How to fix lxc launch Failed getting root disk: No root device could be found

Problem:

While trying to launch a lxc container using a command like

lxc launch ubuntu:22.04 mycontainer

you see the following error message:

Creating mycontainer
Error: Failed instance creation: Failed creating instance record: Failed initialising instance: Failed getting root disk: No root device could be found

Solution

You didn’t initialize your LXD storage properly. Run

lxd init

in order to configure the storage for lxd. For most setups except performance-critical production setups, I recommend to use the dir storage backend because it does not require any further configuration. You can leave all other options at their default values.

Name of the storage backend to use (zfs, btrfs, ceph, cephobject, dir, lvm) [default=zfs]: dir