Docker is a convenient tool for many, but with a few bigger images, the root filesystem becomes sooner or later full. Here is how to quickly and efficiently prune everything regarding Docker on your system to start fresh.

Before I introduce you to the one-liner I use, it’s worth noting that you could run Docker without sudo by adding yourself to the docker group:

$ sudo usermod -aG docker $USER && newgrp docker

We can now check how much space Docker assets take up:

$ docker system df

If that’s not what you hoped for, it’s also worth rechecking that Docker is the biggest offender for running out of disk space. I regularly run the ncdu disk utility (from the ncdu package on Fedora) to quickly assess what takes the most space (sudo ncdu /).

Once we are confident we need to do something about Docker images and their layers, we can run the following one-liner:

$ docker stop $(docker ps -a -q) && docker system prune -a --volumes -f

Let’s break it down:

• docker ps -a -q list the running container
• we need to stop the running containers with docker stop so we can truly delete everything
• we run docker system prune -a --volumes -f to forcefully prune stopped containers, unused networks, dangling images, build cache, and the associated volumes (skip the --volumes flag if you don’t want that!)

If you only want to remove images rather than networks and volumes, run docker image prune -a -f instead. If you need more granularity, see the manual.

Check out my book

Deployment from Scratch is unique Linux book about web application deployment. Learn how deployment works from the first principles rather than YAML files of a specific tool.

Published on 07 Jan 2021