Understand the SSH connection

Before choosing a tool or writing more code, make the requirement concrete. The local client verifies the VPS host key before the server checks whether the operator may log in.

SSH protects a client-server connection and separates proof of the server from proof of the user. The useful target is not encyclopedic coverage. Make one deliberate choice, observe its consequences, and know which requirement would make you revise it.

A common failure is to collapse host trust and user login into one vague idea of “the key worked”. The happy path may still work, which makes the mistake easy to miss. draw the handshake in order and identify the credential or key used at each trust decision. Keep the first version small enough that every important input and output remains visible.

This supports the module goal: Connect to the intended host and know exactly which identity, network path, and trust decision made it possible. Capture the request, command, trace, screenshot, test result, or other evidence that proves the result.

Run a verbose connection to the disposable server and annotate the lines for negotiation, host verification, and user authentication. Change one condition on purpose, predict the result, and compare the prediction with what actually happened.