[root@centos var]# service mysqld stop

MySQL manager or server PID file could not be found! [FAILED]

解决办法：

首先查看一下进程

[root@centos mysql]# ps aux |grep mysq*

root 2643 0.0 0.2 4536 1224 ? S 01:09 0:00
/bin/sh /usr/local/mysql/bin/mysqld_safe –datadir=/usr/local/mysql/var
–pid-file=/usr/local/mysql/var/centos.pid

mysql 2757 0.0 1.2 36976 6608 ? Sl 01:09 0:00
/usr/local/mysql/libexec/mysqld –basedir=/usr/local/mysql
–datadir=/usr/local/mysql/var –user=mysql
–log-error=/usr/local/mysql/var/centos.err
–pid-file=/usr/local/mysql/var/centos.pid –socket=/tmp/mysql.sock
–port=3306

root 4788 0.0 0.1 3920 684 pts/2 R+ 11:11 0:00 grep mysq*

如果看到上面的内容，那说明，Mysql的进程卡死了，这时用就要把这些卡死的进程都关闭

[root@centos mysql]# kill 2643

[root@centos mysql]# kill 2757

启动Mysql 就ok了

[root@centos mysql]# service mysqld start

Starting MySQL.