I’ve been playing around a lot with docker. It’s awesome, and it creates a whole new world of possibilities, and I’m constantly coming up with new ideas of where it could be useful.

After playing with docker for about a week on my development server, I logged in to find that my disk was completely full. I guess after dynamically spinning up dozens of containers, and building a bunch of projects with Dockerfiles I had accumulated quite a few stopped containers and untagged images. I suspect the build process to be the biggest contributor to this, as each step in your dockerfile creates a new container, which serves as the base for the next step. This is usfeul because it can cache the containers and speed up builds, but it does consume a bit of space.

I was not able to find any built-in commands for clearing stopped containers and untagged images, so I was able to put together a couple commands.

Remove all stopped containers.

docker rm $(docker ps -a -q)

This will remove all stopped containers by getting a list of all containers with docker ps -a -q and passing their ids to docker rm. This should not remove any running containers, and it will tell you it can’t remove a running image.

Remove all untagged images

In the process of running docker I had accumulated several images that are not tagged. To remove these I use this command:

docker rmi $(docker images | grep "^<none>" | awk "{print $3}")

This works by using rmi with a list of image ids. To get the image ids we call docker images then pipe it to grep "^<none>". The grep will filter it down to only lines with the value “<none>” in the repository column. Then to extract the id out of the third column we pipe it to awk "{print $3}" which will print the third column of each line passed to it.

After running these two commands I recovered 15G of space. There may be more I could do to recover more space, my docker graph directory still is over 5G, but for now this works.

from:http://jimhoskins.com/2013/07/27/remove-untagged-docker-images.html

Remove Untagged Images From Docker