02-错误日志

错误日志是MySQL中最重要的日志之一，它记录了当mysqld启动和停止时，以及服务器在运行过程中发生任何严重错误时的相关信息。当数据库出现任何故障导致无法正常使用时，可以首先查看此日志。

可以用--log-error[=file_name]选项来指定mysqld（MySQL服务器）保存错误日志文件的位置。如果没有给定file_name值，mysqld使用错误日志名host_name.err（host_name为主机名）并默认在参数DATADIR（数据目录）指定的目录中写入日志文件。

以下是MySQL正常启动和关闭的一段日志，不同的版本可能略有不同：

[root@localhost mysql]# more localhost.localdomain.err

070727 04:24:46 mysqld started

InnoDB: The first specified data file ./ibdata1 did not exist:

InnoDB: a new database to be created!

070727 4:24:46 InnoDB: Setting file ./ibdata1 size to 10 MB

InnoDB: Database physically writes the file full: wait...

070727 4:24:46 InnoDB: Log file ./ib_logfile0 did not exist: new to be created

InnoDB: Setting log file ./ib_logfile0 size to 5 MB

InnoDB: Database physically writes the file full: wait...

070727 4:24:46 InnoDB: Log file ./ib_logfile1 did not exist: new to be created

InnoDB: Setting log file ./ib_logfile1 size to 5 MB

InnoDB: Database physically writes the file full: wait...

InnoDB: Doublewrite buffer not found: creating new

InnoDB: Doublewrite buffer created

InnoDB: Creating foreign key constraint system tables

InnoDB: Foreign key constraint system tables created

070727 4:24:47 InnoDB: Started; log sequence number 0 0

070727 4:24:47 [Note] /usr/sbin/mysqld: ready for connections.

Version: '5.0.41-community' socket: '/var/lib/mysql/mysql.sock' port: 3306 MySQL Community Edition (GPL)

070727 6:20:27 [Note] /usr/sbin/mysqld: Normal shutdown

070727 6:20:27 InnoDB: Starting shutdown...

070727 6:20:28 InnoDB: Shutdown completed; log sequence number 0 43655

070727 6:20:28 [Note] /usr/sbin/mysqld: Shutdown complete

070727 06:20:28 mysqld ended