What is the easiest way to get a EC2 public dns inside a running instance?

Question

I'm writing a bash script that needs to use the instance's public dns name. What's the easiest way to obtain it from inside the running instance?

Answer 1

You can fetch data about the running instance from a little http API using curl like this:

#/bin/bash
public_name=$(curl -s http://169.254.169.254/latest/meta-data/public-hostname)
echo $public_name

Other values you can fetch include:

• ami-id
• hostname
• instance-id
• local-ipv4
• local-hostname
• public-hostname
• public-ipv4

There are more but those are some of the most useful. Things like the SSH keys you specify at instance launch can also be retrieved from there.