Pruning Docker when no space left

Learn how to clean your docker containers when no space left

Solve the dreaded no space left in Docker

Frequently when you're working in a project with multiple containers and services, you eventually run out of space.

Sometimes you'll notice that your server is not out of a strange service failing or something not that clear.

If previously your services were working fine and out of nowhere you get a strange error.

That's the first signal this might be an issue with disk space.

Let's assume we have a simple Dockerfile and a docker-composer.yml

version: '3.1'
services:
  mysql:
    image: mysql:8.0.28
    command: --default-authentication-plugin=mysql_native_password
    environment:
      MYSQL_ROOT_PASSWORD: example
    ports:
      - '3306:3306'
    volumes:
      - db_data:/var/lib/mysql
volumes:
  db_data:

Good approach to find out quick the potential issues

  • Let's run first docker logs mysql

if you see an error like:


[System] [MY-013169] [Server] /usr/sbin/mysqld (mysql 8.0.28) initializing of server in progress as process 10
mysqld: Error writing file '/var/lib/mysql/auto.cnf' (OS errno 28 - No space left on device)

The next thing to do is check for storage:

$ docker system df

Probably, there will be a Containers row at 99% capacity

Then the best step is to just prune all your containers, hopefully you have reproducible steps like scripts to get your desired mysql database state.

Remember -a means all unused images and -f means force so you won't be asked for permission to delete those resources

$ docker system prune -af

Then let's move to unused volumes, again, make sure you have a way to reproduce your desired state. Using -f will force deletion of unused volumes.

$ docker volume ls
$ docker volume prune -f

Double check that no longer we have kept any stopped containers or images

$ docker ps -a
$ docker rm $(docker ps -aq)

Clean images

$ docker imags -q | xargs docker rmi -f

Finally if you check your docker system af, you'll see you've removed most of your containers.

This is a great practice to do it every now and then to keep your system healthy and tight.