Backup MySQL/MariaDB Databases

I need assistance backing up all MySQL/MariaDB databases on my Contabo Linux VPS. I can only access the VPS through rescue mode, as I'm unable to log in via SSH normally.

Requirements:
- Access the VPS in rescue mode
- Backup all MySQL/MariaDB databases as .sql files
- Deliver the backup files securely

Ideal Skills:
- Experience with Contabo VPS
- Proficiency in MySQL/MariaDB
- Familiarity with Linux command line in rescue mode

Please ensure the backups are complete and can be restored without issues.