Create route53 entry with the Name tag of an instance, as CNAME to the public DNS entry provided by AWS

update_public_dns.sh

#!/bin/bash

# best to use a dedicated IAM user, see http://cantina.co/automated-dns-for-aws-instances-using-route-53/
# for a guide
export AWS_ACCESS_KEY_ID="your access key"
export AWS_SECRET_ACCESS_KEY="your secret access key"
export ZONE="delegated-to-route53.example.com"
export TTL="600"

# get the aws cli with "pip install awscli"
# run aws configure first or create this manually, e.g.
# root@ip-172-31-14-23:~# cat ~/.aws/config
# [default]
# region = eu-central-1
# aws_access_key_id = your access key
# aws_secret_access_key = your secret access key
shortname=$(aws ec2 describe-tags --filters "Name=resource-id,Values=$(ec2metadata --instance-id)" \
	--output text | grep Name | awk '{print $5}')

# ec2metadata comes with the default installation 
target=$(ec2metadata --public-hostname)

# pip install cli53
cli53 rrcreate $ZONE $shortname CNAME $target --replace --ttl $TTL