qubes-doc/DiskTRIM.md

layout	title	permalink	redirect_from
doc	DiskTRIM	/doc/DiskTRIM/	/wiki/DiskTRIM/

VMs have already TRIM enabled by default, but dom0 doesn't. There are some security implications (read for example this article), but IMO not very serious.

To enable TRIM in dom0 you need:

1. Get your LUKS device UUID:

   {% highlight trac-wiki %} ls /dev/mapper/luks-* {% endhighlight %}

2. Add entry to /etc/crypttab (replace luks-<UUID> with the device name and the <UUID> with UUID alone):

   {% highlight trac-wiki %} luks- UUID= none allow-discards {% endhighlight %}

3. Add rd.luks.allow-discards=1 to kernel cmdline (/etc/default/grub, GRUB_CMDLINE_LINUX line)

4. Rebuild grub config (grub2-mkconfig -o /boot/grub2/grub.cfg)

5. Rebuild initrd in hostonly mode:

   {% highlight trac-wiki %} dracut -H -f {% endhighlight %}

6. Add "discard" option to /etc/fstab for root device

7. Reboot the system, verify that allow-discards is really enabled (dmsetup table)

There is a bug affecting allow-discards option, once it will be fixed, first two steps will be no longer needed.