在linux上安装mysql后 启动mysql，或者在使用mysql过程中启动mysql 可能出现以下错：

常见错误以下三种，可循环解决！  让报错无所遁形！！！

报错一：

ERROR! MySQL is running but PID file could not be found

1.先打印MYSQL进程

ps aux | grep mysql

2.然后Kill进程

kill -9 pid1 pid2 …

3.再启动MYSQL

/etc/init.d/mysql start

4.再检查mysql运行状态

/etc/init.d/mysql status

报错二：

Starting MySQL. ERROR! The server quit without updating PID file (/var/lib/mysql/hadoop01.pid).

1. ps -ef | grep mysql

kill -9 PID

2. ls -laF /usr/local/var/mysql/

前两步如果不奏效，请直接执行更改当前用户权限：

sudo chown -R hadoop.hadoop /var/lib/mysql

3.再启动MYSQL

/etc/init.d/mysql start

4.再检查mysql运行状态

/etc/init.d/mysql status

报错三：

ERROR! MySQL is not running, but lock file (/var/lock/subsys/mysql) exists

之后保存再重启还是出错。
最后检查可能和log文件有关，于是将log文件给移除了，再重启MySQL终于OK了。

1./etc/init.d/mysql status
coming back with:
mysql is not running but lock exists
Solved by removing the lock file:
2.rm /var/lock/subsys/mysql
If this happens again it may also be necessary to remove the pid file from /var/lib/mysql