Linux Commands

Navigation Commands

pwd - Print Working Directory

pwd

Displays the full path of the current working directory.

ls - List Directory Contents

ls              # Basic listing
ls -l           # Long format listing
ls -a           # Show hidden files
ls -la          # Long listing including hidden files
ls -lh          # Long listing with human-readable file sizes

cd - Change Directory

cd /path/to/directory   # Change to specific directory
cd ~                    # Change to home directory
cd ..                   # Move up one directory
cd -                    # Return to previous directory

File Operations

touch - Create Empty Files

touch file.txt          # Create a new file or update timestamp
touch file1.txt file2.txt   # Create multiple files

mkdir - Create Directories

mkdir directory         # Create a new directory
mkdir -p dir1/dir2/dir3 # Create nested directories

cp - Copy Files and Directories

cp source.txt destination.txt         # Copy a file
cp -r source_dir destination_dir      # Copy directories recursively

mv - Move or Rename Files

mv old_name.txt new_name.txt          # Rename a file
mv file.txt /path/to/destination/     # Move a file

rm - Remove Files and Directories

rm file.txt             # Delete a file
rm -i file.txt          # Interactive deletion (prompts before deleting)
rm -r directory         # Delete directory and contents recursively
rm -rf directory        # Force delete directory without prompts (use with caution!)

File Viewing Commands

cat - Concatenate and Display File Contents

cat file.txt            # Display entire file content
cat file1.txt file2.txt # Display multiple files

less - View File Content with Pagination

less file.txt           # View file with pagination

Use arrow keys to navigate, press q to exit.

head - Display Beginning of File

head file.txt           # Display first 10 lines
head -n 20 file.txt     # Display first 20 lines

tail - Display End of File

tail file.txt           # Display last 10 lines
tail -n 20 file.txt     # Display last 20 lines
tail -f log.txt         # Follow a file in real-time (useful for logs)

grep - Search Text Patterns

grep "pattern" file.txt         # Search for pattern in file
grep -i "pattern" file.txt      # Case-insensitive search
grep -r "pattern" directory/    # Recursive search in directory

System Information Commands

uname - Print System Information

uname -a               # All system information
uname -s               # Kernel name
uname -r               # Kernel release

df - Disk Space Usage

df                     # Show disk space usage
df -h                  # Human-readable format

free - Memory Usage

free                   # Show memory usage
free -h                # Human-readable format

top - Process Monitoring

top                    # Dynamic real-time view of processes

Press q to exit.

ps - Process Status

ps                     # Show current processes
ps aux                 # Show all processes in detail

User Management Commands

whoami - Print Current User

whoami                # Display current username

su - Switch User

su username           # Switch to another user
su -                  # Switch to root user (with environment)

sudo - Execute Command as Superuser

sudo command          # Execute command with superuser privileges
sudo -i               # Start a shell as root

passwd - Change Password

passwd                # Change your password
sudo passwd username  # Change another user's password (as admin)

File Permissions

chmod - Change File Permissions

chmod 755 file.txt    # Change permissions using octal notation
chmod u+x script.sh   # Add execute permission for user
chmod -R 755 directory # Change permissions recursively

chown - Change File Owner

chown user:group file.txt     # Change owner and group
chown -R user directory       # Change recursively

Network Commands

ping - Test Network Connectivity

ping google.com       # Send ICMP echo requests
ping -c 4 google.com  # Send only 4 packets

ifconfig/ip - Network Interface Configuration

ifconfig              # Show network interfaces
ip addr show          # Modern equivalent

netstat - Network Statistics

netstat -tuln         # Show listening ports

ssh - Secure Shell

ssh username@hostname  # Connect to remote host

Archiving and Compression

tar - Archive Files

tar -cvf archive.tar directory/   # Create archive
tar -xvf archive.tar              # Extract archive
tar -zcvf archive.tar.gz directory/ # Create compressed archive
tar -zxvf archive.tar.gz          # Extract compressed archive

zip/unzip - Zip Files

zip -r archive.zip directory/     # Create zip archive
unzip archive.zip                 # Extract zip archive

Package Management

Debian/Ubuntu (apt)

apt update                        # Update package lists
apt upgrade                       # Upgrade installed packages
apt install package_name          # Install packages
apt remove package_name           # Remove packages

Red Hat/Fedora (dnf/yum)

dnf update                        # Update packages
dnf install package_name          # Install packages
dnf remove package_name           # Remove packages

Redirects and Pipes

Redirecting Output

command > file.txt                # Redirect output to file (overwrite)
command >> file.txt               # Append output to file
command 2> error.log              # Redirect errors to file

Pipes

command1 | command2               # Pipe output of command1 to command2
ls -la | grep "pattern"           # List files and filter with grep

Practice Exercises

1. Navigate to your home directory and create a new directory called "linux_practice"
2. Create five empty files inside this directory named file1.txt through file5.txt
3. Create a text file with some content using a command
4. List all files, including hidden ones, in long format
5. Rename file1.txt to first_file.txt
6. Copy file2.txt to backup_file2.txt
7. Move file3.txt to a subdirectory
8. Delete file4.txt
9. Check how much disk space is available on your system
10. Find all files in your home directory that contain the word "linux"

In the next sections, we'll dive deeper into the Linux file system, permissions, and process management.