On 4/17/21 11:03 PM, Stickstoff wrote:
Hello everyone,I lost a somewhat important file from a software crash in an appvm. Within the VM, I couldn't find a way to recover it. I copied the appvm filesystem containers ('private.img', 'private-cow.img', 'private-cow.img.old'). As I understand it, 'private-cow.img' contains the old version of files that were changed since last appvm startup. However, '-cow.img' files contain no filesystem, but "binary patch" data, thus can't be mounted or read directly or without their corresponding'.img' files. I found only little info online. Qubes documentation [1] says about reverting template 'root-cow.img' changes:1. Ensure that no other VMs uses this template. 2. Prepare snapshot device with root-cow.img.old instead of root-cow.img (/etc/xen/scripts/block-snapshot prepare). 3. Replace snapshot device-mapper target with snapshot-merge, other parameters (chunk size etc) remains untouched. Now kernel starts merging changes stored in root-cow.img.old into root.img. d-m device can be used normally (if needed). 4. Waits for merge completed: dmsetup status shows used snapshot blocks – it should be equal to metadata size when completed. 5. Replace snapshot-merge d-m target back to snapshot. 6. Cleanup snapshot device (if nobody uses it at the moment). 7. Move root-cow.img.old to root-cow.img (overriding existing file).I tried to apply these steps to 'private.img' and 'private-cow.img', but already failed with the second step, where I couldn't really figure out how to use the '/etc/xen/scripts/block-snapshot' script. Is there any hope to recover an older version of a changed/deleted file from 'private-cow.img'? Can anyone give me a pointer how to access its content, aka "apply its content as a patch to 'private.ig'"?
Use `qvm-volume revert` to go back to previous snapshots for a VM. For the file pool you cited above there's just one previous revision available though. It should indeed be in the files you mentioned, but the other doc is somewhat unrelated. If you start the VM, the old snaphot will be deleted, i.e. better create a backup before applying your changes.
Thank you in advance, Stickstoff [1] https://www.qubes-os.org/doc/template-implementation/
-- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/4d244dad-3412-d1de-8604-0af23740dc8e%40hackingthe.net.
smime.p7s
Description: S/MIME Cryptographic Signature
