gitlab-org--gitlab-foss/doc/administration/geo/replication/configuration.md

---
stage: Enablement
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
---

# Geo configuration **(PREMIUM ONLY)**

## Configuring a new **secondary** node

NOTE:
This is the final step in setting up a **secondary** Geo node. Stages of the
setup process must be completed in the documented order.
Before attempting the steps in this stage, [complete all prior stages](../setup/index.md#using-omnibus-gitlab).

The basic steps of configuring a **secondary** node are to:

- Replicate required configurations between the **primary** node and the **secondary** nodes.
- Configure a tracking database on each **secondary** node.
- Start GitLab on each **secondary** node.

You are encouraged to first read through all the steps before executing them
in your testing/production environment.

NOTE:
**Do not** set up any custom authentication for the **secondary** nodes. This will be handled by the **primary** node.
Any change that requires access to the **Admin Area** needs to be done in the
**primary** node because the **secondary** node is a read-only replica.

### Step 1. Manually replicate secret GitLab values

GitLab stores a number of secret values in the `/etc/gitlab/gitlab-secrets.json`
file which *must* be the same on all nodes. Until there is
a means of automatically replicating these between nodes (see [issue #3789](https://gitlab.com/gitlab-org/gitlab/-/issues/3789)),
they must be manually replicated to the **secondary** node.

1. SSH into the **primary** node, and execute the command below:

   ```shell
   sudo cat /etc/gitlab/gitlab-secrets.json
   ```

   This will display the secrets that need to be replicated, in JSON format.

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

   ```shell
   sudo -i
   ```

1. Make a backup of any existing secrets:

   ```shell
   mv /etc/gitlab/gitlab-secrets.json /etc/gitlab/gitlab-secrets.json.`date +%F`
   ```

1. Copy `/etc/gitlab/gitlab-secrets.json` from the **primary** node to the **secondary** node, or
   copy-and-paste the file contents between nodes:

   ```shell
   sudo editor /etc/gitlab/gitlab-secrets.json

   # paste the output of the `cat` command you ran on the primary
   # save and exit
   ```

1. Ensure the file permissions are correct:

   ```shell
   chown root:root /etc/gitlab/gitlab-secrets.json
   chmod 0600 /etc/gitlab/gitlab-secrets.json
   ```

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

   ```shell
   gitlab-ctl reconfigure
   gitlab-ctl restart
   ```

### Step 2. Manually replicate the **primary** node's SSH host keys

GitLab integrates with the system-installed SSH daemon, designating a user
(typically named `git`) through which all access requests are handled.

In a [Disaster Recovery](../disaster_recovery/index.md) situation, GitLab system
administrators will promote a **secondary** node to the **primary** node. DNS records for the
**primary** domain should also be updated to point to the new **primary** node
(previously a **secondary** node). Doing so will avoid the need to update Git remotes and API URLs.

This will cause all SSH requests to the newly promoted **primary** node to
fail due to SSH host key mismatch. To prevent this, the primary SSH host
keys must be manually replicated to the **secondary** node.

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

   ```shell
   sudo -i
   ```

1. Make a backup of any existing SSH host keys:

   ```shell
   find /etc/ssh -iname ssh_host_* -exec cp {} {}.backup.`date +%F` \;
   ```

1. Copy OpenSSH host keys from the **primary** node:

   If you can access your **primary** node using the **root** user:

   ```shell
   # Run this from the secondary node, change `<primary_node_fqdn>` for the IP or FQDN of the server
   scp root@<primary_node_fqdn>:/etc/ssh/ssh_host_*_key* /etc/ssh
   ```

   If you only have access through a user with `sudo` privileges:

   ```shell
   # Run this from your primary node:
   sudo tar --transform 's/.*\///g' -zcvf ~/geo-host-key.tar.gz /etc/ssh/ssh_host_*_key*

   # Run this from your secondary node:
   scp <user_with_sudo>@<primary_node_fqdn>:geo-host-key.tar.gz .
   tar zxvf ~/geo-host-key.tar.gz -C /etc/ssh
   ```

