The [official documentation](https://www.qubes-os.org/doc/resize-disk-image/#shrinking-a-disk-image) describes a safe(ish) way of "shrinking" a VM's volume. This is the recommended approach of shrinking an AppVM's private volume, but it has two caveats:
Note: Qubes 4.0 uses *thin* LVM storage: only the data present on a volume uses disk space, free space isn't allocated physically. If your only concern is disk space, you may simply be careful with how much data you store in a given volume and avoid having to shrink a volume (use `sudo lvs` in dom0 and compare the `LSize` vs `Data%` fields to find out about real disk usage).
The procedure for shrinking a volume on Ext4 and most other filesystems is a bit convoluted because they don't support online shrinking, and we don't want to process any untrusted data in dom0.
Alternatively, you could setup a loop device in dom0 associated to largeVM's private volume and attach it to a running VM but this is outside the scope of this document (see `losetup` and `qvm-block`).
6. in dom0, resize the lvm volume to the **SAME** size you used at step 4. (specifying a lower size than the underlying filesystem's size would corrupt the filesystem and either destroy some of your data or trigger filesystem exceptions when the filesystem tries to write at a location that doesn't exist):
The procedure is the same for other OSes (eg. MS Windows) but you'll have to use OS specific tools to resize the volume at step 4. and to be careful to specify the right shrinked size at step 6.
