centos7启动MySQL报 Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details.

/var/run/mysqld/的属主和属组属于root，mysql并不能在其中创建文件

手动的新建目录

[root@iz2zei43l28m7vcezzzyyjz apache-tomcat-9.0.0]# mkdir -p /var/run/mysqld/

[root@iz2zei43l28m7vcezzzyyjz apache-tomcat-9.0.0]#  ls -ld /var/run/mysqld/
drwxr-xr-x 2 root root 40 May  6 17:58 /var/run/mysqld/
[root@iz2zei43l28m7vcezzzyyjz apache-tomcat-9.0.0]# chown mysql.mysql /var/run/mysqld/
[root@iz2zei43l28m7vcezzzyyjz apache-tomcat-9.0.0]# /etc/init.d/mysqld start
Starting mysqld (via systemctl):                           [  OK  ]