my server (CentOS) contains lots of website, which collect data from lots of sources with cron. the mysql config is the default recently, PHP failed to communicate with mysql. Firstly I just restart the server but after restarted, PHP still failed to communicate with mysql I've tried: ps ax | grep mysql Then run: kill -9 #### (I've also tried killall -9 ####) - this failed, ps ax | grep mysql showing the killed process id is still there service mysqld start (I've also tried /etc/init.d/mysqld start) - I got reply Timeout error occurred trying to start MySQL Daemon. when run top, mysqld_safe is appeared on top with about 50% of CPU usage. I dont know the size of all the database. I really confused