启动mysql 从库的时候报错：
# /etc/init.d/mysqld start
Starting MySQL (Percona Server)............................................................
The server quit without updating PID file (/tol/mysql/d[FAILED]db.pid).

查看错误日志：
# tail -30f mysql.err 
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
141117 16:10:28  InnoDB: Unable to open the first data file
InnoDB: Error in opening ./ibdata1
141117 16:10:28  InnoDB: Operating system error number 11 in a file operation.
InnoDB: Error number 11 means 'Resource temporarily unavailable'.
InnoDB: Some operating system error numbers are described at
InnoDB: http://dev.mysql.com/doc/refman/5.5/en/operating-system-error-codes.html
141117 16:10:28 InnoDB: Could not open or create data files.
141117 16:10:28 InnoDB: If you tried to add new data files, and it failed here,
141117 16:10:28 InnoDB: you should now edit innodb_data_file_path in my.cnf back
141117 16:10:28 InnoDB: to what it was, and remove the new ibdata files InnoDB created
141117 16:10:28 InnoDB: in this failed attempt. InnoDB only wrote those files full of
141117 16:10:28 InnoDB: zeros, but did not yet use them in any way. But be careful: do not
141117 16:10:28 InnoDB: remove old data files which contain your precious data!
141117 16:10:28 [ERROR] Plugin 'InnoDB' init function returned error.
141117 16:10:28 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
141117 16:10:29 [ERROR] Unknown/unsupported storage engine: InnoDB
141117 16:10:29 [ERROR] Aborting

141117 16:10:29 [Note] /tol/mysql/home/bin/mysqld: Shutdown complete

141117 16:10:29 mysqld_safe mysqld from pid file /tol/mysql/data/coredb.pid ended

查看mysql进程
# ps aux | grep mysql
root      7332  0.0  0.0 103240   868 pts/0    S+   16:13   0:00 grep mysql
root     23914  0.0  0.0 106220  1416 ?        S    Nov14   0:00 /bin/sh /tol/mysql/home/bin/mysqld_safe --datadir=/tol/mysql/data --pid-file=/tol/mysql/data/localhost.localdomain.pid
mysql    24514  0.2  0.3 2056984 172400 ?      Sl   Nov14  10:15 /tol/mysql/home/bin/mysqld --basedir=/tol/mysql/home --datadir=/tol/mysql/data --plugin-dir=/tol/mysql/home/lib/plugin --user=mysql --log-error=/tol/mysql/mylog/mysql.err --pid-file=/tol/mysql/data/localhost.localdomain.pid --socket=/tmp/mysql.sock --port=3306

停止mysql也报错
# /etc/init.d/mysqld stop
MySQL (Percona Server) PID file could not be found!        [FAILED]

再次启动也报错
# /etc/init.d/mysqld start
Starting MySQL (Percona Server).....................................................................................................
The server quit without updating PID file (/tol/mysql/da[FAILED]1g.pid).

kill 掉上面的两个进程
# kill -9 23914 24514

重启ok
# /etc/init.d/mysqld start
Starting MySQL (Percona Server)...                         [  OK  ]