Basic Linux Tutorial

1. Introduction to Linux

Linux is an open-source Unix-like operating system kernel, first released by Linus Torvalds in 1991. Today, Linux has become a mainstream operating system in fields such as servers, embedded devices, and supercomputers.

Linux Distributions

Ubuntu – A popular distribution suitable for beginners

CentOS/RHEL – Commonly used in enterprise-level servers

Debian – A stable and reliable distribution

Arch Linux – A rolling release distribution aimed at advanced users

Fedora – A community distribution supported by Red Hat

2. Basic Commands

File System Operations

pwd        # Display current working directory
ls         # List directory contents
ls -l      # Detailed list
ls -a      # Show hidden files
cd directory_name   # Change directory
mkdir directory # Create directory
rmdir directory # Remove empty directory
touch file # Create empty file
rm file     # Remove file
rm -r directory  # Recursively remove directory
cp source target # Copy file/directory
mv source target # Move/rename file/directory

File Viewing and Editing

cat file    # Display file content
less file   # View file page by page
head file   # Show the beginning of the file
tail file   # Show the end of the file
nano file   # Simple text editor
vi/vim file # Advanced text editor

System Information

uname -a    # Display system information
df -h       # Show disk usage
free -h     # Show memory usage
top         # Display process information
ps aux      # Show all processes

Permission Management

chmod permissions file # Change file permissions
chown user:group file # Change file owner
sudo command      # Execute command with superuser privileges
su username      # Switch user

3. User and Group Management

useradd username  # Add user
passwd username   # Set user password
userdel username  # Delete user
groupadd group_name   # Add group
usermod -aG group_name username # Add user to group

4. Network Related Commands

ifconfig      # Display network interface information (old version)
ip addr       # Display network interface information (new version)
ping host     # Test network connection
netstat -tuln # Show network connections and listening ports
ssh user@host # Remote login
scp file user@host:path # Securely copy file
wget URL      # Download file
curl URL      # Transfer data

5. Package Management

Debian/Ubuntu (APT)

sudo apt update         # Update package list
sudo apt upgrade        # Upgrade all packages
sudo apt install package_name    # Install package
sudo apt remove package_name     # Remove package
sudo apt search keyword   # Search for package

RHEL/CentOS (YUM/DNF)

sudo yum update         # Update all packages (YUM)
sudo dnf update         # Update all packages (DNF)
sudo yum install package_name    # Install package (YUM)
sudo dnf install package_name    # Install package (DNF)
sudo yum remove package_name     # Remove package (YUM)

6. Process Management

ps aux           # View all processes
top              # Dynamically view processes
htop             # Enhanced version of top (requires installation)
kill PID         # Terminate process
kill -9 PID      # Force terminate process
bg              # Run suspended process in background
fg              # Bring background process to foreground
jobs            # Display background processes

7. File Permissions

Linux file permissions are divided into three categories:

Owner (u)

Group (g)

Other users (o)

Permission Types:

Read (r)=4

Write (w)=2

Execute (x)=1

Example:

chmod 755 file  # rwxr-xr-x
chmod 644 file  # rw-r--r--
chmod +x file   # Add execute permission

8. Basic Shell Scripting

A simple shell script example:

#!/bin/bash
# This is a comment
echo "Hello, World!"

Run the script:

chmod +x script_name.sh
./script_name.sh

9. Common Shortcuts

Ctrl+C: Terminate current command

Ctrl+D: Exit current shell

Ctrl+Z: Suspend current process

Ctrl+A: Move to the beginning of the line

Ctrl+E: Move to the end of the line

Ctrl+R: Search command history

Tab: Command/file name auto-completion