Automate docker container and image cleanup

docker-cleanup.md

Automate container and image cleanup

To automatically delete Docker containers and images older than 15 days, we can set up a cron job that runs a script at specified intervals.

Step 1: Create a Cleanup Script

Create a file named docker-cleanup.sh with the following content:

#!/bin/bash

# Define cutoff date in Unix timestamp (15 days ago)
cutoff=$(date -d '15 days ago' +%s)

# Remove containers that are exited for more than 15 days
docker ps -a -q -f "status=exited" --format "{{.ID}} {{.CreatedAt}}" | while read -r container_id created_at; do
    created_timestamp=$(date -d "$created_at" +%s)
    if [ $created_timestamp -lt $cutoff ]; then
        echo "Removing container $container_id (created at $created_at)"
        docker rm $container_id
    fi
done

# Remove images older than 15 days
docker images --format "{{.Repository}}:{{.Tag}} {{.ID}} {{.CreatedAt}}" | while read -r line; do
    image_info=($line)
    image_name=${image_info[0]}
    image_id=${image_info[1]}
    image_created_at=${image_info[2]}
    image_timestamp=$(date -d "$image_created_at" +%s)

    # Skip if image ID is <none> (invalid reference format)
    if [ "$image_id" == "<none>" ]; then
        continue
    fi

    if [ $image_timestamp -lt $cutoff ]; then
        echo "Removing unused image $image_name (ID: $image_id, created at $image_created_at)"
        docker rmi $image_id
    else
        echo "Skipping image $image_name (ID: $image_id) removal because it is not older than 15 days or still in use"
    fi
done

Save this script to a convenient location, for example, /opt/docker-cleanup/docker-cleanup.sh. Make sure the script is executable:

chmod +x /opt/docker-cleanup/docker-cleanup.sh

Step 2: Test the Cleanup Script

./docker-cleanup.sh

Step 3: Set Up a Cron Job

Now, automate the cleanup process using a cron job. Open the crontab editor:

crontab -e

Add the following line to run the cleanup script every day at a specific time (for example, 9:00 AM):

0 9 * * * /opt/docker-cleanup/docker-cleanup.sh >> /var/log/docker-cleanup.log 2>&1

The output of the script will be logged to /var/log/docker-cleanup.log for monitoring and troubleshooting purposes.