How to Remove a Docker Image

TLDR

Use docker rmi <image> to remove a Docker image. If the image is in use by a container, stop and remove the container first. Use docker image prune to clean up dangling images.

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Docker images can pile up quickly, especially during development or CI/CD runs. Removing unused images helps free up disk space and keeps your environment tidy.

Why Remove Docker Images?

• Save Disk Space: Old images can consume gigabytes of storage.
• Reduce Clutter: Fewer images make it easier to manage and find what you need.
• Avoid Conflicts: Outdated images can cause version mismatches.

Listing Images

Before removing, list your images to see what's available:

docker images

This shows all images, their tags, and IDs.

Removing a Specific Image

To remove an image by name or ID:

# Remove by name
docker rmi nginx:alpine

# Remove by image ID
docker rmi 1a2b3c4d5e6f

If the image is used by a container, you'll see an error. Stop and remove the container first:

docker ps -a  # Find the container using the image
docker stop <container_id>
docker rm <container_id>
docker rmi <image>

Removing Dangling and Unused Images

Dangling images are layers not tagged or referenced by any container. Clean them up with:

docker image prune

To remove all unused images (not just dangling):

docker image prune -a

Note: This command will remove all images not currently used by any container, so use it with caution.

Best Practices

• Regularly clean up unused images, especially on CI/CD runners.
• Use tags to keep track of image versions.
• Automate cleanup with scheduled jobs if needed.

By managing your Docker images proactively, you keep your development environment fast and reliable.

Good luck with your project!