18.3. Live KVM migration with virsh

A guest can be migrated to another host with the virsh command. The migrate command accepts parameters in the following format:

# virsh migrate --live GuestName DestinationURL

The GuestName parameter represents the name of the guest which you want to migrate.

The DestinationURL parameter is the URL or hostname of the destination system. The destination system must run the same version of Red Hat Enterprise Linux, be using the same hypervisor and have libvirt running.

Once the command is entered you will be prompted for the root password of the destination system.

Example: live migration with virsh

This example migrates from test1.example.com to test2.example.com. Change the host names for your environment. This example migrates a virtual machine named RHEL4test.

This example assumes you have fully configured shared storage and meet all the prerequisites (listed here: Migration requirements).

Verify the guest is running

From the source system, test1.example.com, verify RHEL4test is running:

[root@test1 ~]# virsh list
Id Name                 State
----------------------------------
 10 RHEL4                running

Migrate the guest
Execute the following command to live migrate the guest to the destination, test2.example.com. Append /system to the end of the destination URL to tell libvirt that you need full access.
```
# virsh migrate --live RHEL4test qemu+ssh://test2.example.com/system
```
Once the command is entered you will be prompted for the root password of the destination system.
Wait
The migration may take some time depending on load and the size of the guest. virsh only reports errors. The guest continues to run on the source host until fully migrated.

Verify the guest has arrived at the destination host

From the destination system, test2.example.com, verify RHEL4test is running:

[root@test2 ~]# virsh list
Id Name                 State
----------------------------------
 10 RHEL4                running

The live migration is now complete.

Other networking methods

libvirt supports a variety of networking methods including TLS/SSL, unix sockets, SSH, and unencrypted TCP. Refer to Chapter 19, Remote management of virtualized guests for more information on using other methods.