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，logrotate部署为每天运行的cron job，你可以在目录/etc/cron.daily里找到名为logrotate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：
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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/logrotate将会自动执行 ， 下面是它的内容：
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#!/bin/sh /usr/sbin/logrotate /etc/logrotate.conf EXITVALUE=http://www.zuomama.com/qiaomen/youxi/$? 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：
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EXITVALUE=http://www.zuomama.com/qiaomen/youxi/$? 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 0664 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/nullthen /opt/mysql/bin/mysqladmin flush-logs fi endscript }logrotate常见选项:
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
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[mysqladmin] password = *** user= rootchmod 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
【利用logrotate对MySQL日志进行轮转】/usr/sbin/logrotate -f /etc/logrotate.d/mysql-log-rotate
