What Is SSH and How to Connect to Another Linux Machine Remotely
Including the fingerprint verification that many accept without understanding.
SSH (Secure Shell) is the standard protocol for controlling another Linux machine remotely, with everything encrypted — from a cloud server to a Raspberry Pi in your own home.
Connecting for the first time
ssh user@ip-address-or-name
Example: ssh pi@192.168.1.50. It will ask for that
account's password (or use your
SSH key
if you've already set one up).
The "fingerprint" message on the first connection
The first time you connect to a new machine, you'll see a message asking whether you trust its "fingerprint". This isn't just a formality — it's a real check that you're connecting to the correct machine, and not another one impersonating it. If you recognise the machine you're trying to connect to, you can safely confirm.
Warning: if on a later connection to a machine you already knew, SSH warns you the fingerprint has unexpectedly changed, don't just ignore the warning — it could mean something as simple as a reinstall of the remote system, but it could also be a sign of a man-in-the-middle attack. Verify through another channel if you have doubts.
Exiting the remote session
exit
Returns you to your own terminal, without affecting the remote machine at all, which keeps running normally.
Changing the default port (optional, more security)
SSH uses port 22 by default — changing to another port doesn't make it "unbreakable", but it does reduce the noise from generic automated scans that probe that default port across the internet.
Frequently asked questions
What happens if I accept the fingerprint of a machine I don't recognise?
You confirm you trust that connection without verifying its real identity — if you don't recognise the machine you're connecting to, it's better to verify through another channel before accepting.
Why did the fingerprint of a machine I already knew change?
It's usually due to a reinstall of the remote operating system, which generates new keys. Even so, if you didn't expect that change, it's worth verifying through another channel before continuing, since it could also indicate a security problem.
Does SSH work the same to connect to my own Raspberry Pi as to a cloud server?
Yes, the protocol and commands are the same regardless of whether the remote machine is at home or on an external server — only the address you connect to changes.