How to add a sound card to a KVM guest?

I have a windows Xp virtual machine running in my laptop on top of Fedora 10 KVM. One day I accidentally deleted the sound card from virt-manager -> Hardware tab for that guest. I then understood my mistake and tried to add it via "Add Hardware" wizard. To my dismay, there was no option to add a sound card.

Then how did I add the sound card back to the guest?

- I did "virsh dumpxml anotherguest" which has sound card attached to it and was able to see the below line in the output.

....................
sound model='es1370'
....................

- I then did "virsh dumpxml xp" and was not able to see the above line in it. So fixing this is as simple as adding the above line to winxp configuration file.

How to do that?

- Dump the xml file to a file in the disk.

# virsh dumpxml xp > xp.xml

- Edit the xp.xml and add the below line to it.

sound model='es1370'

I added this immediately before the "devices" line.

- Then redefine the guest using the new configuration file.

# virsh define xp.xml

Restart the guest and the network card would be present in the guest. Hope we can add the sound card in F11 through virt-manager GUI.

How to migrate guests using virsh commands?

Usually "xm migrate -l" is used to migrate a guest from one system to other system. There is no option in virt-manager to migrate a guest from one host to another. Libvirt based virsh command can be used to do this. The syntax of "virsh migrate" is a bit confusing to a lot of beginners. Details given below would help in solving those confusions.

- There are two systems - HostA and HostB. HostA is the source machine and HostB is the destination machine.

1 - If you are currently logged into HostA as root, below command can be used to migrate a guest to HostB.

# virsh migrate --live xen+ssh://HostB

Replace HostB with its ip or FQDN. You would be asked for the root password of HostB. Upon entering the right password for HostB, migration would happen successfully.

2 - If you are currently logged into a third system in the network which has "virsh" command available in it, the below command can be used to migrate a guest from HostA to HostB.

# virsh --connect xen+ssh://HostA migrate --live xen+ssh://HostB

Replace HostA and HostB with its ip addresses or FQDNs. You would be asked for the root password of HostA first, then the HostB. Upon entering the right password for both hosts, migration would happen successfully.

3 - If you are currently logged into HostB and want to migrate a guest from HostA to HostB, can this be done using virsh? Try it out yourself.

Libvirt connection over ssh (xen+ssh) is the the method used in the above example. Libvirt remote TLS connection can also be established using certificates. Since that needs a bit more deails to setup, that is apt for another doc.