Docker service doesn't auto start after moving the docker image data directory to external driv-CodePudding

Following this page, I have moved the docker data directory and created a symbolic link to it. It works. But everytime after rebooting my computer, the Docker service doesn't start automatically any more. How can I solve this problem?

journalctl -u docker.service returns:

Jun 30 10:29:55 ubuntu systemd[1]: Starting Docker Application Container Engine...
Jun 30 10:29:55 ubuntu dockerd[2358]: time="2022-06-30T10:29:55.426467188 10:00" level=info msg="S>
Jun 30 10:29:55 ubuntu dockerd[2358]: mkdir /var/lib/docker: file exists
Jun 30 10:29:55 ubuntu systemd[1]: docker.service: Main process exited, code=exited, status=1/FAIL>
Jun 30 10:29:55 ubuntu systemd[1]: docker.service: Failed with result 'exit-code'.
Jun 30 10:29:55 ubuntu systemd[1]: Failed to start Docker Application Container Engine.
Jun 30 10:29:57 ubuntu systemd[1]: docker.service: Scheduled restart job, restart counter is at 3.
Jun 30 10:29:57 ubuntu systemd[1]: Stopped Docker Application Container Engine.
Jun 30 10:29:57 ubuntu systemd[1]: docker.service: Start request repeated too quickly.
Jun 30 10:29:57 ubuntu systemd[1]: docker.service: Failed with result 'exit-code'.
Jun 30 10:29:57 ubuntu systemd[1]: Failed to start Docker Application Container Engine.

Before moving the data directory "/var/lib/docker", it was a directory used by Docker, now it is a symbolic link that points to the external directory where the docker image data is stored. Why there is a mkdir command?

If I run dockerd, it returns:

INFO[2022-06-30T20:53:05.143671302 10:00] Starting up                                  
dockerd needs to be started with root privileges. To run dockerd in rootless mode as an unprivileged user, see https://docs.docker.com/go/rootless/

If I run sudo service docker start, docker can start without error. But I don't want to run this everyday. Docker used to start automatically. Any ideas?

CodePudding user response：

I was able to reproduce the error message with the same configuration:

 systemd[1]: Starting Docker Application Container Engine...
 dockerd[47623]: time="2022-06-30T16:36:20.047741616Z" level=in..
 dockerd[47623]: mkdir /data/docker: file exists
 systemd[1]: docker.service: Main process exited, code=exited, ..

The reason was that my external drive wasn't mounted yet.

Adding systemd mount/automount units resolve the issue. Or you can add your external drive to your /etc/fstab (Add nofail for avoid the 90 seconds wait when you don't have it with you).

Also from Docker doc:

You can configure the Docker daemon to use a different directory, using the data-root configuration option.

So editing your /etc/docker/daemon.json with:

{
  "data-root": "/data/docker"
}

is probably better than using symlinks.