Greetings, due to hardware failure I had to replace my workstation which has a different CPU. I have a VM with several snapshots and I need to revert to a specific one. While reverting to it, I get an error due to unsupported CPU features. Therefore, I try to edit the snapshot XML through the command: virsh snapshot-edit <domain_name> <snapshot_name> When I save the changes I get the error message: error: intermal error: unexpected domain snapshot <snapshot_name> already exists Tried to look around for solution but didn't find any information related to my problem. Am I doing something wrong? It's quite critical for me to be able to revert to that state of the machine. Is there any chance to do so via libvirt? Thank you.
Kashyap Chamarthy
2015-Apr-29 08:40 UTC
Re: [libvirt-users] unable to edit existing snapshot
On Wed, Apr 29, 2015 at 10:08:54AM +0300, NoxDaFox wrote:> Greetings, > > due to hardware failure I had to replace my workstation which has a > different CPU. I have a VM with several snapshots and I need to revert > to a specific one.I'll assume these are external snapshots? You might want to note how exactly you created your snapshot (including the CLI).> While reverting to it, I get an error due to unsupported CPU features.Noting your exact error can be useful.> Therefore, I try to edit the snapshot XML through the command: > > virsh snapshot-edit <domain_name> <snapshot_name> > > When I save the changes I get the error message: error: intermal > error: unexpected domain snapshot <snapshot_name> already exists > > Tried to look around for solution but didn't find any information > related to my problem. > > Am I doing something wrong? It's quite critical for me to be able to > revert to that state of the machine. Is there any chance to do so via > libvirt?Assuming you're referring to an external snapshot, maybe you can try the manual operation of editing the domain's XML (not the snapshot's XML) and point to the exact disk image that you want to revert to? -- /kashyap
On 04/29/2015 01:08 AM, NoxDaFox wrote:> Greetings, > > due to hardware failure I had to replace my workstation which has a > different CPU. I have a VM with several snapshots and I need to revert to a > specific one. > > While reverting to it, I get an error due to unsupported CPU features. > Therefore, I try to edit the snapshot XML through the command: > > virsh snapshot-edit <domain_name> <snapshot_name> > > When I save the changes I get the error message: > error: intermal error: unexpected domain snapshot <snapshot_name> alreadyI hope that typo "intermal" is just a copy-paste bug on your part, and not in the source code.> exists > > Tried to look around for solution but didn't find any information related > to my problem. > > Am I doing something wrong? It's quite critical for me to be able to revert > to that state of the machine. Is there any chance to do so via libvirt?Changing the CPU features is guest visible. Generally, it is a bad idea to change what hardware a guest sees (particularly if the guest was already running as it may crash apps in the guest, but also even if the guest is offline but is a picky OS like Windows that requires revalidation), so even if you can get virsh snapshot-edit to work, I doubt libvirt will let you use it to change CPU features. Is your snapshot from a running guest state, or offline? If offline, just edit the <domain> to point to the correct disk state at the same time you remove the CPU features, to get a fresh boot, rather than trying to revert to the snapshot state. Also, is your snapshot internal or external? Depending on how the snapshot was created may affect how to alter the <domain> to point at the desired disk state. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
Sorry for the lack of information, my bad. The snapshot is an internal one and the machine is running. The whole thing was set-up by another person and left to me to cope with. The typo is mine, as the machine is isolated I cannot actually copy-paste it so have to do it in the traditional way. I am aware of the issue which come when changing HW but I couldn't do otherwise. I am only interested in reverting the disk's state. I guess qemu-img can deal with it that but can libvirt as well? What puzzled me was the error output which is kinda misleading. Is it so that libvirt prevents editing snapshot configuration when running? Is it due to the fact that the snapshots are internal? Thank for the help. 2015-04-29 17:38 GMT+03:00 Eric Blake <eblake@redhat.com>:> On 04/29/2015 01:08 AM, NoxDaFox wrote: > > Greetings, > > > > due to hardware failure I had to replace my workstation which has a > > different CPU. I have a VM with several snapshots and I need to revert > to a > > specific one. > > > > While reverting to it, I get an error due to unsupported CPU features. > > Therefore, I try to edit the snapshot XML through the command: > > > > virsh snapshot-edit <domain_name> <snapshot_name> > > > > When I save the changes I get the error message: > > error: intermal error: unexpected domain snapshot <snapshot_name> already > > I hope that typo "intermal" is just a copy-paste bug on your part, and > not in the source code. > > > exists > > > > Tried to look around for solution but didn't find any information > related > > to my problem. > > > > Am I doing something wrong? It's quite critical for me to be able to > revert > > to that state of the machine. Is there any chance to do so via libvirt? > > Changing the CPU features is guest visible. Generally, it is a bad idea > to change what hardware a guest sees (particularly if the guest was > already running as it may crash apps in the guest, but also even if the > guest is offline but is a picky OS like Windows that requires > revalidation), so even if you can get virsh snapshot-edit to work, I > doubt libvirt will let you use it to change CPU features. Is your > snapshot from a running guest state, or offline? If offline, just edit > the <domain> to point to the correct disk state at the same time you > remove the CPU features, to get a fresh boot, rather than trying to > revert to the snapshot state. Also, is your snapshot internal or > external? Depending on how the snapshot was created may affect how to > alter the <domain> to point at the desired disk state. > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > >