Setting Up Watchtower with Docker Compose¶

Introduction to Watchtower¶

Watchtower is an application that automatically updates your running Docker containers to the latest images. It monitors all containers and updates them in real-time whenever a new image is released.

Docker Compose Configuration for Watchtower¶

This Docker Compose setup deploys Watchtower in a Docker container, ensuring your other containers are always up-to-date with the least amount of hassle.

Docker Compose File (`docker-compose.yml`)¶

version: '3'
services:
  watchtower:
    image: containrrr/watchtower
    command:
      - --cleanup=true
    restart: always
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock

Key Components of the Configuration¶

Image¶

containrrr/watchtower: The Docker image used for Watchtower.

Command¶

--cleanup=true: Enables cleanup of old images after updating.

Restart Policy¶

always: Ensures the Watchtower container restarts automatically after a crash or reboot.

Volumes¶

/var/run/docker.sock:/var/run/docker.sock: Mounts the Docker socket so Watchtower can interact with the Docker daemon.

Deploying Watchtower¶

Save the Docker Compose configuration in a docker-compose.yml file.
Run docker compose up -d to start Watchtower in detached mode.

How Watchtower Works¶

Watchtower updates ALL containers by default

By default, Watchtower will automatically update every running container on your Docker host. This includes stateful services where a version bump may cause data loss or breaking configuration changes.

To limit Watchtower to specific containers, add --label-enable to the command and add com.centurylinklabs.watchtower.enable=true as a label on containers you want to be monitored. Alternatively, use com.centurylinklabs.watchtower.enable=false to exclude specific containers.

Once deployed, Watchtower automatically checks for updates to the images of all running containers at the specified interval. The default check interval is 24 hours. Customise it with --interval <seconds>, for example --interval 3600 for hourly checks. If a new image is found, Watchtower updates the container without downtime.

Remember to ensure that your containers are configured to handle updates gracefully!

Updating Watchtower¶

Ironically, Watchtower does not update itself by default. The same commands apply to Watchtower's own container:

docker compose pull
docker compose up -d

Watchtower is stateless — its only mount is the Docker socket — so there is no data to back up before updating.

Youtube Video¶

If there is an issue with this guide or you wish to suggest changes, please raise an issue on GitHub.