mysql重启后报错
信息如下
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Redirecting to /bin/systemctl start mysql.service
Job for mysqld.service failed because the control process exited with error code.
See "systemctl status mysqld.service" and "journalctl -xe" for details.
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查看服务运行信息
systemctl status mysqld.service
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● mysqld.service - LSB: start and stop MySQL
Loaded: loaded (/etc/rc.d/init.d/mysqld; generated)
Active: failed (thawing) (Result: exit-code) since Thu 2021-04-08 23:22:55 PDT; 6min ago
Docs: man:systemd-sysv-generator(8)
Process: 13546 ExecStop=/etc/rc.d/init.d/mysqld stop (code=exited, status=0/SUCCESS)
Process: 33545 ExecStart=/etc/rc.d/init.d/mysqld start (code=exited, status=1/FAILURE)
Apr 08 23:22:54 primary systemd[1]: Starting LSB: start and stop MySQL...
Apr 08 23:22:55 primary mysqld[33545]: Starting MySQL. ERROR! The server quit without updating PID file (/var/run/mysqld/mysqld.pid).
Apr 08 23:22:55 primary systemd[1]: mysqld.service: Control process exited, code=exited status=1
Apr 08 23:22:55 primary systemd[1]: mysqld.service: Failed with result 'exit-code'.
Apr 08 23:22:55 primary systemd[1]: Failed to start LSB: start and stop MySQL.
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情形一.异常数据文件影响服务启动
截取错误日志/var/log/mysqld.log
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2021-04-09T06:38:24.889010Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2021-04-09T06:38:24.889074Z 0 [Note] --secure-file-priv is set to NULL. Operations related to importing and exporting data are disabled
2021-04-09T06:38:24.889090Z 0 [Note] /usr/local/mysql/bin/mysqld (mysqld 5.7.23-log) starting as process 35083 ...
mysqld: File '/usr/local/mysql/bin-log/master-bin.index' not found (Errcode: 21 - Is a directory)
2021-04-09T06:38:24.895144Z 0 [ERROR] Aborting
2021-04-09T06:38:24.895151Z 0 [Note] Binlog end
2021-04-09T06:38:24.895251Z 0 [Note] /usr/local/mysql/bin/mysqld: Shutdown complete
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日志说未找到/usr/local/mysql/bin-log/master-bin.index文件
迁移或清空对应路径下文件master-bin.index后恢复
mv master-bin.index master-bin.index.bak
再次重启后成功
具体什么原因最好的办法是先查看下错误日志：
1、可能是/usr/local/mysql/data/mysql.pid文件没有写的权限
解决方法 ：给予权限，执行 “chown -R mysql:mysql /var/data” “chmod -R 755 /usr/local/mysql/data” 然后重新启动mysqld！
2、可能进程里已经存在mysql进程
解决方法：用命令“ps -ef|grep mysqld”查看是否有mysqld进程，如果有使用“kill -9 进程号”杀死，然后重新启动mysqld！
3、可能是第二次在机器上安装mysql，有残余数据影响了服务的启动。
解决方法：去mysql的数据目录/data看看，如果存在mysql-bin.index，就赶快把它删除掉吧，它就是罪魁祸首了。本人就是使用第三条方法解决的 ！
4、mysql在启动时没有指定配置文件时会使用/etc/my.cnf配置文件，请打开这个文件查看在[mysqld]节下有没有指定数据目录(datadir)。
解决方法：请在[mysqld]下设置这一行：datadir = /usr/local/mysql/data
5、skip-federated字段问题
解决方法：检查一下/etc/my.cnf文件中有没有没被注释掉的skip-federated字段，如果有就立即注释掉吧。
6、错误日志目录不存在
解决方法：使用“chown” “chmod”命令赋予mysql所有者及权限
7、selinux惹的祸，如果是centos系统，默认会开启selinux
解决方法：关闭它，打开/etc/selinux/config，把SELINUX=enforcing改为SELINUX=disabled后存盘退出重启机器试试。
以上摘抄https://blog.csdn.net/miss1181248983/article/details/82426283
情形二.非正常关机导致pid文件丢失
截取错误日志/var/log/mysqld.log
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2021-04-10T05:58:06.290754Z 0 [ERROR] InnoDB: Table mysql.innodb_table_stats not found.
2021-04-10T05:58:06.290791Z 0 [ERROR] InnoDB: Fetch of persistent statistics requested for table mysql.gtid_executed but the required system tables mysql.innodb_table_stats and mysql.innodb_index_stats are not present or have un
expected structure. Using transient stats instead.
2021-04-10T05:58:06.291796Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without certificate and private key
2021-04-10T05:58:06.292262Z 0 [Note] Server hostname (bind-address): '*'; port: 3306
2021-04-10T05:58:06.292598Z 0 [Note] IPv6 is available.
2021-04-10T05:58:06.292609Z 0 [Note] - '::' resolves to '::';
2021-04-10T05:58:06.292634Z 0 [Note] Server socket created on IP: '::'.
2021-04-10T05:58:06.294492Z 0 [ERROR] Can't start server: can't check PID filepath: No such file or directory
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1.确认pid文件路径
more /etc/my.cnf |grep -i pid
2.依照my.cnf文件配置，创建对应的文件并修改权限(root特权执行)
mkdir -p /var/run/mysqld
chown mysql:mysql /var/run/mysqld
touch /var/run/mysqld/mysqld.pid
chown mysql:mysql /var/run/mysqld/mysqld.pid
3.再次尝试重启
情形三.如有用户权限启动问题，可尝试如下修改
cp /etc/init.d/mysqld mysqld.bak
修改mysql启动文件/etc/init.d/mysqld中start模块
添加--user=root到mysqld_safe
(bindir/mysqld_safe --user=root --datadir=")datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null &
尝试重启