How do I get ec2 Linux instance info while logged-in on the command-line (public dns, AMI, etc.)

I'm assuming you want to do this from the bash shell rather than with the boto python library or similar...

You should be able to query the metadata service on 169.254.169.254.

e.g.

AMI_ID=$(curl http://169.254.169.254/latest/meta-data/ami-id)

You can get a listing of what meta-data is available with:

curl http://169.254.169.254/latest/meta-data/

This is documented at http://docs.amazonwebservices.com/AWSEC2/latest/UserGuide/AESDG-chapter-instancedata.html

Note: I am more familiar with openstack's metadata service, but that was modelled on the Amazon EC2 service. The quantity and types of data available are different, but accessing it is the same.