1）获取当前系统剩余内存的值 [root@node1 ~]# free -m total used free shared buff/cache available Mem: 1999 120 1527 8 351 1685 Swap: 4095 0 4095 #取avaliable的值 [root@node1 ~]# free -m|awk 'NR==2{print $NF}' 1685 2）配置邮件报警（可采用第三方邮件服务器） 发邮件的客户端常见的有mail或mutt；服务端有sendmail服务（CentOS 5下默认的）、postfix服务（CentOS 6下默认的）。这里不使用本地的邮件服务，而是使用本地的mail客户端，以及第三方的邮件服务商，例如：163.com（需要提前注册用户），利用这个邮件账号来给接收报警的人发送报警邮件。 [root@node1 ~]#echo -e "set from=yaowangxi@163.com smtp=smtp.163.com set smtp-auth-user=yaowangxi@163.com smtp-auth-password=VCASBMTUKXOGKHAL smtp-auth=login" >>/etc/mail.rc #set from=yaowangxi@163.com # 发件人 #set smtp=smtp.163.com # smtp #set smtp-auth=login #set smtp-auth-user=yaowangxi@163.com # smtp认证邮箱 #set smtp-auth-password=VCASBMTUKXOGKHAL # 注意现在163邮箱密码并不是网页登录密码，是一个专用的SMTP密码 [root@node1 ~]# systemctl restart postfix.service [root@node1 ~]# echo test |mail -s "test" yaowangxi@163.com 3）编写Shell脚本。 #! /bin/bash MEM=$(free -m |awk 'NR==2{print $NF}') #取剩余可用的MEM值 if [ $MEM -le 2000 ];then echo "$MEM less than 2000M" |tee /tmp/mem_log echo "$(date +%F-%T)_system_mem is $MEM, less 2000M"|mail -s "MEM warry" yaowangxi@163.com fi #MEM小于2000M则发送警告并给yaowangxi@163.com发送邮件
测试脚本：
[root@node1 scripts]# bash check_mem.sh 1681 less than 2000M
4)把脚本加入定时任务 [root@node1 scripts]# crontab -l */3 * * * * /usr/bin/bash /scripts/check_mem.sh [root@node1 scripts]# tailf /var/log/cron Oct 10 00:01:01 node1 CROND[24146]: (root) CMD (run-parts /etc/cron.hourly) Oct 10 00:01:01 node1 run-parts(/etc/cron.hourly)[24146]: starting 0anacron Oct 10 00:01:01 node1 anacron[24155]: Anacron started on 2020-10-10 Oct 10 00:01:01 node1 anacron[24155]: Normal exit (0 jobs run) Oct 10 00:01:01 node1 run-parts(/etc/cron.hourly)[24157]: finished 0anacron Oct 10 00:49:32 node1 crontab[26801]: (root) BEGIN EDIT (root) Oct 10 00:50:25 node1 crontab[26801]: (root) REPLACE (root) Oct 10 00:50:25 node1 crontab[26801]: (root) END EDIT (root) Oct 10 00:50:29 node1 crontab[26854]: (root) LIST (root) Oct 10 00:51:01 node1 CROND[26904]: (root) CMD (/usr/bin/bash /scripts/check_mem.sh) Oct 10 00:54:01 node1 CROND[27077]: (root) CMD (/usr/bin/bash /scripts/check_mem.sh) Oct 10 00:57:01 node1 CROND[27238]: (root) CMD (/usr/bin/bash /scripts/check_mem.sh) #定时任务在正常运行
方法一：使用单分支
#! /bin/bash #把$1赋值给a,把$2赋值给b a=$1 b=$2 #判断脚本后紧跟了2个参数$1 $2 if [ $# -ne 2 ];then echo "Usage: $0 age1 age2!" exit 0 fi #判断$1和$2为正整数 expr $a + $b + 10 > /dev/null if [ $? -ne 0 ];then echo "Please enter 2 positive integers!" exit 0 fi #单分支比较2个数的大小 if [ $a -gt $b ];then echo "$a > $b" fi if [ $a -lt $b ];then echo "$a < $b" fi if [ $a -eq $b ];then echo "$a = $b" fi
