SSH access to servers

DevOps
#1

I’m having trouble understanding workflow of SSH access to servers in “SSL & TLS Basics” section of “Devops Pre-Requisite course”

This is all I’ve understood until now:

  1. We can generate new SSH keys with ssh-keygen (private and public key)
  2. We can ssh into server using “ssh -i ~/.ssh/private_key user@<server_IP_address>”

Q) Do we share our public key with server? If so when and how? (How does our key reach ~/.ssh/authorized_keys file)
I want to understand, how does server know which public key to use when a specific user is trying to login into server. What happens under the hood, when we are trying to login.

#2

Let’s start with the “what happens under the hood” part. You need to append your public key to a file on the remote account you want to reach to ~user/.ssh/authorized_keys, using your example.

An easy way to do this is to use the ssh-copy-id command, as so:

$ ssh-copy-id -i ~/.ssh/id_rsa.pub user@<server_ip_address>

This will create the needed directory and file, and give them the correct permissions and ownership.

If you don’t have that command available, then you’ll:

  1. Need to create an .ssh directory on the remote system with “user read only” belonging to user.
  2. Copy your public key into that directory as “authorized_keys”, readable only by user, and belonging to user.

This should allow you to use ssh to get into the system as user “user”, without supplying a password.