On 03/28/2013 06:21 AM, Daniel P. Berrange wrote:
We decided on using xattrs, instead of an in-memory record, because we want the data to be accessible to multiple libvirtd daemons on different hosts. This does not imply we actually need to store the xattrs on the files themselves. Perhaps we should have been creating some parallel files to record the original ownership, which are permanently root owned.
eg For a file /var/lib/libvirt/images/foo.img add a /var/lib/libvirt/images/.libvirt.dac.foo.img file to record the original information.
Or as with the lock manager, just use a single directory like /var/lib/libvirt/dac/ and create files in there based on the SHA256SUM of the filename, and declare that you must share that directory between hosts ?
Out of the box, libvirt is not set up for sharing unless you mount /var/lib/libvirt/images on shared storage or add your own storage pool pointing to shared storage. Since setting up shared storage pools is already an admin action, I would be okay with also requiring an admin action to set up a shared directory that tracks ownership information across a shared pool. It might also be nice to make it easy to associate a shared subdirectory for metainformation inside any storage pool based on top of a shared directory (although that approach doesn't really scale to other storage pools such as iscsi or LVM where the pool isn't really exposing a file system to hold a subdirectory). For that matter, there have already been requests to allow 'virsh managedsave' dump memory into a storage pool, rather than into /etc, since saved state can occupy a lot more space than the / partition is prepared to handle. Also, we have the question of coming up with a default name for saved state files in external snapshots. Both of these problems would also benefit from the ability to designate where libvirt should stick metadata associated with a storage pool, but where a fallback to a default within /var/lib/libvirt are still okay for out-of-the-box installation on a single machine. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org