[SOLVED] How to remove old and unused Docker images - docker

[SOLVED] A Simple Guide to Removing Old and Unused Docker Images

In Docker, it is important for us to manage our images well. This helps to keep our performance good and save space. Old and unused Docker images can pile up. This makes our development environment messy and slow. This article will give you different ways to remove old and unused Docker images. We will look at easy steps to make your Docker setup better. This way, we can focus on what is important—building great applications. Here are the solutions we will look at:

• Solution 1: List all Docker images
• Solution 2: Remove unused Docker images with docker image prune
• Solution 3: Remove specific old Docker images by ID
• Solution 4: Remove all unused images and containers
• Solution 5: Automate image cleanup with cron jobs
• Solution 6: Use docker system prune for full cleanup

By following this guide, we will learn how to keep our Docker environment clean and working well. For more info on Docker, you can check our links on how to copy Docker images from one host to another or understanding where Docker images are stored. Now let’s start with the solutions!

Solution 1 - List all Docker images

To start managing old and unused Docker images, we first need to list all Docker images on our system. This helps us see what images we have. It also helps us find which images are outdated or not needed anymore.

We can list all Docker images by running this command in the terminal:

docker images

Output Explanation

This command gives us a list with several columns:

• REPOSITORY: This is the name of the image repository.
• TAG: This shows the tag linked to the image. It often tells the version.
• IMAGE ID: This is the special ID for the image.
• CREATED: This tells us when the image was made.
• SIZE: This shows how big the image is on disk.

Example Output

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
myapp               latest              d1e5e5437b5a        2 days ago          200MB
nginx               1.21                a8a1f2b3e6f3        3 weeks ago        132MB
ubuntu              20.04               44b7f7a2f3a5        4 months ago       64MB

Filtering Images

If we want to find certain images, we can use the --filter option. For example, to list images made more than 30 days ago, we can run:

docker images --filter "before=nginx:latest"

This command will only show images made before the image we picked.

Next Steps

After we get the list of images, we can find the old and unused Docker images we might want to delete. To learn how to remove these images easily, check out Solution 2 - Remove unused Docker images with docker image prune.

For more info on Docker image management, look at this link about where Docker images are stored.

Solution 2 - Remove unused Docker images with docker image prune

To clean up our Docker environment and get rid of old and unused Docker images, we can use the docker image prune command. This command helps us to remove dangling images. Dangling images are images that are not tagged and not used by any containers. Here is how we can do it:

Step-by-step Instructions

1. Open your terminal: Make sure we have access to the command line where Docker is installed.

2. Run the prune command: Use this command to start removing unused images:

   docker image prune

   This command will ask us for confirmation before it deletes anything.

3. Remove all unused images: If we want to remove all unused images without confirming each time, we can add the -f (force) flag:

   docker image prune -f

4. Remove unused images including unused volumes: If we also want to remove unused volumes, we can run:

   docker image prune --volumes

Options for Customization

• Prune images older than a certain time: We can use the --filter option to remove images based on how old they are. For example, to remove images created more than 24 hours ago, we can use:

  docker image prune --filter "until=24h"

• View what will be removed: If we want to see which images will be pruned before we actually remove them, we can use the --dry-run option. Note that this option might not be in all Docker versions:

  docker image prune --dry-run

Additional Considerations

• Understanding dangling images: If we want to learn more about how Docker images are stored and what a dangling image is, we can check this article on where Docker images are stored.

• Regular cleanup: Using docker image prune in our regular routine can help us manage disk space well and keep our environment neat.

By following these steps, we can easily remove unused Docker images and free up important storage space in our system.

Solution 3 - Remove specific old Docker images by ID

To remove old Docker images by their ID, we first need to find the images we want to delete. Docker has a command that shows all images with their IDs. After we get the image ID, we can remove it using the right command.

Step 1: List All Docker Images

We can use this command to see all our Docker images and their IDs:

docker images

This command will show a list of images like this:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
my-image            latest              abc123def456        2 weeks ago        200MB
old-image           v1.0                xyz789ghi012        3 months ago       150MB

Step 2: Remove a Specific Docker Image by ID

When we find the specific old Docker image ID we want to remove, we can use the docker rmi command with the image ID to delete it. For example, to remove the image with ID xyz789ghi012, we run:

docker rmi xyz789ghi012

Important Considerations

• Dependencies: We need to make sure that no running containers are using the image we want to delete. If there are containers using it, we will see an error message. We can stop and remove these containers with:

  docker ps -a               # List all containers
  docker stop <container_id> # Stop the container
  docker rm <container_id>   # Remove the container

• Force Removal: If we want to forcefully remove an image, even if there are containers using it, we can add the -f option:

  docker rmi -f xyz789ghi012

Additional Resources

For more information on managing Docker images, we can check the article on how to remove old and unused Docker images. If we want to learn where Docker images are stored, we can look at where Docker images are stored.

