Watch each command run in a real-looking terminal, see what every part of it means, then try it yourself with practice tasks. From ls to kubectl.
The first three commands on any server: where am I, what's here, and how full is the disk.
Test reachability and DNS, call HTTP endpoints, connect over SSH, and see which ports are listening.
pingCheck if a host answers and how fastBeginnertracerouteTrace the routers between you and a hostIntermediatedigQuery DNS and read the full answerIntermediatenslookupLook up DNS names quicklyBeginnercurlMake HTTP requests and debug APIsBeginnerwgetDownload files reliablyBeginnersshLog in to remote servers securelyIntermediatessSee listening ports and open connectionsIntermediatenetstatLegacy network statistics (and their ss/ip twins)BeginneripShow and change interfaces, addresses and routesIntermediateifconfigLegacy interface configuration (read it, prefer ip)Beginner