Problem:  Hard drives can fill up, and when they do, no good can come of it.  Wouldn’t you like to be notified before impending disaster so you can correct the situation?

Solution:  Here is a simple script that I put in /etc/cron.hourly (would probably be better in cron.daily, but I’m overly paranoid)

#!/bin/sh
# set -x
# Shell script to monitor or watch the disk space
# It will send an email to $ADMIN, if the (free available) percentage of space is >= 90%.
# ————————————————————————-
# Set admin email so that you can get email.
ADMIN=”[email protected]”
# set alert level 90% is default
ALERT=80
# Exclude list of unwanted monitoring, if several partions then use “|” to separate the partitions.
# An example: EXCLUDE_LIST=”/dev/hdd1|/dev/hdc5″
EXCLUDE_LIST=”/boot”
#
#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
#
function main_prog() {
while read output;
do
#echo $output
usep=$(echo $output | awk ‘{ print $1}’ | cut -d’%’ -f1)
partition=$(echo $output | awk ‘{print $2}’)
if [ $usep -ge $ALERT ] ; then
echo “Running out of space \”$partition ($usep%)\” on server $(hostname), $(date)” | \
mail -s “Alert: Almost out of disk space $usep%” $ADMIN
fi
done
}

if [ “$EXCLUDE_LIST” != “” ] ; then
df -H | grep -vE “^Filesystem|tmpfs|cdrom|${EXCLUDE_LIST}” | awk ‘{print $5 ” ” $6}’ | main_prog
else
df -H | grep -vE “^Filesystem|tmpfs|cdrom” | awk ‘{print $5 ” ” $6}’ | main_prog
fi

Download:  diskalert.sh

Credit:  http://www.cyberciti.biz/tips/shell-script-to-watch-the-disk-space.html