ec2-autohostname

This startup script utilizes the hostname tag of an ec2 instance to set its hostname and update the corresponding entry in Route 53.

Installation

Preparation

1. Create a user and a group for the purpose of updating the DNS. A restrictive group policy for that purpose can be found in ec2-authostname.policy.
2. Adjust the hosted zone ID in the policy to match the ID of your Route 53 hosted zone domain/subdomain. The ID is found in the main overview of hosted zones.
3. ec2-autohostname.template holds three parameters that can (and must!) be customized. Don't modify the file directly, copy it to ec2-autohostname and edit that file.
4. Adjust the aws_access_key_id and aws_secret_access_key to match the newly created user.
5. Adjust the zone_id variable to match the zone ID you retrieved in the second preparation step.

All the variables in the script are marked with Xs.

Using the install script

The install script works for debian squeeze only!

Run ./install-ec2-autohostname and you are done.

Manual setup

1. Copy the script to /etc/init.d/
2. chmod it, so that the script and -- most importantly -- the AWS credentials can only be read by root
3. Use insserv to make it run at boot

cp ec2-autohostname /etc/init.d/ec2-autohostname
chmod 700 /etc/init.d/ec2-autohostname
insserv -d ec2-autohostname

Dependencies

The script depends on the boto python library. The library in the debian package repository does not support Route 53, so you will need to install it via pip:

apt-get install -y python-pip
pip install boto

Bootstrapping

An installation plugin for ec2debian-build-ami is included. Include it by specifying the --plugin parameter like so:

./ec2debian-build-ami --plugin ec2-autohostname/bootstrap-ec2-autohostname

Usage

Specify a tag named hostname in your AWS EC2 interface containing the desired subdomain as a value. When the instance is started the hostname should automatically be updated. Upon shutdown the CNAME is automatically removed. If the hostname is already taken the script will fail and not try to rebind it. Run /etc/init.d/ec2-autohostname status to see what the configured hostname points to and which records point to the current instance.