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taradiddles ff171b77ac new "shrinking volumes under 4.0" doc
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Shrinking volumes on Qubes 4.0

The official documentation 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:

  • it requires copying data, which can take a while
  • it is limited to the private volume of VMs based on TemplateVMs

This document describes how to shrink any volume.

The instructions given below are error-prone. ALWAYS BACKUP your data before attempting to shrink a volume.. qvm-clone or qvm-backup are your friends. Do not rely only on snapshots (yet).

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.

The instructions show how to resize a VM's private volume. Simply swap the -private volume suffix with -root to resize a VM's root volume.

  1. backup your data (qvm-clone , qvm-backup, ...)

  2. stop the VM whose volume need to be resized (let's name this VM 'largeVM')

  3. start another VM (eg. 'tempVM') with largeVM's private volume attached.

    qvm-start --hddisk dom0:/dev/qubes_dom0/vm-largeVM-private tempVM`

    (alternatively, you could setup a loop device to point to largeVM's private volume and attach it to a running VM).

  4. in tempVM, resize the attached volume to 2G (for instance):

    sudo e2fsck -f /dev/xvdi
sudo resize2fs /dev/xvdi 2G

  5. shutdown tempVM

  6. in dom0, resize the lvm volume to the same size you used at step 4.:

    sudo lvresize -L2G /dev/qubes_dom0/vm-largeVM-private

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 be careful to specify the right shrinked size at step 6.