A short script to register or deregister an instance with an Elastic Load-balancer. Will require IAM permissions and is assumed to be run from the instance.

register_or_deregister_with_elb

#!/bin/bash
if [ $#  -eq 0 ]; then
  echo "Usage: $0 register|deregister <LOAD_BALANCER_NAME>"
  echo "e.g. $0 register load-balancer-name"
else
  INSTANCE_ID=$(wget -q -O- http://169.254.169.254/latest/meta-data/instance-id)
  REGION=$(wget -q -O- http://169.254.169.254/latest/meta-data/placement/availability-zone | sed -e 's/\([1-9]\).$/\1/g')
  if [ "$1" == "deregister" ]; then
    aws elb $1-instances-from-load-balancer \
      --load-balancer-name $2 \
      --instances $INSTANCE_ID \
      --region $REGION
  elif [ "$1" == "register" ]; then
    aws elb $1-instances-with-load-balancer \
      --load-balancer-name $2 \
      --instances $INSTANCE_ID \
      --region $REGION
  fi
fi