Updating Docker Apps automagically with Watchtower✨🐳

Have you ever deployed a Docker app on a server, but everytime you push a new version of your image to a Docker registry you need to manually restart your app? If you want to automate this restarting, this blog post is for you! I am now going to show you how you can do this with literally 1 simple command using Watchtower!

This tutorial assumes that you already have a flow to automatically build and push your containers to a registry. If you do not have that, I suggest you to read and follow this tutorial or simply use a ready-to-go solution such as Sliplane

Let's get started! 🚀

Setup

First, run your container that you want to automatically update. Then, run the following command after replacing username, password, and container_to_watch

docker run -d \
  --name watchtower \
  -e REPO_USER=username \
  -e REPO_PASS=password \
  -v /var/run/docker.sock:/var/run/docker.sock \
  containrrr/watchtower container_to_watch --debug --interval 300

This will run the watchtower container (containerrr/watchtower) in the background (-d), name it watchtower, and pass in the username and password for your Docker container registry (-e REPO_USER=username -e REPO_PASS=password)

Watchtower will now periodically check if your Docker image has changed (in your remote repository!) and pull a new version once it has changed. It will then gracefully shut down your old container and restart it with the same configuration but with a new image. The default polling interval is 24 hours, which is quite conservative if you ask me. You can change the polling interval with --interval x where x is the number of seconds to wait. If you want to check for updates every 5 minutes you would add --interval 300

Conclusion

That's it! Now your cool dockerized app should update everytime you push a new image to your Docker repository. If you want to deploy a Docker app without all of the devops pain and without any Docker repositories, check out Sliplane