抽时间找了一个centos/linux负载过高自动重启apache的脚本，保护你的vps不因超负荷被关闭。稍微改了点，适合所有可以通过service httpd start | stop 来重启apache的vps或服务器。最后别忘记在crontab设置每隔几分钟执行一次即可。

一行命令自动安装，安装成功后请看 crontab -l ：

wget  http://www.ctohome.com/linux-vps-pack/restart_apache_by_load.sh;sh restart_apache_by_load.sh;

2011年10月1日 增加内存占用过高，自动重启的监控：

TOP_SYS_LOAD_NUM表示到达这个负载的时候，就会停止apache。然后过段时间负载降下来后，再尝试启动apache

MIN_RAM表示系统可用内存如果小于此设置的时候（单位MB），就会停止apache。然后过段时间负载降下来后，再尝试启动apache

#!/bin/sh

# crontab usage: */3 * * * * /backup/www.ctohome.com/loadavg_restart_apache.sh >> /backup/www.ctohome.com/restart_apache.log

TOP_SYS_LOAD_NUM=5
SYS_LOAD_NUM=`uptime | awk '{print $(NF-2)}' | sed 's/,//'`  

MIN_RAM=120
FREE_RAM=`free -m| grep Mem|awk '{print $4}'`

echo $(date +"%y-%m-%d") `uptime`
if [ `echo "$TOP_SYS_LOAD_NUM < $SYS_LOAD_NUM"|bc` -eq 1 ] ||  [ `echo "$FREE_RAM < $MIN_RAM"|bc` -eq 1 ]
then 
then  
    echo "#0#" $(date +"%y-%m-%d %H:%M:%S") "pkill httpd" `ps -ef | grep httpd | wc -l`
    /usr/sbin/apachectl stop
    sleep 8
    pkill httpd  
    sleep 8  
    for i in 1 2 3  
    do  
        if [ `pgrep httpd | wc -l` -le 0 ]  
        then  
            /usr/sbin/apachectl start 
            sleep 30  
            echo "#1#" $(date +"%y-%m-%d %H:%M:%S") "start httpd" `ps -ef | grep httpd | wc -l`  
        fi  
    done  
else  
    if [ `pgrep httpd | wc -l` -le 0 ]  
    then  
        /usr/sbin/apachectl start  
        sleep 30  
        echo "#2#" $(date +"%y-%m-%d %H:%M:%S") "start httpd" `ps -ef | grep httpd | wc -l`  
    fi  
fi

没有什么坏处，至少还可以监控系统的历史负载。下面的是某个vps设置了最大负载3的重启apache情况，效果不错：
tail -f restart_apache.log
10-07-17 13:57:01 up 14:53, 2 users, load average: 0.34, 1.09, 1.14
10-07-17 14:00:01 up 14:56, 2 users, load average: 0.97, 1.06, 1.11
10-07-17 14:03:01 up 14:59, 2 users, load average: 1.38, 1.26, 1.18
10-07-17 14:06:01 up 15:02, 2 users, load average: 0.63, 0.92, 1.06
10-07-17 14:09:01 up 15:05, 2 users, load average: 0.98, 0.81, 0.98
10-07-17 14:12:01 up 15:08, 2 users, load average: 0.55, 0.71, 0.90
10-07-17 14:15:01 up 15:11, 2 users, load average: 0.46, 0.59, 0.81
10-07-17 14:18:02 up 15:14, 2 users, load average: 3.06, 1.30, 1.01
#0# 10-07-17 14:18:02 pkill httpd 38
#1# 10-07-17 14:18:51 start httpd 34
10-07-17 14:21:01 up 15:17, 2 users, load average: 1.14, 1.59, 1.20
10-07-17 14:24:01 up 15:20, 2 users, load average: 1.19, 1.45, 1.21
10-07-17 14:27:01 up 15:23, 2 users, load average: 0.29, 0.95, 1.05
10-07-17 14:30:01 up 15:26, 2 users, load average: 0.99, 0.85, 0.98
10-07-17 14:33:01 up 15:29, 2 users, load average: 1.15, 1.22, 1.12
10-07-17 14:36:01 up 15:32, 2 users, load average: 4.58, 2.94, 1.78
#0# 10-07-17 14:36:01 pkill httpd 36
#1# 10-07-17 14:36:49 start httpd 27
10-07-17 14:39:01 up 15:35, 2 users, load average: 2.24, 2.49, 1.79
10-07-17 14:42:01 up 15:38, 2 users, load average: 1.37, 1.87, 1.66
10-07-17 14:45:01 up 15:41, 2 users, load average: 0.69, 1.44, 1.54
10-07-17 14:48:01 up 15:44, 2 users, load average: 1.73, 1.68, 1.62
10-07-17 14:51:01 up 15:47, 2 users, load average: 0.81, 1.34, 1.49
10-07-17 14:54:01 up 15:50, 2 users, load average: 1.71, 1.25, 1.41
10-07-17 14:57:01 up 15:53, 2 users, load average: 1.93, 1.52, 1.47
10-07-17 15:00:01 up 15:56, 2 users, load average: 1.29, 1.43, 1.44
10-07-17 15:03:01 up 15:59, 2 users, load average: 1.45, 1.42, 1.43
10-07-17 15:06:01 up 16:02, 2 users, load average: 0.73, 1.24, 1.36
10-07-17 15:09:01 up 16:05, 2 users, load average: 1.66, 1.55, 1.47
10-07-17 15:12:03 up 16:08, 2 users, load average: 3.59, 2.02, 1.63
#0# 10-07-17 15:12:07 pkill httpd 35
#1# 10-07-17 15:12:55 start httpd 28
10-07-17 15:15:01 up 16:11, 2 users, load average: 1.19, 1.78, 1.63
10-07-17 15:18:01 up 16:14, 2 users, load average: 1.38, 1.60, 1.58
10-07-17 15:21:01 up 16:17, 2 users, load average: 3.32, 2.20, 1.79
#0# 10-07-17 15:21:01 pkill httpd 33
#1# 10-07-17 15:21:50 start httpd 33
10-07-17 15:24:01 up 16:20, 2 users, load average: 1.18, 1.66, 1.64
10-07-17 15:27:01 up 16:23, 2 users, load average: 1.67, 1.73, 1.67
10-07-17 15:30:01 up 16:26, 2 users, load average: 1.15, 1.55, 1.60
10-07-17 15:33:01 up 16:29, 2 users, load average: 0.85, 1.30, 1.49
10-07-17 15:36:01 up 16:32, 2 users, load average: 0.30, 0.89, 1.30
10-07-17 15:39:01 up 16:35, 2 users, load average: 0.37, 0.90, 1.25

 脚本执行如果报错

/backup/www.cthome.com/loadavg_restart_apache.sh: line 6: bc: command not found
/backup/www.cthome.com/loadavg_restart_apache.sh: line 6: [: -eq: unary operator expected

表示没有bc命令，centos可以用 yum -y install bc 安装它