Removal of Containers and Images

Overview

Teaching: 5 min
Exercises: 5 min

Questions

• How do you cleanup old containers?

• How do you delete images?

Objectives

• Learn how to cleanup after Docker

You can cleanup/remove a container docker rm

docker rm <CONTAINER ID>

Remove old containers

Start an instance of the tutorial container, exit it, and then remove it with docker rm

Solution

docker run matthewfeickert/intro-to-docker:latest
docker ps -a
docker rm <CONTAINER ID>
docker ps -a

CONTAINER ID        IMAGE         COMMAND             CREATED            STATUS                     PORTS               NAMES
<generated id>      <image:tag>   "/bin/bash"         n seconds ago      Exited (0) t seconds ago                       <name>

<generated id>

CONTAINER ID        IMAGE         COMMAND             CREATED            STATUS                     PORTS               NAMES

You can remove an image from your computer entirely with docker rmi

docker rmi <IMAGE ID>

Remove an image

Pull down the Python 2.7 image from Docker Hub and then delete it.

Solution

docker pull python:2.7
docker images python
docker rmi <IMAGE ID>
docker images python

2.7: Pulling from library/python
<some numbers>: Pull complete
<some numbers>: Pull complete
<some numbers>: Pull complete
<some numbers>: Pull complete
<some numbers>: Pull complete
<some numbers>: Pull complete
<some numbers>: Pull complete
<some numbers>: Pull complete
Digest: sha256:<the relevant SHA hash>
Status: Downloaded newer image for python:2.7
docker.io/library/python:2.7

REPOSITORY   TAG                 IMAGE ID       CREATED         SIZE
python       3.8                 79372a158581   4 days ago      909MB
python       3.9                 e2d7fd224b9c   4 days ago      912MB
python       3.9-bullseye        e2d7fd224b9c   4 days ago      912MB
python       2.7                 68e7be49c28c   18 months ago   902MB

Untagged: python@sha256:<the relevant SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>
Deleted: sha256:<layer SHA hash>

REPOSITORY   TAG                 IMAGE ID       CREATED         SIZE
python       3.8                 79372a158581   4 days ago      909MB
python       3.9                 e2d7fd224b9c   4 days ago      912MB
python       3.9-bullseye        e2d7fd224b9c   4 days ago      912MB

Helpful cleanup commands

What is helpful is to have Docker detect and remove unwanted images and containers for you. This can be done with prune, which depending on the context will remove different things.

• docker container prune removes all stopped containers, which is helpful to clean up forgotten stopped containers.
• docker image prune removes all unused or dangling images (images that do not have a tag). This is helpful for cleaning up after builds.
• docker system prune removes all stopped containers, dangling images, and dangling build caches. This is very helpful for cleaning up everything all at once.

Worth cleaning up to save disk

Docker images are just lots of compressed archives, and they can take up lots of disk pretty fast. You can monitor the total disk being used by Docker with df

docker system df

TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              n                   0                   X.YGB               X.YGB (100%)
Containers          0                   0                   0B                  0B
Local Volumes       m                   0                   A.BkB               A.BkB (100%)
Build Cache         0                   0                   0B                  0B

and for lots of detailed information you can use the -v verbose flag

docker system df -v

Key Points

• Remove containers with docker rm

• Remove images with docker rmi

• Perform faster cleanup with docker container prune, docker image prune, and docker system prune