Docker container doesn't start after reboot with enabling systemd script

Question

I have the following systemd script:

[Unit]
Description=Hub docker container
After=docker.service

[Service]
User=root
ExecStart=/home/hub/hub.sh
ExecStop=/bin/docker stop hub
ExecStopPost=/bin/docker rm hub

[Install]
WantedBy=multi-user.target

Running the command: systemctl start/stop hub works fine. I also created the symlink by using systemctl enable hub. Why doesn't my service start up after I reboot the entire laptop? I followed the docker guide so that Docker starts up on reboot, but for some reason my container doesn't start up. Am I missing a field in my script?

The command I am using my ExecStart, "/home/hub/hub.sh" script is:

docker run --net=host --restart=always --name hub -t hub

After reboot I get the following when I type systemctl status hub:

● hub.service - Hub docker container
   Loaded: loaded (/etc/systemd/system/hub.service; enabled; vendor preset: disabled)
   Active: inactive (dead)

Answer 1

In my case, I already had the containers set to restart=always (btw you can inspect a container's restart policy with docker inspect -f "{{ .HostConfig.RestartPolicy.Name }}" <container> and/or change it with docker update --restart=always <container>) but the containers still were not starting up until I ran a command like docker ps.

It turns out that the socket was enabled in systemd, but the service itself was disabled and so wouldn't start until a command was issued against it.

Inspecting via systemctl status docker.socket and systemctl status docker.service verified this:

root@poke:~# systemctl status docker.socket
● docker.socket - Docker Socket for the API
   Loaded: loaded (/lib/systemd/system/docker.socket; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2020-07-30 18:28:38 EDT; 18h ago
   Listen: /var/run/docker.sock (Stream)
    Tasks: 0 (limit: 4647)
   CGroup: /system.slice/docker.socket
   
root@poke:~# systemctl status docker.service
● docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; disabled; vendor preset: enabled)
   Active: active (running) since Fri 2020-07-31 13:19:53 EDT; 5min ago
     Docs: https://docs.docker.com
 Main PID: 3094 (dockerd)
    Tasks: 20
   CGroup: /system.slice/docker.service
           ├─3094 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
           └─3426 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 6379 -container-ip 172.17.0.3 -container-

(Note the "disabled" for docker.service, even though it was running at the time.)

I was able to fix this by running systemctl enable --now docker.service:

root@poke:~# systemctl enable --now docker.service
Synchronizing state of docker.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable docker

Many thanks to this reddit user's reply for tipping me off.

Answer 2

In order to start container after reboot you need to add this property: --restart=always to your container start script. For example: docker run -d -p 80:5000 --restart=always image_name