Installation guide

Maintenance Procedures

The following procedure describes how to reinstall the current version of the XenServer Host

over an existing installation of XenServer Host 4.1.0, and preserve settings an VMs.

When reinstalling your host, be aware that any custom RPMs which you might have installed on

the XenServer Host control domain will not be preserved.

Procedure B.4. To reinstall XenServer Host from version 4.1.0

1. Perform an orderly shutdown on the VMs hosted on the XenServer Host. If any of your VMs

are in the in the suspended state, resume them first, and then perform an orderly shutdown

on them too.

To shut down all the VMs automatically, you can also type service xapi-domains stop into

the control domain terminal.

2. Reboot the XenServer Host, and boot from the Installation CD.

3. The installation script will identify the version and prompt you whether you want to reinstall

over the existing installation and preserve VMs. Select OK to proceed with the installation.

4. Follow the rest of the installation procedure as described in Section 3.1, “Installing the

XenServer Host”.

5. Run XenCenter and connect to the upgraded XenServer Host.

B.4. Rolling upgrade from version 4.0.1 to the current version

XenServer allows you to upgrade a pool of XenServer Hosts running the 4.0.1 version, while

keeping VMs on that pool running and thus avoiding downtime of your services. This is achieved

by upgrading on a host-by-host basis, with only one XenServer Host offline at a time.

You can use XenCenter or the command line interface to migrate VMs running on a XenServer

Host running an older version of the product to one running either the same version or higher.

It is not possible to migrate VMs located on a XenServer Host with a newer XenServer version

to one running an older version.

You should plan your upgrade path carefully, as we strongly advise against running a mixed-

mode pool (one with multiple versions of XenServer co-existing) for longer than necessary. This

is because the pool will be operating in a degraded state during the upgrade: all VMs will con-

tinue to function as normal, but control operations other than migration might not be available.

In particular, it is not safe to perform storage-related operations such as adding, removing or

resizing virtual disks in this mode.

B.4.1. Backup

It is strongly recommended that you take a backup of the state of your existing v4.0.1 pool using

the pool-dump-database CLI command (see the XenServer Administrator's Guide). This will

allow you revert a partially complete rolling upgrade back to its original state without losing any

VM data.

Note that since it is not possible to migrate a VM from an upgraded XenServer Host to a XenServ-

er Host running an older version of XenServer, it may be necessary to shut down VMs if you

need to revert the rolling upgrade for any reason.