方法二：if多分支比较
#! /bin/bash #把$1赋值给a,把$2赋值给b a=$1 b=$2 #判断脚本后紧跟了2个参数$1 $2 if [ $# -ne 2 ];then echo "Usage: $0 age1 age2!" exit 0 fi #判断$1和$2为正整数 expr $a + $b + 10 &> /dev/null if [ $? -ne 0 ];then echo "Please enter 2 positive integers!" exit 0 fi #多分支比较2个数的大小 if [ $a -gt $b ];then echo "$a > $b" elif [ $a -lt $b ];then echo "$a < $b" else echo "$a = $b" fi
脚本测试：
[root@node1 scripts]# bash bijiaodaxiao.sh Usage: bijiaodaxiao.sh age1 age2! [root@node1 scripts]# bash bijiaodaxiao.sh 10 20 10 < 20 [root@node1 scripts]# bash bijiaodaxiao.sh 100 20 100 > 20 [root@node1 scripts]# bash bijiaodaxiao.sh 100 100 100 = 100 [root@node1 scripts]# bash bijiaodaxiao.sh 100 ads expr: non-integer argument Please enter 2 positive integers! [root@node1 scripts]#
该案例的nginx使用yum安装
[root@node1 scripts]# yum install -y nginx #启动nginx [root@node1 scripts]# systemctl start nginx [root@node1 scripts]# pidof nginx 15694 15693 [root@node1 scripts]# netstat -antp|grep ":80" tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 15693/nginx: master tcp6 0 0 :::80 :::* LISTEN 15693/nginx: master
#! /bin/bash #判断nginx是否正常运行，pidof nginx|wc -l来判断，值为0，则nginx没有运行需要重启nginx服务，不为0，nginx工作正常 NGX_NUM1=$(pidof nginx |wc -l) if [ $NGX_NUM1 -eq 0 ];then systemctl stop nginx &> /dev/null sleep 3 systemctl start nginx &>/dev/null #重启后nginx是否正常运行,正常则打印"nginx server restart ok!",不正常则打印"Plesae check nginx server worry!" NGX_NUM2=$(pidof nginx |wc -l) if [ $NGX_NUM2 -ne 0 ];then echo "nginx server restart ok!" else echo "Plesae check nginx server worry!" fi else echo "nginx running !" fi
脚本测试：
1、nginx工作正常 [root@node1 scripts]# ps -ef |grep nginx root 24333 1 0 22:09 ? 00:00:00 nginx: master process nginx nginx 24334 24333 0 22:09 ? 00:00:00 nginx: worker process root 24345 14794 0 22:09 pts/0 00:00:00 grep --color=auto nginx [root@node1 scripts]# pidof nginx 24334 24333 [root@node1 scripts]# bash nginx_check.sh nginx running ! 2、停止nginx [root@node1 scripts]# nginx -s stop [root@node1 scripts]# pidof nginx [root@node1 scripts]# ps -ef |grep nginx root 24400 14794 0 22:10 pts/0 00:00:00 grep --color=auto nginx [root@node1 scripts]# bash nginx_check.sh nginx server restart ok! [root@node1 scripts]# ps -ef |grep nginx root 24439 1 0 22:10 ? 00:00:00 nginx: master process /usr/sbin/nginx nginx 24440 24439 0 22:10 ? 00:00:00 nginx: worker process root 24449 14794 0 22:10 pts/0 00:00:00 grep --color=auto nginx [root@node1 scripts]# pidof nginx 24440 24439 #nginx重启成功 3、输出nginx [root@node1 scripts]# yum remove -y nginx [root@node1 scripts]# bash nginx_check.sh Plesae check nginx server worry! #提示nginx重启失败，需要手动处理