Introduction to Linux

1. Operating system

An operating system sits between users and hardware. It manages memory, processes, files, and devices while exposing a graphical or command-line interface.

Common operating systems

• Linux
• iOS
• Android
• macOS
• Windows

Linux distributions

Examples include Ubuntu, Fedora, Arch, Debian, and openSUSE.

A Linux distribution is the combination of the Linux kernel, user space tools, and the shell environment.

---

2. Terminal and shell basics

The terminal gives users a text-based interface to run commands.

Typical terminal prompt

• environment indicator
• username
• hostname
• current directory
• time
• prompt symbol

Command flow

1. The user types a command.
2. Press Enter to send it to the shell.
3. The shell interprets and executes it.
4. The shell prints the result.

---

3. Useful shell commands

echo "hello"
echo $HOME
man ls
clear
date
which python
uname -a
whoami
top

echo

echo -n "No newline"
echo -e "Hello\nWorld"

man

man man

---

4. File system layout

Linux uses a single root filesystem:

• / root directory
• /bin/ system binaries
• /dev/ device files
• /etc/ system configuration
• /home/ user home directories
• /mnt/ mounted external filesystems
• /tmp/ temporary files
• /usr/ user programs and shared files

ls

ls -lh /

Permissions

Permissions are usually shown as rwx r-x r-x for owner/group/others.

chmod 755 file.txt
chown user file.txt

---

Summary

Linux is a foundational operating system for software development, servers, and data science workflows. Learning the shell, filesystem, and permissions is essential for effective daily use.