Update your hosts

Updates can often be applied with minimal service interruption. Citrix recommends that customers use XenCenter to apply all updates. If you are updating a XenServer pool, you can avoid VM downtime by using the Install Update wizard in XenCenter. The Install Update wizard applies updates, updating one host at a time, automatically migrating VMs away from each host as the hotfix or update is applied.

You can configure XenCenter to check periodically for available XenServer and XenCenter updates and new versions. Any Alerts are displayed in the Notifications pane.

Types of update

Citrix releases the following types of updates for XenServer:

  • Current Releases (CRs), which are full releases of XenServer from the CR stream. CRs can be applied as updates to the supported versions of XenServer from the CR stream.

  • Hotfixes, which generally supply bug fixes to one or more specific issues. Hotfixes are provided for XenServer releases in the Long Term Service Release (LTSR) and Current Release (CR) streams and for earlier supported releases that are not part of either stream.

  • Cumulative Updates, which contain previously released hotfixes and may contain support for new guests and hardware. Cumulative updates are applied to XenServer releases from the Long Term Service Release (LTSR) stream.

Supplemental packs provided by our partners can also be applied as updates to XenServer.

Current Releases

XenServer 7.6 is a Current Release of XenServer. The following table shows which previous versions of XenServer you can apply XenServer 7.6 to as an update:

Version Apply XenServer 7.6 as an update?
XenServer 7.5 CR Yes
XenServer 7.4 CR Yes
XenServer 7.1 Cumulative Update 1 LTSR No
XenServer 7.0 No

For those versions of XenServer that cannot have XenServer 7.6 applied as an update, instead use the Base Installation ISO and upgrade your existing installation.

Notes:

  • If you use XenCenter to update your hosts, you must update your XenCenter installation to the latest version before beginning.

  • Always update the pool master before updating any other hosts in a pool.

Warning:

When applying XenServer 7.6 as an update to an existing XenServer installation that uses the legacy disk partition layout, the update might fail with insufficient space. If this failure occurs, create a fresh installation of XenServer 7.6 instead.

Hotfixes

Citrix might release hotfixes for XenServer 7.6 that provide fixes for specific issues.

Hotfixes for XenServer 7.6 are made available from the Citrix Knowledge Center. Citrix recommends that customers regularly check the Knowledge Center for new updates. Alternatively, you can subscribe to email alerts for updates to XenServer by registering for an account at http://www.citrix.com/support/.

Hotfixes on the latest CR is available to all XenServer customers. However, hotfixes on previous CRs that are still in support are only available for customers with an active Citrix Customer Success Services (CSS) account.

Hotfixes on the LTSR stream are available to customers with an active CSS account. For more information, See Licensing.

Cumulative Updates

Cumulative Updates are provided for LTSRs of XenServer. These updates provide fixes for issues, and may contain support for new guests and hardware.

Cumulative Updates are available to customers with an active CSS account.

XenServer 7.6 is a Current Release. No Cumulative Updates are provided for this release.

Prepare a pool for an update

Updates to XenServer can be delivered as a Hotfix or a Cumulative Update or a Current Release. Pay careful attention to the release notes published with each update. Each update can have unique installation instructions, particularly regarding preparatory and post-update operations. The following sections offer general guidance and instructions for applying updates to your XenServer systems.

Important:

Before you apply an update to the XenServer pool, pay careful attention to the following:

  • (Applies to XenServer 7.6 hotfixes only) All hosts in the pool must be running XenServer 7.6 before you apply the hotfix.

  • Back up your data before applying an update. For backup procedures, see Disaster recovery and backup.

  • Update all servers in a pool within a short period: running a mixed-mode pool (a pool that includes updated and non-updated servers) is not a supported configuration. Scheduled your updates to minimize the amount of time that a pool runs in a mixed state.

  • Update all servers within a pool sequentially, always starting with the pool master. XenCenter’s Install Update wizard manages this process automatically.

  • After applying an update to all hosts in a pool, update any required driver disks before restarting XenServer hosts.

  • After applying a Cumulative Update or Current Release to all hosts in a pool, update the XenServer Tools on all VMs. For more information, see Manage VMs.

    If you upgrade or update through multiple versions of XenServer, do not update the XenServer Tools until you have finished all updates.

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 Before Upgrading a Single XenServer Host.

  • If applicable, disable high availability.

Apply updates to a pool

The update installation mechanism in XenCenter allows you to download and extract the selected update from the Citrix Support website. You can apply an update to multiple hosts and pools simultaneously using the Install Update wizard. During the process, the Install Update wizard completes the following steps for each server:

  • Migrates VMs off the server
  • Places the server in maintenance mode
  • Applies the update to the server
  • Reboots the host if necessary
  • Migrates the VMs back to the updated host.

