moby--moby/docs/sources/use/workingwithrepository.md

page_title: Share Images via Repositories page_description: Repositories allow users to share images. page_keywords: repo, repositories, usage, pull image, push image, image, documentation

Share Images via Repositories

Introduction

Docker is not only a tool for creating and managing your own containers – Docker is also a tool for sharing. A repository is a shareable collection of tagged images that together create the file systems for containers. The repository's name is a label that indicates the provenance of the repository, i.e. who created it and where the original copy is located.

You can find one or more repositories hosted on a registry. There are two types of registry: public and private. There's also a default registry that Docker uses which is called Docker.io. Docker.io is the home of "top-level" repositories and public "user" repositories. The Docker project provides Docker.io to host public and private repositories, namespaced by user. We provide user authentication and search over all the public repositories.

Docker acts as a client for these services via the docker search, pull, login and push commands.

Repositories

Local Repositories

Docker images which have been created and labeled on your local Docker server need to be pushed to a Public (by default they are pushed to Docker.io) or Private registry to be shared.

Public Repositories

There are two types of public repositories: top-level repositories which are controlled by the Docker team, and user repositories created by individual contributors. Anyone can read from these repositories – they really help people get started quickly! You could also use Trusted Builds if you need to keep control of who accesses your images.

• Top-level repositories can easily be recognized by not having a / (slash) in their name. These repositories represent trusted images provided by the Docker team.
• User repositories always come in the form of <username>/<repo_name>. This is what your published images will look like if you push to the public Docker.io registry.
• Only the authenticated user can push to their username namespace on a Docker.io repository.
• User images are not curated, it is therefore up to you whether or not you trust the creator of this image.

Private repositories

You can also create private repositories on Docker.io. These allow you to store images that you don't want to share publicly. Only authenticated users can push to private repositories.

Find Public Images on Docker.io

You can search the Docker.io registry or using the command line interface. Searching can find images by name, user name or description:

$ sudo docker help search
Usage: docker search NAME

Search the docker index for images

  -notrunc=false: Don᾿t truncate output
$ sudo docker search centos
Found 25 results matching your query ("centos")
NAME                             DESCRIPTION
centos
slantview/centos-chef-solo       CentOS 6.4 with chef-solo.
...

There you can see two example results: centos and slantview/centos-chef-solo. The second result shows that it comes from the public repository of a user, slantview/, while the first result (centos) doesn't explicitly list a repository so it comes from the trusted top-level namespace. The / character separates a user's repository and the image name.

Once you have found the image name, you can download it:

# sudo docker pull <value>
$ sudo docker pull centos
Pulling repository centos
539c0211cd76: Download complete

What can you do with that image? Check out the Examples and, when you're ready with your own image, come back here to learn how to share it.

Contributing to Docker.io

Anyone can pull public images from the Docker.io registry, but if you would like to share one of your own images, then you must register a unique user name first. You can create your username and login on Docker.io, or by running

$ sudo docker login

This will prompt you for a username, which will become a public namespace for your public repositories.

If your username is available then docker will also prompt you to enter a password and your e-mail address. It will then automatically log you in. Now you're ready to commit and push your own images!

Note: Your authentication credentials will be stored in the .dockercfg authentication file.

Committing a Container to a Named Image

When you make changes to an existing image, those changes get saved to a container's file system. You can then promote that container to become an image by making a commit. In addition to converting the container to an image, this is also your opportunity to name the image, specifically a name that includes your user name from Docker.io (as you did a login above) and a meaningful name for the image.

# format is "sudo docker commit <container_id> <username>/<imagename>"
$ sudo docker commit $CONTAINER_ID myname/kickassapp

Pushing a repository to its registry

In order to push an repository to its registry you need to have named an image, or committed your container to a named image (see above)

Now you can push this repository to the registry designated by its name or tag.

# format is "docker push <username>/<repo_name>"
$ sudo docker push myname/kickassapp

Trusted Builds

Trusted Builds automate the building and updating of images from GitHub, directly on Docker.io. It works by adding a commit hook to your selected repository, triggering a build and update when you push a commit.

To setup a trusted build

1. Create a Docker.io account and login.
2. Link your GitHub account through the Link Accounts menu.
3. Configure a Trusted build.
4. Pick a GitHub project that has a Dockerfile that you want to build.
5. Pick the branch you want to build (the default is the master branch).
6. Give the Trusted Build a name.
7. Assign an optional Docker tag to the Build.
8. Specify where the Dockerfile is located. The default is /.

Once the Trusted Build is configured it will automatically trigger a build, and in a few minutes, if there are no errors, you will see your new trusted build on the Docker.io Registry. It will will stay in sync with your GitHub repo until you deactivate the Trusted Build.

If you want to see the status of your Trusted Builds you can go to your Trusted Builds page on the Docker index, and it will show you the status of your builds, and the build history.

Once you've created a Trusted Build you can deactivate or delete it. You cannot however push to a Trusted Build with the docker push command. You can only manage it by committing code to your GitHub repository.

You can create multiple Trusted Builds per repository and configure them to point to specific Dockerfile's or Git branches.

Private Registry

Private registries are possible by hosting your own registry.

Note

: You can also use private repositories on Docker.io.

To push or pull to a repository on your own registry, you must prefix the tag with the address of the registry's host (a . or : is used to identify a host), like this:

# Tag to create a repository with the full registry location.
# The location (e.g. localhost.localdomain:5000) becomes
# a permanent part of the repository name
$ sudo docker tag 0u812deadbeef localhost.localdomain:5000/repo_name

# Push the new repository to its home location on localhost
$ sudo docker push localhost.localdomain:5000/repo_name

Once a repository has your registry's host name as part of the tag, you can push and pull it like any other repository, but it will not be searchable (or indexed at all) on Docker.io, and there will be no user name checking performed. Your registry will function completely independently from the Docker.io registry.

See also

Docker Blog: How to use your own registry

Authentication File

The authentication is stored in a JSON file, .dockercfg, located in your home directory. It supports multiple registry URLs.

The docker login command will create the:

[https://index.docker.io/v1/](https://index.docker.io/v1/)

key.

The docker login https://my-registry.com command will create the:

[https://my-registry.com](https://my-registry.com)

key.

For example:

{
     "https://index.docker.io/v1/": {
             "auth": "xXxXxXxXxXx=",
             "email": "email@example.com"
     },
     "https://my-registry.com": {
             "auth": "XxXxXxXxXxX=",
             "email": "email@my-registry.com"
     }
}

The auth field represents

base64(<username>:<password>)