Re: [libvirt-users] Questions related to the snapshot
On 07/19/2012 05:38 AM, lin tan wrote:
Hi,
I faced two problems with the snapshot:
First issue, I can use the snapshot functions via the virsh correctly such
as snapshot-list.
So far, so good.
And when I removed the snapshot XML files from
/var/lib/libvirt/qemu/snapshot/**/,
Ouch. You should never modify files in /var/lib/libvirt - they are
internal only. If you want to remove a snapshot, you should do so
through the public API (virsh snapshot-delete, in this case).
I don't see the snapshot of the Virtual
Machine any more. That's correct.
No, it's sheer dumb luck. You mucked with libvirt's internal storage,
so all bets are off.
But after I copying the XML files back, I can't see the the
snapshot as
well. Only if I restart my laptop can I see them.
You might also get lucky and see them by restarting just libvirtd,
rather than your entire computer.
However, restarting is
what I want to avoid. Because I wish I could utilize the functions in a
server in the future.
Does anyone have ideas about this, Did I do something wrong or it's a
limitation.
What are you really trying to do? Then we can tell you how to do it
using the APIs instead of mucking around with files behind libvirt's back.
So far, I am using the qemu-img command to check the snapshot and do
the
revert without restarting my laptop. Because the snapshots are already
embedded in the img file.
Second issue, I find if I create the XML file of snapshot by using
getXMLDesc and output to a new file in python, there is a slightly
different. But, the new XML file can't be recognized even if I restart my
laptop. The new XML file miss the attribute <active> as far as I can see,
is it so important?
The attribute <active> is an internal-only detail, it only shows up in
the /var/lib/libvirt locations because that is where libvirt stores
internal-only information. You should never directly manipulate it.
Instead, if you want to reinstate XML for a snapshot description after
having previously erased that metadata, the correct approach is:
virsh snapshot-create $dom $file --redefine [--current]
where the optional use of --current will control whether
/var/lib/libvirt sets the <active> internal element to 0 or 1.
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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