Any actions taken at the precheck stage to enable the updates to be applied, such as turning off HA, are reverted.

The Install Update wizard carries out a series of checks known as Prechecks before starting the update process. These checks ensure that the pool is in a valid configuration state. It then manages the update path and VM migration automatically. If you prefer to control the update path and VM migration manually, you can update each host individually.

Apply updates automatically

XenCenter allows you to apply automated updates that are required to bring your servers up-to-date. You can apply these updates to one or more pools. When you apply automated updates, XenCenter applies the minimum set of updates that are required to bring the selected pool or the standalone server up-to-date. XenCenter minimizes the number of reboots required to bring the pool or the standalone server pool up-to-date. Where possible, XenCenter limits it to a single reboot at the end. For more information, see Apply Automated Updates.

View available updates

The Updates section of the Notifications view lists the updates that are available for all connected servers and pools.

Notes:

  • By default, XenCenter periodically checks for XenServer and XenCenter updates. Click Refresh to check manually for available updates.

  • If the Updates tab cannot find any updates because you have disabled automatic check for updates, a message appears on the Updates tab. Click Check for Updates Now to check for updates manually.

You can select from the View list whether to view the list of updates By Update or By Server.

When you view the list of updates By Update, XenCenter displays the list of updates. You can order these updates by Server / Pool or by Date.

  • Cumulative Updates and new releases are displayed at the top of this list. Not all new releases can be applied as an update.

  • To export this information as a .csv file, click Export All. The .csv file lists the following information:
    • Update name
    • Description of the update
    • Servers that this update can be applied to
    • Timestamp of the update
    • A reference to the webpage that the update is downloaded from
  • To apply an update to a server, from the Actions list for that update select Download and Install. This option extracts the update and opens the Install Update wizard on the Select Servers page with the relevant servers selected. For more information, see Apply an update to a pool.

  • To open the release note of an update in your browser, click the Actions list and select Go to Web Page.

When you view the list of updates By Server, XenCenter displays the list of servers connected to XenCenter. This list shows both the updates that can be applied to the servers and the updates that are installed on the servers.

  • To export this information as a .csv file, click Export All. The .csv file lists the following information:
    • Pool that the server belongs to
    • Server name
    • Status of the installed XenServer
    • Update status of the server
    • Required updates for this server
    • Installed updates for this server.
  • To apply the updates, click Install Updates. This choice opens the Install Update wizard on the Select Update page. For more information, see Apply an update to a pool.

Apply an update to a pool

To apply an update to a Pool by using XenCenter:

  1. From the XenCenter menu, select Tools and then Install Update.

  2. Read the information displayed on the Before You Start page and then click Next.

  3. The Install Update wizard lists available updates on the Select Update page. Select the required update from the list and then click Next.

  4. On the Select Servers page, select the pool and servers that you want to update.

    When applying a Cumulative Update or a Current Release, you can also select whether to apply the minimal set of hotfixes for the CU or CR.

    Click Next.

  5. The Install Update wizard performs several update prechecks, to ensure that the pool is in a valid configuration state. The wizard also checks whether the hosts must be rebooted after the update is applied and displays the result. The Install Update wizard also checks whether a live patch is available for the hotfix and if the live patch can be applied to the hosts. For information about Live Patching, see Live Patching.

  6. Follow the on-screen recommendations to resolve any update prechecks that have failed. If you want XenCenter to resolve all failed prechecks automatically, click Resolve All. When the prechecks have been resolved, click Next.

  7. If you are installing a CU or a CR, XenCenter downloads the updates, uploads them to the default SR of the pool, and installs the updates. The Upload and Install page displays the progress.

    Notes:

    • If the default SR in a pool is not shared, or does not have enough space, XenCenter tries to upload the update to another shared SR. If none of the shared SRs have sufficient space, the update is uploaded to local storage of the pool master.
    • If the update process cannot complete for any reason, XenCenter halts the process. This allows you to fix the issue and resume the update process by clicking the Retry button.

    See Step 10. to complete the installation process.

  8. If you are installing a hotfix, choose an Update Mode. Review the information displayed on the screen and select an appropriate mode. If the hotfix contains a live patch that can be successfully applied to the hosts, it displays No action required on the Tasks to be performed screen.

    Note:

    If you click Cancel at this stage, the Install Update wizard reverts the changes and removes the update file from the server.

  9. Click Install update to proceed with the installation. The Install Update wizard shows the progress of the update, displaying the major operations that XenCenter performs while updating each server in the pool.

  10. When the update is applied, click Finish to close Install Update wizard. If you chose to perform post-update tasks manually, do so now.

