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Linux basics

The handful of shell commands you need to move around, read files and search — the ground every CTF stands on.

Track
Basics
Estimated time
20 min
Level
Beginner
Your progress in this track0%

Before this lesson

Most servers, tools and CTF challenges live on Linux, and you drive it from a text shell. You do not need to be an expert — a dozen commands cover almost everything in the challenges on this platform.

Moving around and reading

terminal
pwd                 # print the current directory
ls -la              # list everything here, including hidden files
cd evidence         # change into the evidence directory
cat note.txt        # print a file
less big.log        # page through a large file (q to quit)

Hidden files start with a dot and are easy to miss — ls -la shows them, and a surprising number of CTF flags hide in a .secret or .bash_history.

Review questionWhich command lists files including the hidden ones that start with a dot?

Searching and inspecting

terminal
grep -r "HTF{" .           # search every file here for the flag format
strings binary.bin         # pull readable text out of a binary file
file mystery               # guess what kind of file something is
xxd data.bin | head        # view the raw bytes as hex
base64 -d token.txt        # decode base64

grep, strings and file are the three you will reach for constantly: find text, pull text out of binary, and identify an unknown file before you waste time on it.

Review questionYou have an unknown file and want readable text that might be inside it. Which command helps most?

Labs

The labs for this lesson are in preparation.

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