libvirt users - Aug 2014 - Re: Live blockcopy onto storage pool that is an NFS mount?

Hello,

I am running qemu-kvm 1.4.0 and libvirt 1.0.2 on Ubuntu 12.04. I have two NFS
mountpoints configured as two separate pools in virsh:
<pool type='dir'>
  <name>nfs1</name>
  <uuid>419d799c-2493-6ebc-6848-53b0919e7bad</uuid>
  <capacity unit='bytes'>6836057014272</capacity>
  <allocation unit='bytes'>0</allocation>
  <available unit='bytes'>6836057014272</available>
  <source>
  </source>
  <target>
    <path>/var/lib/libvirt/images/nfs1</path>
    <permissions>
      <mode>0711</mode>
      <owner>0</owner>
      <group>0</group>
    </permissions>
  </target>
</pool>

The XML for the nfs2 pool is similar, with the mountpoint being
/var/lib/libvirt/images/nfs2.

I would like to be able to move the VM disk from one of the NFS mountpoints to
another (nfs1 --> nfs2) live. I followed the instructions here:
http://thr3ads.net/libvirt-users/2013/02/2174486-Migrate-VMs-to-different-storage-pool

However when I attempt the blockcopy command, I receive this error:
Failed to create file '/var/lib/libvirt/images/nfs2/vm.qcow2': Operation
not permitted

Is it not possible to blockcopy in this way to an NFS mount?

Thanks,

Andrew

On 08/01/2014 03:29 PM, Andrew Martin wrote:
> Hello,
> 
> I am running qemu-kvm 1.4.0 and libvirt 1.0.2 on Ubuntu 12.04. I have two
NFS
> mountpoints configured as two separate pools in virsh:
> 
> I would like to be able to move the VM disk from one of the NFS mountpoints
to
> another (nfs1 --> nfs2) live. I followed the instructions here:
>
http://thr3ads.net/libvirt-users/2013/02/2174486-Migrate-VMs-to-different-storage-pool
More than a year old, but they should still work.
> 
> However when I attempt the blockcopy command, I receive this error:
> Failed to create file '/var/lib/libvirt/images/nfs2/vm.qcow2':
Operation not permitted
Hmm, I know we've had problems in the past about labeling NFS files
correctly, particularly when root squash is in play.  Do you have root
squash turned on in your NFS servers?  If so, can you turn it off, and
see if that improves the situation?  Also, libvirt 1.0.2 is a bit old;
you may be encountering a bug that has been fixed in the meantime.
Would you mind retrying with 1.2.7-rc2, to see if we need a last-minute
bug-fix before this weekend's release of 1.2.7?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

----- Original Message -----
> From: "Eric Blake" <eblake@redhat.com>
> To: "Andrew Martin" <amartin@xes-inc.com>,
libvirt-users@redhat.com
> Sent: Friday, August 1, 2014 4:40:28 PM
> Subject: Re: [libvirt-users] Live blockcopy onto storage pool that is an
NFS mount?
> 
> > 
> > However when I attempt the blockcopy command, I receive this error:
> > Failed to create file '/var/lib/libvirt/images/nfs2/vm.qcow2':
Operation
> > not permitted
> 
> Hmm, I know we've had problems in the past about labeling NFS files
> correctly, particularly when root squash is in play.  Do you have root
> squash turned on in your NFS servers?  If so, can you turn it off, and
> see if that improves the situation?  Also, libvirt 1.0.2 is a bit old;
> you may be encountering a bug that has been fixed in the meantime.
> Would you mind retrying with 1.2.7-rc2, to see if we need a last-minute
> bug-fix before this weekend's release of 1.2.7?
> 
> --
Eric,

Thanks for the help. Mounting the NFS exports with no_root_squash solved
the problem! In fact, I was able to successfully blockpull from one NFS
mountpoint to another with only these steps (without making it transient):
virsh snapshot-create-as --domain <vm_name> --disk-only --atomic
--no-metadata --diskspec
vda,snapshot=external,file=/path/to/nfs1/<vm_name>.qcow2
virsh blockpull --domain <vm_name> --path
/path/to/nfs2/<vm_name>.qcow2

Since this works in libvirt 1.0.2 I imagine it will work just as well in
libvirt 1.2.7 as well.

Thanks,

Andrew