Bash Script For Docker Image Cleanup

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Introduction

As a Docker user, managing your Docker images can be a daunting task, especially when you have a large number of images and repositories. Over time, your Docker image repository can become cluttered with old and unused images, taking up valuable disk space and slowing down your Docker workflow. In this article, we will discuss a bash script that can help you clean up old Docker images while keeping the latest tag for each repository and skipping images currently in use.

The Problem with Docker Image Cleanup

Docker images can be a significant source of disk space consumption, especially when you have a large number of images and repositories. If you don't regularly clean up your Docker images, you may find yourself running out of disk space, which can lead to performance issues and other problems. Additionally, having too many old and unused Docker images can make it difficult to manage your Docker workflow, as you may need to spend a lot of time searching for the images you need.

The Solution: A Bash Script for Docker Image Cleanup

To address the problem of Docker image cleanup, I've developed a bash script that can help you clean up old Docker images while keeping the latest tag for each repository and skipping images currently in use. The script uses the docker images command to list all Docker images, and then uses a combination of grep and awk commands to filter out the images that are currently in use and keep the latest tag for each repository.

The Bash Script

Here is the bash script that I've developed for Docker image cleanup:

#!/bin/bash

MIN_AGE=30



docker_images=$(docker images -a --format "{.Repository}}{{.Tag}")



while IFS= read -r line; do



repository=(echo "line" | cut -d':' -f1)
tag=(echo "line" | cut -d':' -f2)



if ! docker ps -a --format "{.Image}}" | grep -q "$repositorytag"; then
    # Get the creation date of the image
    creation_date=(docker inspect -f '{{.Created}' "repository:repository:tag")


# Convert the creation date to a Unix timestamp
creation_timestamp=$(date -d "$creation_date" +%s)

# Calculate the age of the image in days
age_in_days=$((($(date +%s) - creation_timestamp) / 86400))

# Check if the image is older than the minimum age
if [ $age_in_days -ge $MIN_AGE ]; then
  # Delete the image
  docker rmi "$repository:$tag"
  echo "Deleted image $repository:$tag"
fi



fi
done <<< "$docker_images"

How the Script Works

The script works by first getting the list of all Docker images using the docker images command. It then loops through each image and checks if it's currently in use by checking if the image is listed the output of the docker ps -a command. If the image is not currently in use, the script gets the creation date of the image using the docker inspect command and calculates the age of the image in days. If the image is older than the minimum age specified by the MIN_AGE variable, the script deletes the image using the docker rmi command.

Using the Script

To use the script, simply save it to a file (e.g. docker_image_cleanup.sh), make the file executable using the chmod command (e.g. chmod +x docker_image_cleanup.sh), and then run the script using the ./ command (e.g. ./docker_image_cleanup.sh). The script will delete all Docker images that are older than the minimum age specified by the MIN_AGE variable and are not currently in use.

Tips and Variations

Here are a few tips and variations that you can use to customize the script to your needs:

  • To change the minimum age for images to be deleted, simply modify the MIN_AGE variable at the top of the script.
  • To skip images that are currently in use, the script already does this by checking if the image is listed in the output of the docker ps -a command.
  • To delete all Docker images, regardless of age, simply remove the if [ $age_in_days -ge $MIN_AGE ] check.
  • To delete only specific Docker images, simply modify the docker_images variable to only include the images you want to delete.

Conclusion

Q: What is the purpose of the bash script for Docker image cleanup?

A: The purpose of the bash script for Docker image cleanup is to help you manage your Docker image repository by deleting old and unused images, while keeping the latest tag for each repository and skipping images currently in use.

Q: How does the script determine which images to delete?

A: The script uses a combination of docker commands and grep and awk commands to filter out the images that are currently in use and keep the latest tag for each repository. It checks if an image is currently in use by checking if it's listed in the output of the docker ps -a command. If an image is not currently in use, it calculates the age of the image in days and deletes it if it's older than the minimum age specified by the MIN_AGE variable.

Q: How do I customize the script to my needs?

A: You can customize the script to your needs by modifying the MIN_AGE variable at the top of the script to change the minimum age for images to be deleted. You can also modify the docker_images variable to only include the images you want to delete.

Q: Can I delete all Docker images using the script?

A: Yes, you can delete all Docker images using the script by removing the if [ $age_in_days -ge $MIN_AGE ] check. However, be careful when doing this, as it will delete all images, including those that are currently in use.

Q: Can I delete only specific Docker images using the script?

A: Yes, you can delete only specific Docker images using the script by modifying the docker_images variable to only include the images you want to delete.

Q: How do I run the script?

A: To run the script, simply save it to a file (e.g. docker_image_cleanup.sh), make the file executable using the chmod command (e.g. chmod +x docker_image_cleanup.sh), and then run the script using the ./ command (e.g. ./docker_image_cleanup.sh).

Q: What are the benefits of using the script?

A: The benefits of using the script include:

  • Keeping your Docker image repository clean and organized
  • Avoiding running out of disk space
  • Improving your Docker workflow by reducing the number of images to manage

Q: Are there any potential risks or issues with using the script?

A: Yes, there are potential risks or issues with using the script, including:

  • Deleting images that are currently in use
  • Deleting images that are not old enough to be deleted
  • Modifying the script to delete images that are not intended to be deleted

Q: How do I troubleshoot issues with the script?

A: To troubleshoot issues with the script, you can use the following steps:

  • Check the script's output for any errors or warnings
  • Verify that the script is running correctly by checking the Docker logs
  • Modify the script to include additional logging or debugging statements to help diagnose issues

Q: Can I use the script with other Docker tools or plugins?

A: Yes, you can use the script with other Docker tools or plugins, such as Docker Compose or Docker Swarm. However, you may need to modify the script to work with these tools or plugins.