Automate Linux Memory & Swap Monitoring with msmtp, mutt, and Cron

1. Install msmtp (a lightweight mail client)

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

2. Create the msmtp configuration file (~/.msmtprc) and restrict its 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

3. Configure mutt to use msmtp as its sendmail program

# 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"

4. Test email sending with mutt

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

5. Monitor system memory using the free command # free -m Key values can be extracted with:

Physical free memory: # free -m | grep Mem | awk '{print $4}' Buffers free: # free -m | grep - | awk '{print $4}' Swap free: # free -m | grep Swap | awk '{print $4}' 6. Bash script to collect memory data ( /scripts/free-mem.sh )

#!/bin/bash
# Record timestamp
date >> /scripts/date-time.txt
# Record physical free memory
echo Mem-free: `free -m | grep Mem | awk '{print $4}'`M >> /scripts/mem-free.txt
# Record buffers free
echo buffers/cache-free: `free -m | grep - | awk '{print $4}'`M >> /scripts/buffers-free.txt
# Record swap free
echo Swap-free: `free -m | grep Swap | awk '{print $4}'`M >> /scripts/swap-free.txt
# Combine into one file
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

7. Bash script to email the memory report ( /scripts/sendmail-mem.sh )

#!/bin/bash
# Server IP
IP=`ifconfig eth0 | grep "inet addr" | cut -f 2 -d ":" | cut -f 1 -d " "`
# Current date
today=`date -d "0 day" +%Y年%m月%d日`
# Send email with attachment
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

8. Bash script to warn when swap usage exceeds 80% ( /scripts/swap-warning.sh )

#!/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

9. Schedule the scripts with cron

# crontab -e
*/10 * * * * /scripts/free-mem.sh
*/10 * * * * /scripts/swap-warning.sh
0 8 * * * /scripts/sendmail-mem.sh
# service crond restart

These steps provide a fully automated solution for collecting memory and swap statistics on a Linux server, emailing daily reports, and sending immediate alerts when swap usage becomes critical.