Update a pool of XenServer hosts by using the xe CLI

To update a pool of XenServer hosts by using the xe CLI:

  1. Download the update file to a known location on the computer running the xe CLI. Note the path to the file.

  2. Upload the update file to the pool you want to update by running the following:

    xe -s server -u username -pw password update-upload file-name=filename [sr-uuid=storage_repository_uuid]
    

    Here, -s refers to the name of the pool master. XenServer assigns the update file a UUID, which this command prints. Note the UUID.

    Tip:

    Once an update file has been uploaded to the XenServer host, you can use the update-list and update-param-list commands to view information about the file.

  3. If XenServer detects any errors or preparatory steps that have not been taken, it alerts you. Be sure to follow any guidance before continuing with the update.

    If necessary, you can shut down or suspend any VMs on the hosts that you want to update by using the vm-shutdown or vm-suspend commands.

    To migrate specified VMs to specified hosts, use the vm-migrate command. By using the vm-migrate command, you have full control over the distribution of migrated VMs to other hosts in the pool.

    To live migrate all VMs to other hosts in the pool automatically, use the host-evacuate command. By using the host-evacuate command, you leave the distribution of migrated VMs to XenServer.

  4. Update the pool, specifying the UUID of the update file, by running the following:

    xe update-pool-apply uuid=UUID_of_file
    

    This command applies the update or hotfix to all hosts in the pool, starting with the pool master.

    Or, to update and restart hosts in a rolling manner, you can apply the update file to an individual host by running the following command:

    xe update-apply host=host uuid=UUID_of_file
    

    Ensure that you update the pool master before you update any other pool member.

  5. Verify that the update was applied by using the update-list command. If the update has been successful, the hosts field contains the host UUID.

  6. Perform any post-update operations that are required, such as restarting the XAPI toolstack or rebooting the hosts. Perform these operation on the pool master first.

Update individual hosts by using the xe CLI

To update individual hosts by using the xe CLI:

  1. Download the update file to a known location on the computer running the xe CLI. Note the path to the file.

  2. Shut down or suspend any VMs on the hosts that you want to update by using the vm-shutdown or vm-suspend commands.

  3. Upload the update file to the host you want to update by running the following:

    xe -s server -u username -pw password update-upload file-name=filename [sr-uuid=storage_repository_uuid]
    

    Here, -s refers to the hostname. XenServer assigns the update file a UUID, which this command prints. Note the UUID.

    Tip:

    After an update file has been uploaded to the XenServer host, you can use the update-list and update-param-list commands to view information about the update file.

  4. If XenServer detects any errors or preparatory steps that have not been taken, it alerts you. Be sure to follow any guidance before continuing with the update.

  5. Update the host, specifying the UUIDs of the host and the update file, by running the following:

    xe update-apply host-uuid=UUID_of_host uuid=UUID_of_file
    

    If the host is a member of a pool, ensure that you update the pool master before you update any other pool member.

  6. Verify that the update has been successfully applied by using the update-list command. If the update has been successful, the hosts field contains the host UUID.

  7. Perform any post-update operations, as necessary (such as, restarting the XAPI toolstack, or rebooting the host).

Apply Automated Updates

Automated Updates mode applies any hotfixes and Cumulative Updates that are available for a host. This mode minimizes the number of reboots required to bring the pool or the standalone server pool up-to-date. Where possible, Automated Updates mode limits it to a single reboot at the end.

If a new Current Release version is available as an update, Automated Updates mode does not apply this update. Instead, you must select manually to update to the new Current Release.

XenCenter requires internet access to fetch the required updates.

To view the list of required updates, perform the following steps:

  1. Select the host on the Resources pane in XenCenter.

  2. Navigate to the General tab.

  3. Expand the Updates section.

    You can see:

    • Applied – lists already-applied updates.

    • Required Updates – lists the set of updates required to bring the server up-to-date.

      Note:

      If there are no updates required, the Required Updates section is not displayed.

    • Installed supplemental packs – lists supplemental packs that are installed on the server (if any).

      Note:

      If you select a pool instead of a server, the Updates section lists updates that are already applied as Fully Applied.

If you want to choose and install a particular update, see Apply an update to a pool section.

Note:

The Automated Updates feature is available for XenServer Enterprise Edition customers, or those customers who have access to XenServer through their Citrix Virtual Apps and Desktops entitlement. To learn more about XenServer editions, and to find out how to upgrade, visit the Citrix website here. For more information, see Licensing.

Note:

The Automated Updates feature is available for XenServer Enterprise Edition customers.

Apply Automated Updates by using the Install Update wizard

The following section provides step-by-step instructions on how to apply the set of required updates automatically to bring your pool or standalone host up-to-date.

  1. From the XenCenter menu, select Tools and then select Install Update.

  2. Read the information displayed on the Before You Start page and then click Next.

  3. On the Select Update page, select the mechanism to use to install the updates. You can see the following options:

    • Automated Updates – (default) this option is visible only if XenCenter is connected to at least one licensed pool or a licensed standalone server. Select this option to download and install all the current updates from Citrix automatically to bring the pool or a standalone server up-to-date.

