RH124 Ch 10: Key-based SSH Logins

The WebAsha automation scripts must log in to serverb without passwords. Set up SSH keys for `student` and `root`, and give student a short alias for serverb.

Tasks

1. As student, generate an Ed25519 key pair in the default location (~/.ssh/ided25519).
2. Install student's public key on serverb so ssh student@serverb no longer asks for a password.
3. As root, set up key-based login from servera to root@serverb (root password redhat).
4. Create an SSH client alias for student: ssh sb must connect to host serverb as user student.