0.2 SSH, key pairs and remote access
You can generate a key pair and log in to a remote machine without a password.
Before:nothing requiredUnlocks:01. Cloud Foundations
SSH is how every remote machine in this subject gets touched, and the key pair is its heart: a private half that never leaves your machine and a public half you hand to servers. This topic covers generating keys, the config file that saves typing, and why servers disable password login entirely. It sits right after the command line because the next forty topics assume you can reach a machine. The classic confusion is which half goes where — the server gets the public key, and anything that asks you to upload a private key is a mistake or an attack.
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Public/private key pairs and what each half is for
A key pair is two matching halves: one you hand out freely and one you never let leave your machine. Which half goes where is the single fact that makes every later authentication step make sense.
ssh, scp and config files
The commands for opening a remote session and copying files across it, plus the configuration file that saves you from retyping host names and options. Setting that file up once pays back every day after.
Why password login gets disabled on servers
Passwords can be guessed at scale by anyone who finds your server, and servers are found within minutes of appearing online. This item is why key-only login became the default rather than a precaution.
Losing a key: what it costs you, and rotation
If the private half is lost you lose access, and if it is stolen someone else gains it. Both cases are survivable only if you planned the replacement beforehand, which is what rotation means.
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