Update local hostname entry in /etc/hosts when an interface is brought up

sbin-ifup-local

#!/bin/bash

if [[ "$1" == eth* ]]; then
        echo "this part will be executed right after an interface is up."
        # find out the ip
        IP=$( ifconfig | grep "inet " | head -n 1 | awk '{print $2}' | awk 'BEGIN {FS = ":"} ; {print $2}' )
        # delete the existing lines in the file
        FQDN=`hostname`
        HOSTNAME=`hostname -s`
        sed -i "/${HOSTNAME}/d" /etc/hosts
        # add the correct line
        echo "${IP} $HOSTNAME $FQDN" >> /etc/hosts
fi