CentOS7下mysqld服务启动失败终极解决方案

启动mysqld服务失败，报错如下：

[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，先看下有什么帮助没有

[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=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@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 :1.25Jan 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.

然⽽，好像这些信息对我们来说并没有什么⽤处，什么守护进程没启动，我们也不能知如何去启动这些，这个时候我们查看⼀下mysql⾃带的告警⽇志，路径⼀般在/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 directory181207 18:00:20 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

这个时候我们就明⽩了，/var/run/mysqld/这个⽬录不存在，wu，查找下确实没有这个⽂件。这⾥我们有两种解决⽅案第⼀种⾃⼰创建 /var/run/mysqld/ 这个⽬录，重新启动mysqld服务

[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]依旧报错，重新查看告警⽇志，有以下输出

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 denied181207 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

原来，/var/run/mysqld/的属主和属组还是root，mysql并不能在其中创建⽂件，后修改该⽬录的属主和属组，启动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 ]

上⾯第⼀种解决⽅案为临时性的⽅案，你会发现当虚拟机reboot的话，⼜会启动不成功，那个⽬录⼜不删除了，因此我们修改⼀下存放mysqld.pid的⽬录，有两个配置⽂件vi /etc/my.cnf

socket=/var/lib/mysql/mysql.sock

# Disabling symbolic-links is recommended to prevent assorted security riskssymbolic-links=0

log-error=/var/log/mysqld.log

pid-file=/createByhujian/mysqld/mysqld.pidvi /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\"

红⾊的部分是我⾃⼰在根⽬录下创建的⽬录 /createByhujian/mysqldmkdir -p /createByhujian/mysqld

chown mysql.mysql /createByhujian/mysqldservice mysqld start　　

补充：可能会出现还是⽆法启动，查看⽇志

Can't start server: can't create PID file: Permission denied给前⾯的⼀个⽬录增加权限chmod +755 /createByhujian重启mysqld服务成功，⼀劳永逸有什么问题可以下⽅留⾔讨论哦！