Installation guide

Maintenance Procedures

xe host-enable

then restart any halted VMs and/or resume any suspended VMs.

B.2. Applying updates

Between releases of XenServer software, Citrix occasionally releases updates to the software.

These updates typically contain accumulated bug fixes and feature improvements. When an

update is released, it is made accessible on the Internet and an email announcement is sent to

all XenServer customers.

Once downloaded, updates can be applied most readily via XenCenter, but can also be applied

using the CLI. Updates are applied through the Manage Updates dialog box, under the pool

menu. See the XenCenter Help for details.

Updates may have differing after-apply guidance, such as requiring the XenAPI agent to be

restarted. Where possible, updates will be such that they can be applied without interruption, but

in some cases they may require system, or virtual machine restarts to be performed. In cases

where a system restart is required, users can avoid downtime of virtual machines in a pooled

environment by applying the update to each server in turn, migrating virtual machines away from

each server in turn as the update is applied. XenCenter can take care of this update sequence

automatically on your behalf via the Manage Updates option. If you are using the CLI, you will

have to do this manually using the host-evacuate command.

If using the CLI to perform the update, XenServer Hosts to be updated should be prepared for

this operation by the procedures in Section B.1, “Preparing XenServer Hosts for maintenance

operations”. If using XenCenter, this will be taken care of automatically where required.

B.2.1. Applying updates using the CLI

First, the update must be uploaded to the pool or server to which it will be applied. This will cause

a UUID (identifier) to be assigned to the update, and information about which servers it has been

applied to will be tracked. Once an update has been uploaded to a pool or server, you can use the

patch-list and patch-param-list commands to view information about the update. The second

stage is to apply the update. We recommend that the patch-pool-apply command be used to do

this; this will result in the update being applied on all servers in the pool. Alternatively, the patch-

apply command may be used to apply the update to one server in a pool - this may be useful

when applying the update and then restarting individual servers in the pool. Pools should not

be left in an inconsistent update state (one where updates have been installed on some servers

and not others).

Discussion of procedures using the CLI below assume a basic knowledge of the usage of the xe

tool. For information about this, please see the Administrator's Guide.

The update procedure is essentially the same for both a single server and pool scenario, except

that in a pooled scenario you must ensure that the update is applied to all servers in the pool.

This will be achieved either by using the patch-pool-apply command, or by executing the patch-

apply once for each host. These are described below.