mysql 启动失败 Pid无法创建

MySQL 启动报错信息如下：

Starting mysqld (via systemctl):
Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details、 [FAILED]

查看 MySQL 的告警日志：

 [ERROR] /usr/sbin/mysqld: Can't create/write to file ‘/var/run/mysqld/mysqld.pid' (Errcode: 2 - No such file or directory)
[ERROR] Can't start server: can't create PID file: No such file or directory
mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

解决办法

MySQL 服务在启动的时候，不能创建 pid 文件。
在终端看一下该目录是否存在，如果不存在，手动创建：

[root@ ~]# mkdir -p /var/run/mysqld/

再次尝试启动 MySQL 服务，报错如下:

Starting mysqld (via systemctl):
 Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details. [FAILED]

查看 MySQL 的告警日志：

 [ERROR] /usr/sbin/mysqld: Can't create/write to file ‘/var/run/mysqld/mysqld.pid' (Errcode: 13 - Permission denied)2018-09-20T10:28:37.183431Z 0 [ERROR] Can't start server: can't create PID file: Permission denied180920 18:28:37 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended160120 18:32:06 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

权限不正确，/var/run/mysqld/ 的属主和属组还是 root，MySQL 并不能在其中创建文件后修改该目录的属主和属组

[root@ ~]# ls -ld /var/run/mysqld/drwxr-xr-x 2 root root 40 Jan 20 18:28 /var/run/mysqld/
[root@ ~]# chown mysql.mysql /var/run/mysqld/
[root@ ~]# /etc/init.d/mysqld startStarting mysqld (via systemctl):       [ OK ]