openstack team mailing list archive

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Tue, Jul 03, 2012 at 02:48:05PM +0100, Leander Bessa Beernaert wrote:
> Hello all,
> 
> I've been trying to get the live migration to work according to the guide
> http://docs.openstack.org/trunk/openstack-compute/admin/content/configuring-live-migrations.html.
> 
> So far i've setup 2 compute nodes and 1 controller node. They all share the
> /var/lib/nova/instances dir. I've already verified that the nova user id is
> the same across all the servers.
> 
> Currently i'm running into this error when i launch an instance:
> http://paste.openstack.org/show/19221/
> 
> It's certainly a permission issue, so i tried adding the group "nova" to
> the user "libvirt-qemu". However, it still doesn't work. To which user must
> i give the nova group permission in order to be able to write in that
> directory?

So the error message you get here:

  libvirtError: Unable to pre-create chardev file '/var/lib/nova/instances/instance-00000004/console.log': Permission denied

is coming from the libvirt QEMU driver code. This code runs as root:root
in the libvirtd daemon. As such, ordinarily permissions would not be a
problem that blocks libvirtd doing what it wants. NFS is horrible /
special though, and has this capability "root squash" which causes any
client host processes running as root to be treated as if they were
running as 'nfsnobody' or a similar unprivileged user.  So if you want
libvirtd to be able to use this mount point you'll need to make sure
that your NFS server has root squash disabled. eg by adding the option
'no_root_squash' to the /etc/exports file for that mount.


Daniel
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