I’ve not been able to verify that the reboot sequence on Ubuntu shuts down MySQL prior to restarting. So, I usually stop MySQL first, just to be safe:
$ sudo service mysql stop
$ sudo reboot
Broadcast message from server.io
(/dev/pts/0) at 13:58 ...
The system is going down for reboot NOW!
Connection to server.io closed by remote host.
Connection to server.io closed.
Database corruption is a challenging, time consuming event to repair. So, I like to be cautious. If anyone can verify that Ubuntu reboot includes a MySQL stop, please post in the comments.