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.
Copy files between hosts, test ports, scan, trace routes and manage the firewall.
scpCopy files to and from servers over SSHBeginnersftpInteractive and scripted file transfer over SSHBeginnerrsyncSync files and directories efficientlyIntermediatencTest ports and move raw bytes over TCP/UDPIntermediatenmapScan hosts and ports, detect servicesIntermediatetelnetQuick TCP port check (never for logins)BeginneriptablesFilter and NAT packets with netfilter rulesAdvancedfirewall-cmdManage firewalld zones, services and portsIntermediate