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Last pushed: 7 months ago
Short Description
docker registry cleaner
Full Description

Registry Cleaner

This is a small tool to delete tags, or, to be more correct, delete image manifests, from a Docker Registry implementing the API v2.

Please be aware of that this is a soft delete. You've to run the registry garbage collection after this tool has been applied.

For Docker Registry v2 API specification see

Information about the needed garbage collection is described at


  • v0.5 - fix for issue #8 which resulted in deleting more layers then intended; performance improvements; added --metadata-workers attribute
  • v0.4.1 - added --assume-yes and deprecated --quiet flag
  • v0.4 - added support for basic auth secured registry servers, introducing --basicauth-user and --basicauth-pw (thanks to @kekru for his pull request)
  • v0.3 - fixing deletion if a digest is associated with multiple tags, introducing the --ignore-ref-tags flag.
  • v0.2 - added support for registry server using self signed certificates
  • v0.1 - first version with basics

Prerequisites and supported Plattform

This tool was implemented and tested on Ubuntu Linux 14.04, 16.04 and on MacOS 10.12 using Python 2.7. It is developed against Docker Registry version 2.5.1, but tested against 2.6.1 and latest (see

You need to install the Python module requests:

$ pip install requests

Be sure to configure your registry server to allow deletion (see


Download the file or clone this repository to a local directory.

usage: [-h] [-v] -r REGISTRY [-p] [-y] [-q] [-n REPONAME]
                   [-k KEEPIMAGES] [-f REPOSFILE] [-c CACERT] [-i]
                   [-u BASICAUTHUSER] [-pw BASICAUTHPW] [-w MD_WORKERS]

Removes images on a docker registry (v2).

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         The verbosity level. Increase verbosity by multiple
                        usage, e.g. -vvv .
  -r REGISTRY, --registry REGISTRY
                        The registry server to connect to, e.g.
  -p, --proxy           Use system level proxy settings accessing registry
                        server if set. By default, the registry server will be
                        accessed without a proxy.
  -y, --yes, --assume-yes
                        If set no user action will appear and all questions
                        will be answered with YES
  -q, --quiet           [deprecated] If set no user action will appear and all
                        questions will be answered with YES
  -n REPONAME, --reponame REPONAME
                        The name of the repo which should be cleaned up
  -cf, --clean-full-catalog
                        If set all repos of the registry will be cleaned up,
                        keeping the amount of images specified in -k option. 
                        The amount for each repo can be overridden in the repofile (-f).
  -k KEEPIMAGES, --keepimages KEEPIMAGES
                        Amount of images (not tags!) which should be kept for
                        the given repo  (if -n is set) or for each repo of the 
                        registry (if -cf is set).
  -f REPOSFILE, --reposfile REPOSFILE
                        A file containing the list of Repositories and how
                        many images should be kept.
  -c CACERT, --cacert CACERT
                        Path to a valid CA certificate file. This is needed if
                        self signed TLS is used in the registry server.
  -i, --ignore-ref-tags
                        Ignore a digest if it is referenced multiple times in
                        the whole registry server. In this case, a list of all
                        repositories and their images will be retrieved which
                        can be time and memory consuming. ATTENTION: the
                        default is False so an image will be deleted even it
                        is referenced multiple times.
                        The username, if the registry is protected with basic
  -pw BASICAUTHPW, --basicauth-pw BASICAUTHPW
                        The password, if the registry is protected with basic
  -w MD_WORKERS, --metadata-workers MD_WORKERS
                        Parallel workers to retrieve image metadata. Default
                        value is 6.

In addition, you can obtain the public docker image to run it in a container:

docker run --rm hcguersoy/cleanreg:v0.5.0

The image is hosted here:

Hint: latest tag is not provided anymore!


Attention: It is strongly recommended that you use the -i flag even it is more time and memory consuming. If not you can delete images / layers which you not wanted to delete because registry itself doesn't check if a digest is referenced by multiple tags!

Cleaning up a single repository called mysql on registry server and keeping 5 of the latest images:

./ -r -n mysql -k 5

Be aware that you don't keep here the five last tags but digests/images. As a digest can be associated with multiple tags this can result in deletion of images which you not intended in!
Again: to be secure use the -i flag:

./ -r -n mysql -k 5 -i

Same as above but ignore images which are associated with multiple tags.

./ -r -n myalpine -k 50 -i -w 12

If you have a very large registry and enough bandwidth you can increase the parallel workers to retrieve the image metadata. The default is 6. Be aware that you can generate a DoS on your registry server by increasing to much.

Cleaning up all repositories of the registry:

./ -r -cf -k 5 -i

This will clean up all repositories, keeping 5 images per repository.

Cleaning up multiple repositories defined in a configuration file:

./ -r -f cleanreg-example.conf -i

The configuration file has the format <repository name> <images to keep>. An example file can be found in the repository.

The configuration file can be used together with the clean-full-catalog option:

./ -r -cf -k 5 -f cleanreg-example.conf -i

This will clean the repositories with images to keep as defined in the configuration file and it will additionally clean all other repositories of the registry, keeping 5 images per repository.

If you've to use a repositories definition file (parameter -f) while using the image distribution you should mount that file into your container:

docker run --rm -it -v $(pwd)/cleanreg-example.conf:/cleanreg-example.conf hcguersoy/cleanreg:<version> -r -f cleanreg-example.conf -i

There is a simple script added to create multiple image tags (based on busybox) on your registry server.

If you have installed a semi secure registry server using TLS and self signed certificates you have to provide the path to the CA certificate file:

./ -r -c /my/certifacates/ca.pem -f cleanreg-example.conf -i

If you run cleanreg in a container you should not forget to mount the certificate file into the container like the configuration file above.

If your registry is protected with basic auth and the username is test and the password is secret, you have to pass these credentials to cleanreg.

./ -r -u test -pw secret -f cleanreg-example.conf

Runing Garbage Collection

Example on running the garbage collection:

$ docker run --rm \
  -v /docker/registry2:/var/lib/registry:rw \
  registry:latest bin/registry \
  garbage-collect /etc/docker/registry/config.yml

This maps the local directory /docker/registry2 into the container, and calls the garbage collection.
The pointed config file is the default configuration.
The registry itself should be stopped before running this.


Feel free to contribute your changes as a PR. Please ensure that the tests run without errors and provide tests for additional functionality.

Run tests


  • Bash
  • Locally installed Docker engine (remote execution is not yet implemented; runs with Docker for MacOS fine)

You can run all tests, with the script:

cd test

This will run all tests and repeat them for different versions of the Docker Registry.

To run a single test, change to the test/tests directory and run a test script:

cd test/tests

By default the test will start the Docker Registry from Docker Hub with the tag latest. To specify another registry version, write its Docker Hub tag to the environment variable REGISTRYTAG.

cd test/tests
export REGISTRYTAG=2.5.1
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