Citrix recommends that, whenever possible, you leave the installed state of XenServer hosts unaltered. That is,
do not install any additional packages or start additional services on XenServer hosts, and treat them as if they
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are appliances. The best way to restore, then, is to reinstall XenServer host software from the installation media.
If you have multiple XenServer hosts, the best approach is to configure a TFTP server and appropriate answerfiles
for this purpose (see the XenServer Installation Guide).
For VMs, the best approach is to install backup agents on them, just as if they were standard physical servers.
For Windows VMs, as of this release we have tested CA BrightStor ARCserve Backup, and Symantec NetBackup
and Backup Exec.
For more information about backup tools tested, best practices, and backups in general, see the Citrix Knowledge
Base.
Citrix recommends that you frequently perform as many of the following backup procedures as possible to
recover from possible server and/or software failure.

To backup pool metadata
1.

Run the command:
xe pool-dump-database file-name=

Run the command:
xe pool-restore-database file-name= dry-run=true

This command checks that the target machine has an appropriate number of appropriately named NICs,
which is required for the backup to succeed.

To backup host configuration and software
•

Run the command:
xe host-backup host= file-name=

Note:
•

Do not create the backup in the control domain.

•

This procedure may create a large backup file.

•

To complete a restore you have to reboot to the original install CD.

•

This data can only be restored to the original machine.

To backup a VM
1.

Ensure that the VM to be backed up is offline.

Run the command:
xe vm-export vm= filename=

Note:
This backup also backs up all of the VM data. When importing a VM, you can specify the
storage mechanism to use for the backed up data.
Warning:
Because this process backs up all of the VM data, it can take some time to complete.

To backup VM metadata only
•

Run the command:
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xe vm-export vm= filename= metadata=true

8.9.1. Backing up Virtual Machine metadata
XenServer hosts use a database on each host to store metadata about VMs and associated resources such as
storage and networking. When combined with storage repositories, this database forms the complete view of all
VMs available across the pool. Therefore it is important to understand how to backup this database in order to
recover from physical hardware failure and other disaster scenarios.
This section first describes how to backup metadata for single-host installations, and then for more complex pool
setups.

8.9.1.1. Backing up single host installations
Use the CLI to backup the pool database. To obtain a consistent pool metadata backup file, run pool-dumpdatabase on the XenServer host and archive the resulting file. The backup file will contain sensitive authentication
information about the pool, so ensure it is securely stored.
To restore the pool database, use the xe pool-restore-database command from a previous dump file. If your
XenServer host has died completely, then you must first do a fresh install, and then run the pool-restore-database
command against the freshly installed XenServer host.
After a restoration of the pool database, some VMs may still be registered as being Suspended, but if the
storage repository with their suspended memory state (defined in the suspend-VDI-uuid field) was a local
SR, it will no longer be available since the host has been reinstalled. To reset these VMs back to the Halted
state so that they can be started up again, use the xe vm-shutdown vm=vm_name -force command, or use the
xe vm-reset-powerstate vm= -force command.
Warning:
XenServer hosts restored using this method will have their UUIDs preserved. If you restore
to a different physical machine while the original XenServer host is still running, there will
be duplicate UUIDs. The main observable effect of this will be that XenCenter will refuse
to connect to the second XenServer host. Pool database backup is not the recommended
mechanism for cloning physical hosts; use the automated installation support for that (see
the XenServer Installation Guide).

8.9.1.2. Backing up pooled installations
In a pool scenario, the master host provides an authoritative database that is synchronously mirrored to all the
member hosts in the pool. This provides a degree of built-in redundancy to a pool; the master can be replaced
by any member since each of them has an accurate version of the pool database. Please refer to the XenServer
Administrator's Guide for more information on how to transition a member into becoming a master host.
This level of protection may not be sufficient; for example, if your shared storage containing the VM data is backed
up in multiple sites, but your local server storage (containing the pool metadata) is not. To fully recreate a pool
given just a set of shared storage, you must first backup the pool-dump-database file on the master host, and
archive this file.

Subsequently restoring this backup on a brand new set of hosts
1.

Install a fresh set of XenServer hosts from the installation media, or if applicable, network boot from your
TFTP server.

Use the xe pool-restore-database on the host designated to be the new master.

Run the xe host-forget command on the new master to remove the old member machines.

Use the xe pool-join command on the member hosts to connect them to the new pool.

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8.9.2. Backing up XenServer hosts
This section describes the XenServer host control domain backup and restore procedures. These procedures do
not back up the storage repositories that house the VMs, but only the privileged control domain that runs Xen
and the XenServer agent.
Note:
Because the privileged control domain is best left as installed, without customizing it with
other packages, Citrix recommends that you set up a network boot environment to cleanly
perform a fresh installation from the XenServer media as a recovery strategy. In many cases
you will not need to backup the control domain at all, but just save the pool metadata (see
Section 8.9.1, “Backing up Virtual Machine metadata”). This backup method should always
be considered complementary to backing up the pool metadata.
Using the xe commands host-backup and host-restore is another approach that you can take. The xe host-backup
command archives the active partition to a file you specify, and the xe host-restore command extracts an archive
created by xe host-backup over the currently inactive disk partition of the host. This partition can then be made
active by booting off the installation CD and choosing to restore the appropriate backup.
After completing the above steps and rebooting the host, you must ensure that the VM meta-data is restored
to a consistent state. This can be achieved by running xe pool-restore-database on /var/backup/pooldatabase-${DATE}. This file is created by xe host-backup using xe pool-dump-database command before
archiving the running filesystem, to snapshot a consistent state of the VM metadata.

To back up a XenServer host
•

On a remote host with enough disk space, run the command:
xe host-backup file-name= -h -u root -pw

This creates a compressed image of the control domain file system in the location specified by the filename argument.

To restore a running XenServer host
1.

If you want to restore a XenServer host from a specific backup, run the following command while the
XenServer host is up and reachable:
xe host-restore file-name= -h -u root -pw ;

This command restores the compressed image back to the hard disk of the XenServer host on which the
command is run (not the host on which filename resides). In this context “restore” is something of a
misnomer, as the word usually suggests that the backed-up state has been put fully in place. The restore
command here only unpacks the compressed backup file and restores it to its normal form, but it is written
to another partition (/dev/sda2) and does not overwrite the current version of the filesystem.
2.

To use the restored version of the root filesystem, reboot the XenServer host using the XenServer installation
CD and select the Restore from backup option.
After the restore from backup is completed, reboot the XenServer host and it will start up from the restored
image.
Finally, restore the VM meta-data using
xe pool-restore-database file-name=/var/backup/pool-database-*

Note:
Restoring from a backup as described here does not destroy the backup partition.
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Restarting a crashed XenServer host
1.

If your XenServer host has crashed and is not reachable anymore, you need to use the XenServer installation
CD to do an upgrade install. When that is completed, reboot the machine and make sure your host is
reachable with XenCenter or remote CLI.

Then proceed with Section 8.9.2, “Backing up XenServer hosts” above.

8.9.3. Backing up VMs
VMs are best backed up using standard backup tools running on them individually. For Windows VMs, we have
tested CA BrightStor ARCserve Backup.

8.10. VM Snapshots
Important:
Virtual Machine Protection and Recovery (VMPR) and its functionality has been removed
from XenServer 7.0 and later versions. Applications, code, or usage that depend on VMPR will
not function in XenServer 7.0 and later versions. The VM snapshot functionality and other
functionalities that depend on VM snapshot (other than VMPR) remain unaffected. Refer to
CTX137335 for details.
XenServer provides a convenient snapshotting mechanism that can take a snapshot of a VM storage and metadata
at a given time. Where necessary, IO is temporarily halted while the snapshot is being taken to ensure that a selfconsistent disk image can be captured.
Snapshot operations result in a snapshot VM that is similar to a template. The VM snapshot contains all the
storage information and VM configuration, including attached VIFs, allowing them to be exported and restored
for backup purposes. Snapshots are supported on all storage types, though for the LVM-based storage types the
storage repository must have been upgraded if it was created on a previous version of XenServer and the volume
must be in the default format (type=raw volumes cannot be snapshotted).
The snapshotting operation is a 2 step process:
•

Capturing metadata as a template.

•

Creating a VDI snapshot of the disk(s).

Three types of VM snapshots are supported: regular, quiesced, and snapshot with memory

8.10.1. Regular Snapshots
Regular snapshots are crash consistent and can be performed on all VM types, including Linux VMs.

8.10.2. Quiesced Snapshots
Quiesced snapshots take advantage of the Windows Volume Shadow Copy Service (VSS) to generate application
consistent point-in-time snapshots. The VSS framework helps VSS-aware applications (for example Microsoft
Exchange or Microsoft SQL Server) flush data to disk and prepare for the snapshot before it is taken.
Quiesced snapshots are therefore safer to restore, but can have a greater performance impact on a system while
they are being taken. They may also fail under load so more than one attempt to take the snapshot may be
required.
XenServer supports quiesced snapshots on:
•

Windows Server 2012 R2 Server Core

•

Windows Server 2012 R2
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•

Windows Server 2012

•

Windows Server 2008 R2

•

Windows Server 2008 (32/64-bit)

•

Windows Server 2003 (32/64-bit)

Windows 8,1, Windows 8, Windows 7, Windows 2000, and Windows Vista are not supported. For further detail
on quiesced snapshots, see Section 8.10.9.3, “Advanced Notes for Quiesced Snapshots”.

8.10.3. Snapshots with memory
In addition to saving the VMs memory (storage) and metadata, snapshots with memory also save the VMs state
(RAM). This can be useful if you are upgrading or patching software, or want to test a new application, but also
want the option to be able to get back to the current, pre-change state (RAM) of the VM. Reverting back to a
snapshot with memory, does not require a reboot of the VM.
You can take a snapshot with memory of a running or suspended VM via the XenAPI, the xe CLI, or by using
XenCenter.

8.10.4. Creating a VM Snapshot
Before taking a snapshot, see the section called “Preparing for Cloning a Windows VM Using VSS” in XenServer
Virtual Machine User's Guide, and for information about any special operating system-specific configuration and
considerations to take into account, refer to the section called “Preparing to clone a Linux VM”.
Firstly, ensure that the VM is running or suspended so that the memory status can be captured. The simplest
way to select the VM on which the operation is to be performed is by supplying the argument vm=
or vm=> .
Run the vm-snapshot and vm-snapshot-with-quiesce commands to take a snapshot of a VM.
xe vm-snapshot vm= new-name-label=
xe vm-snapshot-with-quiesce vm= new-name-label=

8.10.5. Creating a snapshot with memory
Run the vm-checkpoint command, giving a descriptive name for the snapshot with memory, so that you can
identify it later:
xe vm-checkpoint vm= new-name-label=

When XenServer has completed creating the snapshot with memory - its uuid will be displayed.
For example:
xe vm-checkpoint vm=2d1d9a08-e479-2f0a-69e7-24a0e062dd35 \
new-name-label=example_checkpoint_1
b3c0f369-59a1-dd16-ecd4-a1211df29886

A snapshot with memory requires at least 4MB of disk space per disk, plus the size of the RAM, plus around 20%
overhead. So a checkpoint with 256MB RAM would require approximately 300MB of storage.
Note:
112

During the checkpoint creation process, the VM is paused for a brief period of time, and
cannot be used during this period.

8.10.6. To list all of the snapshots on a XenServer pool
Run the snapshot-list command:
xe snapshot-list

This lists all of the snapshots in the XenServer pool.

8.10.7. To list the snapshots on a particular VM
You will need to know the uuid of the particular VM; to do this run the vm-list command.
xe vm-list

This displays a list of all VMs and their UUIDs. For example:
xe vm-list
uuid ( RO): 116dd310-a0ef-a830-37c8-df41521ff72d
name-label ( RW): Windows Server 2003 (1)
power-state ( RO): halted
uuid ( RO): 96fde888-2a18-c042-491a-014e22b07839
name-label ( RW): Windows XP SP3 (1)
power-state ( RO): running
uuid ( RO): dff45c56-426a-4450-a094-d3bba0a2ba3f
name-label ( RW): Control domain on host
power-state ( RO): running

VMs can also be specified by filtering the full list of VMs on the values of fields.
For example, specifying power-state=halted will select all VMs whose power-state field is equal to 'halted'. Where
multiple VMs are matching, the option --multiple must be specified to perform the operation. The full list of fields
that can be matched can be obtained by the command xe vm-list params=all.
Locate the required VM and then enter the following:
xe snapshot-list snapshot-of=

For example:
xe snapshot-list snapshot-of=2d1d9a08-e479-2f0a-69e7-24a0e062dd35

This lists the snapshots currently on that VM:
uuid ( RO): d7eefb03-39bc-80f8-8d73-2ca1bab7dcff
name-label ( RW): Regular
name-description ( RW):
snapshot_of ( RO): 2d1d9a08-e479-2f0a-69e7-24a0e062dd35
snapshot_time ( RO): 20090914T15:37:00Z
uuid ( RO): 1760561d-a5d1-5d5e-2be5-d0dd99a3b1ef
name-label ( RW): Snapshot with memory
name-description ( RW):
snapshot_of ( RO): 2d1d9a08-e479-2f0a-69e7-24a0e062dd35
snapshot_time ( RO): 20090914T15:39:45Z

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8.10.8. Restoring a VM to its previous state
Ensure that you have the uuid of the snapshot that you wish to revert to, and then run the snapshot-revert
command:
To do this:
1. Run the snapshot-list command to find the UUID of the snapshot or checkpoint that you want to revert to:
xe snapshot-list

2. Note the uuid of the snapshot, and then run the following command to revert:
xe snapshot-revert snapshot-uuid=

For example:
xe snapshot-revert snapshot-uuid=b3c0f369-59a1-dd16-ecd4-a1211df29886

After reverting to a checkpoint, the VM will be suspended.
Note:
If there is insufficient disk space available to thickly provision the snapshot, it will not be
possible to restore to the snapshot until the current disk's state has been freed. If this occurs,
retry the operation.
Note:
It is possible to revert to any snapshot. Existing snapshots and checkpoints are not deleted
during the revert operation.

8.10.8.1. Deleting a snapshot
Ensure that you have the UUID of the checkpoint or snapshot that you wish to remove, and then run the following
command:
1. Run the snapshot-list command to find the UUID of the snapshot or checkpoint that you want to revert to:
xe snapshot-list

2. Note the UUID of the snapshot, and then run the snapshot-uninstall command to remove it:
xe snapshot-uninstall snapshot-uuid=

3. This command alerts you to the VM and VDIs that will be deleted. Type yes to confirm.
For example:
xe snapshot-uninstall snapshot-uuid=1760561d-a5d1-5d5e-2be5-d0dd99a3b1ef
The following items are about to be destroyed
VM : 1760561d-a5d1-5d5e-2be5-d0dd99a3b1ef (Snapshot with memory)
VDI: 11a4aa81-3c6b-4f7d-805a-b6ea02947582 (0)
VDI: 43c33fe7-a768-4612-bf8c-c385e2c657ed (1)
VDI: 4c33c84a-a874-42db-85b5-5e29174fa9b2 (Suspend image)
Type 'yes' to continue
yes
All objects destroyed

If you only want to remove the metadata of a checkpoint or snapshot, run the following command:
114

xe snapshot-destroy snapshot-uuid=

For example:
xe snapshot-destroy snapshot-uuid=d7eefb03-39bc-80f8-8d73-2ca1bab7dcff

8.10.9. Snapshot Templates
8.10.9.1. Creating a template from a snapshot
You can create a VM template from a snapshot, however its memory state will be removed.
To do this:
1. Use the command snapshot-copy and specify a new-name-label for the template:
xe snapshot-copy new-name-label= \
snapshot-uuid=

For example:
xe snapshot-copy new-name-label=example_template_1
snapshot-uuid=b3c0f369-59a1-dd16-ecd4-a1211df29886

Note:
This creates a template object in the SAME pool. This template exists in the XenServer
database for the current pool only.
2. To verify that the template has been created, run the command template-list:
xe template-list

This will list all of the templates on the XenServer host.

8.10.9.2. Exporting a snapshot to a template
When you export a VM snapshot, a complete copy of the VM (including disk images) is stored as a single file on
your local machine, with a .xva file extension.
To do this:
1. Use the command snapshot-export-to-template to create a new template file:
xe snapshot-export-to template snapshot-uuid= \
filename=

For example:
xe snapshot-export-to-template snapshot-uuid=b3c0f369-59a1-dd16-ecd4-a1211df29886 \
filename=example_template_export

The VM export/import feature can be used in a number of different ways:
•

As a convenient backup facility for your VMs. An exported VM file can be used to recover an entire VM in
the event of disaster.

•

As a way of quickly copying a VM, for example, a special-purpose server configuration that you use many
times. You simply configure the VM the way you want it, export it, and then import it to create copies of
your original VM.

•

As a simple method for moving a VM to another server.

For further information on the use of templates refer to the Creating VMs chapter in the XenServer Virtual
Machine User's Guide and also the Managing VMs section in the XenCenter Help.

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8.10.9.3. Advanced Notes for Quiesced Snapshots
Note:
Do not forget to install the Xen VSS provider in the Windows guest in order to support VSS.
This is done using the install- XenProvider.cmd script provided with the XenServer Tools. For
more information, see the XenServer Virtual Machine User's Guide.
In general, a VM can only access VDI snapshots (not VDI clones) of itself using the VSS interface. There is a flag
that can be set by the XenServer administrator whereby adding an attribute of snapmanager=true to the
VM other-config allows that VM to import snapshots of VDIs from other VMs.
Warning:
This opens a security vulnerability and should be used with care. This feature allows
an administrator to attach VSS snapshots using an in-guest transportable snapshot ID as
generated by the VSS layer to another VM for the purposes of backup.
VSS quiesce timeout: the Microsoft VSS quiesce period is set to a non-configurable value of 10 seconds, and it is
quite probable that a snapshot may not be able to complete in time. If, for example the XAPI daemon has queued
additional blocking tasks such as an SR scan, the VSS snapshot may timeout and fail. The operation should be
retried if this happens.
Note:
The more VBDs attached to a VM, the more likely it is that this timeout may be reached.
Citrix recommends attaching no more that 2 VBDs to a VM to avoid reaching the timeout.
However, there is a workaround to this problem. The probability of taking a successful VSS
based snapshot of a VM with more than 2 VBDs can be increased manifold, if all the VDIs for
the VM are hosted on different SRs.
VSS snapshot all the disks attached to a VM: in order to store all data available at the time of a VSS snapshot,
the XAPI manager will snapshot all disks and the VM metadata associated with a VM that can be snapshotted
using the XenServer storage manager API. If the VSS layer requests a snapshot of only a subset of the disks, a
full VM snapshot will not be taken.
vm-snapshot-with-quiesce produces bootable snapshot VM images: To achieve this, the XenServer VSS hardware
provider makes snapshot volumes writable, including the snapshot of the boot volume.
VSS snap of volumes hosted on dynamic disks in the Windows Guest : The vm-snapshot-with-quiesce CLI and the
XenServer VSS hardware provider do not support snapshots of volumes hosted on dynamic disks on the Windows
VM.
Note:
Do not forget to install the Xen VSS provider in the Windows guest in order to support VSS.
This is done using the install-XenProvider.cmd script provided with the XenServer
Tools. For more information, see XenServerVirtual Machine User's Guide.

8.11. Coping with machine failures
This section provides details of how to recover from various failure scenarios. All failure recovery scenarios require
the use of one or more of the backup types listed in Section 8.9, “Backing Up and Restoring XenServer Hosts
and VMs”.

8.11.1. Member failures
In the absence of HA, master nodes detect the failures of members by receiving regular heartbeat messages. If
no heartbeat has been received for 600 seconds, the master assumes the member is dead. There are two ways
to recover from this problem:
116

•

Repair the dead host (e.g. by physically rebooting it). When the connection to the member is restored, the
master will mark the member as alive again.

•

Shutdown the host and instruct the master to forget about the member node using the xe host-forget CLI
command. Once the member has been forgotten, all the VMs which were running there will be marked as
offline and can be restarted on other XenServer hosts. Note it is very important to ensure that the XenServer
host is actually offline, otherwise VM data corruption might occur. Be careful not to split your pool into
multiple pools of a single host by using xe host-forget , since this could result in them all mapping the same
shared storage and corrupting VM data.
Warning:
•

If you are going to use the forgotten host as a XenServer host again, perform a fresh
installation of the XenServer software.

•

Do not use xe host-forget command if HA is enabled on the pool. Disable HA first, then
forget the host, and then re-enable HA.

When a member XenServer host fails, there may be VMs still registered in the running state. If you are sure that
the member XenServer host is definitely down, use the xe vm-reset-powerstate CLI command to set the power
state of the VMs to halted. See Section A.4.26.28, “vm-reset-powerstate” for more details.
Warning:
Incorrect use of this command can lead to data corruption. Only use this command if
absolutely necessary.
Before you can start VMs on another XenServer host, you are also required to release the locks on VM storage.
Each disk in an SR can only be used by one host at a time, so it is key to make the disk accessible to other XenServer
hosts once a host has failed. To do so, run the following script on the pool master for each SR that contains disks
of any affected VMs:
/opt/xensource/sm/resetvdis.py [master]
You need only supply the third string ("master") if the failed host was the SR master — pool master or XenServer
host using local storage — at the time of the crash.
Warning:
Be absolutely sure that the host is down before executing this command. Incorrect use of this
command can lead to data corruption.
If you attempt to start a VM on another XenServer host before running the script above, then you will receive
the following error message: VDI already attached RW.

8.11.2. Master failures
Every member of a resource pool contains all the information necessary to take over the role of master if required.
When a master node fails, the following sequence of events occurs:
1. If HA is enabled, another master is elected automatically.
2. If HA is not enabled, each member will wait for the master to return.
If the master comes back up at this point, it re-establishes communication with its members, and operation
returns to normal.
If the master is really dead, choose one of the members and run the command xe pool-emergency-transitionto-master on it. Once it has become the master, run the command xe pool-recover-slaves and the members
will now point to the new master.
If you repair or replace the server that was the original master, you can simply bring it up, install the XenServer
host software, and add it to the pool. Since the XenServer hosts in the pool are enforced to be homogeneous,
there is no real need to make the replaced server the master.
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When a member XenServer host is transitioned to being a master, you should also check that the default pool
storage repository is set to an appropriate value. This can be done using the xe pool-param-list command and
verifying that the default-SR parameter is pointing to a valid storage repository.

8.11.3. Pool failures
In the unfortunate event that your entire resource pool fails, you will need to recreate the pool database from
scratch. Be sure to regularly back up your pool-metadata using the xe pool-dump-database CLI command (see
Section A.4.15.3, “pool-dump-database”).

To restore a completely failed pool
1.

Install a fresh set of hosts. Do not pool them up at this stage.

For the host nominated as the master, restore the pool database from your backup using the xe poolrestore-database (see Section A.4.15.11, “pool-restore-database”) command.

Connect to the master host using XenCenter and ensure that all your shared storage and VMs are available
again.

Perform a pool join operation on the remaining freshly installed member hosts, and start up your VMs on
the appropriate hosts.

8.11.4. Coping with Failure due to Configuration Errors
If the physical host machine is operational but the software or host configuration is corrupted:

To restore host software and configuration
1.

Run the command:
xe host-restore host= file-name=

Reboot to the host installation CD and select Restore from backup.

8.11.5. Physical Machine failure
If the physical host machine has failed, use the appropriate procedure listed below to recover.
Warning:
Any VMs which were running on a previous member (or the previous host) which has failed
will still be marked as Running in the database. This is for safety-- simultaneously starting
a VM on two different hosts would lead to severe disk corruption. If you are sure that the
machines (and VMs) are offline you can reset the VM power state to Halted:
xe vm-reset-powerstate vm= --force
VMs can then be restarted using XenCenter or the CLI.

Replacing a failed master with a still running member
1.

Run the commands:
xe pool-emergency-transition-to-master
xe pool-recover-slaves

If the commands succeed, restart the VMs.
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To restore a pool with all hosts failed
1.

Run the command:
xe pool-restore-database file-name=

Warning:
This command will only succeed if the target machine has an appropriate number of
appropriately named NICs.
2.

If the target machine has a different view of the storage (for example, a block-mirror with a different IP
address) than the original machine, modify the storage configuration using the pbd-destroy command and
then the pbd-create command to recreate storage configurations. See Section A.4.13, “PBD Commands” for
documentation of these commands.

If you have created a new storage configuration, use pbd-plug or Storage > Repair Storage Repository menu
item in XenCenter to use the new configuration.

Restart all VMs.

To restore a VM when VM storage is not available
1.

Run the command:
xe vm-import filename= metadata=true

If the metadata import fails, run the command:
xe vm-import filename= metadata=true --force

This command will attempt to restore the VM metadata on a 'best effort' basis.
3.

Restart all VMs.

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Chapter 9. Monitoring and Managing
XenServer
XenServer provides detailed monitoring of performance metrics, including CPU, memory, disk, network, C-state/
P-state information and storage. Where appropriate, these metrics are available on a per host and a per VM
basis. These metrics are available directly, or can be accessed and viewed graphically in XenCenter or other third
party applications.
XenServer also provides system and performance alerts. Alerts are notifications that occur in response to selected
system events, or when CPU, memory usage, network, storage throughput, or VM disk activity go over a specified
threshold on a managed host, VM, or storage repository. You can configure these using the xe CLI or by using
XenCenter, to create notifications based on any of the available Host or VM performance metrics see Section 9.2,
“Alerts”.

9.1. Monitoring XenServer Performance
Customers can monitor the performance of their XenServer hosts and Virtual Machines (VMs) using the metrics
exposed through Round Robin Databases (RRDs). These metrics can be queried over HTTP or through the
RRD2CSV tool; in addition, XenCenter uses this data to produce system performance graphs. See Section 9.1.5,
“Using RRDs” and Section 9.1.3, “Analyzing and Visualizing Metrics in XenCenter”.
The following tables list all of the available Host and VM metrics.
Note:
Latency over a period of time is defined as the average latency of operations during that
period.
The availability and utility of certain metrics are SR and CPU dependent.

9.1.1. Available Host Metrics
Metric Name

Description

Condition

XenCenter
Name

avgqu_sz_

Average I/O queue size (requests).

At least one
plugged
VBD in SR
on the
host

Queue
Size

cpu-C

Time CPU spent in C-state in
miliseconds.

C-state
exists on
CPU

CPU
C-state

cpu-P

Time CPU spent in P-state in
miliseconds.

P-state
exists on
CPU

CPU
P-state

cpu

Utilisation of physical CPU (fraction). Enabled
by default.

pCPU

exists

CPU

cpu_avg

Mean utilisation of physical CPUs (fraction). Enabled
by default.

None

Average
CPU

120

Metric Name

Description

Condition

XenCenter
Name

inflight_

Number of I/O requests currently in flight. Enabled
by default.

At least one
plugged
VBD in SR
on the
host

Inflight
Requests

io_throughput_read_

Data read from SR (MiB/s).

At least one
plugged
VBD in SR
on the
host

Read
Throughput

io_throughput_write_

At least one
plugged
VBD in SR
on the
host

Write
Throughput

io_throughput_total_

All SR I/O (MiB/s).

At least one
plugged
VBD in SR
on the
host

Total
Throughput

iops_read_

Read requests per second.

At least one
plugged
VBD in SR
on the
host

Read
IOPS

iops_write_

Write requests per second.

At least one
plugged
VBD in SR
on the
host

Write
IOPS

iops_total_

I/O requests per second.

At least one
plugged
VBD in SR
on the
host

Total
IOPS

iowait_

Percentage of the time waiting for I/O.

At least one
plugged
VBD in SR
on the
host

Wait

latency_

Average I/O latency (milliseconds).

At least one
plugged
VBD in SR
on the
host

Latency

121

Metric Name

Description

Condition

XenCenter
Name

loadavg

Domain0 loadavg. Enabled by default

None

Control
Domain
Load

memory_free_kib

Total amount of free memory (KiB). Enabled by
default.

None

Free
Memory

memory_reclaimed

Host memory reclaimed by squeeze (B).

None

Reclaimed
Memory

memory_reclaimed_max

Host memory that could be reclaimed by squeezed
(B).

None

Potential
Reclaimed
Memory

memory_total_kib

Total amount of memory (KiB) in the host. Enabled
by default.

None

Total
Memory

network/latency

Interval in seconds between the last two heartbeats
transmitted from the local host to all Online hosts.
Disabled by default.

HA Enabled

Network
Latency

statefile//latency

Turn-around time in seconds of the latest State-File
access from the local host. Disabled by default.

HA Enabled

HA
Statefile
Latency

pif__rx

Bytes per second received on physical interface
. Enabled by default.

PIFexists
Receive
(see note)

pif__tx

Bytes per second sent on physical interface .
Enabled by default.

PIFexists
Send (see
note)

pif__rx_errors

Receive errors per second on physical interface .
Disabled by default.

PIFexists
Receive
Errors (see
note)

pif__tx_errors

Transmit errors per second on physical interface
. Disabled by default

PIFexists Send
Errors (see
note)

pif_aggr_rx

Bytes per second received on all physical interfaces.
Enabled by default.

None

Total NIC
Receive

pif_aggr_tx

Bytes per second sent on all physical interfaces.
Enabled by default.

None

Total
Send

sr__cache_size

Size in bytes of the IntelliCache SR. Enabled by
default.

IntelliCache
Enabled

IntelliCache
Cache Size

122

NIC

Metric Name

Description

Condition

XenCenter
Name

sr__cache_hits

Cache hits per second. Enabled by default.

IntelliCache
Enabled

IntelliCache
Cache Hits

sr__cache_misses

Cache misses per second. Enabled by default.

IntelliCache
Enabled

IntelliCache
Cache
Misses

xapi_allocation_kib

Memory (KiB) allocation done by the xapi daemon.
Enabled by default.

None

Agent
Memory
Allocation

xapi_free_memory_kib

Free memory (KiB) available to the xapi daemon.
Enabled by default.

None

Agent
Memory
Free

xapi_healthcheck/
latency_healt

Turn-around time in seconds of the latest xapi status
monitoring call on the local host. Disabled by default

HA Enabled

XenServer
Healthcheck
Latency

xapi_live_memory_kib

Live memory (KiB) used by xapi daemon. Enabled by
default.

None

Agent
Memory
Live

xapi_memory_usage_kib

Total memory (KiB) allocated used by xapi daemon.
Enabled by default.

None

Agent
Memory
Usage

9.1.2. Available VM Metrics
Metric Name

Description

Condition

XenCenter
Name

cpu

Utilisation of vCPU (fraction). Enabled by
default

vCPU

exists

CPU

memory

Memory currently allocated to VM (Bytes).Enabled
by default

None

Total
Memory

memory_target

Target of VM balloon driver (Bytes). Enabled by
default

None

Memory
target

memory_internal_free

Memory used as reported by the guest agent (KiB).
Enabled by default

None

Free
Memory

runstate_fullrun

Fraction of time that all VCPUs are running.

None

VCPUs full
run

runstate_full_contention

Fraction of time that all VCPUs are runnable (i.e.,
waiting for CPU)

None

VCPUs full
contention

runstate_concurrency_hazard
Fraction of time that some VCPUs are running and
some are runnable

None

VCPUs
concurrency
hazard

runstate_blocked

None

VCPUs idle

Fraction of time that all VCPUs are blocked or offline

123

Metric Name

Description

Condition

XenCenter
Name

runstate_partial_run

Fraction of time that some VCPUs are running, and
some are blocked

None

VCPUs
partial run

runstate_partial_contentionFraction of time that some VCPUs are runnable and
some are blocked

None

VCPUs
partial
contention

vbd__write

Writes to device in bytes per second. Enabled
by default

VBD
exists

Disk
Write

vbd__read

Reads from device in bytes per second.
Enabled by default.

VBD
exists

Disk
Read

vbd__write_latency Writes to device in microseconds.

VBD
exists

Disk
Write
Latency

vbd__read_latency

Reads from device in microseconds.

VBD
exists

Disk
Read
Latency

vbd _iops_read

Read requests per second.

A least one
plugged
VBD
for
non-ISO
VDI on the
host

Disk
Read IOPs

vbd _iops_write

Write requests per second.

A least one
plugged
VBD
for
non-ISO
VDI on the
host

Disk
Write IOPS

vbd _iops_total

I/O requests per second.

A least one
plugged
VBD
for
non-ISO
VDI on the
host

Disk
Total IOPS

vbd _iowait

Percentage of time waiting for I/0.

At least one
plugged
VBD
for
non-ISO
VDI on the
host

Disk
IO Wait

vbd _inflight

Number of I/O requests currently in flight.

At least one
plugged
VBD
for
non-ISO
VDI on the
host

Disk
Inflight
Requests

124

Metric Name

Description

Condition

XenCenter
Name

vbd _avgqu_sz

Average I/O queue size.

At least one
plugged
VBD
for
non-ISO
VDI on the
host

Disk
Queue Size

vif__rx

Bytes per second received on virtual interface
number . Enabled by default.

VIF
exists

Receive

vif__tx

Bytes per second transmitted on virtual interface
.Enabled by default.

VIF
exists

Send

vif__rx_errors

Receive errors per second on virtual interface .
Enabled by default.

VIF
exists

Receive
Errors

vif__tx_errors

Transmit errors per second on virtual interface
Enabled by default.

VIF
exists

Send
Errors

Note:
can be any of the following:
NIC

if contains pif_eth#, where # is 0-9

if contains pif_eth#.# or pif_xenbr# or
pif_bond#

Network

if contains pif_xapi# (note that
appears as is)

TAP

if contains pif_tap#

xapi Loopback

if contains pif_lo

9.1.3. Analyzing and Visualizing Metrics in XenCenter
The Performance tab in XenCenter provides real time monitoring of performance statistics across resource pools
as well as graphical trending of virtual and physical machine performance. By default, graphs showing CPU,
memory, network and disk I/O are included on the Performance tab, but you can add additional metrics, change
the appearance of the existing graphs or create additional ones. See Section 9.1.3.1, “Configuring Performance
Graphs”.
•

You can view up to 12 months of performance data and zoom in to take a closer look at activity spikes.

•

XenCenter can generate performance alerts when CPU, memory usage, network I/O, storage I/O or disk I/O
usage go over a specified threshold on a managed server, VM or storage repository. Refer to Section 9.2.1,
“Using XenCenter to View Alerts”
Note:
You must install the XenServer Tools (paravirtualized drivers) in order to see full VM
performance data .

9.1.3.1. Configuring Performance Graphs
To Add A New Graph
125

1. On the Performance tab, click Actions and then New Graph. The New Graph dialog box will be displayed.
2. In the Name field, enter a name for the graph.
3. From the list of Datasources, select the check boxes for the datasources you want to include in the graph.
4. Click Save.
To Edit An Existing Graph
1. Navigate to the Performance tab, and select the graph that you would like to modify.
2. Right-click on the graph and select Actions, or click the Actions button. Then select Edit Graph.
3. On the graph details window, make the necessary changes, and click OK.

9.1.3.1.1. Configuring the Graph Type
Data on the performance graphs can be displayed as lines or as areas:
Line Graph:

Area Graph:

To change the Graph Type
1. On the Tools menu, click Options and select Graphs.
2. To view performance data as a line graph, click on the Line graph radio button
3. To view performance data as an area graph, click on the Area graph radio button
4. Click OK to save your changes.
Comprehensive details for configuring and viewing XenCenter Performance Graphs can be found in the XenCenter
Help in the section Monitoring System Performance.

9.1.4. Configuring Metrics
Note:
C-states and P-states are power management features of some processors. The range of states
available is dependent on the physical capabilities of the host, as well power management
configuration.
Both host and VM commands return the following:
•

A full description of the data source

•

The units applied to the metric

•

The range of possible values that may be used

For example:
126

name_label:
name_description:
enabled:
standard:
min:
max:
units:

cpu0-C1
Proportion of time CPU 0 spent in C-state 1
true
true
0.000
1.000
Percent

Enabling a Specific Metric
Most metrics are enabled and collected by default, to enable those that are not, enter the following:
xe host-data-source-record data-source= host=

Disabling a Specific Metric
You may not wish to collect certain metrics on a regular basis. To disable a previously enabled metric, enter the
following:
xe host-data-source-forget data-source= host=

Displaying a List of Currently Enabled Host Metrics
To list the host metrics currently being collected, enter the following:
xe host-data-source-list host=

Displaying a List of Currently Enabled VM Metrics
To host the VM metrics currently being collected, enter the following:
xe vm-data-source-list vm=

9.1.5. Using RRDs
In order to store performance metrics, XenServer uses (RRDs). These consist of multiple Round Robin Archives
(RRAs) in a fixed size database.
Each archive in the database samples its particular metric on a specified granularity:
•

Every 5 seconds for the duration of 10 minute

•

Every minute for the past two hours

•

Every hour for the past week

•

Every day for the past year

The sampling that takes place every 5 seconds records actual data points, however the following RRAs use
Consolidation Functions (CF) instead. The CFs supported by XenServer are:
•

AVERAGE

•

MIN

•

MAX

RRDs exist for individual VMs (including dom0) and the XenServer host. VM RRDs are stored on the host on which
they run, or the pool master when not running. Therefore the location of a VM must be known in order to retrieve
the associated performance data.
For detailed information on how to use XenServer RRDs, refer to the Citrix Developer Network article: Using
XenServer RRDs.
127

9.1.5.1. Analysing RRDs using HTTP
RRDs can be downloaded over HTTP from the XenServer host specified using the HTTP handler registered at /
host_rrd or /vm_rrd. Both addresses require authentication either by HTTP auth, or by providing a valid
XenAPI session references as a query argument. For example:
Downloading a Host RRD
wget http:///host_rrd?session_id=OpaqueRef:>
Downloading a VM RRD
wget http:///vm_rrd?session_id=OpaqueRef:>&uuid=>
Both of these calls will download XML in a format that can be imported into the rrdtool for analysis, or parsed
directly.
For detailed information on how to use XenServer RRDs with HTTP, refer to the Citrix Developer Network article:
Using XenServer RRDs.

9.1.5.2. Analysing RRDs using rrd2csv
In addition to viewing performance metrics in XenCenter the rrd2csv tool logs RRDs to Comma Separated Value
(CSV) format. Man and help pages are provided. To display the rrd2csv tool man or help pages run the following:
man rrd2csv

or
rrd2csv --help

Note:
Where multiple options are used, they should be supplied individually. For example: to return
both the UUID and the name-label associated with a VM or a host, rrd2csv should be called
as shown below:
rrd2csv -u -n

The UUID returned is unique and suitable as a primary key, however the name-label of an
entity may not necessarily be unique.
The man page (rrd2csv --help) is the definitive help text of the tool.

9.2. Alerts
You can configure XenServer to generate alerts based on any of the available Host or VM Metrics. In addition,
XenServer provides preconfigured alarms that trigger when hosts undergo certain conditions and states. You can
view these alerts using XenCenter or the xe CLI.

9.2.1. Using XenCenter to View Alerts
You can view different types of alerts in XenCenter by clicking Notifications and thenAlerts. The Alerts view
displays various types of alerts, including:
•

Section 9.2.1.1, “XenCenter Performance Alerts”

•

Section 9.2.1.2, “XenCenter Alerts”

•

Section 9.2.1.3, “XenCenter Software Update Alerts”

9.2.1.1. XenCenter Performance Alerts
Performance alerts can be generated when CPU, memory usage, network, storage throughput, or VM disk activity
exceeds a specified threshold on a managed host, VM, or storage repository (SR).
128

By default, the alert repeat interval is set to 60 minutes, it can be modified if required. Alerts will be displayed
on the Alerts page in the Notifications area in XenCenter. In addition, you can configure XenCenter to send an
email for any specified performance alerts along with other serious system alerts. In addition, any customised
alert configured using the xe CLI, will also display on the Alerts page in XenCenter.
Each alert has a corresponding priority/severity level. You can modify these and optionally choose to receive an
email when the alert is triggered. The default alert priority/severity is set at 3.
Priority

Name

Description

Default Email Alert

Critical

Take action now or data may be permanently lost/
corrupted.

Yes

Major

Take action now or some services may fail.

Yes

Warning

Take action now or a service may suffer.

Yes

Minor

Notice that something just improved.

Information

Day-to-day information (VM Start, Stop, Resume
etc.)

Unknown

Unknown error

9.2.1.1.1. To Configure Performance Alerts
To configure performance alerts:
1. In the Resources pane, select the relevant host, VM, or SR, then click the General tab and then Properties.
2. Click the Alerts tab.
•

CPU alerts for a host or VM: select the Generate CPU usage alerts check box, then set the CPU usage and
time threshold that will trigger the alert

•

Network alerts for a host or VM: select the Generate network usage alerts check box, then set the
network usage and time threshold that will trigger the alert.

•

Memory alerts for a host: select the Generate memory usage alerts check box, and then set the memory
usage and time threshold that will trigger the alert.

•

Disk usage alerts for a VM: select the Generate disk usage alerts check box, then set the disk usage and
time threshold that will trigger the alert.

•

Storage throughput alerts for a SR: select the Generate storage throughput alerts check box, then set
the storage throughput and time threshold that will trigger the alert.
Note:
Physical Block Devices (PBD) represent the interface between a specific XenServer host and an
attached SR. When the total read/write SR throughput activity on a PBD exceeds the threshold
you have specified, alerts will be generated on the host connected to the PBD. Unlike other
XenServer host alerts, this must be configured on the SR.

•

To change the alert repeat interval, enter the number of minutes in the Alert repeat interval box. Once
an alert threshold has been reached and an alert generated, another alert will not be generated until
after the alert repeat interval has elapsed.

