MySQL数据库出现The server quit without updating PID file.

一、服务器环境

　　操作系统：CentOS-6.4

　　服务器环境：集成环境LNMP1.0

二、步骤重现

　　1、安装LNMP1.0，具体操作方法见这里，安装成功；

　　2、因个人需求，现将MySQL数据库存放在/data/mysql/var，修改/etc/my.cnf的datadir=/data/mysql/var，别忘了将/var目录的权限设置为chown -R mysql.mysql /data/mysql; 

　　3、重启服务，/root/lnmp restart；

　　4、提示错误：Starting MySQL...The server quit without updating PID file [失败]/mysql/var/localhost.localdomain.pid).；

三、解决错误

　　1、根据提示可能是PID的错误，按照常规解决方法kill相关进程、清除selinux，问题仍然存在；

　　2、查看错误日志，/usr/local/mysql/var/localhost.localdomain.pid

140513 11:59:34 mysqld_safe Starting mysqld daemon with databases from /data/mysql/var
/usr/local/mysql/bin/mysqld: Table 'mysql.plugin' doesn't exist
140513 11:59:34 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
140513 11:59:34 InnoDB: The InnoDB memory heap is disabled
140513 11:59:34 InnoDB: Mutexes and rw_locks use GCC atomic builtins
140513 11:59:34 InnoDB: Compressed tables use zlib 1.2.3
140513 11:59:34 InnoDB: Initializing buffer pool, size = 16.0M
140513 11:59:34 InnoDB: Completed initialization of buffer pool
InnoDB: The first specified data file /data/mysql/var/ibdata1 did not exist:
InnoDB: a new database to be created!
140513 11:59:34  InnoDB: Setting file /data/mysql/var/ibdata1 size to 10 MB
InnoDB: Database physically writes the file full: wait...
140513 11:59:34  InnoDB: Log file /data/mysql/var/ib_logfile0 did not exist: new to be created
InnoDB: Setting log file /data/mysql/var/ib_logfile0 size to 5 MB
InnoDB: Database physically writes the file full: wait...
140513 11:59:34  InnoDB: Log file /data/mysql/var/ib_logfile1 did not exist: new to be created
InnoDB: Setting log file /data/mysql/var/ib_logfile1 size to 5 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Doublewrite buffer not found: creating new
InnoDB: Doublewrite buffer created
InnoDB: 127 rollback segment(s) active.
InnoDB: Creating foreign key constraint system tables
InnoDB: Foreign key constraint system tables created
140513 11:59:35  InnoDB: Waiting for the background threads to start
140513 11:59:36 InnoDB: 1.1.8 started; log sequence number 0
140513 11:59:36 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
140513 11:59:36 [Note]   - '0.0.0.0' resolves to '0.0.0.0';
140513 11:59:36 [Note] Server socket created on IP: '0.0.0.0'.
140513 11:59:36 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
140513 11:59:36 mysqld_safe mysqld from pid file /data/mysql/var/localhost.localdomain.pid ended

　　3、根据日志提示，可能是mysql.plugin数据表不存在，拷贝原数据库目录/usr/local/mysql/var/*到/data/mysql/var/，重启mysql服务/etc/init.d/mysql start，发现问题仍然存在；

　　4、返回数据库目录查看数据权限发现全是root.root，重新设置数据权限：chown mysql.mysql /data/mysql/，重启mysql服务/etc/init.d/mysql start，问题解决。；

四、总结

　　在配置Linux环境出现错误再所难免，MySQL故障的错误日志不是很清晰，需要经验和对错误日志分析把控。那啥，数据一定要作好日常备份，发生数据灾难时也有可以恢复的源。