SSH Between Unix-like Systems - Wed, Jun 12, 2024

Quick SSH setup between two Unix-like systems.

Preface

In this tutorial we are a client setting up an SSH connection to a hypothetical Linux server kokos.cy.

Server Setup

1. On the server, install the openssh-server package. This package provides the server-side of the SSH protocol.

   sudo apt install openssh-server
   

2. Start the SSH service.

   sudo systemctl start ssh
   

   To enable the service to start on boot, run:

   sudo systemctl enable ssh
   

3. Create user accounts on the server.

   sudo adduser nicolas
   

4. Set a password for the user.

   sudo passwd nicolas
   
   Enter new UNIX password:
   Retype new UNIX password:
   passwd: password updated successfully
   

Client Setup

1. Ensure that SSH is installed on the client.

2. Generate a digital signature if you do not have one.

    ssh-keygen -t ed25519 -C "[email protected]"
   

   Note: If you are using a legacy system that does not support the Ed25519 algorithm, you can use RSA:

   ssh-keygen -t rsa -b 4096 -C "[email protected]"
   

3. Then create an alias for the server. Create the file ~/.ssh/config and add:

   Host kokos
       HostName kokos.cy
       user nicolas
   

4. Copy the public key to the server. For this you can use SCP, or manually copy over the key.

   scp ~/.ssh/id_ed25519.pub kokos:~/.ssh/authorized_keys
   

5. You can now login by typing ssh kokos without typing in a password.