[Linux] 利用logrotate对MySQL日志进行轮转

日志轮转特别适用于具有固定文件名的日志文件，比如MySQL的出错日志、常规查询日志、慢查询日志等。Linux系统有一个非常好用的根据logratate可以实现自动轮转，本文介绍它的原理和用法。

默认情况下，logratate部署为每天运行的cron job，你可以在目录/etc/cron.daily里找到名为logratate的配置文件。那么它是在每天的上面时候运行的呢？打开文件/etc/crontab就知道了，下面是我机器上的情况：

[plain]

SHELL=/bin/bash

PATH=/sbin:/bin:/usr/sbin:/usr/bin

MAILTO=root

HOME=/

# run-parts

01 * * * * root run-parts /etc/cron.hourly

02 4 * * * root run-parts /etc/cron.daily

22 4 * * 0 root run-parts /etc/cron.weekly

42 4 1 * * root run-parts /etc/cron.monthly

从上面的配置我们可以知道，/etc/cron.daily是在每天凌晨4:02执行。也就是说，每天4:02分/etc/cron.daily/logratate将会自动执行，下面是它的内容：

[plain]

#!/bin/sh

/usr/sbin/logrotate /etc/logrotate.conf

EXITVALUE=$?

if [ $EXITVALUE != 0 ]; then

/usr/bin/logger -t logrotate "ALERT exited abnormally with [$EXITVALUE]"

fi

exit 0

从上面我们可以知道，logratate默认的配置文件是/etc/logratate.conf，下面是它的内容：

[plain]

EXITVALUE=$?

if [ $EXITVALUE != 0 ]; then

/usr/bin/logger -t logrotate "ALERT exited abnormally with [$EXITVALUE]"

fi

exit 0

[root@lx202 /etc/cron.daily ]# cat /etc/logrotate.conf

# see "man logrotate" for details

# rotate log files weekly

weekly

# keep 4 weeks worth of backlogs

rotate 4

# create new (empty) log files after rotating old ones

create

# uncomment this if you want your log files compressed

#compress

# RPM packages drop log rotation information into this directory

include /etc/logrotate.d

# no packages own wtmp -- we'll rotate them here

/var/log/wtmp {

monthly

minsize 1M

create 06 root utmp

rotate 1

}

/var/log/btmp {

missingok

monthly

minsize 1M

create 0600 root utmp

rotate 1

}

从上面我们可以知道，这个默认的配置文件将读取目录/etc/logrotate.d，所以我们只要把自己写的配置文件放到该目录下即可。

MySQL本省提供了一个rotate的参考配置文件，在support-files目录下，文件名为mysql-log-rotate，内容如下：

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# This logname can be set in /etc/my.cnf

# by setting the variable "err-log"

# in the [safe_mysqld] section as follows:

#

# [safe_mysqld]

# err-log=/opt/mysql/data/mysqld.log

#

# If the root user has a password you have to create a

# /root/.my.cnf configuration file with the following

# content:

#

# [mysqladmin]

# password =

# user= root

#

# where "" is the password.

#

# ATTENTION: This /root/.my.cnf should be readable ONLY

# for root !

/opt/mysql/data/mysqld.log {

# create 600 mysql mysql

notifempty

daily

rotate 3

missingok

compress

postrotate

# just if mysqld is really running

if test -x /opt/mysql/bin/mysqladmin && /

/opt/mysql/bin/mysqladmin ping &>/dev/null

then

/opt/mysql/bin/mysqladmin flush-logs

fi

endscript

}

logrotate常见选项:

选项 含义

compress 压缩日志文件的所有非当前版本

copy 复制当前的日志文件,忽略create参数

copytruncate 复制当前的日志文件,并置空当前文件

daily 每天轮日志文件i

dateext 轮换的日志后缀为-YYYYMMDD格式

delaycompress 压缩除了当前和最近之外的所有其他版本

missingok 如果日志不存在,不会报错

notifempty 如果日志为空,则不轮换

rotate n 在轮换方案中包含n个版本的日志

size=logsize 如果日志文件大于logsize才轮换

我们只要根据自己的需要，修改相应配置即可，下面是一个例子：

1）创建MySQL root密码文件

vi /root/.my.cnf

[plain]

[mysqladmin]

password = ***

user= root

chmod 600 /root/.my.cnf

2）把mysql-log-rotate拷贝至/etc/logrotate.d目录下，修改其内容为：

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/data/mysql/log/slow.log

/data/mysql/log/alert.log {

create 600 mysql mysql

notifempty

daily

rotate 7

missingok

# compress

postrotate

# just if mysqld is really running

if test -x /opt/mysql/bin/mysqladmin && /

/opt/mysql/bin/mysqladmin ping &>/dev/null

then

/opt/mysql/bin/mysqladmin flush-logs

fi

endscript

}

3）执行以下命令测试

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/usr/sbin/logrotate -f /etc/logrotate.d/mysql-log-rotate