How to Set Up Automated Email Alerts for Linux Memory and Swap Monitoring

1. Install msmtp email client

Download and extract the source, then compile and install:

# tar jxvf msmtp-1.4.16.tar.bz2
# cd msmtp-1.4.16
# ./configure --prefix=/usr/local/msmtp
# make
# make install

Create configuration and log files (replace host, user, password as needed):

# vim ~/.msmtprc

account default
host 126.com
from [email protected]
auth login
user test
password 123456
logfile ~/.msmtp.log

# chmod 600 ~/.msmtprc
# touch ~/.msmtp.log

2. Configure mutt to use msmtp

# vim ~/.muttrc

set sendmail="/usr/local/msmtp/bin/msmtp"
set use_from=yes
set realname="memory"
set [email protected]
set envelope_from=yes
set rfc2047_parameters=yes
set charset="utf-8"

Test sending an email:

# echo "邮件内容123456" | mutt -s "邮件标题测试邮件" -a /scripts/test.txt [email protected]

3. Monitor memory with free command

Show memory usage in megabytes:

# free -m
total used free shared buffers cached
Mem: 3952 3414 538 0 168 484
-/+ buffers/cache: 2760 1191
Swap: 8191 86 8105

Extract specific free values:

# free -m | grep Mem | awk '{print $4}'
# free -m | grep - | awk '{print $4}'
# free -m | grep Swap | awk '{print $4}'

4. Script to record memory statistics

# vim /scripts/free-mem.sh
#!/bin/bash
date >> /scripts/date-time.txt
echo Mem-free: `free -m | grep Mem | awk '{print $4}'`M >> /scripts/mem-free.txt
echo buffers/cache-free: `free -m | grep - | awk '{print $4}'`M >> /scripts/buffers-free.txt
echo Swap-free: `free -m | grep Swap | awk '{print $4}'`M >> /scripts/swap-free.txt
paste /scripts/date-time.txt /scripts/mem-free.txt /scripts/buffers-free.txt /scripts/swap-free.txt > /scripts/freemem.txt
chmod a+x /scripts/free-mem.sh
# /scripts/free-mem.sh

5. Email the memory report

# vim /scripts/sendmail-mem.sh
#!/bin/bash
IP=`ifconfig eth0 | grep "inet addr" | cut -f2 -d ":" | cut -f1 -d " "`
today=`date -d "0 day" +%Y年%m月%d日`
echo "这是$IP服务器$today的内存监控报告，请下载附件。" | mutt -s "$IP服务器$today内存监控报告" -a /scripts/freemem.txt [email protected]
chmod a+x /scripts/sendmail-mem.sh

6. Warn when swap usage exceeds 80%

# vim /scripts/swap-warning.sh
#!/bin/bash
IP=`ifconfig eth0 | grep "inet addr" | cut -f2 -d ":" | cut -f1 -d " "`
swap_total=`free -m | grep Swap | awk '{print $2}'`
swap_free=`free -m | grep Swap | awk '{print $4}'`
swap_used=`free -m | grep Swap | awk '{print $3}'`

if ((swap_used != 0)); then
  swap_per=0`echo "scale=2;$swap_free/$swap_total" | bc`
  swap_warn=0.20
  swap_now=`expr $swap_per > $swap_warn`
  if (($swap_now == 0)); then
    echo "$IP服务器swap交换分区只剩下 $swap_free M 未使用，剩余不足20%，使用率已经超过80%，请及时处理。" | mutt -s "$IP 服务器内存告警" [email protected]
  fi
fi
chmod a+x /scripts/swap-warning.sh

7. Schedule tasks with cron

# crontab -e

*/10 * * * * /scripts/free-mem.sh
*/10 * * * * /scripts/swap-warning.sh
0 8 * * * /scripts/sendmail-mem.sh

service crond restart