Deploy a registry server

Estimated reading time: 18 minutes

Before you can deploy a registry, you need to install Docker on the host. A registry is an instance of the registry image, and runs within Docker.

This topic provides basic information about deploying and configuring a registry. For an exhaustive list of configuration options, see the configuration reference.

If you have an air-gapped datacenter, see Considerations for air-gapped registries.

Run a local registry

Use a command like the following to start the registry container:

$ docker run -d -p 5000:5000 --restart=always --name registry registry:2

The registry is now ready to use.

Warning: These first few examples show registry configurations that are only appropriate for testing. A production-ready registry must be protected by TLS and should ideally use an access-control mechanism. Keep reading and then continue to the configuration guide to deploy a production-ready registry.

Copy an image from Docker Hub to your registry

You can pull an image from Docker Hub and push it to your registry. The following example pulls the ubuntu:16.04 image from Docker Hub and re-tags it as my-ubuntu, then pushes it to the local registry. Finally, the ubuntu:16.04 and my-ubuntu images are deleted locally and the my-ubuntu image is pulled from the local registry.

Pull the ubuntu:16.04 image from Docker Hub.
```
$ docker pull ubuntu:16.04
```
Tag the image as localhost:5000/my-ubuntu. This creates an additional tag for the existing image. When the first part of the tag is a hostname and port, Docker interprets this as the location of a registry, when pushing.
```
$ docker tag ubuntu:16.04 localhost:5000/my-ubuntu
```
Push the image to the local registry running at localhost:5000:
```
$ docker push localhost:5000/my-ubuntu
```
Remove the locally-cached ubuntu:16.04 and localhost:5000/my-ubuntu images, so that you can test pulling the image from your registry. This does not remove the localhost:5000/my-ubuntu image from your registry.
```
$ docker image remove ubuntu:16.04
$ docker image remove localhost:5000/my-ubuntu
```
Pull the localhost:5000/my-ubuntu image from your local registry.
```
$ docker pull localhost:5000/my-ubuntu
```

Stop a local registry

To stop the registry, use the same docker container stop command as with any other container.

$ docker container stop registry

To remove the container, use docker container rm.

$ docker container stop registry && docker container rm -v registry

Basic configuration

To configure the container, you can pass additional or modified options to the docker run command.

The following sections provide basic guidelines for configuring your registry. For more details, see the registry configuration reference.

Start the registry automatically

If you want to use the registry as part of your permanent infrastructure, you should set it to restart automatically when Docker restarts or if it exits. This example uses the --restart always flag to set a restart policy for the registry.

$ docker run -d \
  -p 5000:5000 \
  --restart=always \
  --name registry \
  registry:2

Customize the published port

If you are already using port 5000, or you want to run multiple local registries to separate areas of concern, you can customize the registry’s port settings. This example runs the registry on port 5001 and also names it registry-test. Remember, the first part of the -p value is the host port and the second part is the port within the container. Within the container, the registry listens on port 5000 by default.

$ docker run -d \
  -p 5001:5000 \
  --name registry-test \
  registry:2

If you want to change the port the registry listens on within the container, you can use the environment variable REGISTRY_HTTP_ADDR to change it. This command causes the registry to listen on port 5001 within the container:

$ docker run -d \
  -e REGISTRY_HTTP_ADDR=0.0.0.0:5001 \
  -p 5001:5001 \
  --name registry-test \
  registry:2

Storage customization

Customize the storage location

By default, your registry data is persisted as a docker volume on the host filesystem. If you want to store your registry contents at a specific location on your host filesystem, such as if you have an SSD or SAN mounted into a particular directory, you might decide to use a bind mount instead. A bind mount is more dependent on the filesystem layout of the Docker host, but more performant in many situations. The following example bind-mounts the host directory /mnt/registry into the registry container at /var/lib/registry/.

