解決MySQL因不能建立 PID 致使沒法啓動的方法

問題描述

MySQL 啓動報錯信息以下：

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1 2	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 查看服務啓動失敗的緣由。

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[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.

這些信息並不能提供服務啓動失敗的真正緣由。

查看 MySQL 的告警日誌：

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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

解決辦法

MySQL 服務在啓動的時候，不能建立 pid 文件。

在終端看一下該目錄是否存在，若是不存在，手動建立：

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

再次嘗試啓動 MySQL 服務，報錯以下:

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1 2	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]

查看 MySQL 的告警日誌：

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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

權限不正確，/var/run/mysqld/ 的屬主和屬組仍是 root，MySQL 並不能在其中建立文件後修改該目錄的屬主和屬組

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[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 ]

總結

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