mysql在CentOS7.0服务启动失败的解决办法

中午公司网络问题（当时不知道网络问题），连不上SSH，就在阿里云的控制面板强制重启了服务器，结果Mysql数据库无法启动了，运行mysql 命令直接报错

Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock'

[root@izx5uaa5mz0yf0z ~]# /etc/init.d/mysqld start
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.
[失败]

通过看日志没看出什么问题

[root@izx5uaa5mz0yf0z ~]# systemctl status mysqld.service
● mysqld.service - LSB: start and stop MySQL server
Loaded: loaded (/etc/rc.d/init.d/mysqld; bad; vendor preset: disabled)
Active: failed (Result: exit-code) since 一 2018-01-22 21:44:36 CST; 51s ago
Docs: man:systemd-sysv-generator(8)
Process: 7214 ExecStart=/etc/rc.d/init.d/mysqld start (code=exited, status=1/FAILURE)

1月 22 21:44:34 izx5uaa5mz0yf0z systemd[1]: Starting LSB: start and stop My....
1月 22 21:44:36 izx5uaa5mz0yf0z mysqld[7214]: MySQL Daemon failed to start.
1月 22 21:44:36 izx5uaa5mz0yf0z mysqld[7214]: Starting mysqld:  [FAILED]
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: mysqld.service: control process...1
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: Failed to start LSB: start and ....
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: Unit mysqld.service entered fai....
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: mysqld.service failed.
Hint: Some lines were ellipsized, use -l to show in full.
[root@izx5uaa5mz0yf0z ~]# journalctl -xe
--
-- The start-up result is done.
1月 22 21:44:34 izx5uaa5mz0yf0z polkitd[488]: Registered Authentication Agent fo
1月 22 21:44:34 izx5uaa5mz0yf0z systemd[1]: Starting LSB: start and stop MySQL s
-- Subject: Unit mysqld.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel --
-- Unit mysqld.service has begun starting up.
1月 22 21:44:36 izx5uaa5mz0yf0z mysqld[7214]: MySQL Daemon failed to start.
1月 22 21:44:36 izx5uaa5mz0yf0z mysqld[7214]: Starting mysqld:  [FAILED]
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: mysqld.service: control process exit
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: Failed to start LSB: start and stop
-- Subject: Unit mysqld.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel --
-- Unit mysqld.service has failed.
--
-- The result is failed.
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: Unit mysqld.service entered failed s
1月 22 21:44:36 izx5uaa5mz0yf0z systemd[1]: mysqld.service failed.
1月 22 21:44:36 izx5uaa5mz0yf0z polkitd[488]: Unregistered Authentication Agent

百度上的资料也都是千篇一律，也都没有用

最后查看mysql服务的启动日志，发现mysql服务启动的时候不能创建PID文件。

最后通过以下命令成功启动了mysql

[root@izx5uaa5mz0yf0z ~]# ls -ld /var/run/mysqld/
drwxr-xr-x 2 mysql mysql 60 1月  22 21:48 /var/run/mysqld/
[root@izx5uaa5mz0yf0z ~]# mkdir -p /var/run/mysqld
[root@izx5uaa5mz0yf0z ~]# ls -ld /var/run/mysqld/
drwxr-xr-x 2 mysql mysql 60 1月  22 21:48 /var/run/mysqld/
[root@izx5uaa5mz0yf0z ~]# chown mysql.mysql /var/run/mysqld/
[root@izx5uaa5mz0yf0z ~]# /etc/init.d/mysqld start
Starting mysqld (via systemctl):                           [  确定  ]

最后劝下大家最好不要通过控制台去强制重启云服务器，血淋淋的教训啊