"hostfile" an AWS ALB

aws-alias-host

#!/bin/bash

set -e
set -o pipefail

if [ $EUID -ne 0 ]; then
	exec sudo "$0" "$@"
fi

readonly hostname=$1
readonly target=$2

if [[ -z "$hostname" || -z "$target" ]]; then
	echo "Usage: $0 <hostname-to-alias> <elb-dns-name-to-target>" >&2
	exit 1
fi

echo "Updating /etc/hosts entry for $hostname..."
IP=$(dig +short $target a | sort | head -n 1)

if [ $? -ne 0 -o -z "$IP" ]; then
	echo "Could not get IP address" >&2
	exit 3
fi

# Update the hosts file
if test -n "$IP"; then
	hash puppet > /dev/null 2>&1
	if [[ $? -eq 0 ]]; then
		echo "Setting it to $IP via \`puppet resource host $hostname ip=$IP\`"
		puppet resource host $hostname ip=$IP
	else
		echo "Setting it to $IP via tmpfile"
		tmpfile=$(mktemp)
		chown root: $tmpfile
		chmod 644 $tmpfile
		grep -v "\s$hostname\$" /etc/hosts > $tmpfile
		echo -e "$IP\t$hostname"  >> $tmpfile
		mv $tmpfile /etc/hosts
	fi
fi