Re: Live backups create-snapshot-as and memspec

El 25/2/2021 a las 11:37, Peter Krempa escribió: > On Wed, Feb 24, 2021 at 14:49:19 -0300, David Wells wrote: > > Hi all! > > > > I've been using libvirt for some time and until now I have treated backups > > of virtual computers as if they where physical computers installing the > > backup client on the guest. I am now however facing the need to backup a > > couple a couple of guest at the host level so I've been trying to catch up > > by reading, googling and by trial and error too. Up to now I've been able to > > backup a live machine whith a command like the following > > > > > virsh snapshot-create-as --domain test --name backup --atomic --diskspec > > > vda,snapshot=external --disk-only > > This command creates a file test.backup and in the meantime I can backup the > > original test.qcow2 but for what I saw this disk image is in a "dirty" > > state, as if the machine I could restore from this file had been turned off > > whithout a proper shutdown. > > > > I know that I can later restore the machine to its original state by issuing > > a command like this > > > > > virsh blockcommit --domain test vda --active --pivot > > > virsh snapshot-delete test --metadata backup > > I have seen that it is possible to create the snapshot using a memspec > > parameter which would make the backup of the guest as if it where in a clean > > state, however I haven't found the equivalent of the blockcommit for the > > memory file, in a sort of speak, to be able to restore the guest to it's > > original state. > The memory image file doesn't depend on any other state nor does the VM > use it after the snapshot is taken, if you don't need it you can delete > it. > > The disk overlay you create by 'virsh snapshot-create-as' records only > differences to the original image, but for memory state it doesn't make > much sense as the memory is small and changes a lot, so we take a > snapshot of the whole memory. > > Now to restore the state of a VM to a snapshot taken with memory, > libvirt's native APIs for reverting don't work on external snapshots > yet. > > You can use 'virsh restore memimg' to load VM's state as the memory > snaphsot images have the same format as images created by 'virsh save'. > > Please note though that the configuration of the VM is taken from the > save image if you do so, which includes paths to disk images, which may > no longer be correct or desired, but virsh save-image-edit can be used > to modify the XML if needed. > Hi all! Peter, thank you very much for your reply! So if I understood correctly there is no way, at this time, to backup a live guest in a way that I can restore it to a "clean" state. Also, if I understood correctly, the

probability of a corrupt system on restore of the vm is minimized having the qemu guest agent installed on the guest and issue the virsh create-snapshot-as with the --quiesce parameter, is this correct?