3. Click OK to save your changes.
For comprehensive details on how to view, filter and configure severities for performance alerts, see the
XenCenter online help.
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9.2.1.2. XenCenter Alerts
The following table displays the system events/conditions that will a trigger an alert to be displayed on the Alerts
page in XenCenter.
Name

Priority/
Severity

Description

license_expires_soon

XenServer License agreement expires soon.

ha-statefile_lost

Lost contact with the HA Storage Repository,
take action soon.

ha-heartbeat_approaching_timeout

HA approaching timeout, host may reboot
unless action is taken.

ha_statefile_approaching_timeout

HA approaching timeout, host may reboot
unless action is taken.

haxapi_healthcheck_approaching_timeout

HA approaching timeout, host may reboot
unless action is taken.

ha_network_bonding_error

Potential service loss. Loss of network that sends
HA heartbeat

ha_pool_overcommited

Potential service loss. HA is unable to guarantee
protection for configured VMs

ha_poor_drop_in_plan_exists_for

HA coverage has dropped, more likely to fail, no
loss present yet

ha_protected_vm_restart_failed

Service Loss. HA was unable to restart a
protected VM

ha_host_failed

HA detected that a host failed

ha_host_was_fenced

HA rebooted a host to protect against VM
corruption

redo_log_healthy

The xapi redo log has recovered from a previous
error

redo_log_broken

The xapi redo log has encountered an error

ip_configured_pif_can_unplug

An IP configured NIC can be unplugged by xapi
when using HA, possibly leading to HA failure.

host_sync_data_failed

Failed to synchronize XenServer performance
statistics

host_clock_skew_detected

The host clock is not synchronized with other
hosts in the pool

host_clock_went_backwards

The host clock is corrupted

pool_master_transition

A new host has been specified as Pool Master

pbd_plug_failed_on_server_start

The host failed to connect to Storage at boot
time.

130

Name

Priority/
Severity

Description

auth_external_init_failed

The host failed to enable external AD
authentication

auth_external_pool_non-homogeneous

Hosts in a pool have different AD authentication
configuration.

multipath_period_alert

A path to a SR has failed or recovered.

bond-status-changed

A link in a bond has disconnected or
reconnected

9.2.1.3. XenCenter Software Update Alerts
Alert

Description

XenCenter old

XenServer expects a newer version but can still connect to the current version

XenCenter out of date

XenCenter is too old to connect to XenServer

XenServer out of date

XenServer is an old version that the current XenCenter cannot connect to

License expired alert

XenServer license has expired

Missing IQN alert

XenServer uses iSCSI storage but the host IQN is blank

Duplicate IQN alert

XenServer uses iSCSI storage, and there are duplicate host IQNs

9.2.2. Configuring Performance Alerts Using the xe CLI
Note:
Triggers for alerts are checked at a minimum interval of five minutes (this avoids placing
excessive load on the system to check for these conditions and reporting of false positives);
setting an alert repeat interval smaller than this will result in the alerts still being generated
at the five minute minimum interval.
The performance monitoring perfmon tool runs once every 5 minutes and requests updates from XenServer
which are averages over 1 minute. These defaults can be changed in /etc/sysconfig/perfmon.
The perfmon tool reads updates every 5 minutes of performance variables running on the same host. These
variables are separated into one group relating to the host itself, and a group for each VM running on that host.
For each VM and XenServer host, perfmon reads the parameter other-config:perfmon and uses this string
to determine which variables to monitor, and under which circumstances to generate a message.
For example, the following shows an example of configuring a VM "CPU usage" alert by writing an XML string
into the parameter other-config:perfmon:
xe vm-param-set uuid= other-config:perfmon=\
'

131

Note:
Multiple nodes are allowed
After setting the new configuration, use the following command to refresh perfmon for each host:
xe host-call-plugin host= plugin=perfmon fn=refresh

If this is not done, there will be a delay before the new configuration takes effect, since by default, perfmon checks
for new configuration once every thirty minutes. This default can be changed in /etc/sysconfig/perfmon.

Valid VM Elements
name
The name of the variable (no default). If the name value is either cpu_usage, network_usage, or
disk_usage the rrd_regex and alarm_trigger_sense parameters are not required as defaults
for these values will be used.
alarm_priority
The priority of the alerts generated (default 3).
alarm_trigger_level
The level of value that triggers an alert (no default).
alarm_trigger_sense
high if alarm_trigger_level is a maximum value otherwise low if the alarm_trigger_level
is a minimum value (the default high).
alarm_trigger_period
The number of seconds that values (above or below the alert threshold) can be received before an alert is
sent (the default is 60).
alarm_auto_inhibit_period
The number of seconds this alarm will be disabled after an alarm is sent (the default is 3600).
consolidation_fn
Combines variables from rrd_updates into one value. For cpu-usage the default is average, for fs_usage
the default isget_percent_fs_usage and for all others - sum.
rrd_regex
Matches the names of variables from xe vm-data-sources-list uuid=, to compute performance
values. This parameter has defaults for the named variables:
•

cpu_usage

•

network_usage

•

disk_usage

If specified, the values of all items returned by xe vm-data-source-list whose names match the specified
regular expression will be consolidated using the method specified as the consolidation_fn.

Valid Host Elements
name
The name of the variable (no default).
alarm_priority
The priority of the alerts generated (default 3).
alarm_trigger_level
The level of value that triggers an alarm (no default).
alarm_trigger_sense
high if alarm_trigger_level is a maximum value otherwise low if the alarm_trigger_level
is a minimum value. (default high)
132

alarm_trigger_period
The number of seconds that values (above or below the alert threshold) can be received before an alarm
is sent (default 60).
alarm_auto_inhibit_period
The number of seconds that the alert is disabled for after an alert is sent. (default 3600).
consolidation_fn
Combines variables from rrd_updates into one value (default sum - or average)
rrd_regex
A regular expression to match the names of variables returned by the xe vm-data-source-list
uuid= command that should be used to compute the statistical value. This parameter has defaults
for the following named variables:
•

cpu_usage

•

network_usage

•

memory_free_kib

•

sr_io_throughput_total_xxxxxxxx (where xxxxxxxxis the first eight characters of the SR-UUID).
Note:
SR Throughput: Storage throughput alerts must be configured on the SR rather than the host.
For example:
xe sr-param-set uuid= other-config:perfmon=\
'

9.2.2.1. Generic Example Configuration
The following example shows a generic configuration:

...

9.3. Configuring Email Alerts
Customers can configure XenServer to send email notifications when alerts are generated by XenServer hosts.
This can be done either by using XenCenter, or by using the xe Command Line Interface (CLI).
133

9.3.1. Enabling Email Alerts Using XenCenter
1. In the Resources pane, right-click on a pool and select Properties.
2. In the Properties window, select Email Options.
3. Select the Send email alert notifications check box and enter the email address and SMTP server details.
Note:
Enter the details of an SMTP server which does not require authentication

9.3.2. Enabling Email Alerts using the xe CLI
Important:
When using XenCenter or the xe CLI to enable email notifications, customers should enter the
details of an SMTP server, which does not require authentication. Emails sent through SMTP
servers which require authentication will not be delivered.
To configure this, specify the email address and SMTP server:
xe pool-param-set uuid= other-config:mail-destination=
xe pool-param-set uuid= other-config:ssmtp-mailhub=

You can also specify the minimum value of the priority (known as 'severity' in XenCenter) field in the message
before the email will be sent:
xe pool-param-set uuid= other-config:mail-max-priority=

The default priority level is 4.
Note:
Some SMTP servers only forward mails with addresses that use FQDNs. If you find that emails
are not being forwarded it may be for this reason, in which case you can set the server
hostname to the FQDN so this is used when connecting to your mail server.

9.3.2.1. Sending Email Alerts Through Authenticated SMTP Servers
The mail-alarm utility in XenServer uses sSMTP to send email notifications. Before sending email notifications,
the mail-alarm utility looks for the configuration file, mail-alarm.conf. If the configuration file exists, the
contents of the file will be used to configure sSMTP, otherwise the details available in the XAPI database (as
configured using XenCenter or the xe CLI) will be used to send email alerts. To send email notifications through
authenticated SMTP servers, customers should create a mail-alarm.conf file in /etc/ with the following
contents:
root=postmaster
authUser=
authPass=
mailhub=:

Note:
This configuration file will be used for all alerts generated by XenServer hosts.

9.3.2.1.1. Additional Configuration Options
Each SMTP server can differ slightly in its setup and may require additional configuration. Refer to the following
extract from the ssmtp.conf man page for the correct syntax and available options:
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NAME
ssmtp.conf – ssmtp configuration file
DESCRIPTION
ssmtp reads configuration data from /etc/ssmtp/ssmtp.conf The file contains keyword-argument pairs, one per line. Lines starting with '#'
and empty lines are interpreted as comments.
The possible keywords and their meanings are as follows (both are caseinsensitive):
Root
The user that gets all mail for userids less than 1000. If blank,
address rewriting is disabled.
Mailhub
The host to send mail to, in the form host | IP_addr port [:
port]. The default port is 25.
RewriteDomain
The domain from which mail seems to come. For user authentication.
Hostname
The full qualified name of the host. If not specified, the host
is queried for its hostname.
FromLineOverride
Specifies whether the From header of an email, if any, may override the default domain. The default is "no".
UseTLS
Specifies whether ssmtp uses TLS to talk to the SMTP server.
The default is "no".
UseSTARTTLS
Specifies whether ssmtp does a EHLO/STARTTLS before starting SSL
negotiation. See RFC 2487.
TLSCert
The file name of an RSA certificate to use for TLS, if required.
AuthUser
The user name to use for SMTP AUTH. The default is blank, in
which case SMTP AUTH is not used.
AuthPass
The password to use for SMTP AUTH.
AuthMethod
The authorization method to use. If unset, plain text is used.
May also be set to "cram-md5".

9.4. Custom Fields and Tags
XenCenter supports the creation of tags and custom fields, which allows for organization and quick searching of
VMs, storage and so on. See the XenCenter Help for more information.

9.5. Custom Searches
XenCenter supports the creation of customized searches. Searches can be exported and imported, and the results
of a search can be displayed in the navigation pane. See the XenCenter Help for more information.
135

9.6. Determining throughput of physical bus adapters
For FC, SAS and iSCSI HBAs you can determine the network throughput of your PBDs using the following
procedure.

To determine PBD throughput
1.

List the PBDs on a host.

Determine which LUNs are routed over which PBDs.

For each PBD and SR, list the VBDs that reference VDIs on the SR.

For all active VBDs that are attached to VMs on the host, calculate the combined throughput.

For iSCSI and NFS storage, check your network statistics to determine if there is a throughput bottleneck at the
array, or whether the PBD is saturated.

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Chapter 10. Troubleshooting
10.1. Support
Citrix provides two forms of support: free, self-help support on the Citrix Support website and paid-for Support
Services, which you can purchase from the Support site. With Citrix Technical Support, you can open a Support
Case online or contact the support center by phone if you experience technical difficulties.
The Citrix Knowledge Center hosts a number of resources that may be helpful to you if you experience odd
behavior, crashes, or other problems. Resources include: Forums, Knowledge Base articles, White Papers, product
documentation, hotfixes and other updates .
If you experience technical difficulties with a XenServer host, this chapter is meant to help you solve the problem
if possible and, failing that, describes where the application logs are located and other information that can help
your Citrix Solution Provider and Citrix track and resolve the issue.
Troubleshooting of installation issues is covered in the XenServer Installation Guide. Troubleshooting of Virtual
Machine issues is covered in the XenServer Virtual Machine User's Guide.
Important:
We recommend that you follow the troubleshooting information in this chapter solely under
the guidance of your Citrix Solution Provider or Citrix Support.
Note:
In some support cases, serial console access is required for debug purposes. Therefore,
when setting up a XenServer configuration, it is recommended that serial console access
is configured. For hosts that do not have physical serial port (such as a Blade server) or
where suitable physical infrastructure is not available, customers should investigate if an
embedded management device, such as Dell DRAC or HP iLO can be configured. For more
information on setting up serial console access, see CTX121442 , How to Set Up a Serial Cable
for Troubleshooting on XenServer.

10.2. Health Check
The Health Check feature enables customers to automate the process of generating and uploading the server
status report to Citrix Insight Services (CIS) and receive CIS analysis reports in XenCenter.
When you connect any eligible pool to XenCenter, you will be prompted to enable Health Check for the pool.
During the enrollment process, you can specify the schedule at which you would like to automatically upload the
server status report to CIS, enter XenServer credentials that will be used to establish a connection with the pool,
and authenticate your uploads with CIS. After the pool is successfully enrolled to Health Check, you will receive
notifications in XenCenter regarding the health of the pool. This enables you to proactively monitor the health
of the XenServer systems based on the report that CIS generates.

Requirements
In order to use the Health Check feature:
•

All hosts in the pool should be running XenServer 7.0

•

You should connect to the XenServer pool using XenCenter shipped with XenServer 7.0

•

XenCenter should have access to the internet

•

The Health Check Service should be installed and running on the XenCenter machine.

•

If using Active Directory (AD), you should have a Pool Operator or a higher role
137

For detailed information about Health Check and for step-by-step instructions on enrolling a pool to Health Check,
see the XenCenter Help.

10.3. XenServer host logs
XenCenter can be used to gather XenServer host information. Click on Server Status Report in the Tools menu to
open the Server Status Report wizard. You can select from a list of different types of information (various logs,
crash dumps, etc.). The information is compiled and downloaded to the machine that XenCenter is running on.
For details, see the XenCenter Help.
Additionally, the XenServer host has several CLI commands to make it simple to collate the output of logs and
various other bits of system information using the utility xen-bugtool. Use the xe command host-bugreportupload to collect the appropriate log files and system information and upload them to the Citrix Support ftp site.
Please refer to Section A.4.9.4, “host-bugreport-upload” for a full description of this command and its optional
parameters. If you are requested to send a crashdump to Citrix Support, use the xe command host-crashdumpupload. Please refer to Section A.4.9.6, “host-crashdump-upload” for a full description of this command and its
optional parameters.
It is possible that sensitive information might be written into the XenServer host logs.

10.3.1. Sending host log messages to a central server
Rather than have logs written to the control domain filesystem, you can configure a XenServer host to write
them to a remote server. The remote server must have the syslogd daemon running on it to receive the logs and
aggregate them correctly. The syslogd daemon is a standard part of all flavors of Linux and Unix, and third-party
versions are available for Windows and other operating systems.

To write logs to a remote server
1.

Set the syslog_destination parameter to the hostname or IP address of the remote server where you want
the logs to be written:
xe host-param-set uuid= logging:syslog_destination=

Issue the command:
xe host-syslog-reconfigure uuid=

to enforce the change. (You can also execute this command remotely by specifying the host parameter.)

10.4. XenCenter logs
XenCenter also has client-side log. This file includes a complete description of all operations and errors that occur
when using XenCenter. It also contains informational logging of events that provide you with an audit trail of
various actions that have occurred. The XenCenter log file is stored in your profile folder. If XenCenter is installed
on Windows XP, the path is
%userprofile%\AppData\Citrix\XenCenter\logs\XenCenter.log
If XenCenter is installed on Windows Vista, the path is
%userprofile%\AppData\Citrix\Roaming\XenCenter\logs\XenCenter.log
To quickly locate the XenCenter log files, for example, when you want to open or email the log file, click on View
Application Log Files in the XenCenter Help menu.

10.5. Troubleshooting connections between XenCenter and the
XenServer host
If you have trouble connecting to the XenServer host with XenCenter, check the following:
138

•

Is your XenCenter an older version than the XenServer host you are attempting to connect to?
The XenCenter application is backward-compatible and can communicate properly with older XenServer
hosts, but an older XenCenter cannot communicate properly with newer XenServer hosts.
To correct this issue, install a XenCenter version that is the same, or newer, than the XenServer host version.

•

Is your license current?
You can see the expiration date for your License Key in the XenServer host General tab under the License
Details section in XenCenter.
For details on licensing a host, see the chapter "Licensing XenServer" in the XenServer Installation Guide.

•

The XenServer host talks to XenCenter using HTTPS over port 443 (a two-way connection for commands and
responses using the XenAPI), and 5900 for graphical VNC connections with paravirtual Linux VMs. If you have
a firewall enabled between the XenServer host and the machine running the client software, make sure that
it allows traffic from these ports.

139

Appendix A. Command Line Interface
This chapter describes the XenServer command line interface (CLI). The xe CLI enables the writing of scripts for
automating system administration tasks and allows integration of XenServer into an existing IT infrastructure.
The xe command line interface is installed by default on XenServer hosts and is included with XenCenter. A standalone remote CLI is also available for Linux.
On Windows, the xe.exe CLI executable is installed along with XenCenter.
To use it, open a Windows Command Prompt and change directories to the directory where the file resides
(typically C:\Program Files\Citrix\XenCenter), or add its installation location to your system path.
On RPM-based distributions (such as, Red Hat and CentOS), you can install the stand-alone xe CLI executable from
the RPM named xe-cli-6.00-@BUILD_NUMBER@.i386.rpm on the main XenServer installation ISO, as
follows:
rpm -ivh xe-cli-6.00-@BUILD_NUMBER@.i386.rpm

Basic help is available for CLI commands on-host by typing:
xe help command

A list of the most commonly-used xe commands is displayed if you type:
xe help

or a list of all xe commands is displayed if you type:
xe help --all

A.1. Basic xe Syntax
The basic syntax of all XenServer xe CLI commands is:
xe ...
Each specific command contains its own set of arguments that are of the form argument=value. Some
commands have required arguments, and most have some set of optional arguments. Typically a command will
assume default values for some of the optional arguments when invoked without them.
If the xe command is executed remotely, additional connection and authentication arguments are used. These
arguments also take the form argument=argument_value.
The server argument is used to specify the hostname or IP address. The username and password
arguments are used to specify credentials. A password-file argument can be specified instead of the
password directly. In this case an attempt is made to read the password from the specified file (stripping CRs and
LFs off the end of the file if necessary), and use that to connect. This is more secure than specifying the password
directly at the command line.
The optional port argument can be used to specify the agent port on the remote XenServer host (defaults to
443).
Example: On the local XenServer host:
xe vm-list

Example: On the remote XenServer host:
xe vm-list -user -password -server

Shorthand syntax is also available for remote connection arguments:
140

-u

username

-pw

password

-pwf

password file

-p

port

-s

server

Example: On a remote XenServer host:
xe vm-list -u -pw -s

Arguments are also taken from the environment variable XE_EXTRA_ARGS, in the form of comma-separated
key/value pairs. For example, in order to enter commands on one XenServer host that are run on a remote
XenServer host, you could do the following:
export XE_EXTRA_ARGS="server=jeffbeck,port=443,username=root,password=pass"

This command means that you will not need to specify the remote XenServer host parameters anymore, in each
xe command you execute.
Using the XE_EXTRA_ARGS environment variable also enables tab completion of xe commands when issued
against a remote XenServer host, which is disabled by default.

A.2. Special Characters and Syntax
To specify argument/value pairs on the xe command line, write:
argument=value
Unless the value includes spaces, do not use quotes. There should be no whitespace in between the argument
name, the equals sign (=), and the value. Any argument not conforming to this format will be ignored.
For values containing spaces, write:
argument="value with spaces"
If you use the CLI while logged into a XenServer host, commands have a tab completion feature similar to that
in the standard Linux bash shell. If you type, for example xe vm-l and then press the TAB key, the rest of the
command will be displayed when it is unambiguous. If more than one command begins with vm-l, pressing TAB
a second time will list the possibilities. This is particularly useful when specifying object UUIDs in commands.
Note:
When executing commands on a remote XenServer host, tab completion does not normally
work. However if you put the server, username, and password in an environment variable
called XE_EXTRA_ARGS on the machine from which you are entering the commands, tab
completion is enabled. See Section A.1, “Basic xe Syntax” for details.

A.3. Command Types
Broadly speaking, the CLI commands can be split in two halves: Low-level commands concerned with listing and
parameter manipulation of API objects, and higher level commands for interacting with VMs or hosts in a more
abstract level. The low-level commands are:
•

-list
141

•

-param-get

•

-param-set

•

-param-list

•

-param-add

•

-param-remove

•

-param-clear

where is one of:
•

bond

•

console

•

host

•

host-crashdump

•

host-cpu

•

network

•

patch

•

pbd

•

pif

•

pool

•

task

•

template

•

vbd

•

vdi

•

vif

•

vlan

•

Note that not every value of has the full set of -param- commands; some have just a subset.

