Disk full because of tmpdir, safe to restart

The issue is that the system cannot assign any memory to the process to be able to start, you either need to stop some other processes so that memory is free to be allocated to MariaDB or you need to add more RAM or SWAP space to the server so that the processes can start correctly.

Finally, I found the solution after 12 days of testing the MySQL start after killed automatically with hundreds of page visits.

The answer depends on the question System OS (CentOS) and MySQL Mariadb service

Solution: Just add some seconds before make service start - in my case I've added 45 seconds

Add the following lines under [service] section in {/etc/systemd/system/multi-user.target.wants/mariadb.service} - Of course the path depends on your system OS and MySQL service name (not all have mariadb.service)

Restart=always
RestartSec=45s

Do NOT forget to run the following commands

sudo systemctl daemon-reload

sudo systemctl restart mariadb.service