Docker is a fantastic tool for isolating your apps in containers to increase portability and scalability. However, over time, you might notice your disk space dwindling, thanks to old Docker images that are no longer in use. This tutorial will guide you on how to clean up these old Docker images and recover disk space.
Understanding Docker Images
Before we dive into the cleanup process, it’s essential to understand what Docker images are. Docker images are read-only templates used to build containers. They are built from a set of instructions written in a Dockerfile. Over time, as you update your applications and build new images, old and unused Docker images can accumulate, taking up a significant amount of disk space. (source)
Checking Disk Usage
The first step in cleaning up old Docker images is to check the current disk usage by Docker. You can do this using the Docker system df command:
docker system df
Removing Unused Docker Images
Once you’ve identified unused Docker images, you can remove them using the docker image prune command. This command removes all unused images. If you want to remove both unused and dangling images, use the -a flag:
docker image prune -a
Automating Docker Cleanup
If you frequently use Docker, it might be beneficial to automate the cleanup process. You can do this by setting up a cron job that runs the cleanup command at regular intervals. Here’s an example of a cron job that cleans up Docker every day at midnight:
0 0 * * * /usr/bin/docker image prune -a -f
Cleaning up old Docker images is a crucial part of Docker management. It helps you recover disk space and keeps your system running smoothly. Remember, automation is your friend in this process. Happy Dockering!