A.3.1. Parameter Types
The objects that are addressed with the xe commands have sets of parameters that identify them and define
their states.
Most parameters take a single value. For example, the name-label parameter of a VM contains a single string
value. In the output from parameter list commands such as xe vm-param-list, such parameters have an indication
in parentheses that defines whether they can be read and written to, or are read-only. For example, the output
of xe vm-param-list on a specified VM might have the lines
user-version ( RW): 1
is-control-domain ( RO): false

The first parameter, user-version, is writable and has the value 1. The second, is-control-domain, is
read-only and has a value of false.
The two other types of parameters are multi-valued. A set parameter contains a list of values. A map parameter
is a set of key/value pairs. As an example, look at the following excerpt of some sample output of the xe vmparam-list on a specified VM:
142

platform (MRW): acpi: true; apic: true; pae: true; nx: false
allowed-operations (SRO): pause; clean_shutdown; clean_reboot; \
hard_shutdown; hard_reboot; suspend

The platform parameter has a list of items that represent key/value pairs. The key names are followed by a
colon character (:). Each key/value pair is separated from the next by a semicolon character (;). The M preceding
the RW indicates that this is a map parameter and is readable and writable. The allowed-operations
parameter has a list that makes up a set of items. The S preceding the RO indicates that this is a set parameter
and is readable but not writable.
In xe commands where you want to filter on a map parameter, or set a map parameter, use the separator : (colon)
between the map parameter name and the key/value pair. For example, to set the value of the foo key of the
other-config parameter of a VM to baa, the command would be
xe vm-param-set uuid= other-config:foo=baa

Note:
In previous releases the separator - (dash) was used in specifying map parameters. This syntax
still works but is deprecated.

A.3.2. Low-level Parameter Commands
There are several commands for operating on parameters of objects: -param-get, -param-set,
-param-add, -param-remove, -param-clear, and -param-list. Each of these takes a
uuid parameter to specify the particular object. Since these are considered low-level commands, they must be
addressed by UUID and not by the VM name label.
-param-list uuid=
Lists all of the parameters and their associated values. Unlike the class-list command, this will list the values
of "expensive" fields.
-param-get uuid= param-name= [param-key=]
Returns the value of a particular parameter. If the parameter is a map, specifying the param-key will get the
value associated with that key in the map. If param-key is not specified, or if the parameter is a set, it will
return a string representation of the set or map.
-param-set uuid= param=...
Sets the value of one or more parameters.
-param-add uuid= param-name= [=...] [param-key=]
Adds to either a map or a set parameter. If the parameter is a map, add key/value pairs using the
= syntax. If the parameter is a set, add keys with the = syntax.
-param-remove uuid= param-name= param-key=
Removes either a key/value pair from a map, or a key from a set.
-param-clear uuid= param-name=
Completely clears a set or a map.

A.3.3. Low-level List Commands
The -list command lists the objects of type . By default it will list all objects, printing a subset of the
parameters. This behavior can be modified in two ways: it can filter the objects so that it only outputs a subset,
and the parameters that are printed can be modified.
To change the parameters that are printed, the argument params should be specified as a comma-separated list
of the required parameters. For example:
xe vm-list params=name-label,other-config

Alternatively, to list all of the parameters, use the syntax:
143

xe vm-list params=all

Note that some parameters that are expensive to calculate will not be shown by the list command. These
parameters will be shown as, for example:
allowed-VBD-devices (SRO):

To obtain these fields, use either the command -param-list or -param-get
To filter the list, the CLI will match parameter values with those specified on the command-line, only printing
objects that match all of the specified constraints. For example:
xe vm-list HVM-boot-policy="BIOS order" power-state=halted

This command will only list those VMs for which both the field power-state has the value halted, and for
which the field HVM-boot-policy has the value BIOS order.
It is also possible to filter the list based on the value of keys in maps, or on the existence of values in a set. The
syntax for the first of these is map-name:key=value, and the second is set-name:contains=value
For scripting, a useful technique is passing --minimal on the command line, causing xe to print only the first
field in a comma-separated list. For example, the command xe vm-list --minimal on a XenServer host with three
VMs installed gives the three UUIDs of the VMs, for example:
a85d6717-7264-d00e-069b-3b1d19d56ad9,aaa3eec5-9499-bcf3-4c03-af10baea96b7, \
42c044de-df69-4b30-89d9-2c199564581d

A.4. xe Command Reference
This section provides a reference to the xe commands. They are grouped by objects that the commands address,
and listed alphabetically.

A.4.1. Appliance Commands
Commands for creating and modifying VM appliances (also known as vApps). For more information on vApps,
see the XenServer Virtual Machine User's Guide.

A.4.1.1. Appliance Parameters
Appliance commands have the following parameters
Parameter Name

Description

Type

uuid

appliance uuid

required

name-description

appliance description

optional

paused
force

optional
force shutdown

optional

A.4.1.2. appliance-assert-can-be-recovered
appliance-assert-can-be-recovered uuid= database:vdi-uuid=
Tests whether storage is available to recover this VM appliance/vApp.

A.4.1.3. appliance-create
appliance-create name-label= [name-description=]
Creates an appliance/vApp. For example:
144

xe appliance-create name-label=my_appliance

Add VMs to the appliance:
xe vm-param-set uuid= appliance= \
xe vm-param-set uuid= appliance=

A.4.1.4. appliance-destroy
appliance-destroy uuid=
Destroys an appliance/vApp. For example:
xe appliance-destroy uuid=

A.4.1.5. appliance-recover
appliance-recover uuid= database:vdi-uuid= [paused=]
Recover a VM appliance/vAPP from the database contained in the supplied VDI.

A.4.1.6. appliance-shutdown
appliance-shutdown uuid= [force=]
Shuts down all VMs in an appliance/vApp. For example:
xe appliance-shutdown uuid=

A.4.1.7. appliance-start
appliance-start uuid= [paused=]
Starts an appliance/vApp. For example:
xe appliance-start uuid=

A.4.2. Audit Commands
Audit commands download all of the available records of the RBAC audit file in the pool. If the optional parameter
since is present, it downloads only the records from that specific point in time.

A.4.2.1. audit-log-get parameters
audit-log-get has the following parameters
Parameter Name

Description

Type

filename

Write the audit log of the pool to

required

since

specific date/time point

optional

A.4.2.2. audit-log-get
audit-log-get [since=] filename=
For example, to obtain audit records of the pool since a precise millisecond timestamp, run the following
command:
Run the following command:
xe audit-log-get since=2009-09-24T17:56:20.530Z \
filename=/tmp/auditlog-pool-actions.out

145

A.4.3. Bonding Commands
Commands for working with network bonds, for resilience with physical interface failover. See Section 4.4.5,
“Creating NIC Bonds on a Standalone Host” for details.
The bond object is a reference object which glues together master and member PIFs. The master PIF is the bonding
interface which must be used as the overall PIF to refer to the bond. The member PIFs are a set of two or more
physical interfaces that have been combined into the high-level bonded interface.

A.4.3.1. Bond Parameters
Bonds have the following parameters:
Parameter Name

Description

Type

uuid

unique identifier/object reference for the
bond

read only

master

UUID for the master bond PIF

read only

members

set of UUIDs for the underlying bonded PIFs

read only set parameter

A.4.3.2. bond-create
bond-create network-uuid= pif-uuids=
Create a bonded network interface on the network specified from a list of existing PIF objects. The command will
fail if PIFs are in another bond already, if any member has a VLAN tag set, if the referenced PIFs are not on the
same XenServer host, or if fewer than 2 PIFs are supplied.

A.4.3.3. bond-destroy
bond-destroy uuid=
Deletes a bonded interface specified by its UUID from a XenServer host.

A.4.4. CD Commands
Commands for working with physical CD/DVD drives on XenServer hosts.

A.4.4.1. CD Parameters
CDs have the following parameters:
Parameter Name

Description

Type

uuid

unique identifier/object reference for the
CD

read only

name-label

Name for the CD

read/write

name-description

Description text for the CD

read/write

allowed-operations

A list of the operations that can be
performed on this CD

read only set parameter

current-operations

A list of the operations that are currently in
progress on this CD

read only set parameter

146

Parameter Name

Description

Type

sr-uuid

The unique identifier/object reference for
the SR this CD is part of

read only

sr-name-label

The name for the SR this CD is part of

read only

vbd-uuids

A list of the unique identifiers for the VBDs
on VMs that connect to this CD

read only set parameter

crashdump-uuids

Not used on CDs since crashdumps cannot
be written to them

read only set parameter

virtual-size

Size of the CD as it appears to VMs (in bytes)

read only

physical-utilisation

amount of physical space that the CD image
is currently taking up on the SR (in bytes)

read only

type

Set to User for CDs

read only

sharable

Whether or not the CD drive is sharable.
Default is false.

read only

read-only

Whether the CD is read-only, if false, the
device is writable. Always true for CDs.

read only

storage-lock

true if this disk is locked at the storage level

read only

parent

Reference to the parent disk, if this CD is part
of a chain

read only

missing

true if SR scan operation reported this CD as
not present on disk

read only

other-config

A list of key/value pairs that specify
additional configuration parameters for the
CD

read/write map parameter

location

The path on which the device is mounted

read only

managed

true if the device is managed

read only

xenstore-data

Data to be inserted into the xenstore tree

read only map parameter

sm-config

names and descriptions of storage manager
device config keys

read only map parameter

is-a-snapshot

True if this template is a CD snapshot

read only

snapshot_of

The UUID of the CD that this template is a
snapshot of

read only

snapshots

The UUID(s) of any snapshots that have been
taken of this CD

read only

snapshot_time

The timestamp of the snapshot operation

read only

A.4.4.2. cd-list
cd-list [params=] [parameter=...]
147

List the CDs and ISOs (CD image files) on the XenServer host or pool, filtering on the optional argument params.
If the optional argument params is used, the value of params is a string containing a list of parameters of this
object that you want to display. Alternatively, you can use the keyword all to show all parameters. If params
is not used, the returned list shows a default subset of all available parameters.
Optional arguments can be any number of the CD parameters listed at the beginning of this section.

A.4.5. Console Commands
Commands for working with consoles.
The console objects can be listed with the standard object listing command (xe console-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.5.1. Console Parameters
Consoles have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object reference for
the console

read only

vm-uuid

The unique identifier/object reference of
the VM this console is open on

read only

vm-name-label

The name of the VM this console is open on

read only

protocol

Protocol this console uses. Possible values
are vt100: VT100 terminal, rfb: Remote
FrameBuffer protocol (as used in VNC), or
rdp: Remote Desktop Protocol

read only

location

URI for the console service

read only

other-config

A list of key/value pairs that specify
additional configuration parameters for the
console.

read/write map parameter

A.4.6. Disaster Recovery (DR) Commands
Commands for recovering VMs in the event of disaster

A.4.6.1. drtask-create
drtask-create type= sr-whitelist= device-config=
Creates a disaster recovery task. For example, to connect to an iSCSI SR in preparation for Disaster Recovery:
xe dr-task-create type=lvmoiscsi device-config:target= \
device-config:targetIQN= device-config:SCSIid= \
sr-whitelist=

Note:
sr-whitelist lists SR UUIDs, drtask-create will only introduce and connect to an SR which has
one of the whitelisted UUIDs
148

A.4.6.2. drtask-destroy
drtask-destroy uuid=
Destroys a disaster recovery task and forgets the introduced SR.

A.4.6.3. vm-assert-can-be-recovered
vm-assert-can-be-recovered uuid= database:vdi-uuid=
Tests whether storage is available to recover this VM.

A.4.6.4. appliance-assert-can-be-recovered
appliance-assert-can-be-recovered uuid= database:vdi-uuid=
Checks whether the storage (containing the appliance's/vAPP disk) is visible.

A.4.6.5. appliance-recover
appliance-recover uuid= database:vdi-uuid= [force=]
Recover an appliance/vAPP from the database contained in the supplied VDI.

A.4.6.6. vm-recover
vm-recover uuid= database:vdi-uuid= [force=]
Recovers a VM from the database contained in the supplied VDI.

A.4.6.7. sr-enable-database-replication
sr-enable-database-replication uuid=
Enables xapi database replication to the specified (shared) SR. For example:
xe sr-enable-database-replication uuid=

A.4.6.8. sr-disable-database-replication
sr-disable-database-replication uuid=
Disables xapi database replication to the specified SR. For example:
xe sr-enable-database-replication uuid=

A.4.6.9. Example Usage
The example below shows the DR CLI commands in context:
On the primary site, enable database replication:
xe sr-database-replication uuid=

In the event of disaster, on the secondary site, connect to the SR:(note device-config has the same fields as srprobe).
xe drtask-create type=lvmoiscsi \
device-config:target= \
device-config:targetIQN= \
device-config:SCSIid= \
sr-whitelist=

149

Look for database VDIs on the SR:
xe vdi-list sr-uuid= type=Metadata

Query a database VDI for VMs present:
xe vm-list database:vdi-uuid=

Recover a VM:
xe vm-recover uuid= database:vdi-uuid=

Destroy the DR task; any SRs introduced by the DR task and not required by VMs are destroyed:
xe drtask-destroy uuid=

A.4.7. Event Commands
Commands for working with events.

A.4.7.1. Event Classes
Event classes are listed in the following table:
Class name

Description

pool

A pool of physical hosts

A Virtual Machine

host

A physical host

network

A virtual network

vif

A virtual network interface

pif

A physical network interface (separate VLANs are represented as several PIFs)

A storage repository

vdi

A virtual disk image

vbd

A virtual block device

pbd

The physical block devices through which hosts access SRs

A.4.7.2. event-wait
event-wait class= [=] [=/=]
Blocks other commands from executing until an object exists that satisfies the conditions given on the command
line. x=y means "wait for field x to take value y", and x=/=y means "wait for field x to take any value other
than y".
Example: wait for a specific VM to be running.
xe event-wait class=vm name-label=myvm power-state=running
Blocks other commands until a VM called myvm is in the power-state "running."
Example: wait for a specific VM to reboot:
150

xe event-wait class=vm uuid=$VM start-time=/=$(xe vm-list uuid=$VM params=start-time --minimal)
Blocks other commands until a VM with UUID $VM reboots (i.e. has a different start-time value).
The class name can be any of the event classes listed at the beginning of this section, and the parameters can be
any of those listed in the CLI command class-param-list.

A.4.8. GPU Commands
Commands for working with physical GPUs, GPU groups and virtual GPUs.
The GPU objects can be listed with the standard object listing commands (xe pgpu-list, xe gpu-group-list,
and xe vgpu-list), and the parameters manipulated with the standard parameter commands. For details, see
Section A.3.2, “Low-level Parameter Commands”.

A.4.8.1. Physical GPU (pGPU) Parameters
pGPUs have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object
reference for the pGPU

Read only

vendor-name

The vendor name of the pGPU

Read only

device-name

The name assigned by the
vendor to this pGPU model

Read only

gpu-group-uuid

The unique identifier/object
reference for the GPU group
that this pGPU has been
automatically assigned to by
XenServer; identical pGPUs
across hosts in a pool are
grouped together

Read only

gpu-group-name-label

The name of the GPU group to
which the pGPU is assigned

Read only

host-uuid

The unique identifier/object
reference for the XenServer
host to which the pGPU is
connected

Read only

host-name-label

The name of the XenServer host
to which the pGPU is connected

Read only

pci-id

PCI identifier

Read only

dependencies

Lists the dependent PCI devices
passed-through to the same VM

Read/write map parameter

other-config

A list of key/value pairs that
specify additional configuration
parameters for the pGPU

Read/write map parameter

supported-VGPU-types

List of virtual GPU types
supported by the underlying
hardware

Read only

151

Parameter Name

Description

Type

enabled-VGPU-types

List of virtual GPU types which
have been enabled for this
pGPU

Read/Write

resident-VGPUs

List of vGPUs running on this
pGPU

Read only

A.4.8.2. pGPU Operations
Commands for working with pGPU Groups

A.4.8.2.1. pgpu-param-set
pgpu-param-set uuid= gpu-group-uuid=
Moves a pGPU to a different GPU group. Command is not allowed if there are running VMs using virtual GPUs
resident on the destination group.

A.4.8.2.2. pgpu-param-get-uuid
pgpu-param-get-uuid
types>

uuid=

param-name=
types=

enabled_VGPU-

Changes the set of enabled virtual GPU types for this type of pGPU.

A.4.8.2.4. pgpu-param-add-uuid
pgpu-param-add-uuid
key=

uuid=

param-name=

Enables a virtual GPU on this pGPU.

A.4.8.3. GPU Group Parameters
GPU groups have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object
reference for the GPU group

Read only

name-label

The name of the GPU group

Read/write

name-description

The descriptive text of the GPU
group

Read/write

VGPU-uuids

Lists the unique identifier/
object references for the virtual
GPUs in the GPU group

Read only set parameter

152

param-

Parameter Name

Description

Type

PGPU-uuids

Lists the unique identifier/
object references for the pGPUs
in the GPU group

Read only set parameter

other-config

A list of key/value pairs that
specify additional configuration
parameters for the GPU group

Read/write map parameter

supported-VGPU-types

Union of all virtual GPU types
supported by the underlying
hardware

Read only

enabled-VGPU-types

Union of all virtual GPU types
which have been enabled on the
underlying pGPUs

Read only

allocation-algorithm

Depth-first/Breadth-first setting
for allocation virtual GPUs on
pGPUs within the group

Read/write enum parameter

A.4.8.3.1. GPU Group Operations
Commands for working with GPU Groups
A.4.8.3.1.1. gpu-group-create

gpu-group-create name-label= [name-description=]
Creates a new (empty) GPU Group into which pGPUs can be moved.
A.4.8.3.1.2. gpu-group-destroy

gpu-group-destroy uuid=
Destroys the GPU Group; only permitted for empty groups.
A.4.8.3.1.3. gpu-group-get-remaining-capacity

gpu-group-get-remaining-capacity uuid= vgpu-type-uuid=
Returns how many more virtual GPUs of the specified type can be instantiated in this GPU Group.
A.4.8.3.1.4. gpu-group-param-set

gpu-group-param-set uuid= allocation-algorithm=
Changes the GPU Group's allocation algorithm for allocating virtual GPUs to pGPUS.
A.4.8.3.1.5. gpu-group-param-get-uuid

gpu-group-param-get-uuid
vGPU-types>

uuid=

Returns the supported or enabled types for this GPU Group.

A.4.8.4. Virtual GPU Parameters
Virtual GPUs have the following parameters:
153

param-name=
uuid=]

gpu_group_uuid=

[vgpu-type-

Creates a virtual GPU. This command attaches the VM to the specified GPU group and optionally specifies the
virtual GPU type. If no virtual GPU type is specified, the 'pass-through' type is assumed.

A.4.8.6.2. vgpu-destroy
vgpu-destroy uuid=
Destroy the specified virtual GPU.

A.4.8.6.3. Disabling VNC for VMs with virtual GPU
xe vm-param-add uuid=param-name=platform vgpu_vnc_enabled=
Using false disables the VNC console for a VM as it passes disablevnc=1 through to the display emulator.
By default, VNC is enabled.

A.4.9. Host Commands
Commands for interacting with XenServer host.
XenServer hosts are the physical servers running XenServer software. They have VMs running on them under the
control of a special privileged Virtual Machine, known as the control domain or domain 0.
The XenServer host objects can be listed with the standard object listing command (xe host-list, xe host-cpulist, and xe host-crashdump-list), and the parameters manipulated with the standard parameter commands. See
Section A.3.2, “Low-level Parameter Commands” for details.

