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Chapter 8. Applying Updates and Hotfixes
to XenServer
Between releases of XenServer, Citrix occasionally releases updates and hotfixes. Hotfixes fix one or more specific
issues; updates contain accumulated bug fixes and, occasionally, small feature improvements. This chapter
describes the general procedures for applying updates and hotfixes to your XenServer deployment through
XenCenter and the xe CLI.
Public hotfixes and updates are made available for download from the Citrix Knowledge Center. Specific
information and instructions regarding each download are published alongside. It is best to check the Knowledge
Center for new updates and hotfixes. You may also receive an e-mail or an alert in XenCenter when a particularly
important hotfix or update is released for the version of XenServer that you are running. XenCenter also provides
you an option to check for available updates manually at any time by choosing the Tools > Check for Updates
option from the XenCenter menu.
Hotfixes and updates can often be applied with minimal service interruption. If you are updating a pool of
XenServer hosts, you can avoid downtime of VMs by updating one host at a time, migrating VMs away from each
host as the hotfix or update is applied. XenCenter can take care of this update sequence automatically. If you are
using the xe CLI, you will have to do this manually.
8.1. Before You Apply an Update or Hotfix
Important:
It is important to follow the Readme that comes with each update file. Each update file has
unique instructions for installation, particularly with regard to preparatory and post-update
operations. The following sections offer general guidance and instructions for applying
hotfixes and updates to your XenServer deployment.
Before you update XenServer hosts, it is important to be aware of the following:
• It is best to update all hosts in a pool within a short period, as running a mixed-mode pool (a pool that includes
updated and non-updated hosts) for general operation is not supported.
• Citrix recommends that you reboot any hosts that you plan to update to ensure that the hosts are healthy
and configurations correct (for example, to ensure that VMs start and that storage is accessible). Rebooting is
particularly important if you have made any critical, low-level changes and have not restarted your XenServer
host(s) for some time. If there are any pre-existing configuration issues, the update will fail.
Note:
XenCenter will reboot each host automatically (as part of the Install Update wizard), before
applying the update file. If you are using the xe CLI, you will have to reboot hosts manually.
• Citrix also strongly recommends that you take a backup of the state of the pool (or individual hosts) that you
wish to update, just as you would with any other maintenance operations. For backup procedures, see the
XenServer Administrator's Guide.
Before you begin updating:
• Log into a user account with full access permissions (for example, as a Pool Administrator or using a local root
account).
• Empty the CD/DVD drives of any VMs you plan to suspend. For details and instructions, see Section 7.2.1,
“Before You Upgrade a Single XenServer Host”.
• Disable HA, if applicable.
If you are applying an update or hotfix using XenCenter, XenCenter runs a series of prechecks to ensure that
the selected hosts are prepared to be updated and compatible with the required update file. These prechecks