Check mount for available capacity

Fist we need a shell script that does the checking:

Source code

ADMIN="admin@youradress.com"
ALERT=80
df -H | grep -vE "^[^/]|tmpfs|cdrom" | awk '{ print $5 " " $1 }' | while read output;
do
  usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1  )
  partition=$(echo $output | awk '{ print $2 }' )
  if [ $usep -ge $ALERT ]; then
    echo "Disk space alert: \"$partition ($usep%)\" on $(hostname) as on $(date)" |
     mail -s "Alert: Almost out of disk space $usep" $ADMIN
  else
    echo "Drive \"$partition ($usep%)\" is has enough space left"
  fi
 
done

Then as your system trys to mail you the alert and the mailutil is not install. install it using:

sudo apt-get install mailutils

Now configure mail using ssmtp

Install and configure sstmp

sudo apt-get install ssmtp

sudo nano /etc/ssmtp/ssmtp.conf

Uncomment FromLineOverride=YES by deleting the #

Add those lines for using gmail as an email server

AuthUser=<user>@gmail.com
AuthPass=Your-Gmail-Password
mailhub=smtp.gmail.com:587
UseSTARTTLS=YES

now the script should be working