A.4.9.1. Host Selectors
Several of the commands listed here have a common mechanism for selecting one or more XenServer hosts on
which to perform the operation. The simplest is by supplying the argument host=.
XenServer hosts can also be specified by filtering the full list of hosts on the values of fields. For example,
specifying enabled=true will select all XenServer hosts whose enabled field is equal to true. Where
multiple XenServer hosts are matching, and the operation can be performed on multiple XenServer hosts,
the option --multiple must be specified to perform the operation. The full list of parameters that can be
matched is described at the beginning of this section, and can be obtained by running the command xe hostlist params=all. If no parameters to select XenServer hosts are given, the operation will be performed on all
XenServer hosts.
155

A.4.9.2. Host Parameters
XenServer hosts have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object
reference for the XenServer
host

read only

name-label

The name of the XenServer host

read/write

name-description

The description string of the
XenServer host

read only

enabled

false if disabled which prevents
any new VMs from starting
on them, which prepares the
XenServer hosts to be shut
down or rebooted; true if the
host is currently enabled

read only

API-version-major

major version number

read only

API-version-minor

minor version number

read only

API-version-vendor

identification of API vendor

read only

API-version-vendor-implementation

details
of
implementation

read only map parameter

logging

logging configuration

read/write map parameter

suspend-image-sr-uuid

the unique identifier/object
reference for the SR where
suspended images are put

read/write

crash-dump-sr-uuid

the unique identifier/object
reference for the SR where
crash dumps are put

read/write

software-version

list of versioning parameters
and their values

read only map parameter

capabilities

list of Xen versions that the
XenServer host can run

read only set parameter

other-config

A list of key/value pairs that
specify additional configuration
parameters for the XenServer
host

read/write map parameter

chipset-info

A list of key/value pairs that
specify information about the
chipset

Read only map parameter

hostname

XenServer host hostname

read only

address

XenServer host IP address

read only

156

vendor

Parameter Name

Description

Type

license-server

•

A list of key/value pairs that
specify information about
the license server

Read only map parameter

•

The default port for
communications with Citrix
products is 27000. For
information on changing
port numbers due to
conflicts, see Change port
numbers topic on Citrix
Product
Documentation
website.

supported-bootloaders

list of bootloaders that the
XenServer host supports, for
example, pygrub, eliloader

read only set parameter

memory-total

total amount of physical RAM
on the XenServer host, in bytes

read only

memory-free

total amount of physical RAM
remaining that can be allocated
to VMs, in bytes

read only

host-metrics-live

true if the host is operational

read only

logging

The syslog_destination
key can be set to the hostname
of a remote listening syslog
service.

read/write map parameter

allowed-operations

lists the operations allowed in
this state. This list is advisory
only and the server state may
have changed by the time this
field is read by a client.

read only set parameter

current-operations

lists the operations currently in
process. This list is advisory only
and the server state may have
changed by the time this field is
read by a client

read only set parameter

patches

Set of host patches

read only set parameter

blobs

Binary data store

read only

memory-free-computed

A conservative estimate of the
maximum amount of memory
free on a host

read only

ha-statefiles

The UUID(s) of all HA statefiles

read only

ha-network-peers

The UUIDs of all hosts that could
host the VMs on this host in case
of failure

read only

157

Parameter Name

Description

Type

external-auth-type

Type of external authentication,
for example, Active Directory.

read only

external-auth-service-name

The name of the external
authentication service

read only

external-auth-configuration

Configuration information for
the external authentication
service.

read only map parameter

XenServer hosts contain some other objects that also have parameter lists.
CPUs on XenServer hosts have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object reference for
the CPU

read only

number

the number of the physical CPU core within
the XenServer host

read only

vendor

the vendor string for the CPU name, for
example, "GenuineIntel"

read only

speed

The CPU clock speed, in Hz

read only

modelname

the vendor string for the CPU model, for
example, "Intel(R) Xeon(TM) CPU 3.00GHz"

read only

stepping

the CPU revision number

read only

flags

the flags of the physical CPU (a decoded
version of the features field)

read only

Utilisation

the current CPU utilisation

read only

host-uuid

the UUID if the host the CPU is in

read only

model

the model number of the physical CPU

read only

family

the physical CPU family number

read only

Crash dumps on XenServer hosts have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object reference for
the crashdump

read only

host

XenServer host the crashdump corresponds
to

read only

timestamp

Timestamp of the date and time that
the crashdump occurred, in the form
yyyymmdd-hhmmss-ABC, where ABC is the
timezone indicator, for example, GMT

read only

158

Parameter Name

Description

Type

size

size of the crashdump, in bytes

read only

A.4.9.3. host-backup
host-backup file-name= host=
Download a backup of the control domain of the specified XenServer host to the machine that the command is
invoked from, and save it there as a file with the name file-name.
While the xe host-backup command will work if executed on the local host (that is, without a
specific hostname specified), do not use it this way. Doing so would fill up the control domain
partition with the backup file. The command should only be used from a remote off-host
machine where you have space to hold the backup file.

A.4.9.4. host-bugreport-upload
host-bugreport-upload [=...] [url=]
[http-proxy=]
Generate a fresh bug report (using xen-bugtool, with all optional files included) and upload to the Citrix Support
ftp site or some other location.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.
Optional parameters are http-proxy: use specified http proxy, and url: upload to this destination URL. If
optional parameters are not used, no proxy server is identified and the destination will be the default Citrix
Support ftp site.

A.4.9.5. host-crashdump-destroy
host-crashdump-destroy uuid=
Delete a host crashdump specified by its UUID from the XenServer host.

A.4.9.6. host-crashdump-upload
host-crashdump-upload uuid=
[url=]
[http-proxy=]
Upload a crashdump to the Citrix Support ftp site or other location. If optional parameters are not used, no proxy
server is identified and the destination will be the default Citrix Support ftp site. Optional parameters are httpproxy: use specified http proxy, and url: upload to this destination URL.

A.4.9.7. host-disable
host-disable [=...]
Disables the specified XenServer hosts, which prevents any new VMs from starting on them. This prepares the
XenServer hosts to be shut down or rebooted.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.

A.4.9.8. host-dmesg
host-dmesg [=...]
159

Get a Xen dmesg (the output of the kernel ring buffer) from specified XenServer hosts.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.

A.4.9.9. host-emergency-management-reconfigure
host-emergency-management-reconfigure interface=
Reconfigure the management interface of this XenServer host. Use this command only if the XenServer host is
in emergency mode, meaning that it is a member in a resource pool whose master has disappeared from the
network and could not be contacted for some number of retries.

A.4.9.10. host-enable
host-enable [=...]
Enables the specified XenServer hosts, which allows new VMs to be started on them.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.

A.4.9.11. host-evacuate
host-evacuate [=...]
Live migrates all running VMs to other suitable hosts on a pool. The host must first be disabled using the hostdisable command.
If the evacuated host is the pool master, then another host must be selected to be the pool master. To change the
pool master with HA disabled, you need to use the pool-designate-new-master command. See Section A.4.15.2,
“pool-designate-new-master” for details. With HA enabled, your only option is to shut down the server, which
will cause HA to elect a new master at random. See Section A.4.9.29, “host-shutdown”.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.

A.4.9.12. host-forget
host-forget uuid=
The xapi agent forgets about the specified XenServer host without contacting it explicitly.
Use the --force parameter to avoid being prompted to confirm that you really want to perform this operation.
Warning:
Do not use this command if HA is enabled on the pool. Disable HA first, then enable it again
after you've forgotten the host.
Tip:
This command is useful if the XenServer host to "forget" is dead; however, if the XenServer
host is live and part of the pool, you should use xe pool-eject instead.

A.4.9.13. host-get-system-status
host-get-system-status filename=
[entries=] [output=] [=...]
160

Download system status information into the specified file. The optional parameter entries is a commaseparated list of system status entries, taken from the capabilities XML fragment returned by the host-getsystem-status-capabilities command. See Section A.4.9.14, “host-get-system-status-capabilities” for details. If
not specified, all system status information is saved in the file. The parameter output may be tar.bz2 (the
default) or zip; if this parameter is not specified, the file is saved in tar.bz2 form.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above).

A.4.9.14. host-get-system-status-capabilities
host-get-system-status-capabilities [=...]
Get system status capabilities for the specified host(s). The capabilities are returned as an XML fragment that
looks something like this:

...

Each capability entity has a number of attributes.
Attribute

Description

key

A unique identifier for the capability.

content-type

Can be either text/plain or application/data. Indicates whether a UI
can render the entries for human consumption.

default-checked

Can be either yes or no. Indicates whether a UI should select this
entry by default.

min-size, max-size

Indicates an approximate range for the size, in bytes, of this entry.
-1 indicates that the size is unimportant.

min-time, max-time

Indicate an approximate range for the time, in seconds, taken to
collect this entry. -1 indicates the time is unimportant.

pii

Personally identifiable information. Indicates whether the entry
would have information that would identify the system owner, or
details of their network topology. This is one of:
•

no: no PII will be in these entries

•

yes: PII will likely or certainly be in these entries

•

maybe: you might wish to audit these entries for PII

•

if_customized if the files are unmodified, then they will contain
no PII, but since we encourage editing of these files, PII may have
been introduced by such customization. This is used in particular
for the networking scripts in the control domain.

Passwords are never to be included in any bug report, regardless of
any PII declaration.

161

The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above).

A.4.9.15. host-is-in-emergency-mode
host-is-in-emergency-mode
Returns true if the host the CLI is talking to is currently in emergency mode, false otherwise. This CLI
command works directly on slave hosts even with no master host present.

A.4.9.16. host-apply-edition
host-apply-edition
socket"><"xendesktop">]

[host-uuid=]

[edition=xenserver_edition=<"free"><"per-

Assigns a XenServer license to a host server. When you assign a license, XenServer contacts the Citrix License
Server and requests the specified type of license. If a license is available, it is then checked out from the license
server.
For Citrix XenServer for XenDesktop editions, use <"xendesktop">.
For initial licensing configuration, see also license-server-address and license-server-port.

A.4.9.17. host-license-add
host-license-add [license-file=] [host-uuid=]
For XenServer (free edition), use to parse a local license file and add it to the specified XenServer host.

A.4.9.18. host-license-view
host-license-view [host-uuid=]
Displays the contents of the XenServer host license.

A.4.9.19. host-logs-download
host-logs-download [file-name=] [=...]
Download a copy of the logs of the specified XenServer hosts. The copy is saved by default in a time-stamped
file named hostname-yyyy-mm-dd T hh:mm:ssZ.tar.gz. You can specify a different filename using
the optional parameter file-name.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.
While the xe host-logs-download command will work if executed on the local host (that is,
without a specific hostname specified), do not use it this way. Doing so will clutter the control
domain partition with the copy of the logs. The command should only be used from a remote
off-host machine where you have space to hold the copy of the logs.

A.4.9.20. host-management-disable
host-management-disable
162

Disables the host agent listening on an external management network interface and disconnects all connected
API clients (such as the XenCenter). Operates directly on the XenServer host the CLI is connected to, and is not
forwarded to the pool master if applied to a member XenServer host.
Warning:
Be extremely careful when using this CLI command off-host, since once it is run it will not be
possible to connect to the control domain remotely over the network to re-enable it.

A.4.9.21. host-management-reconfigure
host-management-reconfigure [interface= ] | [pif-uuid= ]
Reconfigures the XenServer host to use the specified network interface as its management interface, which is
the interface that is used to connect to the XenCenter. The command rewrites the MANAGEMENT_INTERFACE
key in /etc/xensource-inventory.
If the device name of an interface (which must have an IP address) is specified, the XenServer host will
immediately rebind. This works both in normal and emergency mode.
If the UUID of a PIF object is specified, the XenServer host determines which IP address to rebind to itself. It must
not be in emergency mode when this command is executed.
Warning:
Be careful when using this CLI command off-host and ensure that you have network
connectivity on the new interface. Use xe pif-reconfigure to set one up first. Otherwise,
subsequent CLI commands will reach the XenServer host.

A.4.9.22. host-power-on
host-power-on [host= ]
Turns on power on XenServer hosts with Host Power On functionality enabled. Before using this command, hostset-power-on must be enabled on the host.

A.4.9.23. host-get-cpu-features
host-get-cpu-features {features=} [uuid=]
Prints a hexadecimal representation of the host's physical-CPU features.

A.4.9.24. host-set-cpu-features
host-set-cpu-features {features=} [uuid=]
Attempts to mask the host's physical-CPU features to match the given features. The given string must be a 32-digit
hexadecimal number (optionally containing spaces), as given by the host-get-cpu-features command.

A.4.9.25. host-set-power-on
host-set-power-on {host= {power-on-mode=<""> <"wake-on-lan"> <"iLO"> <"DRAC">
<"custom"> } | [power-on-config=<"power_on_ip"><"power_on_user"><"power_on_password_secret">] }
Use to enable Host Power On functionality on XenServer hosts that are compatible with remote power solutions.
When using the host-set-power-on command, you must specify the type of power management solution
on the host (that is, the ). Then specify configuration options using the
163

argument and its associated key-value pairs. To use the secrets feature to store your password, specify the key
"power_on_password_secret".

A.4.9.26. host-reboot
host-reboot [=...]
Reboot the specified XenServer hosts. The specified hosts must be disabled first using the xe host-disable
command, otherwise a HOST_IN_USE error message is displayed.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.
If the specified XenServer hosts are members of a pool, the loss of connectivity on shutdown will be handled and
the pool will recover when the XenServer hosts returns. If you shut down a pool member, other members and
the master will continue to function. If you shut down the master, the pool will be out of action until the master
is rebooted and back on line (at which point the members will reconnect and synchronize with the master) or
until you make one of the members into the master.

A.4.9.27. host-restore
host-restore [file-name=] [=...]
Restore a backup named file-name of the XenServer host control software. Note that the use of the word
"restore" here does not mean a full restore in the usual sense, it merely means that the compressed backup file
has been uncompressed and unpacked onto the secondary partition. After you've done a xe host-restore, you
have to boot the Install CD and use its Restore from Backup option.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.

A.4.9.28. host-set-hostname-live
host-set-hostname host-uuid= hostname=
Change the hostname of the XenServer host specified by host-uuid. This command persistently sets both
the hostname in the control domain database and the actual Linux hostname of the XenServer host. Note that
hostname is not the same as the value of the name_label field.

A.4.9.29. host-shutdown
host-shutdown [=...]
Shut down the specified XenServer hosts. The specified XenServer hosts must be disabled first using the xe hostdisable command, otherwise a HOST_IN_USE error message is displayed.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.
If the specified XenServer hosts are members of a pool, the loss of connectivity on shutdown will be handled and
the pool will recover when the XenServer hosts returns. If you shut down a pool member, other members and
the master will continue to function. If you shut down the master, the pool will be out of action until the master is
rebooted and back on line, at which point the members will reconnect and synchronize with the master, or until
one of the members is made into the master. If HA is enabled for the pool, one of the members will be made
164

into a master automatically. If HA is disabled, you must manually designate the desired server as master with the
pool-designate-new-master command. See Section A.4.15.2, “pool-designate-new-master”.

A.4.9.30. host-syslog-reconfigure
host-syslog-reconfigure [=...]
Reconfigure the syslog daemon on the specified XenServer hosts. This command applies the configuration
information defined in the host logging parameter.
The host(s) on which this operation should be performed are selected using the standard selection mechanism
(see host selectors above). Optional arguments can be any number of the host parameters listed at the beginning
of this section.

A.4.9.31. host-data-source-list
host-data-source-list [=...]
List the data sources that can be recorded for a host.
Select the host(s) on which to perform this operation by using the standard selection mechanism (see host
selectors). Optional arguments can be any number of the host parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all hosts.
Data sources have two parameters — standard and enabled — which can be seen by the output of this
command. If a data source has enabled set to true, then the metrics are currently being recorded to the
performance database. If a data source has standard set to true, then the metrics are recorded to the
performance database by default (and so, enabled will also be set to true for this data source). If a data source
has standard set to false, then the metrics are not recorded to the performance database by default (and
so, enabled will also be set to false for this data source).
To start recording data source metrics to the performance database, run the host-data-source-record command.
This will set enabled to true. To stop, run the host-data-source-forget. This will set enabled to false.

A.4.9.32. host-data-source-record
host-data-source-record data-source= [=...]
Record the specified data source for a host.
This operation writes the information from the data source to the persistent performance metrics database of
the specified host(s). For performance reasons, this database is distinct from the normal agent database.
Select the host(s) on which to perform this operation by using the standard selection mechanism (see host
selectors). Optional arguments can be any number of the host parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all hosts.

A.4.9.33. host-data-source-forget
host-data-source-forget data-source= [=...]
Stop recording the specified data source for a host and forget all of the recorded data.
Select the host(s) on which to perform this operation by using the standard selection mechanism (see host
selectors). Optional arguments can be any number of the host parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all hosts.
165

A.4.9.34. host-data-source-query
host-data-source-query
selector value>...]

data-source=

[= body= [[host-uuid=] | [sruuid=] | [vm-uuid=] | [pool-uuid=]]
Creates a new message.

A.4.10.3. message-destroy
message-destroy {uuid=}
Destroys an existing message. You can build a script to destroy all messages. For example:
# Dismiss all alerts
\
IFS=","; for m in $(xe message-list params=uuid --minimal); do
xe message-destroy uuid=$m \
done

A.4.10.4. message-list
message-list
166

Lists all messages, or messages that match the specified standard selectable parameters.

A.4.11. Network Commands
Commands for working with networks.
The network objects can be listed with the standard object listing command (xe network-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.11.1. Network Parameters
Networks have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object reference for
the network

read only

name-label

The name of the network

read write

name-description

The description text of the network

read write

VIF-uuids

A list of unique identifiers of the VIFs (virtual
network interfaces) that are attached from
VMs to this network

read only set parameter

PIF-uuids

A list of unique identifiers of the PIFs
(physical network interfaces) that are
attached from XenServer hosts to this
network

read only set parameter

bridge

name of the bridge corresponding to this
network on the local XenServer host

read only

default-locking-mode

A network object used with VIF objects for
ARP filtering. Set to to remove
all the filtering rules associated with the VIF.
Set to so the VIF drops all traffic.
See Section 4.4.10.8, “ Using Switch Port
Locking” and VM parameters .

read write

other-config:staticroutes

comma-separated list of / read write
/ formatted entries
specifying the gateway address through
which to route subnets. For example, setting
other-config:static-routes to
172.16.0.0/15/192.168.0.3,172.18.0.0/16/192.168.0.4
causes traffic on 172.16.0.0/15 to be
routed over 192.168.0.3 and traffic
on 172.18.0.0/16 to be routed over
192.168.0.4.

other-config:ethtoolautoneg

set to no to disable autonegotiation of the
physical interface or bridge. Default is yes.

read write

other-config:ethtool-rx

set to on to enable receive checksum, off
to disable

read write

167

Parameter Name

Description

Type

other-config:ethtool-tx

set to on to enable transmit checksum, off
to disable

read write

other-config:ethtool-sg

set to on to enable scatter gather, off to
disable

read write

other-config:ethtool-tso

set to on to enable tcp segmentation
offload, off to disable

read write

other-config:ethtool-ufo

set to on to enable UDP fragment offload,
off to disable

read write

other-config:ethtool-gso

set to on to enable generic segmentation
offload, off to disable

read write

blobs

Binary data store

read only

A.4.11.2. network-create
network-create name-label= [name-description=]
Creates a new network.

A.4.11.3. network-destroy
network-destroy uuid=
Destroys an existing network.

A.4.12. Patch (Update) Commands
Commands for working with XenServer host patches (updates). These are for the standard non-OEM editions
of XenServer for commands relating to updating the OEM edition of XenServer, see Section A.4.20, “Update
Commands” for details.
The patch objects can be listed with the standard object listing command (xe patch-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.12.1. Patch Parameters
Patches have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object reference for
the patch

read only

host-uuid

The unique identifier for the XenServer host
to query

read only

name-label

The name of the patch

read only

name-description

The description string of the patch

read only

applied

Whether or not the patch has been applied;
true or false

read only

168

Parameter Name

Description

Type

size

Whether or not the patch has been applied;
true or false

read only

A.4.12.2. patch-apply
patch-apply host-uuid= uuid=
Apply the specified patch file.

A.4.12.3. patch-pool-clean
patch-pool-clean uuid=
Deletes the specified patch (hotfix) file from all XenServer hosts in the pool. Can be used after applying hotfix
packages through XenCenter or the CLI, or when dom0 is running out of disk space.

A.4.12.4. patch-pool-apply
patch-pool-apply uuid=
Apply the specified patch to all XenServer hosts in the pool.

A.4.12.5. patch-precheck
patch-precheck uuid= host-uuid=
Run the prechecks contained within the specified patch on the specified XenServer host.

A.4.12.6. patch-upload
patch-upload file-name=
Upload a specified patch file to the XenServer host. This prepares a patch to be applied. On success, the UUID
of the uploaded patch is printed out. If the patch has previously been uploaded, a PATCH_ALREADY_EXISTS
error is returned instead and the patch is not uploaded again.

A.4.13. PBD Commands
Commands for working with PBDs (Physical Block Devices). These are the software objects through which the
XenServer host accesses storage repositories (SRs).
The PBD objects can be listed with the standard object listing command (xe pbd-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.13.1. PBD Parameters
PBDs have the following parameters:
Parameter Name

Description

Type

uuid

The unique identifier/object reference for
the PBD.

read only

169

Parameter Name

Description

Type

sr-uuid

the storage repository that the PBD points to

read only

device-config

additional configuration information that is
provided to the SR-backend-driver of a host

read only map parameter

currently-attached

True if the SR is currently attached on this
host, False otherwise

read only

host-uuid

UUID of the physical machine on which the
PBD is available

read only

host

The host field is deprecated. Use host_uuid
instead.

read only

other-config

Additional configuration information.

read/write map parameter

A.4.13.2. pbd-create
pbd-create host-uuid=
sr-uuid=
[device-config:key=...]
Create a new PBD on a XenServer host. The read-only device-config parameter can only be set on creation.
To add a mapping of 'path' -> '/tmp', the command line should contain the argument deviceconfig:path=/tmp
For a full list of supported device-config key/value pairs on each SR type see Chapter 5, Storage.

A.4.13.3. pbd-destroy
pbd-destroy uuid=
Destroy the specified PBD.

A.4.13.4. pbd-plug
pbd-plug uuid=
Attempts to plug in the PBD to the XenServer host. If this succeeds, the referenced SR (and the VDIs contained
within) should then become visible to the XenServer host.

A.4.13.5. pbd-unplug
pbd-unplug uuid=
Attempt to unplug the PBD from the XenServer host.

