When I installed to my 5500 I had both permissions and mapping problems. The following steps hould give you an idea, but they aren't accurate.
1. edit the my.conf file and change the user to root(obvious security problem here but It was the quickes way up, after MySQL is running you can tweak this)
2. The package installed to (something like) /etc/mysql/mysql, but all the conf files pointed to /etc/mysql, I just copied the contents of the subdir to the parent dir
3. run chown 777 root * on the contents of the /etc/mysql dir
4. I have sudo installed so I just ran: sudo mysqlstart
and it finally started.
The only problem I have run into (and this totally baffles me as they are files not symlinks) is that after a REBOOT the mysql dir disappears.
*** edit ***
It turns out that the Cacko 64-0 ROM 'initialises /var on reboot. This is apparently why I lose the files.