check disk and mail root if >80%

check-disk.sh

#!/bin/sh
df -H | grep -vE '^Filesystem|tmpfs|cdrom|none|udev' | awk '{ print $5 " " $1 }' | while read output;
do
  #echo $output
  usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1  )
  partition=$(echo $output | awk '{ print $2 }' )
  if [ $usep -ge 80 ]; then
    echo "Running out of space \"$partition ($usep%)\" on $(hostname) as on $(date)" |
     mail -s "Alert: Almost out of disk space $usep%" root
  fi
done

set up cron using crontab -e:

0 * * * * /home/strands/check-disk.sh

Run it every full hour...