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Hectal
Phase 4Intermediate5 of 9 in Linux

Networking & SSH

Inspect connections, open ports safely, and use SSH the way it's actually used in production — keys, not passwords.

A server is nearly useless if you can't reach it or it can't reach anything else. This phase covers the essential command-line networking toolkit and SSH — the single most important skill for actually operating a remote Linux machine day to day.

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4 topics ~53 min 5 code blocks & diagrams
Start with the first topic
1
4.1

IP Addresses, Interfaces & DNS

Every machine on a network has an address, every request to a domain name gets resolved to one of those addresses first, and a handful of commands let you inspect both directly from the terminal.

13 min 1 diagram 1 code practice

2
4.2

Inspecting Connections

ss, lsof, and curl let you answer three of the most common networking questions on a Linux machine: what's listening on this port, what process owns this connection, and does this endpoint actually respond correctly.

13 min 1 code practice

3
4.3

Firewalls & Ports

A firewall decides which network traffic is allowed in or out — and the default-deny mindset (block everything, then explicitly allow only what's needed) is the single most important security habit this topic teaches.

13 min 1 code practice

4
4.4

SSH: Remote Access Done Right

SSH is how you actually operate a remote Linux server — and key-based authentication, not passwords, is how it's done correctly in any real production environment.

14 min 1 code practice