$ docker run -d \
  -p 5000:5000 \
  --restart=always \
  --name registry \
  -v /mnt/registry:/var/lib/registry \
  registry:2

Customize the storage back-end

By default, the registry stores its data on the local filesystem, whether you use a bind mount or a volume. You can store the registry data in an Amazon S3 bucket, Google Cloud Platform, or on another storage back-end by using storage drivers. For more information, see storage configuration options.

Run an externally-accessible registry

Running a registry only accessible on localhost has limited usefulness. In order to make your registry accessible to external hosts, you must first secure it using TLS.

This example is extended in Run the registry as a service below.

Get a certificate

These examples assume the following:

Your registry URL is https://myregistry.domain.com/.
Your DNS, routing, and firewall settings allow access to the registry’s host on port 443.
You have already obtained a certificate from a certificate authority (CA).

If you have been issued an intermediate certificate instead, see use an intermediate certificate.

Create a certs directory.
```
$ mkdir -p certs
```
Copy the .crt and .key files from the CA into the certs directory. The following steps assume that the files are named domain.crt and domain.key.
Stop the registry if it is currently running.
```
$ docker container stop registry
```

Restart the registry, directing it to use the TLS certificate. This command bind-mounts the certs/ directory into the container at /certs/, and sets environment variables that tell the container where to find the domain.crt and domain.key file. The registry runs on port 443, the default HTTPS port.

$ docker run -d \
  --restart=always \
  --name registry \
  -v "$(pwd)"/certs:/certs \
  -e REGISTRY_HTTP_ADDR=0.0.0.0:443 \
  -e REGISTRY_HTTP_TLS_CERTIFICATE=/certs/domain.crt \
  -e REGISTRY_HTTP_TLS_KEY=/certs/domain.key \
  -p 443:443 \
  registry:2

Docker clients can now pull from and push to your registry using its external address. The following commands demonstrate this:

$ docker pull ubuntu:16.04
$ docker tag ubuntu:16.04 myregistrydomain.com/my-ubuntu
$ docker push myregistrydomain.com/my-ubuntu
$ docker pull myregistrydomain.com/my-ubuntu

Use an intermediate certificate

A certificate issuer may supply you with an intermediate certificate. In this case, you must concatenate your certificate with the intermediate certificate to form a certificate bundle. You can do this using the cat command:

cat domain.crt intermediate-certificates.pem > certs/domain.crt

You can use the certificate bundle just as you use the domain.crt file in the previous example.

Support for Let’s Encrypt

The registry supports using Let’s Encrypt to automatically obtain a browser-trusted certificate. For more information on Let’s Encrypt, see https://letsencrypt.org/how-it-works/ and the relevant section of the registry configuration.

Use an insecure registry (testing only)

It is possible to use a self-signed certificate, or to use our registry insecurely. Unless you have set up verification for your self-signed certificate, this is for testing only. See run an insecure registry.

Run the registry as a service

Swarm services provide several advantages over standalone containers. They use a declarative model, which means that you define the desired state and Docker works to keep your service in that state. Services provide automatic load balancing scaling, and the ability to control the distribution of your service, among other advantages. Services also allow you to store sensitive data such as TLS certificates in secrets.

The storage back-end you use determines whether you use a fully scaled service or a service with either only a single node or a node constraint.

If you use a distributed storage driver, such as Amazon S3, you can use a fully replicated service. Each worker can write to the storage back-end without causing write conflicts.
If you use a local bind mount or volume, each worker node writes to its own storage location, which means that each registry contains a different data set. You can solve this problem by using a single-replica service and a node constraint to ensure that only a single worker is writing to the bind mount.

The following example starts a registry as a single-replica service, which is accessible on any swarm node on port 80. It assumes you are using the same TLS certificates as in the previous examples.

First, save the TLS certificate and key as secrets:

$ docker secret create domain.crt certs/domain.crt

$ docker secret create domain.key certs/domain.key

Next, add a label to the node where you want to run the registry. To get the node’s name, use docker node ls. Substitute your node’s name for node1 below.

