how to check if root login is disabled on ubuntu server

I tried logging in lightsail instance machine as a root user using the ssh key pair.

The response I received was

Please login as the user "ubuntu" rather than user "root".

I want to know how to check whether login with root is disabled and if it is, how to enable it using ssh keys.

Solution

on Ubuntu, for SSH this is configured via SSH server config: /etc/ssh/sshd_config

in there you should have a row:

PermitRootLogin yes

which is what you're looking for.