Restart Docker container on image change

This blog is a static website served from a Docker container. The content is written in markdown and pushed to a Git repository hosted on GitHub. Every time I push to that repository a Docker image containing the new version is built on DockerHub.

While the new image is available on DockerHub there is still a container running containing the old version. Normally I would go to the server where the container is running and perform a manual docker pull command and spin up a new container. I hated doing this manual step and automated it:

👉 The people from containrrr.dev made a simple-to-use piece of software called watchtower. This detects when the image of a container changes. When that happens the changed image is pulled and the container will be restarted.

Watchtower can be started as an individual Docker container with the following command:

docker run -d \
  --name watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  containrrr/watchtower <name of the container to watch : optional>

📓 if no name is given, all containers are watched.

I like to configure and document my containers with a docker-compose file. This is also supported by watchtower.

version: "3"
services:
  cavo:
    image: jurruh/blog:latest
    container_name: jurruh_blog
    ports:
      - "80:80"
  watchtower:
    image: containrrr/watchtower
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    command: jurruh_blog