$ docker node update --label-add registry=true node1

Next, create the service, granting it access to the two secrets and constraining it to only run on nodes with the label registry=true. Besides the constraint, you are also specifying that only a single replica should run at a time. The example bind-mounts /mnt/registry on the swarm node to /var/lib/registry/ within the container. Bind mounts rely on the pre-existing source directory, so be sure /mnt/registry exists on node1. You might need to create it before running the following docker service create command.

By default, secrets are mounted into a service at /run/secrets/<secret-name>.

$ docker service create \
  --name registry \
  --secret domain.crt \
  --secret domain.key \
  --constraint 'node.labels.registry==true' \
  --mount type=bind,src=/mnt/registry,dst=/var/lib/registry \
  -e REGISTRY_HTTP_ADDR=0.0.0.0:443 \
  -e REGISTRY_HTTP_TLS_CERTIFICATE=/run/secrets/domain.crt \
  -e REGISTRY_HTTP_TLS_KEY=/run/secrets/domain.key \
  --publish published=443,target=443 \
  --replicas 1 \
  registry:2

You can access the service on port 443 of any swarm node. Docker sends the requests to the node which is running the service.

Load balancing considerations

One may want to use a load balancer to distribute load, terminate TLS or provide high availability. While a full load balancing setup is outside the scope of this document, there are a few considerations that can make the process smoother.

The most important aspect is that a load balanced cluster of registries must share the same resources. For the current version of the registry, this means the following must be the same:

Storage Driver
HTTP Secret
Redis Cache (if configured)

Differences in any of the above cause problems serving requests. As an example, if you’re using the filesystem driver, all registry instances must have access to the same filesystem root, on the same machine. For other drivers, such as S3 or Azure, they should be accessing the same resource and share an identical configuration. The HTTP Secret coordinates uploads, so also must be the same across instances. Configuring different redis instances works (at the time of writing), but is not optimal if the instances are not shared, because more requests are directed to the backend.

Important/Required HTTP-Headers

Getting the headers correct is very important. For all responses to any request under the “/v2/” url space, the Docker-Distribution-API-Version header should be set to the value “registry/2.0”, even for a 4xx response. This header allows the docker engine to quickly resolve authentication realms and fallback to version 1 registries, if necessary. Confirming this is setup correctly can help avoid problems with fallback.

In the same train of thought, you must make sure you are properly sending the X-Forwarded-Proto, X-Forwarded-For, and Host headers to their “client-side” values. Failure to do so usually makes the registry issue redirects to internal hostnames or downgrading from https to http.

A properly secured registry should return 401 when the “/v2/” endpoint is hit without credentials. The response should include a WWW-Authenticate challenge, providing guidance on how to authenticate, such as with basic auth or a token service. If the load balancer has health checks, it is recommended to configure it to consider a 401 response as healthy and any other as down. This secures your registry by ensuring that configuration problems with authentication don’t accidentally expose an unprotected registry. If you’re using a less sophisticated load balancer, such as Amazon’s Elastic Load Balancer, that doesn’t allow one to change the healthy response code, health checks can be directed at “/”, which always returns a 200 OK response.

Restricting access

Except for registries running on secure local networks, registries should always implement access restrictions.

Native basic auth

The simplest way to achieve access restriction is through basic authentication (this is very similar to other web servers’ basic authentication mechanism). This example uses native basic authentication using htpasswd to store the secrets.

Warning: You cannot use authentication with authentication schemes that send credentials as clear text. You must configure TLS first for authentication to work.

Create a password file with one entry for the user testuser, with password testpassword:

$ mkdir auth
$ docker run \
  --entrypoint htpasswd \
  registry:2 -Bbn testuser testpassword > auth/htpasswd

Stop the registry.
```
$ docker container stop registry
```

Start the registry with basic authentication.