A.4.14. PIF Commands
Commands for working with PIFs (objects representing the physical network interfaces).
The PIF objects can be listed with the standard object listing command (xe pif-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.
170

A.4.14.1. PIF Parameters
PIFs have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object reference for
the PIF

read only

device

machine-readable name of the interface (for
example, eth0)

read only

MAC

the MAC address of the PIF

read only

other-config

Additional PIF configuration name:value
pairs.

read/write map parameter

physical

if true, the PIF points to an actual physical
network interface

read only

currently-attached

is the PIF currently attached on this host?
true or false

read only

MTU

Maximum Transmission Unit of the PIF in
bytes.

read only

VLAN

VLAN tag for all traffic passing through
this interface; -1 indicates no VLAN tag is
assigned

read only

bond-master-of

the UUID of the bond this PIF is the master
of (if any)

read only

bond-slave-of

the UUID of the bond this PIF is the slave of
(if any)

read only

management

is this PIF designated to be a management
interface for the control domain

read only

network-uuid

the unique identifier/object reference of
the virtual network to which this PIF is
connected

read only

network-name-label

the name of the of the virtual network to
which this PIF is connected

read only

host-uuid

the unique identifier/object reference of
the XenServer host to which this PIF is
connected

read only

host-name-label

the name of the XenServer host to which this
PIF is connected

read only

IP-configuration-mode

type of network address configuration used;
DHCP or static

read only

IP address of the PIF, defined here if IPconfiguration-mode is static; undefined if
DHCP

read only

171

Parameter Name

Description

Type

netmask

Netmask of the PIF, defined here if IPconfiguration-mode is static; undefined if
supplied by DHCP

read only

gateway

Gateway address of the PIF, defined here if
IP-configuration-mode is static; undefined if
supplied by DHCP

read only

DNS

DNS address of the PIF, defined here if IPconfiguration-mode is static; undefined if
supplied by DHCP

read only

io_read_kbs

average read rate in kB/s for the device

read only

io_write_kbs

average write rate in kB/s for the device

read only

carrier

link state for this device

read only

vendor-id

the ID assigned to NIC's vendor

read only

vendor-name

the NIC vendor's name

read only

device-id

the ID assigned by the vendor to this NIC
model

read only

device-name

the name assigned by the vendor to this NIC
model

read only

speed

data transfer rate of the NIC

read only

duplex

duplexing mode of the NIC; full or half

read only

pci-bus-path

PCI bus path address

read only

other-config:ethtoolspeed

sets the speed of connection in Mbps

read write

other-config:ethtoolautoneg

set to no to disable autonegotiation of the
physical interface or bridge. Default is yes.

read write

other-config:ethtoolduplex

Sets duplexing capability of the PIF, either
full or half.

read write

other-config:ethtool-rx

set to on to enable receive checksum, off
to disable

read write

other-config:ethtool-tx

set to on to enable transmit checksum, off
to disable

read write

other-config:ethtool-sg

set to on to enable scatter gather, off to
disable

read write

other-config:ethtool-tso

set to on to enable tcp segmentation
offload, off to disable

read write

other-config:ethtool-ufo

set to on to enable udp fragment offload,
off to disable

read write

172

Parameter Name

Description

Type

other-config:ethtool-gso

set to on to enable generic segmentation
offload, off to disable

read write

other-config:domain

comma-separated list used to set the DNS
search path

read write

other-config:bondmiimon

interval between link liveness checks, in
milliseconds

read write

other-config:bonddowndelay

number of milliseconds to wait after link is
lost before really considering the link to have
gone. This allows for transient link loss

read write

other-config:bondupdelay

number of milliseconds to wait after the
link comes up before really considering it
up. Allows for links flapping up. Default is
31s to allow for time for switches to begin
forwarding traffic.

read write

disallow-unplug

True if this PIF is a dedicated storage NIC,
false otherwise

read/write

Note:
Changes made to the other-config fields of a PIF will only take effect after a reboot.
Alternately, use the xe pif-unplug and xe pif-plug commands to cause the PIF configuration
to be rewritten.

A.4.14.2. pif-forget
pif-forget uuid=
Destroy the specified PIF object on a particular host.

A.4.14.3. pif-introduce
pif-introduce host-uuid= mac= device=
Create a new PIF object representing a physical interface on the specified XenServer host.

A.4.14.4. pif-plug
pif-plug uuid=
Attempt to bring up the specified physical interface.

A.4.14.5. pif-reconfigure-ip
pif-reconfigure-ip uuid= [ mode= | mode= ]
gateway= IP=
netmask= [DNS=]
Modify the IP address of the PIF. For static IP configuration, set the mode parameter to static, with the
gateway, IP, and netmask parameters set to the appropriate values. To use DHCP, set the mode parameter
to DHCP and leave the static parameters undefined.
173

Note:
Using static IP addresses on physical network interfaces connected to a port on a switch using
Spanning Tree Protocol with STP Fast Link turned off (or unsupported) results in a period
during which there is no traffic.

A.4.14.6. pif-scan
pif-scan host-uuid=
Scan for new physical interfaces on a XenServer host.

A.4.14.7. pif-unplug
pif-unplug uuid=
Attempt to bring down the specified physical interface.

A.4.15. Pool Commands
Commands for working with pools. A pool is an aggregate of one or more XenServer hosts. A pool uses one or
more shared storage repositories so that the VMs running on one XenServer host in the pool can be migrated in
near-real time (while still running, without needing to be shut down and brought back up) to another XenServer
host in the pool. Each XenServer host is really a pool consisting of a single member by default. When a XenServer
host is joined to a pool, it is designated as a member, and the pool it has joined becomes the master for the pool.
The singleton pool object can be listed with the standard object listing command (xe pool-list), and its parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.15.1. Pool Parameters
Pools have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object
reference for the pool

read only

name-label

the name of the pool

read/write

name-description

the description string of the
pool

read/write

master

the unique identifier/object
reference of XenServer host
designated as the pool's master

read only

default-SR

the unique identifier/object
reference of the default SR for
the pool

read/write

crash-dump-SR

the unique identifier/object
reference of the SR where any
crash dumps for pool members
are saved

read/write

174

Parameter Name

Description

Type

metadata-vdis

all known metadata VDIs for the
pool

read only

suspend-image-SR

the unique identifier/object
reference of the SR where
suspended VMs on pool
members are saved

read/write

other-config

a list of key/value pairs that
specify additional configuration
parameters for the pool

read/write map parameter

supported-sr-types

SR types that can be used by this
pool

read only

ha-enabled

True if HA is enabled for the
pool, false otherwise

read only

ha-configuration

reserved for future use.

read only

ha-statefiles

lists the UUIDs of the VDIs
being used by HA to determine
storage health

read only

ha-host-failures-to-tolerate

the number of host failures
to tolerate before sending a
system alert

read/write

ha-plan-exists-for

the number of hosts failures
that can actually be handled,
according to the calculations of
the HA algorithm

read only

ha-allow-overcommit

True if the pool is allowed
to be overcommitted, False
otherwise

read/write

ha-overcommitted

True if the pool is currently
overcommitted

read only

blobs

binary data store

read only

pool-designate-new-master

A.4.15.2. pool-designate-new-master
pool-designate-new-master host-uuid=
Instruct the specified member XenServer host to become the master of an existing pool. This performs an orderly
hand over of the role of master host to another host in the resource pool. This command only works when the
current master is online, and is not a replacement for the emergency mode commands listed below.

A.4.15.3. pool-dump-database
pool-dump-database file-name=
Download a copy of the entire pool database and dump it into a file on the client.
175

A.4.15.4. pool-eject
pool-eject host-uuid=
Instruct the specified XenServer host to leave an existing pool.

A.4.15.5. pool-emergency-reset-master
pool-emergency-reset-master master-address=
Instruct a slave member XenServer host to reset its master address to the new value and attempt to connect to
it. This command should not be run on master hosts.

A.4.15.6. pool-emergency-transition-to-master
pool-emergency-transition-to-master
Instruct a member XenServer host to become the pool master. This command is only accepted by the XenServer
host if it has transitioned to emergency mode, meaning it is a member of a pool whose master has disappeared
from the network and could not be contacted for some number of retries.
Note that this command may cause the password of the host to reset if it has been modified since joining the
pool (see Section A.4.21, “User Commands”).

A.4.15.7. pool-ha-enable
pool-ha-enable heartbeat-sr-uuids=
Enable High Availability on the resource pool, using the specified SR UUID as the central storage heartbeat
repository.

A.4.15.8. pool-ha-disable
pool-ha-disable
Disables the High Availability functionality on the resource pool.

A.4.15.9. pool-join
pool-join master-address= master-username= master-password=
Instruct a XenServer host to join an existing pool.

A.4.15.10. pool-recover-slaves
pool-recover-slaves
Instruct the pool master to try and reset the master address of all members currently running in emergency
mode. This is typically used after pool-emergency-transition-to-master has been used to set one of the members
as the new master.

A.4.15.11. pool-restore-database
pool-restore-database file-name= [dry-run=]
176

Upload a database backup (created with pool-dump-database) to a pool. On receiving the upload, the master
will restart itself with the new database.
There is also a dry run option, which allows you to check that the pool database can be restored without actually
perform the operation. By default, dry-run is set to false.

A.4.15.12. pool-sync-database
pool-sync-database
Force the pool database to be synchronized across all hosts in the resource pool. This is not necessary in normal
operation since the database is regularly automatically replicated, but can be useful for ensuring changes are
rapidly replicated after performing a significant set of CLI operations.

A.4.16. Storage Manager Commands
Commands for controlling Storage Manager plugins.
The storage manager objects can be listed with the standard object listing command (xe sm-list), and the
parameters manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter
Commands” for details.

A.4.16.1. SM Parameters
SMs have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object reference for
the SM plugin

read only

name-label

the name of the SM plugin

read only

name-description

the description string of the SM plugin

read only

type

the SR type that this plugin connects to

read only

vendor

name of the vendor who created this plugin

read only

required-api-version

minimum SM API version required on the
XenServer host

read only

configuration

names and descriptions
configuration keys

read only

capabilities

capabilities of the SM plugin

read only

driver-filename

the filename of the SR driver.

read only

A.4.17. SR Commands
Commands for controlling SRs (storage repositories).
177

device

The SR objects can be listed with the standard object listing command (xe sr-list), and the parameters manipulated
with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for details.

A.4.17.1. SR Parameters
SRs have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object reference for
the SR

read only

name-label

the name of the SR

read/write

name-description

the description string of the SR

read/write

allowed-operations

list of the operations allowed on the SR in
this state

read only set parameter

current-operations

list of the operations that are currently in
progress on this SR

read only set parameter

VDIs

unique identifier/object reference for the
virtual disks in this SR

read only set parameter

PBDs

unique identifier/object reference for the
PBDs attached to this SR

read only set parameter

physical-utilisation

physical space currently utilized on this SR,
in bytes. Note that for thin provisioned disk
formats, physical utilisation may be less than
virtual allocation

read only

physical-size

total physical size of the SR, in bytes

read only

type

type of the SR, used to specify the SR
backend driver to use

read only

introduced-by

the drtask (if any) which introduced the SR

read only

content-type

the type of the SR's content. Used to
distinguish ISO libraries from other SRs. For
storage repositories that store a library of
ISOs, the content-type must be set to
iso. In other cases, Citrix recommends that
this be set either to empty, or the string
user.

read only

shared

True if this SR is capable of being shared
between multiple XenServer hosts; False
otherwise

read/write

other-config

list of key/value pairs that specify additional
configuration parameters for the SR

read/write map parameter

host

The storage repository host name

read only

virtual-allocation

sum of virtual-size values of all VDIs in this
storage repository (in bytes)

read only

178

Parameter Name

Description

Type

sm-config

SM dependent data

read only map parameter

blobs

binary data store

read only

A.4.17.2. sr-create
sr-create name-label= physical-size= type=
content-type= device-config:=
[host-uuid=] [shared=]
Creates an SR on the disk, introduces it into the database, and creates a PBD attaching the SR to a XenServer host.
If shared is set to true, a PBD is created for each XenServer host in the pool; if shared is not specified or set
to false, a PBD is created only for the XenServer host specified with host-uuid.
The exact device-config parameters differ depending on the device type. See Chapter 5, Storage for details
of these parameters across the different storage backends.

A.4.17.3. sr-destroy
sr-destroy uuid=
Destroys the specified SR on the XenServer host.

A.4.17.4. sr-enable-database-replication
sr-enable-database-replication uuid=
Enables xapi database replication to the specified (shared) SR. For example:
xe sr-enable-database-replication uuid=

A.4.17.5. sr-disable-database-replication
sr-disable-database-replication uuid=
Disables xapi database replication to the specified SR. For example:
xe sr-enable-database-replication uuid=

A.4.17.6. sr-forget
sr-forget uuid=
The xapi agent forgets about a specified SR on the XenServer host, meaning that the SR is detached and you
cannot access VDIs on it, but it remains intact on the source media (the data is not lost).

A.4.17.7. sr-introduce
sr-introduce name-label=
physical-size=
type=
content-type=
179

uuid=
Just places an SR record into the database. The device-config parameters are specified by deviceconfig:=, for example:
xe sr-introduce device-config:=

Note:
This command is never used in normal operation. It is an advanced operation which might
be useful if an SR needs to be reconfigured as shared after it was created, or to help recover
from various failure scenarios.

A.4.17.8. sr-probe
sr-probe type= [host-uuid=] [device-config:=]
Performs a backend-specific scan, using the provided device-config keys. If the device-config is
complete for the SR backend, then this will return a list of the SRs present on the device, if any. If the deviceconfig parameters are only partial, then a backend-specific scan will be performed, returning results that will
guide you in improving the remaining device-config parameters. The scan results are returned as backendspecific XML, printed out on the CLI.
The exact device-config parameters differ depending on the device type. See Chapter 5, Storage for details
of these parameters across the different storage backends.

A.4.17.9. sr-scan
sr-scan uuid=
Force an SR scan, syncing the xapi database with VDIs present in the underlying storage substrate.

A.4.18. Task Commands
Commands for working with long-running asynchronous tasks. These are tasks such as starting, stopping, and
suspending a Virtual Machine, which are typically made up of a set of other atomic subtasks that together
accomplish the requested operation.
The task objects can be listed with the standard object listing command (xe task-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.18.1. Task Parameters
Tasks have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object reference for
the Task

read only

name-label

the name of the Task

read only

name-description

the description string of the Task

read only

180

Parameter Name

Description

Type

resident-on

the unique identifier/object reference of the
host on which the task is running

read only

status

current status of the Task

read only

progress

if the Task is still pending, this field contains
the estimated percentage complete, from 0.
to 1. If the Task has completed, successfully
or unsuccessfully, this should be 1.

read only

type

if the Task has successfully completed, this
parameter contains the type of the encoded
result, that is, the name of the class whose
reference is in the result field; otherwise,
this parameter's value is undefined

read only

result

if the Task has completed successfully, this
field contains the result value, either Void
or an object reference; otherwise, this
parameter's value is undefined

read only

error_info

if the Task has failed, this parameter
contains the set of associated error
strings; otherwise, this parameter's value is
undefined

read only

allowed_operations

list of the operations allowed in this state

read only

created

time the task has been created

read only

finished

time task finished (i.e. succeeded or failed).
If task-status is pending, then the value of
this field has no meaning

read only

subtask_of

contains the UUID of the tasks this task is a
sub-task of

read only

subtasks

contains the UUID(s) of all the subtasks of
this task

read only

A.4.18.2. task-cancel
task-cancel [uuid=]
Direct the specified Task to cancel and return.

A.4.19. Template Commands
Commands for working with VM templates.
Templates are essentially VMs with the is-a-template parameter set to true. A template is a "gold image"
that contains all the various configuration settings to instantiate a specific VM. XenServer ships with a base set
of templates, which are generic "raw" VMs that can boot an OS vendor installation CD (e.g. RHEL, CentOS, SLES,
Windows). With XenServer you can create VMs, configure them in standard forms for your particular needs, and
save a copy of them as templates for future use in VM deployment.
181

The template objects can be listed with the standard object listing command (xe template-list), and the
parameters manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter
Commands” for details.
Note:
Templates cannot be directly converted into VMs by setting the is-a-template
parameter to false. Setting is-a-template parameter to false is not supported and
results in a VM that cannot be started.

A.4.19.1. VM Template Parameters
Templates have the following parameters:
Parameter Name

Description

Type

uuid

the
unique
identifier/object
reference for the template

read only

name-label

the name of the template

read/write

name-description

the description string of the template

read/write

user-version

string for creators of VMs and
templates to put version information

read/write

is-a-template

true if this is a template. Template
VMs can never be started, they are
used only for cloning other VMs. After
this value has been set to true it
cannot be reset to false. Template
VMs cannot be converted into VMs
using this parameter.

read/write

is-control-domain

true if this is a control domain
(domain 0 or a driver domain)

read only

power-state

current power state; always halted
for a template

read only

memory-dynamic-max

dynamic maximum memory in bytes.
Currently unused, but if changed
the following constraint must
be obeyed: memory_static_max
>= memory_dynamic_max >=
memory_dynamic_min
>=
memory_static_min.

read/write

memory-dynamic-min

dynamic minimum memory in bytes.
Currently unused, but if changed
the same constraints for memorydynamic-max must be obeyed.

read/write

memory-static-max

statically-set (absolute) maximum
memory in bytes. This is the main
value used to determine the amount
of memory assigned to a VM.

read/write

182

Parameter Name

Description

Type

memory-static-min

statically-set (absolute) minimum
memory in bytes. This represents
the absolute minimum memory, and
memory-static-min must be
less than memory-static-max.
This value is currently unused in
normal operation, but the previous
constraint must be obeyed.

read/write

suspend-VDI-uuid

the VDI that a suspend image is
stored on (has no meaning for a
template)

read only

VCPUs-params

configuration parameters for the
selected VCPU policy.

read/write map parameter

You can tune a VCPU's pinning with
xe template-param-set \
uuid= \
VCPUs-params:mask=1,2,3

A VM created from this template will
then run on physical CPUs 1, 2, and 3
only.
You can also tune the VCPU priority
(xen scheduling) with the cap and
weight parameters; for example
xe template-param-set \
uuid= \
VCPUs-params:weight=512
xe template-param-set \
uuid= \
VCPUs-params:cap=100

A VM based on this template with a
weight of 512 will get twice as much
CPU as a domain with a weight of 256
on a contended XenServer host. Legal
weights range from 1 to 65535 and
the default is 256.
The cap optionally fixes the maximum
amount of CPU a VM based on this
template will be able to consume,
even if the XenServer host has idle
CPU cycles. The cap is expressed in
percentage of one physical CPU: 100
is 1 physical CPU, 50 is half a CPU, 400
is 4 CPUs, etc. The default, 0, means
there is no upper cap.
VCPUs-max

maximum number of VCPUs

read/write

VCPUs-at-startup

boot number of VCPUs

read/write

183

Parameter Name

Description

Type

actions-after-crash

action to take if a VM based on this
template crashes

read/write

console-uuids

virtual console devices

read only set parameter

platform

platform specific configuration

read/write map parameter

To disable the emulation of a parallel
port for HVM guests (for example,
Windows guests):
xe vm-param-set \
uuid= \
platform:parallel=none

To disable the emulation of a serial
port for HVM guests:
xe vm-param-set \
uuid= \
platform:hvm_serial=none

To disable the emulation of a USB
controller and a USB tablet device for
HVM guests:
xe vm-param-set \
uuid= \
platform:usb=false
xe vm-param-set \
uuid= \
platform:usb_tablet=false

allowed-operations

list of the operations allowed in this
state

read only set parameter

current-operations

list of the operations that are
currently in progress on this template

read only set parameter

allowed-VBD-devices

list of VBD identifiers available for
use, represented by integers of the
range 0-15. This list is informational
only, and other devices may be used
(but may not work).

read only set parameter

allowed-VIF-devices

list of VIF identifiers available for use,
represented by integers of the range
0-15. This list is informational only,
and other devices may be used (but
may not work).

read only set parameter

HVM-boot-policy

the boot policy for HVM guests.
Either BIOS Order or an empty
string.

read/write

184

Parameter Name

Description

Type

HVM-boot-params

the order key controls the HVM
guest boot order, represented as a
string where each character is a boot
method: d for the CD/DVD, c for the
root disk, and n for network PXE boot.
The default is dc.

