Linux中使用logrotate對MySQL日志進行輪轉

日志輪轉特別適用於具有固定文件名的日志文件，比如MySQL的出錯日志、常規查詢日志、慢查詢日志 等。Linux系統有一個非常好用的根據logratate可以實現自動輪轉，本文介紹它的原理和用法。

默認情況下，logrotate部署為每天運行的cron job，你可以在目錄/etc/cron.daily裡找到名為 logrotate的配置文件。那麼它是在每天的上面時候運行的呢？打開文件/etc/crontab就知道了，下面是 我機器上的情況：

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

從上面的配置我們可以知道，/etc/cron.daily是在每天凌晨4:02執行。也就是說，每天4:02 分/etc/cron.daily/logrotate將會自動執行，下面是它的內容：

#!/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

從上面我們可以知道，logratate默認的配置文件是/etc/logratate.conf，下面是它的內容：

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 0664 root utmp  
    rotate 1  
}  
     
/var/log/btmp {  
    missingok  
    monthly  
    minsize 1M  
    create 0600 root utmp  
    rotate 1  
}

從上面我們可以知道，這個默認的配置文件將讀取目錄/etc/logrotate.d，所以我們只要把自己寫的 配置文件放到該目錄下即可。

MySQL本省提供了一個rotate的參考配置文件，在support-files目錄下，文件名為mysql-log-rotate ，內容如下：

# 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 = <secret>  
# user= root  
#  
# where "<secret>" 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常見選項:

我們只要根據自己的需要，修改相應配置即可，下面是一個例子：

1）創建MySQL root密碼文件

vi /root/.my.cnf

[mysqladmin]  
password = ***  
user= root

chmod 600 /root/.my.cnf

2）把mysql-log-rotate拷貝至/etc/logrotate.d目錄下，修改其內容為 ：

/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）執行以下命令測試

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