Method to solve the problem that MySQL cannot be started because PID cannot be created

Problem description

The MySQL startup error message is as follows:

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]

According to the prompt, use systemctl status mysqld.service And journalctl -xe View the reason why the service failed to start.

[root@ ~]# systemctl status mysqld.servicemysqld.service - SYSV: MySQL database server.Loaded: loaded (/etc/rc.d/init.d/mysqld)Active: failed (Result: exit-code) since Wed 2016-01-20 18:26:57 CST; 40s agoDocs: man:systemd-sysv-generator(8)Process: 2979 ExecStart=/etc/rc.d/init.d/mysqld start (code=exited, status=1/FAILURE)Jan 20 18:26:56 spark01 systemd[1]: Starting SYSV: MySQL database server … .Jan 20 18:26:57 spark01 mysqld[2979]: MySQL Daemon failed to start.Jan 20 18:26:57 spark01 mysqld[2979]: Starting mysqld: [FAILED]Jan 20 18:26:57 spark01 systemd[1]: mysqld.service: control process exited, code=exited status=1Jan 20 18:26:57 spark01 systemd[1]: Failed to start SYSV: MySQL database server..Jan 20 18:26:57 spark01 systemd[1]: Unit mysqld.service entered failed state.Jan 20 18:26:57 spark01 systemd[1]: mysqld.service failed.[root@ ~]# journalctl -xeUnit session-2.scope has begun starting up.Jan 20 18:26:48 spark01 sshd[2916]: pam_unix(sshd:session): session opened for user spark by (uid=0)Jan 20 18:26:52 spark01 su[2944]: (to root) spark on pts/1Jan 20 18:26:52 spark01 su[2944]: pam_unix(su-l:session): session opened for user root by spark(uid=1000)Jan 20 18:26:56 spark01 polkitd[909]: Registered Authentication Agent for unix-process:2974:117137 (system bus name :1.25Jan 20 18:26:56 spark01 systemd[1]: Starting SYSV: MySQL database server … . -  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.Jan 20 18:26:57 spark01 mysqld[2979]: MySQL Daemon failed to start.Jan 20 18:26:57 spark01 mysqld[2979]: Starting mysqld: [FAILED]Jan 20 18:26:57 spark01 systemd[1]: mysqld.service: control process exited, code=exited status=1Jan 20 18:26:57 spark01 systemd[1]: Failed to start SYSV: MySQL database server.. -  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.Jan 20 18:26:57 spark01 systemd[1]: Unit mysqld.service entered failed state.Jan 20 18:26:57 spark01 systemd[1]: mysqld.service failed.Jan 20 18:26:57 spark01 polkitd[909]: Unregistered Authentication Agent for unix-process:2974:117137 (system bus name :1.

This information does not provide the real reason for the service startup failure.

View the alarm log of MySQL:

2016-01-20T10:00:19.935771Z 0 [ERROR] /usr/sbin/mysqld: Can't create/write to file  ' /var/run/mysqld/mysqld.pid' (Errcode: 2 - No such file or directory)2016-01-20T10:00:19.935795Z 0 [ERROR] Can't start server: can't create PID file: No such file or directory160120 18:00:20 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

Solution

The pid file cannot be created when the MySQL service is started.

See if the directory exists under 1 at the terminal. If it does not exist, create it manually:

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

Try to start the MySQL service again and report the following error:

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]

View the alarm log of MySQL:

2016-01-20T10:28:37.183387Z 0 [ERROR] /usr/sbin/mysqld: Can't create/write to file  ' /var/run/mysqld/mysqld.pid' (Errcode: 13 - Permission denied)2016-01-20T10:28:37.183431Z 0 [ERROR] Can't start server: can't create PID file: Permission denied160120 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

Permission is incorrect. The owner and group of/var/run/mysqld is still root, and MySQL cannot modify the owner and group of this directory after creating a file in it

[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 ]

Summarize