Watchtower: automatic Docker image updates for running containers

There’s an interesting image called containrrr/watchtower that is used for automating the process of updating Docker containers.

When an image is updated in the registry, Watchtower pulls the new image and restarts the container.

docker-compose.yml:

version: "2"
services:
  watchtower:
    container_name: watchtower
    image: containrrr/watchtower
    restart: always
    command: --interval 60
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /home/andrew/.docker/config.json:/config.json

Standalone run:

docker run -d --name watchtower \
    --restart always \
    -v /var/run/docker.sock:/var/run/docker.sock \
    containrrr/watchtower --interval 60

When using private images on Docker Hub, the containers being watched needs to use the full image name, including the repository prefix index.docker.io.

// instead of:
myuser/myimage

// use: 
index.docker.io/myuser/myimage

Also, after such changes we need to recreate the containers.

Custom containers

If we want to be updating only specific containers instead of all of them, we should specify them like this:

version: "2"
services:
  watchtower:
    container_name: watchtower
    image: containrrr/watchtower
    command: --cleanup --interval 60 dorokhov.dev.app dorokhov.codes.app
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /home/andrew/.docker/config.json:/config.json

Options

Flag --cleanup removes old images after updating.

When this flag is specified, watchtower will remove the old image after restarting a container with a new image.

Use this option to prevent the accumulation of orphaned images on your system as containers are updated.