Linux essentials
Everything above this layer assumes you can read permissions at a glance, reason about processes and signals, drive systemd, and find the log you need. This is the true starting path: the shell and filesystem, the permission model, users and sudo, processes and services, and networking and packages — plus a detailed command reference where every core command is shown with a real example and its actual output. Each topic is explained plainly with the security angle a DevSecOps engineer needs. Twenty-five lessons across seven sections, each ending with a self-test.
01File & directory commandsls, cd, cp, mv, rm, mkdir, touch, ln — with output.16 min02Viewing & editing filescat, less, head, tail, wc, nano, vim.14 min03Text processinggrep, sed, awk, sort, uniq, cut, tr.16 min04Finding files & commandsfind, locate, which, whereis, xargs.12 min05Archiving, compression & transfertar, gzip, zip, scp, rsync, curl, wget.14 min06System info & monitoringdf, du, free, uname, uptime, date, who.14 min
01Environment variables & PATHexport, $VAR, .bashrc, and how $PATH works.12 min02Connecting with SSHssh, keys, scp — reach a remote server.12 min03Wildcards, aliases & shortcutsGlobbing, tab-completion, history, chaining.12 min04Scheduling tasks with cronRun things automatically on a schedule.12 min
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Final exam
Test yourself on everything
80 questions drawn from all 7 sections — every answer explained as you pick.