1. On your **secondary** node, ensure the file permissions are correct:

   ```shell
   chown root:root /etc/ssh/ssh_host_*_key*
   chmod 0600 /etc/ssh/ssh_host_*_key*
   ```

1. To verify key fingerprint matches, execute the following command on both nodes:

   ```shell
   for file in /etc/ssh/ssh_host_*_key; do ssh-keygen -lf $file; done
   ```

   You should get an output similar to this one and they should be identical on both nodes:

   ```shell
   1024 SHA256:FEZX2jQa2bcsd/fn/uxBzxhKdx4Imc4raXrHwsbtP0M root@serverhostname (DSA)
   256 SHA256:uw98R35Uf+fYEQ/UnJD9Br4NXUFPv7JAUln5uHlgSeY root@serverhostname (ECDSA)
   256 SHA256:sqOUWcraZQKd89y/QQv/iynPTOGQxcOTIXU/LsoPmnM root@serverhostname (ED25519)
   2048 SHA256:qwa+rgir2Oy86QI+PZi/QVR+MSmrdrpsuH7YyKknC+s root@serverhostname (RSA)
   ```

1. Verify that you have the correct public keys for the existing private keys:

   ```shell
   # This will print the fingerprint for private keys:
   for file in /etc/ssh/ssh_host_*_key; do ssh-keygen -lf $file; done

   # This will print the fingerprint for public keys:
   for file in /etc/ssh/ssh_host_*_key.pub; do ssh-keygen -lf $file; done
   ```

   NOTE:
   The output for private keys and public keys command should generate the same fingerprint.

1. Restart `sshd` on your **secondary** node:

   ```shell
   # Debian or Ubuntu installations
   sudo service ssh reload

   # CentOS installations
   sudo service sshd reload
   ```

1. Verify SSH is still functional.
    
   SSH into your GitLab **secondary** server in a new terminal. If you are unable to connect,
   verify the permissions are correct according to the previous steps.

### Step 3. Add the **secondary** node

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

   ```shell
   sudo -i
   ```

1. Edit `/etc/gitlab/gitlab.rb` and add a **unique** name for your node. You will need this in the next steps:

   ```ruby
   # The unique identifier for the Geo node.
   gitlab_rails['geo_node_name'] = '<node_name_here>'
   ```

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

   ```shell
   gitlab-ctl reconfigure
   ```

1. Visit the **primary** node's **Admin Area > Geo**
   (`/admin/geo/nodes`) in your browser.
1. Click the **New node** button.
   ![Add secondary node](img/adding_a_secondary_node_v13_3.png)
1. Fill in **Name** with the `gitlab_rails['geo_node_name']` in
   `/etc/gitlab/gitlab.rb`. These values must always match *exactly*, character
   for character.
1. Fill in **URL** with the `external_url` in `/etc/gitlab/gitlab.rb`. These
   values must always match, but it doesn't matter if one ends with a `/` and
   the other doesn't.
1. Optionally, choose which groups or storage shards should be replicated by the
   **secondary** node. Leave blank to replicate all. Read more in
   [selective synchronization](#selective-synchronization).
1. Click the **Add node** button to add the **secondary** node.
1. SSH into your GitLab **secondary** server and restart the services:

   ```shell
   gitlab-ctl restart
   ```

   Check if there are any common issue with your Geo setup by running:

   ```shell
   gitlab-rake gitlab:geo:check
   ```

1. SSH into your **primary** server and login as root to verify the
   **secondary** node is reachable or there are any common issue with your Geo setup:

   ```shell
   gitlab-rake gitlab:geo:check
   ```

Once added to the admin panel and restarted, the **secondary** node will automatically start
replicating missing data from the **primary** node in a process known as **backfill**.
Meanwhile, the **primary** node will start to notify each **secondary** node of any changes, so
that the **secondary** node can act on those notifications immediately.

