Storage pools¶
Qubes OS R3.2 introduced the concept of storage drivers and pools. This feature was a first step towards a saner storage API, which is heavily rewritten in R4. See here for documentation on storage pools in R4.
A storage driver provides a way to store VM images in a Qubes OS system.
Currently, the default driver is xen
which is the default way of
storing volume images as files in a directory tree like
/var/lib/qubes/
.
A storage pool driver can be identified either by the driver name with
the driver
key or by the class name like this:
class=qubes.storage.xen.XenStorage
. Because R3.2 doesn’t use Python
setup_hooks
, to actually use a short driver name for a custom
storage driver, you have to patch qubes-core-admin
. You can use the
class
config key instead, when your class is accessible by
import
in Python.
A pool (in R3.2) is configuration information which can be referenced
when creating a new VM. Each pool is saved in storage.conf
. It has a
name, a storage driver and some driver specific configuration attached.
When installed, the system has, as you can see from the contents of
/etc/qubes/storage.conf
, a pool named default
. It uses the
driver xen
. The default pool is special in R3.2. It will add
dir_path=/var/lib/qubes
configuration value from
defaults[pool_config]
, if not overwritten.
Currently the only supported driver out of the box is xen
. The
benefit of pools (besides that you can write your own storage driver
e.g. for Btrfs) in R3.2 is that you can store your domains in multiple
places.
You can add a pool to storage.conf
like this:
[foo]
driver=xen
dir_path=/opt/qubes-vm
Now, when creating a new VM on the command-line, you may pass the
-Pfoo
argument to qvm-create
to have the VM images stored in
pool foo
. See also qvm-create --help
.
While the current API is not as clean and beautiful as the R4 API, it allows you to write your own storage drivers e.g. for Btrfs today.