啟動mysqld服務失敗，報錯如下：
[root@LCM01GCM01 ~]# service 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]
既然有了提示，先看下有什么幫助沒有
[root@LCM01GCM01 ~]# systemctl status mysqld.service 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@LCM01GCM01 ~]# 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.
然而，好像這些信息對我們來說並沒有什么用處，什么守護進程沒啟動，我們也不能知如何去啟動這些，這個時候我們查看一下mysql自帶的告警日志，路徑一般在/var/log/mysqld.log下面
[root@LCM01GCM01 ~]# tail -200f /var/log/mysqld.log 2018-12-07 T10:00:19.935771Z 0 [ERROR] /usr/sbin/mysqld: Can't create/write to file '/var/run/mysqld/mysqld.pid' (Errcode: 2 - No such file or directory) 2018-12-07T10:00:19.935795Z 0 [ERROR] Can't start server: can't create PID file: No such file or directory 181207 18:00:20 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
這個時候我們就明白了，/var/run/mysqld/這個目錄不存在，wu，查找下確實沒有這個文件。這里我們有兩種解決方案
第一種自己創建 /var/run/mysqld/ 這個目錄，重新啟動mysqld服務
[root@LCM01GCM01 ~]# mkdir -p /var/run/mysqld/ [root@LCM01GCM01 ~]# service 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
2018-12-070T10:28:37.183387Z 0 [ERROR] /usr/sbin/mysqld: Can't create/write to file '/var/run/mysqld/mysqld.pid' (Errcode: 13 - Permission denied) 2018-12-070T10:28:37.183431Z 0 [ERROR] Can't start server: can't create PID file: Permission denied 181207 18:28:37 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended 181207 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並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@LCM01GCM01 ~]# ls -ld /var/run/mysqld/ drwxr-xr-x 2 root root 40 Jan 20 18:28 /var/run/mysqld/ [root@LCM01GCM01 ~]# chown mysql.mysql /var/run/mysqld/ [root@LCM01GCM01~]# service mysqld start Starting mysqld (via systemctl): [ OK ]
上面第一種解決方案為臨時性的方案，你會發現當虛擬機reboot的話，又會啟動不成功，那個目錄又不刪除了，因此我們修改一下存放mysqld.pid的目錄，有兩個配置文件
vi /etc/my.cnf socket=/var/lib/mysql/mysql.sock # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 log-error=/var/log/mysqld.log pid-file=/createByhujian/mysqld/mysqld.pid
vi /etc/init.d/mysqld get_mysql_option mysqld datadir "/var/lib/mysql" datadir="$result" get_mysql_option mysqld socket "$datadir/mysql.sock" socketfile="$result" get_mysql_option mysqld_safe log-error "/var/log/mysqld.log" errlogfile="$result" get_mysql_option mysqld_safe pid-file "/createByhujian/mysqld/mysqld.pid" mypidfile="$result"
紅色的部分是我自己在根目錄下創建的目錄 /createByhujian/mysqld
mkdir -p /createByhujian/mysqld chown mysql.mysql /createByhujian/mysqld
service mysqld start
補充：可能會出現還是無法啟動，查看日志
Can't start server: can't create PID file: Permission denied
給前面的一個目錄增加權限
chmod +755 /createByhujian
重啟mysqld服務成功，一勞永逸
有什么問題可以下方留言討論哦！