Here is one that just bit me bad for several days of head-scratching while installing MariaDB 10.1.6. It kept complaining about a permissions problem trying to access the data directory, which I checked multiple times, shotgunning changes until I had all the files "777", and it STILL wouldn't work!

Keep in mind that you need at least "r-x" permission *all the way up to root* in order to access a directory.

In my case, the data directory was in "/usr/local/var/mysql" and some smart-ass package management system had assumed ownership/groupship of "/usr/local/var" and set the perms to "rwxr-x---". I changed that to "rwxr-xr-x" and it worked.

Be certain whatever user is running your webserver (certainly NOT "root") has at least "r-x" permission all the way up to "/".

:::: The idea that the genetics of novel lifeforms will stay put in GMOs released on farms... is laughable... We are unable to stop the accumulation of risk of catastrophic change resulting from nuclear radiation, the greenhouse effect, or genetic engineering. -- David Holmgren :::: Jan Steinman, EcoReality Co-op ::::