Linux Fundamentals · 3.2

📂 Linux File System & Navigation

Finding your way around the command line⏱ ~3 min

The Linux file system is a tree structure rooted at / (called 'root'). Everything — files, devices, network connections — appears as a node in this tree.

Important Directories

Directory	Contents	Why It Matters
/	Root of the entire file system	Everything starts here
/home	User home folders (/home/alice, /home/bob)	Users' personal files; protect these
/etc	System configuration files	passwd, shadow, group, fstab — critical security files
/boot	Kernel and bootloader files	Don't modify unless you're an expert
/var/log	System log files	auth.log, syslog — investigate attacks here
/tmp	Temporary files; world-writable	Malware often drops files here
/usr/bin	Most user programs and commands	ls, cat, nano, etc.
/sbin /usr/sbin	System administration commands	adduser, ifconfig, service

Essential Navigation Commands

bash

pwd                  # Print Working Directory — where am I?
ls                   # List files in current directory
ls -la               # Long format (-l) + show hidden files (-a)
cd /home/cyberpatriot  # Change to absolute path
cd Documents         # Change to relative path (sub-folder)
cd ..                # Go up one directory
cd ~                 # Go to your home directory
cd -                 # Go back to previous directory

Absolute vs. Relative Paths

•Absolute path — always starts with / and works from anywhere: /home/alice/Documents/report.txt
•Relative path — starts from your current directory: Documents/report.txt (only works if you're in /home/alice/)
•. = current directory, .. = parent directory

Essential File Commands

bash

cat /etc/passwd      # Display contents of a file
cat file1 file2      # Display multiple files concatenated
less /var/log/auth.log  # View large file with scroll (q to quit)
grep 'Failed' /var/log/auth.log  # Search for text in a file
cp source dest       # Copy file
mv source dest       # Move or rename file
rm filename          # Delete file (permanent — no Recycle Bin!)
rm -rf directory/    # Delete directory and all contents (use carefully!)
touch newfile.txt    # Create empty file
mkdir newdir         # Create directory
man ls               # Open manual for any command (q to quit)
ls --help            # Quick help for a command

⚠ Warningrm -rf has no undo. There is no Recycle Bin on the command line. Always double-check your path before running rm commands, especially as root/sudo.

🧠Quick Checkfirst try = +5 XP

Which directory holds Linux system configuration files?

🎮 Practice what you learned

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Password Fort

Build passwords that survive a brute-force siege

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Log Analysis

Hunt attackers through real firewall & access logs

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