I'm experiencing the same problem. Everything working great in OMV and Portainer until updating OMV on Sunday 4/18. Now docker will not start or restart. I have tried uninstalling docker and receive errors upon trying to reinstall.
Below is my systemctl status.
Code
docker.service - Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Tue 2021-04-20 21:29:23 MST; 6min ago
Docs: https://docs.docker.com
Process: 1661 ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock (code=exited, status=1/FAILURE)
Main PID: 1661 (code=exited, status=1/FAILURE)
Apr 20 21:29:23 openmediavault.local systemd[1]: docker.service: Service RestartSec=2s expired, scheduling restart.
Apr 20 21:29:23 openmediavault.local systemd[1]: docker.service: Scheduled restart job, restart counter is at 3.
Apr 20 21:29:23 openmediavault.local systemd[1]: Stopped Docker Application Container Engine.
Apr 20 21:29:23 openmediavault.local systemd[1]: docker.service: Start request repeated too quickly.
Apr 20 21:29:23 openmediavault.local systemd[1]: docker.service: Failed with result 'exit-code'.
Apr 20 21:29:23 openmediavault.local systemd[1]: Failed to start Docker Application Container Engine.