read/write map parameter

PV-kernel

path to the kernel

read/write

PV-ramdisk

path to the initrd

read/write

PV-args

string of kernel command line
arguments

read/write

PV-legacy-args

string of arguments to make legacy
VMs based on this template boot

read/write

PV-bootloader

name of or path to bootloader

read/write

PV-bootloader-args

string of miscellaneous arguments for
the bootloader

read/write

last-boot-CPU-flags

describes the CPU flags on which a
VM based on this template was last
booted; not populated for a template

read only

resident-on

the XenServer host on which a VM
based on this template is currently
resident; appears as for a template

read only

affinity

a XenServer host which a VM based
on this template has preference for
running on; used by the xe vm-start
command to decide where to run the
VM

read/write

other-config

list of key/value pairs that specify
additional configuration parameters
for the template

read/write map parameter

start-time

timestamp of the date and time that
the metrics for a VM based on this
template were read, in the form
yyyymmddThh:mm:ss z, where z
is the single-letter military timezone
indicator, for example, Z for UTC
(GMT); set to 1 Jan 1970 Z (beginning
of Unix/POSIX epoch) for a template

read only

185

Parameter Name

Description

Type

install-time

read only

memory-actual

the actual memory being used by a
VM based on this template; 0 for a
template

read only

VCPUs-number

the number of virtual CPUs assigned
to a VM based on this template; 0 for
a template

read only

VCPUs-Utilization

list of virtual CPUs and their weight

read only map parameter

os-version

the version of the operating system
for a VM based on this template;
appears as
for a template

read only map parameter

PV-drivers-version

the versions of the paravirtualized
drivers for a VM based on this
template; appears as for a template

read only map parameter

PV-drivers-detected

flag for latest version of the
paravirtualized drivers for a VM based
on this template; appears as for a template

read only

memory

memory metrics reported by the
agent on a VM based on this
template; appears as for a template

read only map parameter

disks

disk metrics reported by the agent on
a VM based on this template; appears
as for a
template

read only map parameter

networks

network metrics reported by the
agent on a VM based on this
template; appears as for a template

read only map parameter

other

other metrics reported by the agent
on a VM based on this template;
appears as
for a template

read only map parameter

186

Parameter Name

Description

Type

guest-metrics-last-updated

timestamp when the last write
to these fields was performed by
the in-guest agent, in the form
yyyymmddThh:mm:ss z, where z
is the single-letter military timezone
indicator, for example, Z for UTC
(GMT)

read only

actions-after-shutdown

action to take after the VM has
shutdown

read/write

actions-after-reboot

action to take after the VM has
rebooted

read/write

possible-hosts

list of hosts that could potentially
host the VM

read only

HVM-shadow-multiplier

multiplier applied to the amount of
shadow that will be made available to
the guest

read/write

dom-id

domain ID (if available, -1 otherwise)

read only

recommendations

XML specification of recommended
values and ranges for properties of
this VM

read only

xenstore-data

data to be inserted into the xenstore
tree (/local/domain//vmdata) after the VM is created.

read/write map parameter

is-a-snapshot

True if this template is a VM snapshot

read only

snapshot_of

the UUID of the VM that this template
is a snapshot of

read only

snapshots

the UUID(s) of any snapshots that
have been taken of this template

read only

snapshot_time

the timestamp of the most recent VM
snapshot taken

read only

memory-target

the target amount of memory set for
this template

read only

blocked-operations

lists the operations that cannot be
performed on this template

read/write map parameter

last-boot-record

record of the last boot parameters for
this template, in XML format

read only

ha-always-run

True if an instance of this template
will always restarted on another host
in case of the failure of the host it is
resident on

read/write

ha-restart-priority

restart or best effort

read/write

187

Parameter Name

Description

Type

blobs

binary data store

read only

live

only relevant to a running VM.

read only

A.4.19.2. template-export
template-export template-uuid= filename=
Exports a copy of a specified template to a file with the specified new filename.

A.4.20. Update Commands
Commands for working with updates to the OEM edition of XenServer. For commands relating to updating the
standard non-OEM editions of XenServer, see Section A.4.12, “Patch (Update) Commands” for details.

A.4.20.1. update-upload
update-upload file-name=
Streams a new software image to a OEM edition XenServer host. You must then restart the host for this to take
effect.

A.4.21. User Commands
A.4.21.1. user-password-change
user-password-change old= new=
Changes the password of the logged-in user. The old password field is not checked because you require supervisor
privilege to make this call.

A.4.22. VBD Commands
Commands for working with VBDs (Virtual Block Devices).
A VBD is a software object that connects a VM to the VDI, which represents the contents of the virtual disk. The
VBD has the attributes which tie the VDI to the VM (is it bootable, its read/write metrics, and so on), while the VDI
has the information on the physical attributes of the virtual disk (which type of SR, whether the disk is shareable,
whether the media is read/write or read only, and so on).
The VBD objects can be listed with the standard object listing command (xe vbd-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.22.1. VBD Parameters
VBDs have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object
reference for the VBD

read only

vm-uuid

the unique identifier/object
reference for the VM this VBD is
attached to

read only

vm-name-label

the name of the VM this VBD is
attached to

read only

188

Parameter Name

Description

Type

vdi-uuid

the unique identifier/object
reference for the VDI this VBD is
mapped to

read only

vdi-name-label

the name of the VDI this VBD is
mapped to

read only

empty

if true, this represents an empty
drive

read only

device

the device seen by the guest, for
example hda

read only

userdevice

device number specified by
the device parameter during
vbd-create, for example, 0
for hda, 1 for hdb, etc

read/write

bootable

true if this VBD is bootable

read/write

mode

the mode the VBD should be
mounted with

read/write

type

how the VBD appears to the
VM, for example disk or CD

read/write

currently-attached

True if the VBD is currently
attached on this host, false
otherwise

read only

storage-lock

True if a storage-level lock was
acquired

read only

status-code

error/success code associated
with the last attach operation

read only

status-detail

error/success
information
associated with the last attach
operation status

read only

qos_algorithm_type

the QoS algorithm to use

read/write

qos_algorithm_params

parameters for the chosen QoS
algorithm

read/write map parameter

qos_supported_algorithms

supported QoS algorithms for
this VBD

read only set parameter

io_read_kbs

average read rate in kB per
second for this VBD

read only

io_write_kbs

average write rate in kB per
second for this VBD

read only

189

Parameter Name

Description

Type

allowed-operations

list of the operations allowed in
this state. This list is advisory
only and the server state may
have changed by the time this
field is read by a client.

read only set parameter

current-operations

links each of the running tasks
using this object (by reference)
to a current_operation enum
which describes the nature of
the task.

read only set parameter

unpluggable

true if this VBD will support hotunplug

read/write

attachable

True if the device can be
attached

read only

other-config

additional configuration

read/write map parameter

A.4.22.2. vbd-create
vbd-create vm-uuid= device=
vdi-uuid= [bootable=true] [type=] [mode=]
Create a new VBD on a VM.
The allowable values for the device field are integers from 0-15, and the number must be unique for each VM.
The current allowable values can be seen in the allowed-VBD-devices parameter on the specified VM. This
will be seen as userdevice in the vbd parameters.
If the type is Disk, vdi-uuid is required. Mode can be RO or RW for a Disk.
If the type is CD, vdi-uuid is optional; if no VDI is specified, an empty VBD will be created for the CD. Mode
must be RO for a CD.

A.4.22.3. vbd-destroy
vbd-destroy uuid=
Destroy the specified VBD.
If the VBD has its other-config:owner parameter set to true, the associated VDI will also be destroyed.

A.4.22.4. vbd-eject
vbd-eject uuid=
Remove the media from the drive represented by a VBD. This command only works if the media is of a removable
type (a physical CD or an ISO); otherwise an error message VBD_NOT_REMOVABLE_MEDIA is returned.

A.4.22.5. vbd-insert
vbd-insert uuid= vdi-uuid=
190

Insert new media into the drive represented by a VBD. This command only works if the media is of a removable
type (a physical CD or an ISO); otherwise an error message VBD_NOT_REMOVABLE_MEDIA is returned.

A.4.22.6. vbd-plug
vbd-plug uuid=
Attempt to attach the VBD while the VM is in the running state.

A.4.22.7. vbd-unplug
vbd-unplug uuid=
Attempts to detach the VBD from the VM while it is in the running state.

A.4.23. VDI Commands
Commands for working with VDIs (Virtual Disk Images).
A VDI is a software object that represents the contents of the virtual disk seen by a VM, as opposed to the VBD,
which is a connector object that ties a VM to the VDI. The VDI has the information on the physical attributes of the
virtual disk (which type of SR, whether the disk is shareable, whether the media is read/write or read only, and so
on), while the VBD has the attributes which tie the VDI to the VM (is it bootable, its read/write metrics, and so on).
The VDI objects can be listed with the standard object listing command (xe vdi-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.23.1. VDI Parameters
VDIs have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object reference for
the VDI

read only

name-label

the name of the VDI

read/write

name-description

the description string of the VDI

read/write

allowed-operations

a list of the operations allowed in this state

read only set parameter

current-operations

a list of the operations that are currently in
progress on this VDI

read only set parameter

sr-uuid

SR in which the VDI resides

read only

vbd-uuids

a list of VBDs that refer to this VDI

read only set parameter

crashdump-uuids

list of crash dumps that refer to this VDI

read only set parameter

virtual-size

size of disk as presented to the VM, in
bytes. Note that, depending on the storage
backend type, the size may not be respected
exactly

read only

191

Parameter Name

Description

Type

physical-utilisation

amount of physical space that the VDI is
currently taking up on the SR, in bytes

read only

type

type of VDI, for example, System or User

read only

sharable

true if this VDI may be shared

read only

read-only

true if this VDI can only be mounted readonly

read only

storage-lock

true if this VDI is locked at the storage level

read only

parent

references the parent VDI, if this VDI is part
of a chain

read only

missing

true if SR scan operation reported this VDI as
not present

read only

other-config

additional configuration information for this
VDI

read/write map parameter

sr-name-label

name of the containing storage repository

read only

location

location information

read only

managed

true if the VDI is managed

read only

xenstore-data

data to be inserted into the xenstore
tree (/local/domain/0/backend/
vbd///smdata) after the VDI is attached. This
is generally set by the SM backends on
vdi_attach.

read only map parameter

sm-config

SM dependent data

read only map parameter

is-a-snapshot

true if this VDI is a VM storage snapshot

read only

snapshot_of

the UUID of the storage this VDI is a snapshot
of

read only

snapshots

the UUID(s) of all snapshots of this VDI

read only

snapshot_time

the timestamp of the snapshot operation
that created this VDI

read only

metadata-of-pool

the uuid of the pool which created this
metadata VDI

read only

metadata-latest

flag indicating whether the VDI contains the
latest known metadata for this pool

read only

A.4.23.2. vdi-clone
vdi-clone uuid= [driver-params:]
Create a new, writable copy of the specified VDI that can be used directly. It is a variant of vdi-copy that is capable
of exposing high-speed image clone facilities where they exist.
192

The optional driver-params map parameter can be used for passing extra vendor-specific configuration
information to the back end storage driver that the VDI is based on. See the storage vendor driver documentation
for details.

A.4.23.3. vdi-copy
vdi-copy uuid= sr-uuid=
Copy a VDI to a specified SR.

A.4.23.4. vdi-create
vdi-create sr-uuid=
name-label=
type=
virtual-size=
sm-config-*=
Create a VDI.
The virtual-size parameter can be specified in bytes or using the IEC standard suffixes KiB (210 bytes), MiB
(220 bytes), GiB (230 bytes), and TiB (240 bytes).
Note:
SR types that support thin provisioning of disks (such as Local VHD and NFS) do not enforce
virtual allocation of disks. Users should therefore take great care when over-allocating virtual
disk space on an SR. If an over-allocated SR does become full, disk space must be made
available either on the SR target substrate or by deleting unused VDIs in the SR.
Note:
Some SR types might round up the virtual-size value to make it divisible by a configured
block size.

A.4.23.5. vdi-destroy
vdi-destroy uuid=
Destroy the specified VDI.
Note:
In the case of Local VHD and NFS SR types, disk space is not immediately released on vdidestroy, but periodically during a storage repository scan operation. Users that need to force
deleted disk space to be made available should call sr-scan manually.

A.4.23.6. vdi-forget
vdi-forget uuid=
Unconditionally removes a VDI record from the database without touching the storage backend. In normal
operation, you should be using vdi-destroy instead.

A.4.23.7. vdi-import
vdi-import uuid= filename=
193

Import a raw VDI.

A.4.23.8. vdi-introduce
vdi-introduce uuid=
sr-uuid=
name-label=
type=
location=
[name-description=]
[sharable=]
[read-only=]
[other-config=]
[xenstore-data=]
[sm-config]
Create a VDI object representing an existing storage device, without actually modifying or creating any storage.
This command is primarily used internally to automatically introduce hot-plugged storage devices.

A.4.23.9. vdi-pool-migrate
vdi-pool-migrate = =
Migrate a VDI to a specified SR, while the VDI is attached to a running guest. (Storage XenMotion)
See the chapter "VM Migration" in the XenServer Virtual Machine User's Guide.

A.4.23.10. vdi-resize
vdi-resize uuid= disk-size=
Resize the VDI specified by UUID.

A.4.23.11. vdi-snapshot
vdi-snapshot uuid= [driver-params=]
Produces a read-write version of a VDI that can be used as a reference for backup and/or template creation
purposes. You can perform a backup from a snapshot rather than installing and running backup software inside
the VM. The VM can continue running while external backup software streams the contents of the snapshot to
the backup media. Similarly, a snapshot can be used as a "gold image" on which to base a template. A template
can be made using any VDIs.
The optional driver-params map parameter can be used for passing extra vendor-specific configuration
information to the back end storage driver that the VDI is based on. See the storage vendor driver documentation
for details.
A clone of a snapshot should always produce a writable VDI.

A.4.23.12. vdi-unlock
vdi-unlock uuid= [force=true]
Attempts to unlock the specified VDIs. If force=true is passed to the command, it will force the unlocking
operation.
194

A.4.24. VIF Commands
Commands for working with VIFs (Virtual network interfaces).
The VIF objects can be listed with the standard object listing command (xe vif-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.24.1. VIF Parameters
VIFs have the following parameters:
Parameter Name

Description

Type

uuid

the unique identifier/object reference for the VIF

read only

vm-uuid

the unique identifier/object reference for the VM that this
VIF resides on

read only

vm-name-label

the name of the VM that this VIF resides on

read only

allowed-operations

a list of the operations allowed in this state

read
only
parameter

set

current-operations

a list of the operations that are currently in progress on this
VIF

read
only
parameter

set

device

integer label of this VIF, indicating the order in which VIF
backends were created

read only

MAC

MAC address of VIF, as exposed to the VM

read only

MTU

Maximum Transmission Unit of the VIF in bytes. This
parameter is read-only, but you can override the MTU setting
with the mtu key using the other-config map parameter. For
example, to reset the MTU on a virtual NIC to use jumbo
frames:

read only

xe vif-param-set \
uuid= \
other-config:mtu=9000

currently-attached

true if the device is currently attached

read only

qos_algorithm_type

QoS algorithm to use

read/write

qos_algorithm_params parameters for the chosen QoS algorithm

read/write
parameter

qos_supported_algorithms
supported QoS algorithms for this VIF

read
only
parameter

MAC-autogenerated

True if the MAC address of the VIF was automatically
generated

read only

other-config

Additional configuration key:value pairs

read/write
parameter

other-config:ethtoolrx

set to on to enable receive checksum, off to disable

read write

195

map
set

map

Parameter Name

Description

Type

other-config:ethtooltx

set to on to enable transmit checksum, off to disable

read write

other-config:ethtoolsg

set to on to enable scatter gather, off to disable

read write

other-config:ethtooltso

set to on to enable tcp segmentation offload, off to disable

read write

other-config:ethtoolufo

set to on to enable udp fragment offload, off to disable

read write

other-config:ethtoolgso

set to on to enable generic segmentation offload, off to
disable

read write

otherconfig:promiscuous

true to a VIF to be promiscuous on the bridge, so that it
sees all traffic over the bridge. Useful for running an Intrusion
Detection System (IDS) or similar in a VM.

read write

network-uuid

the unique identifier/object reference of the virtual network
to which this VIF is connected

read only

network-name-label

the descriptive name of the virtual network to which this VIF
is connected

read only

io_read_kbs

average read rate in kB/s for this VIF

read only

io_write_kbs

average write rate in kB/s for this VIF

read only

locking_mode

Affects the VIFs ability to filter traffic to/from a list of MAC
and IP addresses. Requires additional parameters.

read/write

locking_mode:default

Varies according to the default locking mode for the
VIF network. If the default-locking-mode is set to
, XenServer applies a filtering rule so that the VIF
cannot send or receive traffic. If the default-lockingmode is set to , XenServer removes all the
filtering rules associated with the VIF. See also Section A.4.11,
“Network Commands”.

read/write

locking_mode:locked

Only traffic sent to or sent from the specified MAC and
IP addresses is allowed on the VIF. If no IP addresses are
specified, no traffic is allowed.

read/write

locking_mode:unlocked No filters are applied to any traffic going to or from the VIF.

read/write

locking_mode:disabled XenServer applies a filtering rule is applied so that the VIF
drops all traffic.

read/write

A.4.24.2. vif-create
vif-create vm-uuid= device=
network-uuid= [mac=]
Create a new VIF on a VM.
Appropriate values for the device field are listed in the parameter allowed-VIF-devices on the specified
VM. Before any VIFs exist there, the allowable values are integers from 0-15.
196

The mac parameter is the standard MAC address in the form aa:bb:cc:dd:ee:ff. If you leave it unspecified,
an appropriate random MAC address will be created. You can also explicitly set a random MAC address by
specifying mac=random.

A.4.24.3. vif-destroy
vif-destroy uuid=
Destroy a VIF.

A.4.24.4. vif-plug
vif-plug uuid=
Attempt to attach the VIF while the VM is in the running state.

A.4.24.5. vif-unplug
vif-unplug uuid=
Attempts to detach the VIF from the VM while it is running.

A.4.24.6. vif-configure-ipv4
Configure IPv4 settings for this virtual interface. Set IPv4 settings as below:
vif-configure-ipv4
gateway=

uuid=

mode=

address=

For example:
VIF.configure_ipv4(vifObject,"static", " 192.168.1.10/24", " 192.168.1.1")

Clean IPv4 settings as below:
vif-configure-ipv4 uuid= mode=

A.4.24.7. vif-configure-ipv6
Configure IPv6 settings for this virtual interface. Set IPv6 settings as below:
vif-configure-ipv6
gateway=

uuid=

mode=

address=

For example:
VIF.configure_ipv6(vifObject,"static", "fd06:7768:b9e5:8b00::5001/64", "fd06:7768:b9e5:8b00::1")

Clean IPv6 settings as below:
vif-configure-ipv6 uuid= mode=

A.4.25. VLAN Commands
Commands for working with VLANs (virtual networks). To list and edit virtual interfaces, refer to the PIF
commands, which have a VLAN parameter to signal that they have an associated virtual network (see
Section A.4.14, “PIF Commands”). For example, to list VLANs you need to use xe pif-list.

A.4.25.1. vlan-create
vlan-create pif-uuid= vlan= network-uuid=
Create a new VLAN on a XenServer host.

A.4.25.2. pool-vlan-create
pool-vlan-create pif-uuid= vlan= network-uuid=
197

Create a new VLAN on all hosts on a pool, by determining which interface (for example, eth0) the specified
network is on (on each host) and creating and plugging a new PIF object one each host accordingly.

A.4.25.3. vlan-destroy
vlan-destroy uuid=
Destroy a VLAN. Requires the UUID of the PIF that represents the VLAN.

A.4.26. VM Commands
Commands for controlling VMs and their attributes.

A.4.26.1. VM Selectors
Several of the commands listed here have a common mechanism for selecting one or more VMs on which to
perform the operation. The simplest way is by supplying the argument vm=. An easy way to
get the uuid of an actual VM is to, for example, execute xe vm-list power-state=running. (The full list of fields
that can be matched can be obtained by the command xe vm-list params=all. ) For example, specifying powerstate=halted will select all VMs whose power-state parameter is equal to halted. Where multiple VMs
are matching, the option --multiple must be specified to perform the operation. The full list of parameters
that can be matched is described at the beginning of this section, and can be obtained by the command xe vmlist params=all.
The VM objects can be listed with the standard object listing command (xe vm-list), and the parameters
manipulated with the standard parameter commands. See Section A.3.2, “Low-level Parameter Commands” for
details.

