今天，啟動MySQL服務器失敗，如下所示：
[root@spark01 ~]# /etc/init.d/mysqld startStarting 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，分別使用systemctl status mysqld.service和journalctl -xe查看服務啟動失敗的原因
[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=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@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/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.
但，可惜的時，這些信息并不能提供服務啟動失敗的真正原因。
這時候，不妨打開MySQL的告警日志，畢竟，只要MySQL服務啟動，告警日志都會有輸出信息的，果然
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
MySQL服務在啟動的時候，不能創建pid文件。
在終端看一下該目錄是否存在，果然，不存在。
于是，創建了/var/run/mysqld/目錄，重啟MySQL服務
[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]
依舊報錯，重新查看告警日志，有以下輸出
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
原來，/var/run/mysqld/的屬主和屬組還是root，mysql并不能在其中創建文件，后修改該目錄的屬主和屬組，啟動OK。
[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 startStarting mysqld (via systemctl): [ OK ]
總結：
以前在玩Kubernetes的時候，常遇到啟動失敗的情況，根據systemctl的提示，通過systemctl status mysqld.service和journalctl -xe命令查看服務啟動失敗的原因往往并不如人意，反而給了一種錯誤的暗示，以為這個跟系統有關。其實，通過查看服務的日志，往往更能清晰的知道服務啟動失敗的原因。
以上這篇CentOS 7下MySQL服務啟動失敗的快速解決方法就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支持VeVb武林網。
