shell 监控cpu，memory，load average，记录到log，当负载压力时，发电邮通知管理员。
原理：[转载自：http://blog.csdn.net/fdipzone/article/details/23604335]
1.获取cpu，memory，load average的数值
2.判断数值是否超过自定义的范围，例如（CPU>90%，Memory<10%，load average>2）
3.如数值超过范围，发送电邮通知管理员。发送有时间间隔，每小时只会发送一次。
4.将数值写入log。
5.设置crontab 每30秒运行一次。

crontab
* * * * * /home/xxxx/ServerMonitor.sh  
* * * * * sleep 30; /home/xxxx/ServerMonitor.sh

#!/bin/bash  
  
# 系统监控,记录cpu、memory、load average,当超过规定数值时发电邮通知管理员  
  
# *** config start ***  
  
# 当前目录路径  
ROOT=$(cd "$(dirname "$0")"; pwd)  
  
# 当前服务器名  
HOST=$(hostname)  
  
# log 文件路径  
CPU_LOG="${ROOT}/logs/cpu.log"  
MEM_LOG="${ROOT}/logs/mem.log"  
LOAD_LOG="${ROOT}/logs/load.log"  
  
# 通知电邮列表  
NOTICE_EMAIL='admin@admin.com'  
  
# cpu,memory,load average 记录上一次发送通知电邮时间  
CPU_REMARK='/tmp/servermonitor_cpu.remark'  
MEM_REMARK='/tmp/servermonitor_mem.remark'  
LOAD_REMARK='/tmp/servermonitor_loadaverage.remark'  
  
# 发通知电邮间隔时间  
REMARK_EXPIRE=3600  
NOW=$(date +%s)  
  
# *** config end ***  
  
  
# *** function start ***  
  
# 获取CPU占用  
function GetCpu() {  
    cpufree=$(vmstat 1 5 |sed -n '3,$p' |awk '{x = x + $15} END {print x/5}' |awk -F. '{print $1}')  
    cpuused=$((100 - $cpufree))  
    echo $cpuused  
  
    local remark  
    remark=$(GetRemark ${CPU_REMARK})  
  
    # 检查CPU占用是否超过90%  
    if [ "$remark" = "" ] && [ "$cpuused" -gt 90 ]; then  
        echo "Subject: ${HOST} CPU uses more than 90% $(date +%Y-%m-%d' '%H:%M:%S)" | sendmail ${NOTICE_EMAIL}  
        echo "$(date +%s)" > "$CPU_REMARK"  
    fi  
}  
  
# 获取内存使用情况  
function GetMem() {  
    mem=$(free -m | sed -n '3,3p')  
    used=$(echo $mem | awk -F ' ' '{print $3}')  
    free=$(echo $mem | awk -F ' ' '{print $4}')  
    total=$(($used + $free))  
    limit=$(($total/10))  
    echo "${total} ${used} ${free}"  
  
    local remark  
    remark=$(GetRemark ${MEM_REMARK})  
  
    # 检查内存占用是否超过90%  
    if [ "$remark" = "" ] && [ "$limit" -gt "$free" ]; then  
        echo "Subject: ${HOST} Memory uses more than 90% $(date +%Y-%m-%d' '%H:%M:%S)" | sendmail ${NOTICE_EMAIL}  
        echo "$(date +%s)" > "$MEM_REMARK"  
    fi  
}  
  
# 获取load average  
function GetLoad() {  
    load=$(uptime | awk -F 'load average: ' '{print $2}')  
    m1=$(echo $load | awk -F ', ' '{print $1}')  
    m5=$(echo $load | awk -F ', ' '{print $2}')  
    m15=$(echo $load | awk -F ', ' '{print $3}')  
    echo "${m1} ${m5} ${m15}"  
  
    m1u=$(echo $m1 | awk -F '.' '{print $1}')  
  
    local remark  
    remark=$(GetRemark ${LOAD_REMARK})  
  
    # 检查是否负载是否有压力  
    if [ "$remark" = "" ] && [ "$m1u" -gt "2" ]; then  
        echo "Subject: ${HOST} Load Average more than 2 $(date +%Y-%m-%d' '%H:%M:%S)" | sendmail ${NOTICE_EMAIL}  
        echo "$(date +%s)" > "$LOAD_REMARK"  
    fi  
}  
  
# 获取上一次发送电邮时间  
function GetRemark() {  
    local remark  
  
    if [ -f "$1" ] && [ -s "$1" ]; then  
        remark=$(cat $1)  
  
        if [ $(( $NOW - $remark )) -gt "$REMARK_EXPIRE" ]; then  
            rm -f $1  
            remark=""  
        fi  
    else  
        remark=""  
    fi  
  
    echo $remark  
}  
  
  
# *** function end ***  
  
cpuinfo=$(GetCpu)  
meminfo=$(GetMem)  
loadinfo=$(GetLoad)  
  
echo "cpu: ${cpuinfo}" >> "${CPU_LOG}"  
echo "mem: ${meminfo}" >> "${MEM_LOG}"  
echo "load: ${loadinfo}" >> "${LOAD_LOG}"  
  
exit 0