If you don't want to setup to a full monitoring solution such as Nagios you can create your own scripts for monitoring the disk space. The following script alerts you when the root partition of server is almost full:
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#!/bin/bash
CURRENT=$(df / | grep / | awk '{ print $5}' | sed 's/%//g')
THRESHOLD=90
if [ "$CURRENT" -gt "$THRESHOLD" ] ; then
mail -s 'Disk Space Alert' test@domain_name.com << EOF
Your root partition remaining free space is critically low. Used: $CURRENT%
EOF
fi
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The script sends an email when the disk usage cross the percentage specified by the THRESHOLD varialbe (90% here).
To run it daily, for example, save the script to the file sample.sh in your home directory, change the email address with your email, and add the following line at the end of /etc/crontab file:
@daily ~/disk_space_alert.sh