Solution 4 - Remove all unused images and containers

To remove all unused Docker images and containers, we can use the docker system prune command. This command helps us clean up our Docker space. It removes not just unused images but also stopped containers and unused networks.

Steps to Remove All Unused Images and Containers

1. Open your terminal: Make sure you can run Docker commands.

2. Run the prune command: Type this command to remove all unused images, stopped containers, and unused networks:

   docker system prune

   This command will ask for your confirmation before it goes ahead. If you want to skip the confirmation, you can add the -f or --force flag:

   docker system prune -f

3. Include unused volumes (optional): If we also want to remove unused volumes, we can add the --volumes flag to the command:

   docker system prune -a --volumes

   The -a flag tells Docker to remove all unused images, not just the ones that are dangling. This way, we get even more space by removing volumes that are not linked to any containers.

Important Considerations

• Data Loss: We need to be careful when we use this command, especially with the --volumes option. It can delete data that is stored in volumes we are not using right now.

• Review Before Pruning: If we are not sure what will be removed, we should list our images and containers first. We can do this using:

  docker images -a        # List all images
  docker ps -a           # List all containers

• Check Disk Usage: To see how much space we freed up after the prune, we can check our Docker disk usage with:

  docker system df

By using the docker system prune command, we can keep our Docker environment clean. This way, old and unused Docker images and containers will not take up extra disk space. For more details on managing Docker images, you can check this guide.

Solution 5 - Automate image cleanup with cron jobs

We can save time and keep our system neat by automating the cleanup of old and unused Docker images. One good way to do this is by using cron jobs. Cron jobs let us run tasks on a schedule in Unix-based systems. Here are the steps to set up a cron job for cleaning up Docker images.

1. Open the Crontab File: We can edit the crontab file with this command. It opens the crontab editor for the user.

   crontab -e

2. Add a Cron Job: In the editor, we can set the schedule for our cleanup task. For example, to remove unused Docker images every Sunday at 2 AM, we can add this line:

   0 2 * * 0 /usr/bin/docker image prune -af

   In this command:

   • 0 2 * * 0 means it runs at 2 AM every Sunday.
   • /usr/bin/docker image prune -af is the command to run. The -a flag removes all unused images. The -f flag forces the removal without asking for confirmation.

3. Save and Exit: After adding the cron job, we need to save and exit the editor. The cron daemon will see the changes and schedule the task.

4. Verify the Cron Job: To check if our cron job is set up right, we can list all cron jobs for the user:

   crontab -l

5. Check Logs: If we want to make sure the cleanup works like we want, we can check the system logs. For example, we can look in /var/log/syslog or use this command:

   grep CRON /var/log/syslog

Best Practices

• Test Before Automating: Before we automate the cleanup, we should run the docker image prune -af command manually. This way, we can check it does not remove images we still need.

• Use Logging: We can add >> /var/log/docker_cleanup.log 2>&1 to our cron job command to log the output and errors for later review.

  0 2 * * 0 /usr/bin/docker image prune -af >> /var/log/docker_cleanup.log 2>&1

Automating image cleanup helps us save space and keep a clean Docker environment. For more information on managing Docker images, we can check how to remove old and unused Docker images.

Solution 6 - Use Docker system prune for cleanup

We can easily remove old and unused Docker images, containers, networks, and volumes by using the docker system prune command. This command helps us clean up our Docker environment. It helps us get back disk space and keep our system tidy.

How to use docker system prune

1. Basic Command: To run the command, type this in your terminal. It will remove all stopped containers, unused networks, dangling images, and build cache:

   docker system prune

   You will see a message asking if you want to continue. Just type y to go ahead.

2. Include All Unused Images: If we want to remove every unused image, not just the dangling ones, we can add the -a flag:

   docker system prune -a

   This command will delete all unused images, no matter if they are dangling or not.

3. Remove Unused Volumes: By default, docker system prune does not delete unused volumes. If we want to include volumes in the cleanup, we need to use the --volumes flag:

   docker system prune --volumes

4. Combining Options: We can combine options for a complete cleanup. For example, to remove all unused images, containers, networks, and volumes, we can run:

   docker system prune -a --volumes

Important Considerations

• Data Loss: We must be careful when using docker system prune, especially with the -a flag. It will delete images and containers that are not in use. Make sure we really do not need the images or containers we are about to delete.

• Regular Cleanup: Using docker system prune often can help us manage disk space better.

• Manual Review: Before we run the command, we might want to check what we will remove. We can use docker images, docker ps -a, and docker network ls to see images, containers, and networks that we may want to keep.

For more details on managing Docker resources, we can check the Docker commands documentation.

Conclusion

In this article, we looked at different ways to remove old and unused Docker images. This helps us keep a clean and efficient environment.

We can list images and use commands like docker image prune and docker system prune. These methods help us make our Docker setup better.

Cleaning up regularly saves disk space. It also helps improve performance.

For more information, we can read about how Docker images are stored and automating tasks with cron jobs.