How to Set Up Automated Linux Memory & Swap Monitoring with Email Alerts

1. Install msmtp email client (similar to Foxmail)

Download and extract, then configure 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 file ~/.msmtprc with host, user, password, logfile, and set permissions:

# 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 with attachment:

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

3. Monitor system memory with free

Use free -m to view memory usage in megabytes.

Extract specific values:

# free -m | grep Mem | awk '{print $4}'   # physical free
# free -m | grep - | awk '{print $4}'    # buffers/cache free
# free -m | grep Swap | awk '{print $4}' # swap free

Create a Bash script /scripts/free-mem.sh that records timestamp, memory, buffers, swap values and writes them to /scripts/freemem.txt:

#!/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

Send the memory report via email:

#!/bin/bash
IP=`ifconfig eth0 | grep "inet addr" | cut -f 2 -d ":" | cut -f 1 -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

4. Monitor swap usage and send alerts when over 80%

Script /scripts/swap-warning.sh calculates free percentage and compares with a 20% threshold:

#!/bin/bash
IP=`ifconfig eth0 | grep "inet addr" | cut -f 2 -d ":" | cut -f 1 -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

5. 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