Migrating from GitLab Omnibus to Mattermost Standalone - Mattermost

Overview

GitLab has announced the deprecation of Mattermost from the GitLab Omnibus package with GitLab 19.0. As part of this transition, GitLab will continue to support Mattermost up to version 10.11 ESR within the Omnibus installation until the final removal date.

To ensure continuity and long-term support, organizations using Mattermost within GitLab Omnibus should plan to migrate to a standalone Mattermost installation. This approach provides ongoing access to the latest Mattermost releases, security updates, and enterprise capabilities independent of GitLab’s release cycle.

Migrating to a standalone deployment also enables greater flexibility in managing infrastructure, upgrading PostgreSQL, and scaling Mattermost independently to meet performance and compliance requirements.

Prerequisites

Before you begin:

Administrative (root or sudo) access to the GitLab Omnibus server.
A new standalone PostgreSQL server prepared and accessible.
Sufficient disk space for the Mattermost database dump.
A planned maintenance window, as Mattermost downtime is required.
A current full backup of your Mattermost instance, including database and file storage.

Migration Steps

Follow the steps below to safely migrate from GitLab Omnibus to a standalone Mattermost installation.

<Note>

The following procedure assumes your Mattermost database name is mattermost_production and your PostgreSQL user is mmuser. Adjust as needed for your environment.

</Note>

Step 1: Create a Database Dump from GitLab Omnibus

Use the GitLab Omnibus PostgreSQL tools to create a dump of the Mattermost database. Run this command on the GitLab server:

bash

sudo gitlab-psql -- /opt/gitlab/embedded/bin/pg_dump -h /var/opt/gitlab/postgresql --no-owner mattermost_production | gzip > mattermost_dbdump_$(date --rfc-3339=date).sql.gz

This will create a compressed SQL dump file of your Mattermost database.

Step 2: Prepare the New PostgreSQL Server

Set up your new PostgreSQL server following the official Mattermost database preparation guidelines. This includes:

Installing the correct PostgreSQL version supported by your Mattermost server.
Creating a new Mattermost database and user with appropriate permissions.

Step 3: Transfer and Restore the Database Dump

Transfer the database dump file to your new PostgreSQL server, then restore it:

bash

zcat /tmp/mattermost_dbdump.sql.gz | psql -U mmuser -d mattermost

Verify that the database restoration completes successfully without errors.

Step 4: Update Mattermost Configuration

On your standalone Mattermost server, update the config.json file to point to the new PostgreSQL server. Locate the SqlSettings.DataSource parameter and update it as follows:

json

"SqlSettings": {
    "DriverName": "postgres",
    "DataSource": "postgres://mmuser:password@new-postgres-server:5432/mattermost?sslmode=disable&connect_timeout=10"
}

Ensure that credentials, hostnames, and connection settings match your new PostgreSQL configuration.

Step 5: Migrate the Mattermost Application and Data

To move Mattermost application files from the GitLab server to a new standalone server:

Install the same or newer version of Mattermost on the new server. See the Server Deployment Planning.

Copy your existing configuration and data from the GitLab Omnibus instance:

bash

# On the GitLab server
sudo cp /var/opt/gitlab/mattermost/config/config.json /tmp/
sudo cp -r /var/opt/gitlab/mattermost/data /tmp/mattermost_data

# Transfer to new Mattermost server
scp /tmp/config.json mattermost@new-server:/opt/mattermost/config/
scp -r /tmp/mattermost_data mattermost@new-server:/opt/mattermost/data/

Ensure permissions are correctly set on the new server:
bash
```
sudo chown -R mattermost:mattermost /opt/mattermost
```

Step 6: Start Mattermost

Start the Mattermost service on your new standalone installation:

bash

sudo systemctl start mattermost

Mattermost will now connect to your standalone PostgreSQL database.

Step 7: Verify the Migration

After starting Mattermost, perform the following checks:

Confirm that Mattermost starts successfully with no database connection errors.
Review server logs for any startup or connection issues.
Log into Mattermost and verify that all teams, channels, and users are present.
Post test messages and upload files to confirm functionality.
Validate user authentication and permissions.
Confirm that database queries are directed to the new PostgreSQL server.

Important Considerations

Always maintain a full backup of your Mattermost database before migration.
Schedule a maintenance window to minimize user disruption.
Validate performance and monitoring configurations post-migration.
Ensure that your new PostgreSQL server follows Mattermost’s security and tuning best practices.

Troubleshooting

If you encounter errors during the migration:

Review PostgreSQL logs for permission or connection issues.
Verify that the Mattermost PostgreSQL user has full access to the restored database.
Ensure that the config.json file contains the correct database connection string.
Restart the Mattermost service and check mattermost.log for detailed errors.