Before you start the Mattermost Server, you need to edit the configuration file. A default configuration file is located at /opt/mattermost/config/config.json.

We recommend taking a backup of this default config ahead of making changes:

sudo cp /opt/mattermost/config/config.json /opt/mattermost/config/config.defaults.json

Configure the following properties in this file:

• Set DriverName to "postgres". This is the default and recommended database for all Mattermost installations.

• Set DataSource to "postgres://mmuser:<mmuser-password>@<host-name-or-IP>:5432/mattermost?sslmode=disable&connect_timeout=10" replacing mmuser, <mmuser-password>, <host-name-or-IP>, and mattermost with your database name.

• Set your "SiteURL": The domain name for the Mattermost application (e.g. https://mattermost.example.com).

After modifying the config.json configuration file, you can now start the Mattermost server:

sudo systemctl start mattermost

Verify that Mattermost is running: curl http://localhost:8065. You should see the HTML that’s returned by the Mattermost Server.

The final step, depending on your requirements, is to run sudo systemctl enable mattermost.service so that Mattermost will start on system boot.