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docker rmi

Learn to remove images with docker rmi.

docker rmi

docker rmi (docker image rm) deletes an image from the local store. If a container (running or stopped) uses the image, removal is refused; the container must be removed first:

$ docker rmi nginx:alpine
Error response from daemon: conflict: unable to remove repository reference "nginx:alpine" (must force) - container 7c2f4a9e1b3d is using its referenced image
$ docker rm web && docker rmi nginx:alpine
Untagged: nginx:alpine
Deleted: sha256:a5b6c7d8…

Bulk cleanup

Instead of deleting one by one, prune commands are used:

docker image prune          # only dangling images
docker image prune -a       # all images no container uses
docker image prune -a --filter "until=168h"   # those older than a week
docker rmi $(docker images -q -f dangling=true)

-a should be used carefully; images you use often are deleted too and need to be pulled again.

Practice Image cleanup

Write three commands: force-remove the web container; delete the nginx:alpine image; then clean up the dangling images without asking for confirmation.

Starter code

terminal
# buraya yaz

Sample solution

terminal
docker rm -f web
docker rmi nginx:alpine
docker image prune -f

Expected output

web
Untagged: nginx:alpine
Deleted: sha256:a5b6c7d8e9f0
Total reclaimed space: 162MB

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 For an image with several tags, what does docker rmi api:1.0 do?

  • It deletes the containers
  • It removes only that tag; the image stays with the other tags Correct answer
  • It deletes all tags and the image
  • It errors

Explanation: When the last tag goes, the image is deleted too ("Untagged" and "Deleted").

2 Delete all unused images.

Question 
docker image prune ____ -f
Answer 
docker image prune -a -f

Explanation: -a also covers images that are unused but not dangling.

3 Match.

Term Meaning
docker rmi Deletes an image
Untagged Tag removed
image prune Cleans dangling ones
prune -a All unused

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project