MySQL因不能建立 PID 導緻無法啟動的解決辦法

MySQL 啟動報錯資訊如下：

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]

根據提示，使用 systemctl status mysqld.service 和 journalctl -xe 檢視服務啟動失敗的原因。

阿裡雲2018年10月 優惠資訊彙總

[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.

這些資訊并不能提供服務啟動失敗的真正原因。

檢視 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

解決辦法    

MySQL 服務在啟動的時候，不能建立 pid 檔案。

在終端看一下該目錄是否存在，如果不存在，手動建立：

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

再次嘗試啟動 MySQL 服務，報錯如下:

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

檢視 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

權限不正确，/var/run/mysqld/ 的屬主和屬組還是 root，MySQL 并不能在其中建立檔案後修改該目錄的屬主和屬組

[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 ]