I have CentOS 6.4 with NGINX.
When I try to
MySQL server PID file could not be found! [FAILED]
Starting MySQL..The server quit without updating PID file ([FAILED]/mysql/mysqld.pid).
I got the same error on a CentOS 6.3 where I upgraded MySQL to 5.6.14 but I kept the old my.cnf file. After upgrade, MySQL did not start anymore, giving me the same error as you described.
The problem was that I had this setting in my.cnf:
According to this link table_cache renamed table_open_cache..
"Seem like in 5.5 the system variable table_cache was renamed table_open_cache.. In 5.6 mysqld fails if it finds an unknown variable this means that upgrades from versions earlier than 5.5 can have problems if table_cache is specified in my.cnf."
After I changed the above line to
MySQL started perfectly.
So, in the case you have MySQL 5.5+ (and maybe an older my.cnf), I suggest you to do the following:
Hope this helps.