ProGet Documentation

Private Docker Registry

  • Last Modified: 2019-12-20

Using ProGet's Docker Registries, you can manage your own and third-party Docker images in a uniform manner, while defining fine-grained access control. ProGet works transparently with the Docker client, with images created internally or downloaded from remote Docker resources such as Docker Hub.

Internally, Docker registries are represented as feeds, which means:

  • feed-scoped privileges can be applied on Docker registries
  • you can configure Amazon S3 and Azure blob storage
  • the Docker registry name cannot be the same as another feed name

Multiple Docker Registries

ProGet lets you define as many Docker registries as you wish. This enables you to manage each project in a distinct registry and exercise better access control over your Docker images.

Creating and using a Docker Registries in ProGet

Docker requires an SSL connection, so you will need to configure ProGet to use IIS rather than its integrated web server, and configure the web site to use SSL (https). See testing an insecure registry in the Docker documentation for some help on configuring Docker to use a self-signed certificate.

To create a Docker registry in ProGet, go to Containers > Create New Docker Registry, then enter a registry name.

Setting up Docker Client

ProGet supports both token-based authentication (requiring Docker 1.11.0 or newer) and HTTP Basic authentication.

First, you will need to log in to Docker. To do this, use the following command, where progetsv1 is the name of your ProGet server:

[~]$ docker login progetsv1

Any username and password that work to log in via ProGet's web interface should work using this command. Additionally, the username api can be used with an API key as the password.

Docker requires TLS on any domain other than localhost, so the ProGet server must be accessible over HTTPS. Alternatively, the ProGet server name can be added to the Docker daemon's insecure-registries setting, but this is not recommended.

Note that the current user must have permission to use Docker. On Linux, this means being a member of the docker group or using sudo or su to switch to the root user temporarily. On Windows, the cmd or powershell instance must be started with admin privileges.

Publishing an Image

To publish a Docker image to ProGet, you first need to tag the image using Docker in a special format. For example, if we have an image locally called ubuntu:trusty, we need to retag it as follows:

[~]$ docker tag ubuntu:trusty progetsv1:443/dmc/ubuntu:trusty

Or, more generally, the format is: server/feed/image:tag.

Once tagged, the image can now be pushed to ProGet:

[~]$ docker push progetsv1:443/dmc/ubuntu:trusty

Pulling in Images

You can then pull the image in the same fashion:

[~]$ docker pull progetsv1:443/dmc/ubuntu:trusty

Deleting Images

To delete images, you can use Docker's Delete Image API, using a HTTP DELETE request as follows:

DELETE /v2/<repository-name>/manifests/<reference>

Note that the reference must be a digest. Deleting a tag is not allowed via this API, but deleting a manifest will remove any tag that refers directly to it.

In ProGet, the digest is at the top of the image details for a specific tag.

Via the API, the manifest digest can be found for tagged images:

  • To get a list of repositories, request
  • For each repository, you can get a list of tags via
  • From there, the tagged manifests can be accessed via
  • The hash is in the Docker-Content-Digest header for the response

You can also get the digest of an image you have locally via docker inspect -f '{{.Id}}'

When building, pushing, or pulling an image, the digest is printed near the end of the command output. The build command also supports using --iidfile to save the digest to a text file.

Implementation Details: Registries, Repositories, and More

While Docker users rarely need to worry about the implementation details, these may become important when you manage and troubleshoot a private Docker registry.

First, makes sure to familiarize yourself with the following Docker terminology and concepts.

Repositorya named collection of images and tags
Registrya host or server that stores Docker repositories
Imagea manifest and series of layers described in the manifest; this is assembled by the Docker client and instantiated as a container
Layereither a digest that references a blob stored in the same registry, or a url where a blob should be downloaded
Blobthe low-level storage mechanism used for layers and manifests, this is a collection of binary data that is referenced by its digest (hash)
Digest (hash)the identification of a particular blob; this is just the hash of its contents
Containera runtime instance of an image
Taga human-readable alias of a digest (hash) that generally used to version images within a repository
Manifesta JSON-based description of an image and the layers it contains; this is referenced by its digest and stored as a blob
Dockerfilea file written in a procedural language that is used by the Docker client to construct an image; essentially, this is used to generate a manifest

Conceptually, a registry is like a feed, a repository is like a package name, and an image is like a specific package version. However, the differences are a bit more nuanced, so make sure to also read Packages vs Containers.

Chunked and Monolithic Uploading

To support uploading large files over a single HTTP request, the Docker client will generally use a chunked upload process: send an upload initiation, a series of chunks (partial blob files), then an upload completion. ProGet supports this process, and assembles chunks as specified by the Docker API.

During the "FeedCleanUp" scheduled job, ProGet will purge incomplete uploads (i.e. chunks that were sent without an upload completion).

Garbage Collection

Unlike packages, a Docker image is not self-contained: it is a reference to a manifest blob, which in turn references a number of layer blobs. These layer blobs may be referenced by other manifests in the registry, which means that you can't simply delete referenced layer blobs when deleting a manifest blob.

This is where garbage collection comes in; it's the process of removing blobs from the package store when they are no longer referenced by a manifest. ProGet performs garbage collection on Docker registries through the "FeedCleanUp" scheduled job.


As of ProGet v5.1, docker feeds support connectors to other docker registries.

Private Registry Limitations

Windows Integrated Authentication

The Docker client does not support Windows Integrated Authentication, which means that you won't be able to setup "Anonymous" access to a ProGet instance that has this enabled. To workaround this, you can set-up a second site in IIS without Windows Integrated Authentication enabled that points to the same path on disk.

Other Limitations

Docker is designed to tightly integrate with the publicly-hosted Private registries are supported to some extent, but the Docker client and related tooling always assume you will be using their public registry, or at the very least, the official private Docker Registry that they built and support. This can make working with private registries a bit awkward at times, but Docker client support is gradually improving.

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