Monitoring Disk Space

cron will send you (root) any output from scripts run by cron. (No output, no report) So create a script (diskcheck.sh) in /etc/cron.daily and put in it:
#!/bin/sh
# Get the remaining percent of drive space and
# report if it is below the warning threshhold

# Percent space remain threshold (integer with NO '%' sign
WARNLVL=15
# Space delimited list of drives to check. eg: "/ /var /home"
DRIVELIST="/ /home"

WARNING=""
for DRIVE in $DRIVELIST ; do
PCT=`df -h $DRIVE | grep -v Filesystem | sed 's@[[:space:]]\{1,\}@ @g' | cut -d \ -f5 | sed s@%@@`
if (($PCT < $WARNLVL)) ; then
WARNING="$WARNING$DRIVE is low on space! ($PCT Remaining) "
fi
done

if [ "$WARNING" != "" ]; thenecho $WARNING
fi
# End script

Do not forget to set the script executable:
chmod 755 /etc/cron.daily/diskcheck.sh

in addition to woody's script i suggest adding
this line..

mail your_email_addr < $VAR_THAT_HOLDS_RESULT

this would eliminate the user to constantly
executing the script... and would just wait for
the mail every morning...

hmm.. and one more thing it would be best if it
would mail the disk space status without any
constraint.. no more warning level..

We use Big Brother (from bb4.com) to monitor our servers - including disk space. This would be overkill for just 1 server, but it is great for monitoring many servers.

If you wanted to, you could also look for a linux disk checking solution at freshmeat.net

Regards,
Mike.