When running the script, all goes well until:

e2fsck 1.46.5 (30-Dec-2021)
e2fsck: No such file or directory while trying to open /dev/mapper/qubes_dom0-vm--debian--core--private
Possibly non-existent device?

$ ls /dev/mapper

lists only control and luks devices.

This is on BTRFS.

This happens because it’s using the reflink driver. So the filesystems are stored in /var/lib/qubes/.

You would need to modify the script to do

sudo kpartx -av /var/lib/qubes/vm-templates/debian-core/root.img

and the 3rd entry of the 3rd line will be the loop device e.g. loop12p3.

But why are we going to all this effort to shrink them anyway? The space allocated to a VM is not actually taking up any storage. The code to shrink it should be removed, or at least moved to a separate ‘optimizations’ script. The idea being that you want the base install script to be as robust and simple as possible to attract users.

You mentioned on the forum that the solution is probably to just remove it.

Thank you for getting the issue tracker back up!