$ docker run -d \
  -p 5000:5000 \
  --restart=always \
  --name registry \
  -v "$(pwd)"/auth:/auth \
  -e "REGISTRY_AUTH=htpasswd" \
  -e "REGISTRY_AUTH_HTPASSWD_REALM=Registry Realm" \
  -e REGISTRY_AUTH_HTPASSWD_PATH=/auth/htpasswd \
  -v "$(pwd)"/certs:/certs \
  -e REGISTRY_HTTP_TLS_CERTIFICATE=/certs/domain.crt \
  -e REGISTRY_HTTP_TLS_KEY=/certs/domain.key \
  registry:2

Try to pull an image from the registry, or push an image to the registry. These commands fail.
Log in to the registry.
```
$ docker login myregistrydomain.com:5000
```
Provide the username and password from the first step.

Test that you can now pull an image from the registry or push an image to the registry.

X509 errors: X509 errors usually indicate that you are attempting to use a self-signed certificate without configuring the Docker daemon correctly. See run an insecure registry.

More advanced authentication

You may want to leverage more advanced basic auth implementations by using a proxy in front of the registry. See the recipes list.

The registry also supports delegated authentication which redirects users to a specific trusted token server. This approach is more complicated to set up, and only makes sense if you need to fully configure ACLs and need more control over the registry’s integration into your global authorization and authentication systems. Refer to the following background information and configuration information here.

This approach requires you to implement your own authentication system or leverage a third-party implementation.

Deploy your registry using a Compose file

If your registry invocation is advanced, it may be easier to use a Docker compose file to deploy it, rather than relying on a specific docker run invocation. Use the following example docker-compose.yml as a template.

registry:
  restart: always
  image: registry:2
  ports:
    - 5000:5000
  environment:
    REGISTRY_HTTP_TLS_CERTIFICATE: /certs/domain.crt
    REGISTRY_HTTP_TLS_KEY: /certs/domain.key
    REGISTRY_AUTH: htpasswd
    REGISTRY_AUTH_HTPASSWD_PATH: /auth/htpasswd
    REGISTRY_AUTH_HTPASSWD_REALM: Registry Realm
  volumes:
    - /path/data:/var/lib/registry
    - /path/certs:/certs
    - /path/auth:/auth

Replace /path with the directory which contains the certs/ and auth/ directories.

Start your registry by issuing the following command in the directory containing the docker-compose.yml file:

$ docker-compose up -d

Considerations for air-gapped registries

You can run a registry in an environment with no internet connectivity. However, if you rely on any images which are not local, you need to consider the following:

You may need to build your local registry’s data volume on a connected host where you can run docker pull to get any images which are available remotely, and then migrate the registry’s data volume to the air-gapped network.
Certain images, such as the official Microsoft Windows base images, are not distributable. This means that when you push an image based on one of these images to your private registry, the non-distributable layers are not pushed, but are always fetched from their authorized location. This is fine for internet-connected hosts, but not in an air-gapped set-up.

In Docker 17.06 and higher, you can configure the Docker daemon to allow pushing non-distributable layers to private registries, in this scenario. This is only useful in air-gapped set-ups in the presence of non-distributable images, or in extremely bandwidth-limited situations. You are responsible for ensuring that you are in compliance with the terms of use for non-distributable layers.
1. Edit the daemon.json file, which is located in /etc/docker/ on Linux hosts and C:\ProgramData\docker\config\daemon.json on Windows Server. Assuming the file was previously empty, add the following contents:
```
{
  "allow-nondistributable-artifacts": ["myregistrydomain.com:5000"]
}
```
  The value is an array of registry addresses, separated by commas.
  
  Save and exit the file.
2. Restart Docker.
3. Restart the registry if it does not start automatically.
4. When you push images to the registries in the list, their non-distributable layers are pushed to the registry.
  
  Warning: Non-distributable artifacts typically have restrictions on how and where they can be distributed and shared. Only use this feature to push artifacts to private registries and ensure that you are in compliance with any terms that cover redistributing non-distributable artifacts.

Next steps

More specific and advanced information is available in the following sections:

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