---
stage: Systems
group: Geo
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
type: howto
---

# Container Registry for a secondary site **(PREMIUM SELF)**

You can set up a Container Registry on your **secondary** Geo site that mirrors the one on the **primary** Geo site.

## Supported container registries

Geo supports the following types of container registries:
 
- [Docker](https://docs.docker.com/registry/)
- [OCI](https://github.com/opencontainers/distribution-spec/blob/main/spec.md)

## Supported image formats

The following container image formats are support by Geo:

- [Docker V2, schema 1](https://docs.docker.com/registry/spec/manifest-v2-1/)
- [Docker V2, schema 2](https://docs.docker.com/registry/spec/manifest-v2-2/)
- [OCI (Open Container Initiative)](https://github.com/opencontainers/image-spec)

In addition, Geo also supports [BuildKit cache images](https://github.com/moby/buildkit).

## Supported storage 

### Docker

For more information on supported registry storage drivers see
[Docker registry storage drivers](https://docs.docker.com/registry/storage-drivers/)

Read the [Load balancing considerations](https://docs.docker.com/registry/deploying/#load-balancing-considerations)
when deploying the Registry, and how to set up the storage driver for the GitLab integrated 
[Container Registry](../../packages/container_registry.md#use-object-storage).

### Registries that support OCI artifacts

The following registries support OCI artifacts:

- CNCF Distribution - local/offline verification
- Azure Container Registry (ACR)
- Amazon Elastic Container Registry (ECR)
- Google Artifact Registry (GAR)
- GitHub Packages container registry (GHCR)
- Bundle Bar

For more information, see the [OCI Distribution Specification](https://github.com/opencontainers/distribution-spec).

## Configure Container Registry replication

You can enable a storage-agnostic replication so it
can be used for cloud or local storage. Whenever a new image is pushed to the
**primary** site, each **secondary** site pulls it to its own container
repository.

To configure Container Registry replication:

1. Configure the [**primary** site](#configure-primary-site).
1. Configure the [**secondary** site](#configure-secondary-site).
1. Verify Container Registry [replication](#verify-replication).

### Configure **primary** site

Make sure that you have Container Registry set up and working on
the **primary** site before following the next steps.

We need to make Container Registry send notification events to the
**primary** site.

1. SSH into your GitLab **primary** server and login as root:

   ```shell
   sudo -i
   ```

1. Edit `/etc/gitlab/gitlab.rb`:

   ```ruby
   registry['notifications'] = [
     {
       'name' => 'geo_event',
       'url' => 'https://<example.com>/api/v4/container_registry_event/events',
       'timeout' => '500ms',
       'threshold' => 5,
       'backoff' => '1s',
       'headers' => {
         'Authorization' => ['<replace_with_a_secret_token>']
       }
     }
   ]
   ```

   NOTE:
   Replace `<example.com>` with the `external_url` defined in your primary site's `/etc/gitlab/gitlab.rb` file, and
   replace `<replace_with_a_secret_token>` with a case sensitive alphanumeric string
   that starts with a letter. You can generate one with `< /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c 32 | sed "s/^[0-9]*//"; echo`

   NOTE:
   If you use an external Registry (not the one integrated with GitLab), you must add
   these settings to its configuration yourself. In this case, you also have to specify
   notification secret in `registry.notification_secret` section of
   `/etc/gitlab/gitlab.rb` file.

   NOTE:
   If you use GitLab HA, you also have to specify
   the notification secret in `registry.notification_secret` section of
   `/etc/gitlab/gitlab.rb` file for every web node.

1. Reconfigure the **primary** node for the change to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

### Configure **secondary** site

Make sure you have Container Registry set up and working on
the **secondary** site before following the next steps.

The following steps should be done on each **secondary** site you're
expecting to see the container images replicated.

Because we need to allow the **secondary** site to communicate securely with
the **primary** site Container Registry, we need to have a single key
pair for all the sites. The **secondary** site uses this key to
generate a short-lived JWT that is pull-only-capable to access the
**primary** site Container Registry.

For each application and Sidekiq node on the **secondary** site:

1. SSH into the node and login as the `root` user:

   ```shell
   sudo -i
   ```

1. Copy `/var/opt/gitlab/gitlab-rails/etc/gitlab-registry.key` from the **primary** to the node.

1. Edit `/etc/gitlab/gitlab.rb` and add:

   ```ruby
   gitlab_rails['geo_registry_replication_enabled'] = true

   # Primary registry's hostname and port, it will be used by
   # the secondary node to directly communicate to primary registry
   gitlab_rails['geo_registry_replication_primary_api_url'] = 'https://primary.example.com:5050/'
   ```

1. Reconfigure the node for the change to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

### Verify replication

To verify Container Registry replication is working, on the **secondary** site:

1. On the top bar, select **Menu > Admin**.
1. On the left sidebar, select **Geo > Nodes**.
   The initial replication, or "backfill", is probably still in progress.

You can monitor the synchronization process on each Geo site from the **primary** site's **Geo Nodes** dashboard in your browser.