How do I make a Docker container start automatically on system boot?

If you want the container to be started even if no user has performed a login (like the VirtualBox VM that I only start and don't want to login each time). Here are the steps I performed to for Ubuntu 16.04 LTS. As an example, I installed a oracle db container:

$ docker pull alexeiled/docker-oracle-xe-11g
$ docker run -d --name=MYPROJECT_oracle_db --shm-size=2g -p 1521:1521 -p 8080:8080 alexeiled/docker-oracle-xe-11g
$ vim /etc/systemd/system/docker-MYPROJECT-oracle_db.service

and add the following content:

[Unit]
Description=Redis container
Requires=docker.service
After=docker.service

[Service]
Restart=always
ExecStart=/usr/bin/docker start -a MYPROJECT_oracle_db
ExecStop=/usr/bin/docker stop -t 2 MYPROJECT_oracle_db

[Install]
WantedBy=default.target

and enable the service at startup

sudo systemctl enable docker-MYPROJECT-oracle_db.service

For more informations https://docs.docker.com/engine/admin/host_integration/

Yes, docker has restart policies such as docker run --restart=always that will handle this. This is also available in the compose.yml config file as restart: always.

The default restart policy is no.

For the created containers use docker update to update restart policy.

docker update --restart=always 0576df221c0b

0576df221c0b is the container id.