Command Conqueror

Command Conqueror is a capture-the-flag game with 10 levels of Linux command line puzzles. It starts with hidden files and ends with a privilege escalation.

Each level drops you into a small Linux system ruled by Lord Tuxi, who leaves you a riddle and hides a flag. Use real commands to find the flag, submit it and climb the leaderboard.

It's free, and you don't need an account to play. Although, you can link it with your Linux Handbook member account and have your progress saved across time and systems.

Quick start

You need Linux or macOS with Docker running, and Python 3.7 or newer. On Windows, use WSL 2.

Download the game and run it:

curl -fsSLO https://ctf.linuxhandbook.com/play.py
python3 play.py

Pick a handle, then choose Command Conqueror from the menu. Type play to enter the first level and start with:

cat hint.txt

When you find a flag (it looks like LHB{...}), copy it, type exit and submit it:

submit LHB{...}

If Docker complains about permissions, run sudo python3 play.py instead. For the full setup, the commands and the FAQ, see the main CTF page.

The levels

Here's what each level tests, without giving anything away.

That's 3,300 points in total. You solve the levels in order, and each one gives its points once.

The first few are friendly if you've used a terminal before. By level 8, you'll be chaining grep, awk and friends together. Level 10 starts you as an ordinary user and asks you to think like an attacker.

Leaderboard

The leaderboard updates live. Players with the same score are ranked by who got there first. A ✓ next to a handle means it's linked to a Linux Handbook account.

Tips

Read the hint more than once. Lord Tuxi likes wordplay, so read the verses closely, not just the words.

Look beyond the folder you start in. Many flags are elsewhere on the system, or held by something that's running.

If you break a level, type restart to get a fresh copy. It doesn't cost you anything.

Brush up on the skills

Stuck on a level? Rather than looking for a walkthrough, read up on the skill it tests. These tutorials cover everything you need.

• hidden files and ls -a
• find command
• quoting and special characters in file names
• tar and unzip
• cron jobs, base64
• ps, netstat/ss, curl with headers
• /proc and process environment
• grep, awk, tr
• hard links and inodes
• SUID permissions

Play fair

The flags are inside the Docker images on your computer, so you could dig them out instead of solving the puzzles. Please don't. You'd skip exactly the part that teaches you something.

And please don't post flags or full solutions. Share how you approached a level instead.