Be sure the _secondary_ node is running and accessible. You can sign in to the
_secondary_ node with the same credentials as were used with the _primary_ node.

### Step 4. (Optional) Configuring the **secondary** node to trust the **primary** node

You can safely skip this step if your **primary** node uses a CA-issued HTTPS certificate.

If your **primary** node is using a self-signed certificate for *HTTPS* support, you will
need to add that certificate to the **secondary** node's trust store. Retrieve the
certificate from the **primary** node and follow
[these instructions](https://docs.gitlab.com/omnibus/settings/ssl.html)
on the **secondary** node.

### Step 5. Enable Git access over HTTP/HTTPS

Geo synchronizes repositories over HTTP/HTTPS, and therefore requires this clone
method to be enabled. This is enabled by default, but if converting an existing node to Geo it should be checked:

1. Navigate to **Admin Area > Settings** (`/admin/application_settings/general`) on the **primary** node.
1. Expand "Visibility and access controls".
1. Ensure "Enabled Git access protocols" is set to either "Both SSH and HTTP(S)" or "Only HTTP(S)".

### Step 6. Verify proper functioning of the **secondary** node

Your **secondary** node is now configured!

You can sign in to the _secondary_ node with the same credentials you used with
the _primary_ node. Visit the _secondary_ node's **Admin Area > Geo**
(`/admin/geo/nodes`) in your browser to determine if it's correctly identified
as a _secondary_ Geo node, and if Geo is enabled.

The initial replication, or 'backfill', will probably still be in progress. You
can monitor the synchronization process on each Geo node from the **primary**
node's **Geo Nodes** dashboard in your browser.

![Geo dashboard](img/geo_node_dashboard.png)

If your installation isn't working properly, check the
[troubleshooting document](troubleshooting.md).

The two most obvious issues that can become apparent in the dashboard are:

1. Database replication not working well.
1. Instance to instance notification not working. In that case, it can be
   something of the following:
   - You are using a custom certificate or custom CA (see the [troubleshooting document](troubleshooting.md)).
   - The instance is firewalled (check your firewall rules).

Please note that disabling a **secondary** node will stop the synchronization process.

Please note that if `git_data_dirs` is customized on the **primary** node for multiple
repository shards you must duplicate the same configuration on each **secondary** node.

Point your users to the ["Using a Geo Server" guide](using_a_geo_server.md).

Currently, this is what is synced:

- Git repositories.
- Wikis.
- LFS objects.
- Issues, merge requests, snippets, and comment attachments.
- Users, groups, and project avatars.

## Selective synchronization

Geo supports selective synchronization, which allows admins to choose
which projects should be synchronized by **secondary** nodes.
A subset of projects can be chosen, either by group or by storage shard. The
former is ideal for replicating data belonging to a subset of users, while the
latter is more suited to progressively rolling out Geo to a large GitLab
instance.

It is important to note that selective synchronization:

1. Does not restrict permissions from **secondary** nodes.
1. Does not hide project metadata from **secondary** nodes.
   - Since Geo currently relies on PostgreSQL replication, all project metadata
     gets replicated to **secondary** nodes, but repositories that have not been
     selected will be empty.
1. Does not reduce the number of events generated for the Geo event log.
   - The **primary** node generates events as long as any **secondary** nodes are present.
     Selective synchronization restrictions are implemented on the **secondary** nodes,
     not the **primary** node.

### Git operations on unreplicated repositories

> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/2562) in GitLab 12.10 for HTTP(S) and in GitLab 13.0 for SSH.

Git clone, pull, and push operations over HTTP(S) and SSH are supported for repositories that
exist on the **primary** node but not on **secondary** nodes. This situation can occur
when:

- Selective synchronization does not include the project attached to the repository.
- The repository is actively being replicated but has not completed yet.

## Upgrading Geo

See the [updating the Geo nodes document](updating_the_geo_nodes.md).

## Troubleshooting

See the [troubleshooting document](troubleshooting.md).