Home IP Change

README.md

What is this

My home IP changes every now and then, I never had this problem with the many years I had Comcast but now with FIOS it happened three times in less than two months. Of course the IP change always happen in the middle of the night.

I have a server running outside my home network. If my home IP changes it can be problematic for several programs running on the server, mostly mail but also the ability to SSH to the server. I would have to log in to the server through the web interface, acknowledge the new IP is me, change the IP in several configuration files, and then restart the services.

I rather do this automatically :)

Requirements

• Your home IP must be registered with a dynamic DNS service.
• Your home cable modem must be able to update the IP with the DNS provider. I'm sure all of them are.

Installation

• Put all four files in a separate directory.
• Update the vars file with the correct information.
• Run the script change-ip through cron as root.

change-ip

#!/bin/sh
SCRIPT=`realpath $0`
SCRIPTPATH=`dirname $SCRIPT`

# Run script to check if the FIOS IP has changed
${SCRIPTPATH}/check-ip

# Script return exit code 127 if it detected a change
if [ "$?" -eq 127 ]; then
	# Load the var
	. ${SCRIPTPATH}/vars
	
# Replace the IP address in the necessary file 
	sed -i "s/${OLD_IP}/${NEW_IP}/g" /etc/shorewall/rules
	sed -i "s/${OLD_IP}/${NEW_IP}/g" /etc/fail2ban/jail.local
	sed -i "s/${OLD_IP}/${NEW_IP}/g" /etc/postfix/rbl_override
	sed -i "s/${OLD_IP}/${NEW_IP}/g" /etc/postfix/postscreen_access.cidr
	sed -i "s/${OLD_IP}/${NEW_IP}/g" /etc/spamassassin/local.cf

	# Compile files and restart services
	cd /etc/postfix
	postmap rbl_override
	systemctl restart fail2ban.service
	systemctl restart shorewall.service
	systemctl restart postfix.service
	systemctl restart spamassassin.service
	echo "FIOS IP Changed. See separate email for more info"
	echo "Old IP: ${OLD_IP}\nNew IP:${NEW_IP}" |  mail -s "FIOS IP Changed" ${EMAIL}
	
	${SCRIPTPATH}/update-ip-vars
fi

check-ip

#!/bin/sh
SCRIPT=`realpath $0`
SCRIPTPATH=`dirname $SCRIPT`

. ${SCRIPTPATH}/vars

CURRENT_IP=`dig +short ${DOMAIN}`

# If the DNS lookup fails the return is empty.
if [ -z ${CURRENT_IP} ]; then
	echo "${DOMAIN} resulted in an empty IP"
	exit 1
fi

# The current IP has changed, recreat the vars file.
if [ ${CURRENT_IP} != ${OLD_IP} ]; then
	exit 127
fi

# Nothing changed, we're all good.
echo "FIOS IP unchanged"
exit 0

update-ip-vars

#!/bin/sh
SCRIPT=`realpath $0`
SCRIPTPATH=`dirname $SCRIPT`

. ${SCRIPTPATH}/vars

CURRENT_IP=`dig +short ${DOMAIN}`

# If the DNS lookup fails the return is empty.
if [ -z ${CURRENT_IP} ]; then
	echo "${DOMAIN} resulted in an empty IP"
	exit 1
fi

# The current IP has changed, recreat the vars file.
if [ ${CURRENT_IP} != ${OLD_IP} ]; then
	echo "DOMAIN=\"${DOMAIN}\"" > ${SCRIPTPATH}/vars
	echo "OLD_IP=\"${NEW_IP}\"" >> ${SCRIPTPATH}/vars
	echo "NEW_IP=\"${CURRENT_IP}\"" >> ${SCRIPTPATH}/vars
	echo "EMAIL=\"${EMAIL}\"" >> ${SCRIPTPATH}/vars
	exit 127
fi

# Nothing changed, we're all good.
exit 0

vars

EMAIL="myemail"
DOMAIN="myhomedomain"
OLD_IP="x.x.x.x"
NEW_IP="x.x.x.x"