By default root is not allowed to login to Amazon EC2, but you can login as ec2-user as indicated in the steps below. Once you login with ec2-user you can switch to root.
Step 1 – Download putty from – http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
and execute putty.
Step 2 – In the Session tab , input “ec2-user@ec2-ip address of the remote cloud machine.compute-1.amazonaws.com” ( This information can be found from the Console Management of AWS Instance)
Step 3 – Under Connection -> SSH -> Auth – Browse and choose the ppk certificate. Amazon or as a matter of fact almost all the cloud providers generally allow you download the .pem certificate which you need to convert to ppk certificate using puttygen.exe.
Step 4 – Now you will be logged in automatically.
Step 5- Enter the command sudo su which will enable the root mode (without a password).