    • Download update from Citrix – the Install Update wizard lists available updates from the Citrix Support site. To apply the updates, see Apply an update to a pool.

    • Select update or Supplemental pack from disk – to install an update you have already downloaded, see Apply an update to a pool. To install supplemental pack updates, see the Installing Supplemental Packs section in XenCenter Help.

  4. To continue with the automatic application of hotfixes, select Automated Updates and then click Next.

  5. Select one or more pools or standalone servers that you want to update and click Next. Any server or pool that cannot be updated appears unavailable.

  6. The Install Update wizard performs several update prechecks, to ensure that the pool is in a valid configuration state.

    Follow the on-screen recommendations to resolve any update prechecks that have failed. If you want XenCenter to resolve all failed prechecks automatically, click Resolve All. When the prechecks have been resolved, click Next.

  7. The Install Update wizard automatically downloads and installs the recommended updates. The wizard also shows the overall progress of the update, displaying the major operations that XenCenter performs while updating each server in the pool.

    Notes:

    • The updates are uploaded to the default SR of the pool. If the default SR is not shared or does not have enough space, XenCenter tries to upload the update to another shared SR with sufficient space. If none of the shared SRs have sufficient space, the update is uploaded to local storage on each host.

    • The update process cannot complete for any reason, XenCenter halts the process. This allows you to fix the issue and resume the update process by clicking the Retry button.

  8. When all the updates have been applied, click Finish to close Install Update wizard.

Live patching in XenServer

The live patching feature applies to hotfixes only. Current Releases and Cumulative Updates cannot be applied as live patches.

XenServer customers who deploy XenServer hosts can often be required to reboot their hosts after applying hotfixes. This rebooting results in unwanted downtime for the hosts while customers have to wait until the system is restarted. This unwanted downtime can impact business. Live patching enables customers to install some Linux kernel and Xen hypervisor hotfixes without having to reboot the hosts. Such hotfixes include both a live patch, which is applied to the memory of the host, and a hotfix that updates the files on disk. Using live patching can reduce maintenance costs and downtime.

When applying an update by using XenCenter, the Install Update wizard checks whether the hosts must be rebooted after the update is applied. XenCenter displays the result on the Prechecks page. This check enables customers to know the post-update tasks well in advance and schedule the application of hotfixes accordingly.

Note:

XenServer Live Patching is available for XenServer Enterprise Edition customers, or those customers who have access to XenServer through their Citrix Virtual Apps and Desktops entitlement. To learn more about XenServer editions, and to find out how to upgrade, visit the Citrix website. For detailed information about Licensing, see Licensing.

Live patching scenarios

Hotfixes can be live patched across pools, hosts, or on a standalone server. Some require a reboot, some require the XAPI toolstack to be restarted, and some hotfixes do not have any post-update tasks. The following scenarios describe the behavior when a Live Patch is and is not available for an update.

  • Updates with live patch — Some hotfixes that update Linux kernel and the Xen hypervisor usually do not require a reboot after applying the hotfix. However, in some rare cases, when the live patch cannot be applied, a reboot might be required.

  • Updates without live patch — No change in the behavior here. It works as usual.

    Note:

    If a host does not require a reboot, or if the hotfix contains live patches, XenCenter displays No action required on the Update Mode page.

Apply Automated Updates and live patching

Automated Updates mode in XenCenter enables you to download and apply the minimum set of hotfixes required to bring your pool or standalone host up-to-date automatically. Automated Updates mode does apply any Cumulative Updates that are available for a host. However, if a new Current Release version is available as an update, Automated Updates mode does not apply this update. You must manually select to update to the new Current Release.

You can benefit from the Live Patching feature when you apply hotfixes using the Automated Updates mode in XenCenter. You can avoid rebooting hosts if live patches are available and are successfully applied to the hosts that are updated using Automated Updates mode. For more information about the Automated Updates, see Apply Automated Updates.

Enable live patching by using XenCenter and the xe CLI

Live Patching feature is enabled by default. Customers can enable or disable Live Patching using XenCenter or xe CLI command.

Using XenCenter

  1. Select the pool or the standalone host on the Resource pane.

  2. From the Pool menu (Server in case on standalone hosts) menu, select Properties and then click Live Patching.

  3. On the Live Patching page:

    • Select Use live Patching when possible to enable Live Patching.

    • Select Don’t use Live Patching to disable Live Patching.

Using the xe CLI

  • To enable Live Patching, run the following command:

     xe pool-param-set live-patching-disabled=false uuid="pool_uuid"
    
  • To disable Live Patching, run the following command:

     xe pool-param-set live-patching-disabled=true uuid="pool_uuid"