安装Convert OpenVPN Access Server to MySQL Backend

1. Install MySQL/MariaDB if it is not already installed
   sudo apt install mariadb-server
2. Log into OpenVPN Access Server
3. Click Tools > DB Convert in the left navigation
4. Enter the root MySQL password
5. Click the DB Convert button
6. Wait for the process to complete
7. Click the Restart button

Further reading: https://openvpn.net/vpn-server-resources/configuration-database-management-and-backups/