1) recompile php with the mysql libs
2) the root password for mysql is blank i think (i've changed mine to something else a long long long time ago). the mysql & linux permissions are completely seperate.
3) at the command prompt type: "ps -aux | grep mysql" and if you several lines with mysqld then you've got mysql running. if its not running check to see if you've got a script to start mysql in like /etc/rc.d/rc5.d/. if the file starts with Ksomething rename it to Ssomething and run the script like "./S90mysql start". i'm still running redhat 6.2 so i'm not 100% sure where the file is or what its going to be named in redhat 7.0.
brandon