To obtain the EC2 instance ID from within the EC2 instance itself, you can use the instance metadata service provided by AWS. This service allows you to access various details about the instance, including the instance ID.

You can retrieve the instance ID by making a simple HTTP request to the instance metadata service endpoint. Here's an example using the curl command:

$ curl http://169.254.169.254/latest/meta-data/instance-id

The IP address 169.254.169.254 is a link-local address that is automatically assigned to the EC2 instance, and /latest/meta-data/instance-id is the endpoint that provides the instance ID.

When you run the curl command, it will return the instance ID as the output.

Note that the instance metadata service is only accessible from within the EC2 instance itself. Attempting to access it from outside the instance will result in a connection error.