查看MySQL的错误日志的方法

查看MySQL的错误日志可以帮助我们了解MySQL在运行过程中所发生的错误，便于我们及时发现问题并解决。以下是查看MySQL错误日志的方法：

1. 查看MySQL的配置文件

首先，我们需要先查看MySQL的配置文件my.cnf（或my.ini）中的配置项"log_error"是否开启，这个设置控制着MySQL是否在错误发生时将信息输出到错误日志中。我们可以使用如下命令打开my.cnf文件：

sudo vim /etc/mysql/my.cnf

如果"log_error"的值为"/var/log/mysql/error.log"，则表示开启了错误日志功能。如果没有该配置项，或者"log_error"的值为"None"，则表示该功能被关闭了。

1. 查看MySQL的错误日志文件

如果MySQL的错误日志功能被开启，那么我们就可以查看错误日志文件了。错误日志文件的路径可以在my.cnf文件中的"log_error"项中设置，默认情况下是/var/log/mysql/error.log。我们可以使用下面的命令来查看该文件：

sudo tail -f /var/log/mysql/error.log

该命令可以实时查看MySQL错误日志文件的最新内容，方便我们快速发现问题。

示例1：

# sudo tail -f /var/log/mysql/error.log
2021-07-10T09:34:12.836398Z 0 [Note] InnoDB: Starting shutdown...
2021-07-10T09:34:13.938278Z 0 [Note] InnoDB: Shutdown completed; log sequence number 16220212098; 
2021-07-10T09:34:13.940170Z 0 [Note] InnoDB: Removed temporary tablespace data file: "ibtmp1"
2021-07-10T09:34:13.940190Z 0 [Note] Shutting down plugin 'MEMORY'
2021-07-10T09:34:13.940212Z 0 [Note] Shutting down plugin 'CSV'
2021-07-10T09:34:13.940220Z 0 [Note] Shutting down plugin 'sha256_password'
2021-07-10T09:34:13.940223Z 0 [Note] Shutting down plugin 'mysql_native_password'
2021-07-10T09:34:13.940368Z 0 [Note] Shutting down plugin 'binlog'
2021-07-10T09:34:13.944566Z 0 [Note] /usr/sbin/mysqld: Shutdown complete

示例2：

# sudo tail /var/log/mysql/error.log
2021-07-10T10:06:47.917345Z 0 [ERROR] InnoDB: Unable to open './test/temporary_file.ibd': No such file or directory
2021-07-10T10:06:47.917362Z 0 [ERROR] InnoDB: Plugin initialization aborted with error Data structure corruption
2021-07-10T10:06:47.917371Z 0 [ERROR] Plugin 'InnoDB' init function returned error.
2021-07-10T10:06:47.917376Z 0 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2021-07-10T10:06:47.917382Z 0 [ERROR] Failed to initialize plugins.
2021-07-10T10:06:47.917384Z 0 [ERROR] Aborting

2021-07-10T10:06:47.917388Z 0 [Note] Binlog end
2021-07-10T10:06:47.918108Z 0 [Note] /usr/sbin/mysqld: Shutdown complete