Monitor disk usage and send email when disk is nearly full

Linux

Author

Vinh Nguyen

Published

October 17, 2010

This site and this site describe some scripts to monitor disk usage of a computer based on the df command and email the ADMIN when disk usage reaches a certain percentage. The scripts can be ran periodically based on cron.

These scripts did not work on my local NAS because I have one filesystem called /dev/mapper/acer-root that takes up two lines in the output of df; hence, the scripts run into an error when trying to grab the 5th column of the output. Also, in recent versions of Ubuntu, /bin/sh is symbolically linked to dash; to get the scripts to work, remove the function keyword or change to /bin/bash on the shebang (#!) line in order for the scripts to run.

I adapted a script found on this site for my own use:

#!/bin/bash
## adapted from
## http://www.unix.com/unix-dummies-questions-answers/100941-email-warning-script-disk-usage.html
#### check disk space on filesystems listed
filesystems=(/ /boot /h2tb)
for fs in ${filesystems[@]}; do
disk_space=`df -h | grep -E $fs$ | awk '{print $(NF-1)}'`
max_space="80"
disk_space=${disk_space:-$((max_space-1))}
##[[ "${disk_space%'%'}" -ge "$max_space" ]] && { clear ; echo -e "nWARNING...DISK SPACE ON "$fs" IS AT $disk_spacen"; }
[[ "${disk_space%'%'}" -ge "$max_space" ]] && { echo "" | mutt -s "WARNING...DISK SPACE ON "$fs" IS AT $disk_space" MY.EMAIL.ADDRESS ; }
done
unset filesystems fs disk_space max_space
####

Note that I use mutt to send emails; mail would be simpler and more portable, but it isn't set up on my server.

I added the following to cron via crontab -e to get the script to run hourly:

0 * * * * /path/to/diskAlert.sh