[virt-tools-list] Adding a storage pool for a directory with existing guest images

[Eric Blake]

On 10/04/2011 11:11 AM, Philip Durbin wrote:
> I have three KVM hosts running CentOS 5.5 that store their images and
> I've set up a new KVM host running CentOS 6.0 and I'd like to access
> the existing storage so that I can migrate guests from the CentOS 5
> KVM host to the CentOS 6 KVM host.

Live migration is out of the question.  The qemu-kvm binary on CentOS 5 
and CentOS 6 are too far divergent to allow live migration, since they 
do not share the same internal layouts of the migration information. 
Live migration is generally only possible between two hosts running the 
same OS and qemu-kvm binary.

That said, you can do offline migrations.  You can stop the guest on the 
CentOS 5 host, then define a new guest xml on the CentOS 6 host that 
uses the same disk image in shared storage as the CentOS 5 host had been 
using, and generally should be able to boot the newly defined guest 
using the pre-existing disk.

>
> I set up the same symlinks, but I can't create guest from the CentOS
> KVM host due to permission errors on the disk image (though the disk
> image is created).

Another thing to check is to make sure that SELinux is not preventing 
the access - 'getsebool virt_use_nfs' needs to report 'on' if you have 
SELinux enabled on your CentOS 6 host.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org