Hi Jim,
Now normally I just move /var/lib/mysql to /home/mysql and symlink it.
Um... why? This seems like it would be more trouble than it's worth. and with the symlink, I don't see the benefit.
The reason I move it is because I usually make my systems with a 'small' / partition (say 10GB) and a large /home partition.
It is very easy to have large MySQL databases sitting in the default location then use up all space on the / partition which causes all sorts of havoc.
By moving it off to the /home partition it is moved to where the majority of the space is available and away from system data. MySQL databases are user data and should be in the user area.
The symlink allows you then to just start MySQL without changing any of the config files and anything else that expects it to be in /var/lib/mysql can still find it.
This is really how you should move the data directory anyway. Faking it as you were doing works, but it's not 'proper'.
Symlinks were created for this very reason.
WHY is mysqld trying to read / when I told it to use /home/mysql ?
Because you have to get to / before you can get to /home/ and /home/mysql.. Directory traversal vulnerabilities are quite commonplace, which is why you see all the $DOCUMENT_ROOT/../../../etc/somedir/ type attempts in logs occasionally for things like apache.
Well doesn't it have to traverse / to get to the default location of /var/lib/mysql anyway?
I can see where it may not have permission for /home but surely everything can start at / ?