在重启阿里的CentOS7服务器后,重启MySQL 出现错误

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" fordetails.

[FAILED]

按照提示查看错误信息

[root@djaljdw ~]# systemctl status mysqld.service

● mysqld.service -SYSV: MySQL database server.

Loaded: loaded (/etc/rc.d/init.d/mysqld; bad; vendor preset: disabled)

Active: failed (Result: exit-code) since Thu 2019-08-22 14:42:39CST; 1min 25s ago

Docs: man:systemd-sysv-generator(8)

Process:2427 ExecStart=/etc/rc.d/init.d/mysqld start (code=exited, status=1/FAILURE)

Aug22 14:42:37 izw91diu854rguz systemd[1]: Starting SYSV: MySQL database server....

Aug22 14:42:39 izw91diu854rguz mysqld[2427]: MySQL Daemon failed to start.

Aug22 14:42:39 izw91diu854rguz mysqld[2427]: Starting mysqld: [FAILED]

Aug22 14:42:39 izw91diu854rguz systemd[1]: mysqld.service: control process exited, code=exited status=1Aug22 14:42:39 izw91diu854rguz systemd[1]: Failed to start SYSV: MySQL database server..

Aug22 14:42:39 izw91diu854rguz systemd[1]: Unit mysqld.service entered failed state.

Aug22 14:42:39 izw91diu854rguz systemd[1]: mysqld.service failed.

Hint: Some lines were ellipsized, use-l to show in full.

[root@djaljdw ~]#  journalctl -xe

--

-- Unit session-2.scope has begun starting up.

Jan20 18:26:48 spark01 sshd[2916]: pam_unix(sshd:session): session opened for user spark by (uid=0)

Jan20 18:26:52 spark01 su[2944]: (to root) spark on pts/1Jan20 18:26:52 spark01 su[2944]: pam_unix(su-l:session): session opened for user root by spark(uid=1000)

Jan20 18:26:56 spark01 polkitd[909]: Registered Authentication Agent for unix-process:2974:117137(system bus name :1.25Jan20 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.

Jan20 18:26:57 spark01 mysqld[2979]: MySQL Daemon failed to start.

Jan20 18:26:57 spark01 mysqld[2979]: Starting mysqld: [FAILED]

Jan20 18:26:57 spark01 systemd[1]: mysqld.service: control process exited, code=exited status=1Jan20 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 isfailed.

Jan20 18:26:57 spark01 systemd[1]: Unit mysqld.service entered failed state.

Jan20 18:26:57 spark01 systemd[1]: mysqld.service failed.

Jan20 18:26:57 spark01 polkitd[909]: Unregistered Authentication Agent for unix-process:2974:117137(system bus name :1.

发现里面并没有提供有用的错误信息

所以去查看mysql日志信息(/var/log/mysqld.log)

190822 14:44:42 [Note] Plugin 'FEDERATED' isdisabled.190822 14:44:42 InnoDB: The InnoDB memory heap isdisabled190822 14:44:42InnoDB: Mutexes and rw_locks use GCC atomic builtins190822 14:44:42 InnoDB: Compressed tables use zlib 1.2.3

190822 14:44:42InnoDB: Using Linux native AIO190822 14:44:42 InnoDB: Initializing buffer pool, size = 128.0M

190822 14:44:42InnoDB: Completed initialization of buffer pool190822 14:44:42 InnoDB: highest supported file format isBarracuda.

InnoDB: The log sequence numberinibdata files does not match

InnoDB: the log sequence numberin the ib_logfiles!

190822 14:44:42 InnoDB: Database was not shut down normally!InnoDB: Starting crash recovery.

InnoDB: Reading tablespace informationfromthe .ibd files...

InnoDB: Restoring possible half-written data pages fromthe doublewrite

InnoDB: buffer...190822 14:44:42 InnoDB: Waiting forthe background threads to start190822 14:44:43 InnoDB: 5.5.59 started; log sequence number 1940403

190822 14:44:43 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306

190822 14:44:43 [Note] - '0.0.0.0' resolves to '0.0.0.0';190822 14:44:43 [Note] Server socket created on IP: '0.0.0.0'.190822 14:44:43 [ERROR] /usr/libexec/mysqld: Can't create/write to file'/var/run/mysqld/mysqld.pid'(Errcode: 2)

190822 14:44:43 [ERROR] Can't start server: can't create PID file: No such file or directory

问题找到了:不能创建PID文件:没有这样的文件或目录

于是去查看,果然没有文件夹

[root@djaljdw ~]#  cd /var/run

[root@djaljdw ~]#  mkdir mysqld

[root@djaljdw ~]#  cd mysqld

[root@djaljdw ~]#  touch mysqld.pid

重启服务还是报错

于是又查看日志

190822 14:56:51 [Note] Plugin 'FEDERATED' isdisabled.190822 14:56:51 InnoDB: The InnoDB memory heap isdisabled190822 14:56:51InnoDB: Mutexes and rw_locks use GCC atomic builtins190822 14:56:51 InnoDB: Compressed tables use zlib 1.2.3

190822 14:56:51InnoDB: Using Linux native AIO190822 14:56:51 InnoDB: Initializing buffer pool, size = 128.0M

190822 14:56:51InnoDB: Completed initialization of buffer pool190822 14:56:51 InnoDB: highest supported file format isBarracuda.

InnoDB: The log sequence numberinibdata files does not match

InnoDB: the log sequence numberin the ib_logfiles!

190822 14:56:51 InnoDB: Database was not shut down normally!InnoDB: Starting crash recovery.

InnoDB: Reading tablespace informationfromthe .ibd files...

InnoDB: Restoring possible half-written data pages fromthe doublewrite

InnoDB: buffer...190822 14:56:51 InnoDB: Waiting forthe background threads to start190822 14:56:52 InnoDB: 5.5.59 started; log sequence number 1940403

190822 14:56:52 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306

190822 14:56:52 [Note] - '0.0.0.0' resolves to '0.0.0.0';190822 14:56:52 [Note] Server socket created on IP: '0.0.0.0'.190822 14:56:52 [ERROR] /usr/libexec/mysqld: Can't create/write to file'/var/run/mysqld/mysqld.pid'(Errcode: 13)

190822 14:56:52 [ERROR] Can't start server: can't create PID file: Permission denied

发现:无法创建PID文件:权限被拒绝

解决办法:

修改 /var/run/mysqld/权限为mysql

[root@djaljdw ~]#  chown -R mysql /var/run/mysqld

[root@djaljdw ~]#  chgrp -R mysql /var/run/mysqld

[root@djaljdw ~]#  chmod 777 /var/run/mysqld

重启服务完美解决

tip:看日志是解决问题的一个很好的办法!