A.4.26.2. VM Parameters
VMs have the following parameters:
Note:
All writable VM parameter values can be changed while the VM is running, but the new
parameters are not applied dynamically and will not be applied until the VM is rebooted.
Parameter Name

Description

Type

appliance

the appliance/vApp to which
the VM belongs

read/write

uuid

the unique identifier/object
reference for the VM

read only

name-label

the name of the VM

read/write

name-description

the description string of the VM

read/write

order

start order for vApp startup/
shutdown and for startup after
HA failover

read/write

version

the number of times this VM
has been recovered - if a user
wishes to over write a new VM
with an older version, then they
must call vm-recover

read only

user-version

string for creators of VMs
and templates to put version
information

read/write

198

Parameter Name

Description

Type

is-a-template

False unless this is a template;
template VMs can never be
started, they are used only
for cloning other VMs After
this value has been set to
true it cannot be reset to
false. Template VMs cannot be
converted into VMs using this
parameter.

read/write

is-control-domain

True if this is a control domain
(domain 0 or a driver domain)

read only

power-state

current power state

read only

start delay

the delay to wait before a call to
start up the VM returns

read/write

shutdown-delay

the delay to wait before a call to
shutdown the VM returns

read/write

memory-dynamic-max

dynamic maximum in bytes

read/write

memory-dynamic-min

dynamic minimum in bytes

read/write

memory-static-max

statically-set
maximum in bytes.

read/write

(absolute)

If you want to change this value,
the VM must be shut down.
memory-static-min

statically-set
(absolute)
minimum in bytes. If you want
to change this value, the VM
must be shut down.

read/write

suspend-VDI-uuid

the VDI that a suspend image is
stored on

read only

199

Parameter Name

Description

Type

VCPUs-params

configuration parameters for
the selected VCPU policy.

read/write map parameter

You can tune a VCPU's pinning
with
xe vm-param-set \
uuid= \
VCPUs-params:mask=1,2,3

The selected VM will then run
on physical CPUs 1, 2, and 3
only.
You can also tune the VCPU
priority (xen scheduling) with
the cap and weight parameters;
for example
xe vm-param-set \
uuid= \
VCPUs-params:weight=512
xe vm-param-set \
uuid= \
VCPUs-params:cap=100

A VM with a weight of 512 will
get twice as much CPU as a
domain with a weight of 256
on a contended XenServer host.
Legal weights range from 1 to
65535 and the default is 256.
The cap optionally fixes the
maximum amount of CPU a VM
will be able to consume, even if
the XenServer host has idle CPU
cycles. The cap is expressed in
percentage of one physical CPU:
100 is 1 physical CPU, 50 is half
a CPU, 400 is 4 CPUs, etc. The
default, 0, means there is no
upper cap.
VCPUs-max

maximum number of virtual
CPUs.

read/write

VCPUs-at-startup

boot number of virtual CPUs

read/write

200

Parameter Name

Description

Type

actions-after-crash

action to take if the VM crashes.
For PV guests, valid parameters
are: preserve (for analysis only),
coredump_and_restart (record
a coredump and reboot VM),
coredump_and_destroy (record
a coredump and leave VM
halted), restart (no coredump
and restart VM), and destroy
(no coredump and leave VM
halted).

read/write

console-uuids

virtual console devices

read only set parameter

platform

platform-specific configuration

read/write map parameter

allowed-operations

list of the operations allowed in
this state

read only set parameter

current-operations

a list of the operations that are
currently in progress on the VM

read only set parameter

allowed-VBD-devices

list of VBD identifiers available
for use, represented by integers
of the range 0-15. This list is
informational only, and other
devices may be used (but may
not work).

read only set parameter

allowed-VIF-devices

list of VIF identifiers available
for use, represented by integers
of the range 0-15. This list is
informational only, and other
devices may be used (but may
not work).

read only set parameter

HVM-boot-policy

the boot policy for HVM guests.
Either BIOS Order or an
empty string.

read/write

HVM-boot-params

the order key controls
the HVM guest boot order,
represented as a string where
each character is a boot
method: d for the CD/DVD, c for
the root disk, and n for network
PXE boot. The default is dc.

read/write map parameter

HVM-shadow-multiplier

Floating point value which
controls the amount of shadow
memory overhead to grant
the VM. Defaults to 1.0 (the
minimum value), and should
only be changed by advanced
users.

read/write

201

Parameter Name

Description

Type

PV-kernel

path to the kernel

read/write

PV-ramdisk

path to the initrd

read/write

PV-args

string of kernel command line
arguments

read/write

PV-legacy-args

string of arguments to make
legacy VMs boot

read/write

PV-bootloader

name of or path to bootloader

read/write

PV-bootloader-args

string
of
miscellaneous
arguments for the bootloader

read/write

last-boot-CPU-flags

describes the CPU flags on
which the VM was last booted

read only

resident-on

the XenServer host on which a
VM is currently resident

read only

affinity

a XenServer host which the
VM has preference for running
on; used by the xe vm-start
command to decide where to
run the VM

read/write

other-config

A list of key/value pairs that
specify additional configuration
parameters for the VM

read/write map parameter

For example, a VM will
be started automatically after
host boot if the other-config
parameter includes the key/
value pair auto_poweron: true
start-time

timestamp of the date and
time that the metrics for
the VM were read, in the
form yyyymmddThh:mm:ss
z, where z is the single-letter
military timezone indicator, for
example, Z for UTC (GMT)

read only

install-time

timestamp of the date and
time that the metrics for
the VM were read, in the
form yyyymmddThh:mm:ss
z, where z is the single-letter
military timezone indicator, for
example, Z for UTC (GMT)

read only

memory-actual

the actual memory being used
by a VM

read only

202

Parameter Name

Description

Type

VCPUs-number

the number of virtual CPUs
assigned to the VM

read only

For a paravirtualized Linux
VM, this number can differ
from VCPUS-max and can
be changed without rebooting
the VM using the vmvcpu-hotplug command. See
Section A.4.26.34, “vm-vcpuhotplug”. Windows VMs always
run with the number of vCPUs
set to VCPUs-max and must be
rebooted to change this value.
Note that performance will drop
sharply if you set VCPUsnumber to a value greater than
the number of physical CPUs on
the XenServer host.
VCPUs-Utilization

a list of virtual CPUs and their
weight

read only map parameter

os-version

the version of the operating
system for the VM

read only map parameter

PV-drivers-version

the
versions
of
the
paravirtualized drivers for the
VM

read only map parameter

PV-drivers-detected

flag for latest version of the
paravirtualized drivers for the
VM

read only

memory

memory metrics reported by
the agent on the VM

read only map parameter

disks

disk metrics reported by the
agent on the VM

read only map parameter

networks

network metrics reported by
the agent on the VM

read only map parameter

other

other metrics reported by the
agent on the VM

read only map parameter

guest-metrics-last-updated

timestamp when the last write
to these fields was performed
by the in-guest agent, in the
form yyyymmddThh:mm:ss
z, where z is the single-letter
military timezone indicator, for
example, Z for UTC (GMT)

read only

203

Parameter Name

Description

Type

actions-after-shutdown

action to take after the VM has
shutdown

read/write

actions-after-reboot

action to take after the VM has
rebooted

read/write

possible-hosts

potential hosts of this VM

read only

dom-id

domain ID (if available, -1
otherwise)

read only

recommendations

XML
specification
of
recommended values and
ranges for properties of this VM

read only

xenstore-data

data to be inserted into
the xenstore tree (/local/
domain//vmdata) after the VM is created

read/write map parameter

is-a-snapshot

True if this VM is a snapshot

read only

snapshot_of

the UUID of the VM this is a
snapshot of

read only

snapshots

the UUID(s) of all snapshots of
this VM

read only

snapshot_time

the timestamp of the snapshot
operation that created this VM
snapshot

read only

memory-target

the target amount of memory
set for this VM

read only

blocked-operations

lists the operations that cannot
be performed on this VM

read/write map parameter

last-boot-record

record of the last boot
parameters for this template, in
XML format

read only

ha-always-run

True if this VM will always
restarted on another host in
case of the failure of the host it
is resident on

read/write

ha-restart-priority

restart or best effort

read/write

blobs

binary data store

read only

live

True if the VM is running, false
if HA suspects that the VM may
not be running.

read only

A.4.26.3. vm-assert-can-be-recovered
vm-assert-can-be-recovered []
204

Tests whether storage is available to recover this VM.

A.4.26.4. vm-cd-add
vm-cd-add cd-name= device=
[=...]
Add a new virtual CD to the selected VM. The device parameter should be selected from the value of the
allowed-VBD-devices parameter of the VM.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.5. vm-cd-eject
vm-cd-eject [=...]
Eject a CD from the virtual CD drive. This command only works if there is one and only one CD attached to the
VM. When there are two or more CDs, use the command xe vbd-eject and specify the UUID of the VBD.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.6. vm-cd-insert
vm-cd-insert cd-name= [=...]
Insert a CD into the virtual CD drive. This command will only work if there is one and only one empty CD device
attached to the VM. When there are two or more empty CD devices, use the xe vbd-insert command and specify
the UUIDs of the VBD and of the VDI to insert.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.7. vm-cd-list
vm-cd-list [vbd-params] [vdi-params] [=...]
Lists CDs attached to the specified VMs.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
You can also select which VBD and VDI parameters to list.

A.4.26.8. vm-cd-remove
vm-cd-remove cd-name= [=...]
Remove a virtual CD from the specified VMs.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
205

A.4.26.9. vm-clone
vm-clone new-name-label=
[new-name-description=] [=...]
Clone an existing VM, using storage-level fast disk clone operation where available. Specify the name
and the optional description for the resulting cloned VM using the new-name-label and new-namedescription arguments.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.10. vm-compute-maximum-memory
vm-compute-maximum-memory total=
[approximate=]
[=...]
Calculate the maximum amount of static memory which can be allocated to an existing VM, using the total
amount of physical RAM as an upper bound. The optional parameter approximate reserves sufficient extra
memory in the calculation to account for adding extra vCPUs into the VM at a later date.
For example:
xe vm-compute-maximum-memory vm=testvm total=`xe host-list params=memory-free --minimal`

This command uses the value of the memory-free parameter returned by the xe host-list command to set the
maximum memory of the VM named testvm.
The VM or VMs on which this operation will be performed are selected using the standard selection mechanism
(see VM selectors). Optional arguments can be any number of the VM parameters listed at the beginning of this
section.

A.4.26.11. vm-copy
vm-copy new-name-label= [new-name-description=]
[sr-uuid=] [=...]
Copy an existing VM, but without using storage-level fast disk clone operation (even if this is available). The disk
images of the copied VM are guaranteed to be "full images", that is, not part of a copy-on-write (CoW) chain.
Specify the name and the optional description for the resulting copied VM using the new-name-label and
new-name-description arguments.
Specify the destination SR for the resulting copied VM using the sr-uuid. If this parameter is not specified, the
destination is the same SR that the original VM is in.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.12. vm-crashdump-list
vm-crashdump-list [=...]
List crashdumps associated with the specified VMs.
If the optional argument params is used, the value of params is a string containing a list of parameters of this
object that you want to display. Alternatively, you can use the keyword all to show all parameters. If params
is not used, the returned list shows a default subset of all available parameters.
206

The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.13. vm-data-source-list
vm-data-source-list [=...]
List the data sources that can be recorded for a VM.
Select the VM(s) on which to perform this operation by using the standard selection mechanism (see VM
selectors). Optional arguments can be any number of the VM parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all VMs.
Data sources have two parameters — standard and enabled — which can be seen by the output of this
command. If a data source has enabled set to true, then the metrics are currently being recorded to the
performance database. If a data source has standard set to true, then the metrics are recorded to the
performance database by default (and so, enabled will also be set to true for this data source). If a data source
has standard set to false, then the metrics are not recorded to the performance database by default (and
so, enabled will also be set to false for this data source).
To start recording data source metrics to the performance database, run the vm-data-source-record command.
This will set enabled to true. To stop, run the vm-data-source-forget. This will set enabled to false.

A.4.26.14. vm-data-source-record
vm-data-source-record data-source= [=...]
Record the specified data source for a VM.
This operation writes the information from the data source to the persistent performance metrics database of
the specified VM(s). For performance reasons, this database is distinct from the normal agent database.
Select the VM(s) on which to perform this operation by using the standard selection mechanism (see VM
selectors). Optional arguments can be any number of the VM parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all VMs.

A.4.26.15. vm-data-source-forget
vm-data-source-forget data-source= [=...]
Stop recording the specified data source for a VM and forget all of the recorded data.
Select the VM(s) on which to perform this operation by using the standard selection mechanism (see VM
selectors). Optional arguments can be any number of the VM parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all VMs.

A.4.26.16. vm-data-source-query
vm-data-source-query data-source= [=...]
Display the specified data source for a VM.
Select the VM(s) on which to perform this operation by using the standard selection mechanism (see VM
selectors). Optional arguments can be any number of the VM parameters listed at the beginning of this section.
If no parameters to select hosts are given, the operation will be performed on all VMs.
207

A.4.26.17. vm-destroy
vm-destroy uuid=
Destroy the specified VM. This leaves the storage associated with the VM intact. To delete storage as well, use
xe vm-uninstall.

A.4.26.18. vm-disk-add
vm-disk-add disk-size= device=
[=...]
Add a new disk to the specified VMs. Select the device parameter from the value of the allowed-VBDdevices parameter of the VMs.
The disk-size parameter can be specified in bytes or using the IEC standard suffixes KiB (210 bytes), MiB (220
bytes), GiB (230 bytes), and TiB (240 bytes).
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.19. vm-disk-list
vm-disk-list [vbd-params] [vdi-params] [=...]
Lists disks attached to the specified VMs. The vbd-params and vdi-params parameters control the fields
of the respective objects to output and should be given as a comma-separated list, or the special key all for
the complete list.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.20. vm-disk-remove
vm-disk-remove device= [=...]
Remove a disk from the specified VMs and destroy it.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.21. vm-export
vm-export filename=
[metadata=]
[=...]
Export the specified VMs (including disk images) to a file on the local machine. Specify the filename to export the
VM into using the filename parameter. By convention, the filename should have a .xva extension.
If the metadata parameter is true, then the disks are not exported, and only the VM metadata is written to
the output file. This is intended to be used when the underlying storage is transferred through other mechanisms,
and permits the VM information to be recreated (see Section A.4.26.22, “vm-import”).
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
208

A.4.26.22. vm-import
vm-import filename=
[metadata=]
[preserve=]
[sr-uuid=]
Import a VM from a previously-exported file. If preserve is set to true, the MAC address of the original VM
will be preserved. The sr-uuid determines the destination SR to import the VM into, and is the default SR if
not specified.
The filename parameter can also point to an XVA-format VM, which is the legacy export format from XenServer
3.2 and is used by some third-party vendors to provide virtual appliances. This format uses a directory to store the
VM data, so set filename to the root directory of the XVA export and not an actual file. Subsequent exports of
the imported legacy guest will automatically be upgraded to the new filename-based format, which stores much
more data about the configuration of the VM.
Note:
The older directory-based XVA format does not fully preserve all the VM attributes. In
particular, imported VMs will not have any virtual network interfaces attached by default. If
networking is required, create one using vif-create and vif-plug.
If the metadata is true, then a previously exported set of metadata can be imported without their associated
disk blocks. Metadata-only import will fail if any VDIs cannot be found (named by SR and VDI.location) unless
the --force option is specified, in which case the import will proceed regardless. If disks can be mirrored or
moved out-of-band then metadata import/export represents a fast way of moving VMs between disjoint pools
(e.g. as part of a disaster recovery plan).
Note:
Multiple VM imports will be performed faster in serial that in parallel.

A.4.26.23. vm-install
vm-install new-name-label=
[ template-uuid= | [template=]]
[ sr-uuid= | sr-name-label= ]
[ copy-bios-strings-from= ]
Install or clone a VM from a template. Specify the template name using either the template-uuid or
template argument. Specify an SR using either the sr-uuid or sr-name-label argument. Specify to
install BIOS-locked media using the copy-bios-strings-from argument.
Note:
When installing from a template that has existing disks, by default, new disks will be created
in the same SR as these existing disks. Where the SR supports it, these will be fast copies. If
a different SR is specified on the command line, the new disks will be created there. In this
case a fast copy is not possible and the disks will be full copies.
When installing from a template that does not have existing disks, any new disks will be
created in the SR specified, or the pool default SR if not specified.

A.4.26.24. vm-memory-shadow-multiplier-set
vm-memory-shadow-multiplier-set [=...]
[multiplier=]
Set the shadow memory multiplier for the specified VM.
209

This is an advanced option which modifies the amount of shadow memory assigned to a hardware-assisted VM.
In some specialized application workloads, such as Citrix XenApp, extra shadow memory is required to achieve
full performance.
This memory is considered to be an overhead. It is separated from the normal memory calculations for accounting
memory to a VM. When this command is invoked, the amount of free XenServer host memory will decrease
according to the multiplier, and the HVM_shadow_multiplier field will be updated with the actual value
which Xen has assigned to the VM. If there is not enough XenServer host memory free, then an error will be
returned.
The VMs on which this operation should be performed are selected using the standard selection mechanism (see
VM selectors for more information).

A.4.26.25. vm-migrate
vm-migrate [=] [host-uuid=] [host=] [=] [=] [=...]
[=]
[=]
[=] [=]
[=] [=]
This command migrates the specified VMs between physical hosts. The host parameter can be either the name
or the UUID of the XenServer host. For example, to migrate the VM to another host in the pool, where the VM
disks are located on storage shared by both hosts (known as XenMotion):
xe vm-migrate uuid=
host-uuid=

To move VMs between hosts in the same pool, which do not share storage (Storage XenMotion):
xe vm-migrate uuid= remote-master=12.34.56.78 \
remote-username= remote-password= \
host-uuid= vdi=

You can choose the SR where each VDI gets stored:
xe vm-migrate uuid= host-uuid= \
vdi1:= \
vdi2:= \
vdi3:=

Additionally, you can choose which network to attach the VM after migration:
xe vm-migrate uuid= \
vdi1:= \
vdi2:= \
vdi3:= \
vif:=

For cross-pool migration:
xe vm-migrate uuid= remote-master=12.34.56.78
remote-username= remote-password= \
host-uuid= vdi=

For more information on Storage XenMotion, XenMotion and Live VDI Migration, refer to the VM User's Guide.
By default, the VM will be suspended, migrated, and resumed on the other host. The live parameter activates
XenMotion and keeps the VM running while performing the migration, thus minimizing VM downtime to less
than a second. In some circumstances such as extremely memory-heavy workloads in the VM, XenMotion
automatically falls back into the default mode and suspends the VM for a brief period of time before completing
the memory transfer.
210

A.4.26.26. vm-reboot
vm-reboot [=...] [force=]
Reboot the specified VMs.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
Use the force argument to cause an ungraceful shutdown, akin to pulling the plug on a physical server.

A.4.26.27. vm-recover
vm-recover [] [] []
Recovers a VM from the database contained in the supplied VDI.

A.4.26.28. vm-reset-powerstate
vm-reset-powerstate [=...] {force=true}
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
This is an advanced command only to be used when a member host in a pool goes down. You can use this
command to force the pool master to reset the power-state of the VMs to be halted. Essentially this forces the
lock on the VM and its disks so it can be subsequently started on another pool host. This call requires the force
flag to be specified, and fails if it is not on the command-line.

A.4.26.29. vm-resume
vm-resume [=...] [force=] [on=]
Resume the specified VMs.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
If the VM is on a shared SR in a pool of hosts, use the on argument to specify which host in the pool on which to
start it. By default the system will determine an appropriate host, which might be any of the members of the pool.

A.4.26.30. vm-shutdown
vm-shutdown [=...] [force=]
Shut down the specified VM.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
Use the force argument to cause an ungraceful shutdown, similar to pulling the plug on a physical server.
211

A.4.26.31. vm-start
vm-start [=...] [force=] [on=] [-multiple]
Start the specified VMs.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.
If the VMs are on a shared SR in a pool of hosts, use the on argument to specify which host in the pool on which
to start the VMs. By default the system will determine an appropriate host, which might be any of the members
of the pool.

A.4.26.32. vm-suspend
vm-suspend [=...]
Suspend the specified VM.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.33. vm-uninstall
vm-uninstall [=...] [force=]
Uninstall a VM, destroying its disks (those VDIs that are marked RW and connected to this VM only) as well as its
metadata record. To simply destroy the VM metadata, use xe vm-destroy.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed at the
beginning of this section.

A.4.26.34. vm-vcpu-hotplug
vm-vcpu-hotplug new-vcpus= [=...]
Dynamically adjust the number of VCPUs available to a running paravirtual Linux VM within the number bounded
by the parameter VCPUs-max. Windows VMs always run with the number of VCPUs set to VCPUs-max and
must be rebooted to change this value.
The paravirtualized Linux VM or VMs on which this operation should be performed are selected using the standard
selection mechanism (see VM selectors). Optional arguments can be any number of the VM parameters listed
at the beginning of this section.
Note:
When running certain Linux VMs (such as Debian) without XenServer Tools installed,
customers should run the following command on the VM as root to ensure the newly
hotplugged vCPUs are used:
# for i in /sys/devices/system/cpu/cpu[1-9]*/online;
[ "$(cat $i)" = 0 ]; then echo 1 > $i; fi; done

A.4.26.35. vm-vif-list
vm-vif-list [=...]
212

Lists the VIFs from the specified VMs.
The VM or VMs on which this operation should be performed are selected using the standard selection
mechanism (see VM selectors). Note that the selectors operate on the VM records when filtering, and not on the
VIF values. Optional arguments can be any number of the VM parameters listed at the beginning of this section.

213

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