Re: [Qemu-devel] [Bug 1192780] Re: qemu-kvm with snapshot option always fails with Permission denied Could not open disk image

[Eric Blake <eblake@redhat.com>]

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On 07/25/2013 10:09 AM, Deepak C Shetty wrote:
> Hi, quick question, 
>     I thought that using the <transient/> xml tag of <disk> element is the right way to do in libvirt ? 

Yes, that is the designed way.  Unfortunately, it has not been
implemented yet (no one has been clamoring for the feature enough to
write the patch themselves, or for someone else to take interest and
write a patch on their behalf).

> Why is <qemu:commandline> method being used ?

To try and work around the unimplemented nature of the libvirt design.

> 
> Also with -snapshot, iiuc the temp. file is created by QEMU internally,
> so which temp. file and its selinux perms is being referenced above ?
> 

Qemu creating a file itself when libvirt has set SELinux rules on the
qemu instance is very likely to fail, since qemu doesn't know what label
to give the temp file, but the temp file must be labeled to be used.
Hence, this really needs to be implemented properly in libvirt, and is
not a qemu bug.

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


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