Worried about High Disk Usage???

Well if your running on a *nix box then here is a little cron job that will warn you when usage gets high!

Now assuming you're root, create a sub-dir called scripts.

In this directory place the following script and data files.

===========df.script===============
#!/bin/bash
PATH=/sbin:/usr/sbin:/usr/bin:/bin
cd /root/scripts
if test `df | fgrep -c -f
/home/mashton/df.txt` -eq 0
then
 exit 0
else
 df | mail "$1" -s
DANGER_HIGH_DISK_USAGE
fi
===========df.script===============

The script is executing df (which displays your disk usage), and pipes it through fgrep (which scans the output line by line). I've used the -c (which counts the number of matches) and -f (which tells fgrep to get the matching data from a file).

The if condition tests for a value of 0 (no matches) being returned by the fgrep. If 0 exit else run df and email it to whoever you pass thru from the command line (see crontab below).

===========df.txt===============
104%
103%
102%
101%
100%
99%
98%
97%
96%
95%
94%
93%
92%
91%
90%
89%
88%
87%
86%
85%
84%
83%
82%
81%
===========df.txt===============

Now in the data file I've set what I want fgrep to match for. As you can see I'm testing for anything greater then 80% usage.

This gives you ample time to either clean up or plan for another drive, before you get into the 90% range. Since, this is where *nix filesystem performance starts to slow down.

Also the reason for going to beyond 100% is that typically a *nix filesystem has an overflow buffer which allows for more then 100% capacity. There is typically up to an extra 8% not reported.

Remember to do a change mod on the df.script so it will run!

Now just add it to your crontab and your ready to go!

Just do: crontab -e

Then insert a line for when you want it run (I run mine every half hour and send the failure email to alternating people) and whoever you want it sent to.

=========crontab insert===========
15 * * * * /root/scripts/df.script bryan &>
/dev/null
45 * * * * /root/scripts/df.script mike &>
/dev/null
=========crontab insert===========

By setting this up you can avoid a sudden suprise and having your system crap out on you!

Mike