File and Directory Operations

• ls – Lists the contents of a directory.

  ls
  ls -l        # Long listing format
  ls -a        # List all files, including hidden ones
  

• cd – Changes the current directory.

  cd /path/to/directory
  cd ..        # Go up one directory
  cd ~         # Go to the home directory
  

• mkdir – Creates a new directory.

  mkdir new_directory
  

• rmdir – Removes an empty directory.

  rmdir directory_name
  

• cp – Copies files or directories.

  cp source_file destination
  cp -r source_directory destination_directory   # Copy directories recursively
  

• mv – Moves or renames files and directories.

  mv old_name new_name
  mv file_name /path/to/destination/
  

• rm – Removes files or directories.

  rm file_name
  rm -r directory_name   # Remove directories recursively
  

• touch – Creates an empty file or updates the timestamp of an existing file.

  touch file_name
  

File Viewing & Manipulation

• cat – Displays the contents of a file.

  cat file_name
  

• less – Allows you to view file contents page by page.

  less file_name
  

• head – Shows the first 10 lines of a file (default).

  head file_name
  head -n 5 file_name    # Show the first 5 lines
  

• tail – Shows the last 10 lines of a file (default).

  tail file_name
  tail -n 5 file_name    # Show the last 5 lines
  

• grep – Searches for patterns within files.

  grep 'search_term' file_name
  grep -r 'search_term' /path/to/directory    # Search recursively in directories
  

Permissions & Ownership

• chmod – Changes file permissions.

  chmod 755 file_name    # Gives read, write, execute permissions to the owner and read, execute to others
  chmod +x script.sh     # Make file executable
  

• chown – Changes the file owner and group.

  chown user:group file_name
  

• umask – Sets default file creation permissions.

  umask 022   # Sets default permissions to 755 for directories and 644 for files
  

Process Management

• ps – Displays the currently running processes.

  ps
  ps aux      # Show all processes
  

• top – Displays real-time system processes and resource usage.

  top
  

• kill – Terminates a process by its PID.

  kill process_id
  kill -9 process_id    # Forcefully kill a process
  

• htop – Interactive process viewer (requires installation).

  htop
  

System Information

• df – Shows disk space usage.

  df -h      # Human-readable format
  

• du – Shows disk usage for files and directories.

  du -h /path/to/directory
  

• free – Displays memory usage.

  free -h    # Human-readable format
  

• uname – Shows system information.

  uname -a   # Display all system info
  

• uptime – Shows how long the system has been running.

  uptime
  

• whoami – Displays the current logged-in user.

  whoami
  

• hostname – Displays or sets the system's hostname.

  hostname
  

• lscpu – Displays CPU architecture information.

  lscpu
  

Network Commands

• ping – Tests connectivity to a host.

  ping google.com
  

• ifconfig – Displays network interface information (may require net-tools installation on some systems).

  ifconfig
  

• ip – Configures network interfaces and routing.

  ip addr show      # Show IP addresses of network interfaces
  ip route show     # Show routing table
  

• curl – Fetches data from a URL.

  curl https://example.com
  

• wget – Downloads files from the web.

  wget https://example.com/file.zip
  

Package Management

• apt-get (for Debian/Ubuntu-based distributions) – Installs, updates, or removes software packages.

  sudo apt-get update           # Update package list
  sudo apt-get install package  # Install a package
  sudo apt-get remove package   # Remove a package
  

• yum (for RedHat/CentOS-based distributions) – Installs, updates, or removes software packages.

  sudo yum update               # Update package list
  sudo yum install package      # Install a package
  sudo yum remove package       # Remove a package
  

File Compression

• tar – Archives or extracts files.

  tar -czvf archive_name.tar.gz /path/to/directory   # Create a compressed archive
  tar -xzvf archive_name.tar.gz                      # Extract a compressed archive
  

• zip – Compresses files into a zip archive.

  zip archive_name.zip file1 file2
  

• unzip – Extracts a zip archive.

  unzip archive_name.zip
  

Miscellaneous

• echo – Prints a message or variables to the terminal.

  echo "Hello, World!"
  

• date – Displays or sets the system date and time.

  date
  

• alias – Creates an alias for a command.

  alias ll='ls -la'    # Create a shortcut for 'ls -la'
  

• history – Shows the command history.

  history
  

• clear – Clears the terminal screen.

  clear
  

These are just a few of the many powerful commands in Linux, but they cover most of the common operations you'll perform daily.