How to fix docker storage-driver=overlay2 problem

Question

I need to change the underlying storage for a Proxmox LXC Debian Buster container from RAW to ZFS. For this I restored a snapshot to ZFS storage. This is normally transparent for the OS in the container, but in this case docker no longer starts.

The initial problem was that docker wasn't started, and after some digging around I find this:

# dockerd -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock
INFO[2021-08-03T09:24:40.909844803Z] Starting up
...
ERRO[2021-08-03T09:24:56.914420548Z] failed to mount overlay: invalid argument     storage-driver=overlay2
ERRO[2021-08-03T09:24:56.914439880Z] [graphdriver] prior storage driver overlay2 failed: driver not supported
failed to start daemon: error initializing graphdriver: driver not supported

How can I fix this?

EDIT: I tried the suggested fix, but still no cigar:

root@mail:/var/log# systemctl status docker.service
* docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sat 2021-10-09 10:05:49 UTC; 1min 23s ago
     Docs: https://docs.docker.com
  Process: 236 ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock (code=exited, status=1/FAILURE)
 Main PID: 236 (code=exited, status=1/FAILURE)

Oct 09 10:05:49 mail systemd[1]: docker.service: Service RestartSec=2s expired, scheduling restart.
Oct 09 10:05:49 mail systemd[1]: docker.service: Scheduled restart job, restart counter is at 3.
Oct 09 10:05:49 mail systemd[1]: Stopped Docker Application Container Engine.
Oct 09 10:05:49 mail systemd[1]: docker.service: Start request repeated too quickly.
Oct 09 10:05:49 mail systemd[1]: docker.service: Failed with result 'exit-code'.
Oct 09 10:05:49 mail systemd[1]: Failed to start Docker Application Container Engine.

The link offered suggests creating a new zpool within the container. Seems a bit of an overkill for that to be necessary, no?

Answer 1

Configure Docker to use zfs. Edit /etc/docker/daemon.json and set the storage-driver to zfs. If the file was empty before, it should now look like this:

{
  "storage-driver": "zfs"
}

more details: https://docs.docker.com/storage/storagedriver/zfs-driver/