Linux Introduction — File System & Terminal Basics

🎯 Learning Objectives

• Understand Linux history and the philosophy of Unix/Linux
• Navigate the Filesystem Hierarchy Standard (FHS)
• Open and use the terminal effectively
• Understand command syntax and structure
• Use man pages for help

1. What is Linux?

• Open source: Anyone can view, modify, and distribute the code
• Multi-user: Multiple users can use the same system simultaneously
• Multi-tasking: Runs many processes at once
• Stable and secure: Powers most servers, supercomputers, and Android devices

2. The Linux Filesystem Hierarchy

3. The Terminal

bash
# Command structure:
command [options] [arguments]
# Examples:
ls -la /home          # List files with options and path
cp -r source/ dest/   # Copy recursively
grep -i "error" log.txt  # Case-insensitive search

4. Getting Help — man Pages

bash
# Manual page for a command
man ls
man cp
man grep
# Search man pages for keyword
man -k "copy files"
apropos "search text"
# Short description
whatis ls
whatis cp

5. The Shell

• bash: Bourne Again SHell (default on most Linux distributions)
• zsh: Z Shell (enhanced, default on macOS)
• sh: Bourne Shell (original) You can check your shell: echo $SHELL

6. First Commands

bash
# Who am I?
whoami     # Print current username
# Where am I?
pwd        # Print working directory
# What's here?
ls         # List files
ls -l      # Long format (permissions, size, date)
ls -a      # Show hidden files (starting with .)
ls -la     # Combined: long + all
# Navigate
cd /tmp    # Change to /tmp directory
cd ~       # Change to home directory
cd ..      # Go up one directory
cd -       # Go to previous directory
# Print text
echo "Hello, World!"    # Print text
echo $HOME              # Print variable value
echo *                  # Print all files in directory

7. Practice Questions

Q1: What does / represent in Linux?

Answer: The root directory — the top of the filesystem hierarchy. Everything (all files, directories, devices) is under /. Not to be confused with /root (the home directory for the root user). Q2: What's the difference between /bin and /sbin?

Answer: /bin contains essential user commands (ls, cp, cat) that regular users can run. /sbin contains system administration commands (fdisk, mkfs, mount) typically used by the root user. Q3: How do you get help on the grep command?

Answer: man grep (full manual), grep --help (short summary), whatis grep (one-line description), apropos search (search for commands related to "search"). Q4: What does cd .. do?

Answer: Moves up one directory level. If you're in /home/alice/Documents, cd .. takes you to /home/alice. Q5: What is the purpose of /tmp?

Answer: Temporary files directory. Any user or process can write here. Files may be cleared on system reboot. Used for temporary data that doesn't need to persist. Q6: What does ls -la show?

Answer: Lists all files (including hidden ones starting with .) in long format showing: permissions, owner, group, size, modification date, and filename. Q7: How do you switch to a different user on the terminal?

Answer: su username (switch user) or sudo -u username command (run command as user). sudo requires the current user to have sudo privileges. Q8: What does the pwd command do?

Answer: Prints the current working directory (full path from root). Useful when you're lost in the filesystem. No arguments needed.

📐 Key Concepts

🔗 Cross-References

• Next: File Operations Join Discord Next2.1 File Operations