Introduction to Linux

A complete introduction to Linux, from where it came from to writing automation you can trust. It starts with the history and the family tree, gets you a machine you can break, then works through the filesystem, the commands you use every day, users and groups, permissions and the special bits, packages, redirection and the shell's own language, the text processing tools that do most of the real work, bash scripting and scheduling. Twelve hands-on labs, each a real machine reachable from your browser or over ssh. You are an unprivileged user on every one of them: the flag is root owned and mode 0400, you are not in sudoers, and a set-uid checker hands it over only when the work is actually done. The capstone is twenty separate tasks across the whole course on a single box.

1. 1

   What Linux Is, and Where It Came From

   Unix and the habit of small tools, GNU, Linus Torvalds in 1991, why the licence mattered, and the difference between a kernel, a userland and a distribution.

   • Where Linux Came From

   1 quiz

2. 2

   The Family Tree: Distributions

   Debian, Red Hat, Arch and the rest. Package managers, release models, the security distributions, and how to identify a machine you have just landed on.

   • How One Linux Became Hundreds

   1 quiz

3. 3

   Getting Ubuntu Running

   A machine you can break. VirtualBox, the Ubuntu installer, the four things to do immediately afterwards, and getting a terminal you can live in.

   • Getting Ubuntu Running

   1 quiz

4. 4

   The Filesystem Hierarchy

   One tree starting at /. What lives where, absolute versus relative paths, hidden files, and why case sensitivity catches everyone once.

   • The Filesystem Hierarchy

   1 quiz 1 hands-on challenge

5. 5

   Moving Around and Looking

   whoami, id, pwd, ls, cd, man, history and clear, plus the keyboard shortcuts that save the most time.

   • Moving Around and Looking

   1 quiz 1 hands-on challenge

6. 6

   Making Things, and Destroying Them

   mkdir, touch, echo, cat, cp, mv, rm and rmdir. Wildcards, links, and the several ways to lose work.

   • Making and Destroying

   1 quiz 1 hands-on challenge

7. 7

   Users, Groups and Identity

   Where accounts live, uid ranges, creating and removing users and groups, su versus sudo, and reading sudoers.

   • Users, Groups and Identity

   1 quiz 1 hands-on challenge

8. 8

   Permissions and Attributes

   The nine bits, what they mean on a directory, octal, chmod and chown, umask, SUID, SGID, sticky, and the attribute layer underneath.

   • Permissions and Attributes

   1 quiz 1 hands-on challenge

9. 9

   Getting Things Onto the Box

   apt for software from your distribution, wget and curl for everything else, and two habits that keep you out of trouble.

   • Getting Things Onto the Box

   1 quiz 1 hands-on challenge

10. 10

    Redirection and Pipes

    The three streams, and the symbols that decide where each one goes. Greater-than, append, less-than, heredocs, herestrings and the pipe.

    • Redirection and Pipes

    1 quiz 1 hands-on challenge

11. 11

    The Shell's Own Language

    Chaining, the special parameters, history expansion, parameter expansion, exports against locals, set flags, and the quirks that turn up in CTFs.

    • The Shell's Own Language

    1 quiz 1 hands-on challenge

12. 12

    Text Processing: The Tools You Live In

    grep, find, cut, tr, sed and awk, plus sort and uniq, which complete the set.

    • Turning Text Into Answers

    1 quiz 1 hands-on challenge

13. 13

    Bash Scripting

    Shebangs, variables, quoting, arguments, conditionals, loops, functions, exit codes, and the three lines that belong at the top of every script.

    • Bash Scripting

    1 quiz 1 hands-on challenge

14. 14

    Automation: Making It Run Without You

    cron and its four failure modes, systemd timers, backgrounding and tmux, and the habits that make automation you can trust.

    • Automation

    1 quiz 1 hands-on challenge

15. 15

    Capstone: The Whole Box

    Twenty tasks across everything in the course, on one machine, with a checker that marks itself.

    • Capstone: The Whole Box

    1 quiz 1 hands-on challenge