DEPRECATED in favour of `docker image prune` https://docs.docker.com/config/pruning/

docker-registry-clean.sh

#!/bin/sh

base_dir=/var/lib/registry/docker/registry/v2
repository_dir=$base_dir/repositories
image_dir=$base_dir/blobs

output_dir=$(mktemp -d)

all_images=$output_dir/all
used_images=$output_dir/used
unused_images=$output_dir/unused

find "$image_dir/sha256/" -mindepth 2 -type d -exec basename {} \; > "$all_images"

echo "Collecting orphan images">&2
for library in $repository_dir/*; do
    echo "Library $(basename "$library")" >&2

    for repo in $library/*; do
        echo " Repo $(basename "$repo")" >&2

        for tag in $repo/_manifests/tags/*; do
            echo "  Tag $(basename "$tag")" >&2

            image_hash=$(basename $tag/index/sha256/*)
            echo "   Image $image_hash" >&2

            echo "$image_hash"
            jq -r '.config.digest' "$image_dir/sha256/${image_hash:0:2}/$image_hash/data" | sed 's|sha256:||'
            jq -r '.layers[].digest' "$image_dir/sha256/${image_hash:0:2}/$image_hash/data" | sed 's|sha256:||'
        done
    done
done | sort | uniq > "$used_images"

grep -v -F -f "$used_images" "$all_images" > "$unused_images"

all_image_count=$(wc -l < "$all_images")
used_image_count=$(wc -l < "$used_images")
unused_image_count=$(wc -l < "$unused_images")
unused_image_size='0'


echo "${all_image_count} images, ${used_image_count} used, ${unused_image_count} unused"
if [ "$unused_image_count" -gt 0 ]; then
  unused_image_folders=""
  for image_hash in $(cat "$unused_images"); do
    unused_image_folders="$unused_image_folders $image_dir/sha256/${image_hash:0:2}/$image_hash"
  done
  unused_image_size=$(du -hc $unused_image_folders | tail -n1 | cut -f1)
  echo "Unused images consume ${unused_image_size}"
  
  echo "Delete unused Images? [y/n]"
  read confirmation
  if [ "$confirmation" == "y" ]; then
    echo "Cleanup images"
    for image_hash in $(cat "$unused_images"); do
      rm -rf "$image_dir/sha256/${image_hash:0:2}/$image_hash"
    done
  fi
fi

@gael-jurin what do you mean by "shell sh/bash"?

I mean not paying attention about the first line of the script and try to run it with a default bash shell.
@qoomon Right ! but still doing the job if someone want to customize the operation. Thx !