Delete images from a Private Docker Registry

In case you have a private docker, and your builds keep pushing images to the registry, you will eventually run out of space.

To remove old images, you can use the following script.

The script scan all images, and removes any image whose tag is not "latest", and its tag > 950.

Change the skip conditions to match your images removal requirements.

#!/usr/bin/env bash


CheckTag(){
    Name=$1
    Tag=$2

    Skip=0
    if [[ "${Tag}" == "latest" ]]; then
        Skip=1
    fi
    if [[ "${Tag}" -ge "950" ]]; then
        Skip=1
    fi
    if [[ "${Skip}" == "1" ]]; then
        echo "skip ${Name} ${Tag}"
    else
        echo "delete ${Name} ${Tag}"
        Sha=$(curl -v -s -H "Accept: application/vnd.docker.distribution.manifest.v2+json" -X GET http://127.0.0.1:5000/v2/${Name}/manifests/${Tag} 2>&1 | grep Docker-Content-Digest | awk '{print ($3)}')
        Sha="${Sha/$'\r'/}"
        curl -H "Accept: application/vnd.docker.distribution.manifest.v2+json" -X DELETE "http://127.0.0.1:5000/v2/${Name}/manifests/${Sha}"
        return
    fi
}

ScanRepository(){
    Name=$1
    echo "Repository ${Name}"
    curl -s http://127.0.0.1:5000/v2/${Name}/tags/list | jq '.tags[]' |
    while IFS=$"\n" read -r line; do
        line="${line%\"}"
        line="${line#\"}"
        CheckTag $Name $line
    done
}


JqPath=$(which jq)
if [[ "x${JqPath}" == "x" ]]; then
  echo "Couldn't find jq executable."
  exit 2
fi

curl -s http://127.0.0.1:5000/v2/_catalog?n=10000 | jq '.repositories[]' |
while IFS=$"\n" read -r line; do
    line="${line%\"}"
    line="${line#\"}"
    ScanRepository $line
done

Once the cleanup is done, run the docker garbage collector on the docker registry container:

docker exec -it docker-registry bin/registry garbage-collect /etc/docker/registry/config.yml

This would run for several minutes, and then would delete the images from the disk.