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.