aws-ip-rotator.sh

#!/usr/bin/env bash

case $1 in
    'start')
        SCHEDULE='*/10 * * * *' # every ten minutes
        (crontab -l 2> /dev/null; echo "$SCHEDULE $(pwd)/$(basename $0)") | crontab - ;;
    'stop')
        crontab -l | grep -v $(basename $0) | crontab - ;;
    *)
        INSTANCE=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)
        OLD_IP=$(curl -s http://169.254.169.254/latest/meta-data/public-ipv4)
        OLD_ALLOCATION=$(aws ec2 describe-addresses --public-ips $OLD_IP --query Addresses[0].AllocationId --output text)
        NEW_IP=$(aws ec2 allocate-address --query PublicIp --output text)
        echo ''
        echo "Old IP: $OLD_IP"
        echo "New IP: $NEW_IP"
        echo ''
        echo 'Associating new IP...'
        aws ec2 associate-address --instance-id $INSTANCE --public-ip $NEW_IP
        echo 'Releasing old IP...'
        aws ec2 release-address --allocation-id $OLD_ALLOCATION
esac