环境：

MySQL主从，一台主机，一台备机。都是虚拟机。

备机仅仅用来备份，不用于业务。

关闭主机mysql服务，关闭主机系统，加内存。、

备机不变。

开启主机。

内存加好。

EIPDB1:~ # free -m

total used free shared buffers cached

Mem: 48274 2509 45764 0 19 378

-/+ buffers/cache: 2111 46162

Swap: 10236 0 10236

开启mysql服务报错。

EIPDB1:~ # mysqld service status

171016 23:57:43 [ERROR] Fatal error: Please read "Security" section of the manual to find out how to run mysqld as root!

171016 23:57:43 [ERROR] Aborting

171016 23:57:43 [Note] mysqld: Shutdown complete

EIPDB1:~ # service mysqld status

MySQL is running but PID file could not be found failed

EIPDB1:~ # service mysqld start

Starting MySQL.....................................................................................................The server quit without updating PID file (/eipdb1/mysql/data/EIPDB1.pid).

解决：

先查看了下，空间充足，没问题。

EIPDB1:/usr/local # df -h

Filesystem Size Used Avail Use% Mounted on

/dev/sda3 40G 9.1G 29G 25% /

devtmpfs 24G 356K 24G 1% /dev

tmpfs 24G 100K 24G 1% /dev/shm

/dev/sda1 98M 75M 19M 80% /boot

/dev/sdb1 490G 26G 465G 6% /eipdb1

可能是mysqld进程卡死，杀掉进程。

EIPDB1:~ # ps aux | grep mysql

root 3442 0.0 0.0 11292 1576 ? S Oct16 0:00 /bin/sh /eipdb1/mysql/bin/mysqld_safe --datadir=/eipdb1/mysql/data --pid-file=/eipdb1/mysql/data/EIPDB1.pid

mysql 4034 4.2 3.1 5907700 1538808 ? Sl Oct16 1:12 /eipdb1/mysql/bin/mysqld --basedir=/eipdb1/mysql --datadir=/eipdb1/mysql/data --plugin-dir=/eipdb1/mysql/lib/plugin --user=mysql --log-error=/eipdb1/mysql/data/EIPDB1.err --pid-file=/eipdb1/mysql/data/EIPDB1.pid --socket=/tmp/mysql.sock --port=3306

root 5588 0.0 0.0 5704 800 pts/0 S+ 00:22 0:00 grep mysql

EIPDB1:~ # kill -9 3442

EIPDB1:/usr/local # kill -9 4034

重新启动mysql服务：

EIPDB1:/usr/local # service mysqld start

Starting MySQL... done

EIPDB1:/usr/local # service mysqld status

MySQL running (6322) done

EIPDB1:/usr/local # ps aux | grep mysql

root 5733 0.0 0.0 11504 1596 pts/0 S 00:30 0:00 /bin/sh /eipdb1/mysql/bin/mysqld_safe --datadir=/eipdb1/mysql/data --pid-file=/eipdb1/mysql/data/EIPDB1.pid

mysql 6322 1.0 2.1 5839204 1065996 pts/0 Sl 00:30 0:01 /eipdb1/mysql/bin/mysqld --basedir=/eipdb1/mysql --datadir=/eipdb1/mysql/data --plugin-dir=/eipdb1/mysql/lib/plugin --user=mysql --log-error=/eipdb1/mysql/data/EIPDB1.err --pid-file=/eipdb1/mysql/data/EIPDB1.pid --socket=/tmp/mysql.sock --port=3306

root 6398 0.0 0.0 5700 800 pts/0 S+ 00:32 0:00 grep mysql

备库同步正常：

mysql> show slave status \G;

*************************** 1. row ***************************

Slave_IO_State: Waiting for master to send event

Master_Host: 10.0.2.206

Master_User: slave_user

Master_Port: 3306

Connect_Retry: 60

Master_Log_File: master-binlog.000062

Read_Master_Log_Pos: 44601

Relay_Log_File: eipdb2-relay-bin.000166

Relay_Log_Pos: 44751

Relay_Master_Log_File: master-binlog.000062

Slave_IO_Running: Yes

Slave_SQL_Running: Yes

完成。