Monitor disk space on EC2 instance, send email to alert. Install mail, on CentOS/Redhat: yum install mailx on Ubuntu/Debian yum install mailx. See http://tecadmin.net/bash-mail-command-not-found/#. Create the file in home directory "/home" sudo nano diskSpaceAlert.sh, copy the code below and add your email addresses. change the file permissions …

diskSpaceAlert.sh

#!/bin/bash
CURRENT=$(df / | grep / | awk '{ print $5}' | sed 's/%//g')
THRESHOLD=83
SERVER=$(ifconfig | perl -nle 's/dr:(\S+)/print $1/e')
EMAILS="emailAddressHere@gmail.com,anotherEmailAddressHere@gmail.com"

if [ "$CURRENT" -gt "$THRESHOLD" ] ; then
    mail -s 'Disk Space Alert on ELK-STG'  $EMAILS << EOF
Your root partition remaining free space is critically low. Used: $CURRENT%
Please login and clear some space. Elk-Stg-ENV -> $SERVER
EOF
fi