Of Stack

Quick solution to MySQL service startup failure under CentOS 7

  • 2020-12-18 01:57:25
  • OfStack

Today, starting the MySQL server failed as follows: 


[root@spark01 ~]# /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.
                              [FAILED]

As prompted, use systemctl status mysqld.service and ES9en-ES10en, respectively, to see the reason for the service startup failure

[root@spark01 ~]# systemctl status mysqld.service 


?.mysqld.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 ago
   Docs: 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=1
Jan 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@spark01 ~]# journalctl -xe 


-- 
-- Unit 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/1
Jan 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 :1.25
Jan 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=1
Jan 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.

Unfortunately, however, this information does not provide the real reason for service startup failures.

At this time, you might as well open the MySQL alarm log, after all, as long as the MySQL service starts, the alarm log will have output information, sure enough 


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 directory
160120 18:00:20 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

The MySQL service cannot create pid files when started.

Look at the terminal 1 to see if the directory exists. Sure enough, it doesn't.

So, the /var/run/mysqld/ directory is created and the MySQL service is restarted

[root@spark01 ~]# mkdir -p /var/run/mysqld/

[root@spark01 ~]# /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.
                              [FAILED]

Still report an error, re-check the alarm log, there is the following output 


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 denied
160120 18:28:37 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
160120 18:32:06 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql

Originally, the owner and group of /var/run/mysqld were still root, and mysql could not create a file in it. After modifying the owner and group of the directory, OK was started. 


[root@spark01 ~]# ls -ld /var/run/mysqld/
drwxr-xr-x 2 root root 40 Jan 20 18:28 /var/run/mysqld/
[root@spark01 ~]# chown mysql.mysql /var/run/mysqld/
[root@spark01 ~]# /etc/init.d/mysqld start
Starting mysqld (via systemctl):              [ OK ]

Conclusion:

In the past when playing Kubernetes, often encountered startup failure, according to the tips of systemctl, systemctl status ES65en. service and ES67en-ES68en command to see the cause of service startup failure is often not satisfactory, but gave a wrong hint, that this is related to the system. In fact, by looking at the service log, it is often clearer why the service failed to start.

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