Linux Server Recovery and Fix

I'm currently facing a critical issue with my Linux server. It's stuck in recovery mode and fails to boot up properly. The server mainly serves for web hosting, and it contains a vital MariaDB instance that needs to be preserved intact.

Here is a brief on the situation:
- Server is not booting properly, likely a configuration issue, not hardware.
- No recent backups are available, making data preservation a priority.
- Recovery has been attempted by restarting the server, but the issue persists.

What I need is a skilled professional with deep expertise in Linux systems administration, specifically in recovery and troubleshooting. The ideal candidate should be well-versed in the following:
- Linux server troubleshooting and recovery
- MariaDB administration
- Data preservation without recent backups
- Web server management

The goal is to get the server back online without losing any existing data, especially the MariaDB database. Please only apply if you have concrete experience in handling similar critical server issues and are confident in your ability to resolve them.

Will also need you to advise how to prevent something like this from happening again.