Re: Libvirt Snapshot Question

Hey Peter, thanks for the super quick reply, you're awesome! So you mean the first option would be to create a second disk instead of using snapshot for write, when it gets too big I can then unplug the disk, delete it (or wipe entire overlay fs) and recreate it to start fresh? OK I will try that, thanks for the tip! Option 2 with trim/discard I have to do some research, this seems a bit more challenging. Thank you SO much for the great advice. I will try everything out and report back. :-) On Tue, Nov 30, 2021, 3:25 PM Peter Krempa <pkrempa(a)redhat.com&gt; wrote: > On Tue, Nov 30, 2021 at 14:51:54 +0100, Elias Mobery wrote: > > Hello Peter, thank you so much for that detailed info! > > > > Sorry, you were right, when trying to delete my external snapshot via > > snapshot-delete, the error says "deletion of external snapshots > unsupported" > > > > I can't merge the snapshot because the VM image is in a read-only > > filesystem. Sorry I should've said, it's a live system. So the image is > in > > the read-only squashfs and external snapshot in overlay is used for > writing. > > Okay, that changes the situation quite a bit: > > > > > Now I would like the snapshot emptied or deleted/recreated when it > reaches > > 4GB. > > > > Is there even a way to do this with the image being read-only? > > If the base image is on a read-only filesystem you obviously can't > commit to it. > > Now the question is what should happen to the data in the overlay. > > Discarding/recreating the overlay image is possible only once you turn > off the VM because it basically rolls back the state of the disk back to > the time when the overlay was created. This means that everything > written to the disk will be lost. > > Filesystems obviously can't handle that so that's why it simply won't be > possible to do live with the root image. > > You can have a second disk, which you hot-unplug, wipe the overlay and > plug it back. > > Another possibility is to enable trim/discard and just simply delete the > data in the VM which was added after the overlay was created. When > trim/discard is enabled on all layers incluging the guest filesystem, > then deleting stuff inside the VM will also mean that the overlay will > shrink again. > >