how to login to ec2 machine?

Question

I was given some login information for an EC2 machine, basically an ec2-X-X-X.compute-X.amazonaws.com plus a username and password.

How do I access the machine? I tried

Answer 1

Indeed EC2 (Amazon Elastic Compute Cloud) does not allow password authentication to their instances (linux machines) by default.

The only allowed authentication method is with an SSH key that is created when you create the instance. During creation they allow you to download the SSH key just once, so if you loose it, then you have to regenerate it.

This SSH key is only for the primary user - usually named

• "ec2-user" (Amazon Linux, Red Hat Linux, SUSE Linux)
• "root" (Red Hat Linux, SUSE Linux)
• "ubuntu" (Ubuntu Linux distribution)
• "fedora" (Fedora Linux distribution)

or similar (depending on distribution)

See connection instructions: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AccessingInstances.html

If you want to add a new user the recommended way is to generate and add a new SSH key for the new user, but not specify a password (which would be useless anyway since password authentication is not enabled by default).

Managing additional users: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/managing-users.html

After all if you want to enable password authentication, which lowers down the security and is not recommended, but still you might need to do that for your own specific reasons, then just edit

/etc/ssh/sshd_config

For example: sudo vim /etc/ssh/sshd_config

find the line that says:

PasswordAuthentication no

and change it to

PasswordAuthentication yes

Then restart the instance

sudo reboot 

After restarting, you are free to create additional users with password authentication.

sudo useradd newuser
sudo passwd newuser

Add the new user to the sudoers list:

sudo usermod -a -G sudo newuser

Make sure user home folder exists and is owned by the user

sudo mkdir /home/newuser
sudo chown newuser:newuser /home/newuser

New you are ready to try and login with newuser via ssh. Authentication with ssh keys will continue to work in parallel with password authentication.