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Linux Basics

Linux is a powerful open-source operating system. As a contributor, understanding basic command-line usage is key. This guide covers essential commands, system updates, and best practices for command-line work.

Basic Linux Commands

The command line is your main interface. Here are core commands you'll use often:

  • ls (list): Shows directory contents.
    • ls: Lists files and directories in the current location.
      • Example: ls might output documents images myproject.txt
    • ls -l: Provides a "long listing" with details like permissions, size, and date.
      • Example: ls -l might show -rw-r--r-- 1 user group 1024 Jul 10 10:30 myproject.txt
    • ls -a: Shows all files, including hidden ones (starting with a .).
      • Example: ls -a might reveal .bashrc .config documents
  • cd (change directory): Navigates between directories.
    • cd <directory_name>: Moves to a specific directory.
      • Example: cd documents
    • cd ..: Moves up one directory level.
      • Example: If in /home/user/documents, cd .. moves to /home/user/
    • cd ~: Returns to your home directory.
      • Example: No matter where you are, cd ~ takes you to /home/user/
  • pwd (print working directory): Displays your current directory's full path.
    • Example: pwd might output /home/user/myproject
  • mkdir (make directory): Creates a new directory.
    • Example: mkdir new_folder
  • rmdir (remove directory): Deletes an empty directory.
    • Example: rmdir empty_folder
  • touch: Creates an empty file or updates a file's timestamp.
    • Example: touch new_file.txt (creates a new empty file)
  • cp (copy): Copies files or directories.
    • cp <source_file> <destination_file>: Copies a file.
      • Example: cp report.docx report_backup.docx
    • cp -r <source_directory> <destination_directory>: Copies a directory and its contents.
      • Example: cp -r myproject myproject_copy
  • mv (move): Moves or renames files/directories.
    • Example (move): mv old_file.txt documents/ (moves old_file.txt into the documents folder)
    • Example (rename): mv old_name.txt new_name.txt
  • rm (remove): Deletes files or directories.
    • rm <file_name>: Deletes a file.
      • Example: rm unwanted_file.txt
    • rm -r <directory_name>: Recursively deletes a directory (use with extreme caution!).
      • Example: rm -r old_project_folder (Deletes the folder and everything inside it)
  • cat (concatenate): Displays a file's content.
    • Example: cat README.md (shows the content of the README.md file)
  • less / more: Views file content page by page for large files.
    • Example: less /var/log/syslog (allows you to scroll through a large log file; press q to quit)
  • grep: Searches for text patterns within files.
    • Example: grep "error" /var/log/syslog (finds all lines containing "error" in the syslog file)
  • man (manual): Provides documentation for commands.
    • Example: man ls (shows the manual page for the ls command; press q to quit)

How to Update and Upgrade the System

Keeping your system updated is vital for security and new features. For Debian-based systems (like Ubuntu), use apt:

  • sudo apt update: Refreshes the list of available packages from repositories.
    • Example: sudo apt update (You'll see a list of package information being downloaded)
  • sudo apt upgrade: Installs newer versions of all currently installed packages.
    • Example: sudo apt upgrade (Prompts you to confirm the installation of available updates)
  • sudo apt full-upgrade: Performs a more comprehensive upgrade, installing new packages if needed for dependencies and removing obsolete ones.
    • Example: sudo apt full-upgrade (Use for major system version upgrades or when upgrade is insufficient)

To update:

  1. Open your terminal.
  2. Run sudo apt update.
  3. Then, run sudo apt upgrade.
  4. Optionally, use sudo apt full-upgrade for a deeper update.

How sudo and apt Work

  • sudo (SuperUser DO):

    • Function: Allows you to run commands with root (administrator) privileges using your own password.
    • When to use: For tasks requiring elevated permissions, like installing software, modifying system files, or managing services.
    • Caution: Always be careful with sudo; incorrect commands can harm your system.
      • Example: sudo systemctl restart apache2 (restarts the Apache web server, requires root privileges)

  • apt (Advanced Package Tool):

    • Function: A command-line utility for managing software packages (installing, updating, removing) on Debian-based systems. It interacts with software repositories.
    • When to use:
      • apt install <package_name>: Install new software.
        • Example: sudo apt install git (installs the Git version control system)
      • apt remove <package_name>: Uninstall software (leaves configuration files).
        • Example: sudo apt remove firefox
      • apt purge <package_name>: Uninstall software and its configuration files.
        • Example: sudo apt purge apache2
      • apt search <keyword>: Find packages.
        • Example: apt search text editor (lists available text editor packages)

Tips for Command-Line Navigation and Safety

Here are some best practices to make your command-line work more efficient and secure:

  • Tab Completion: Press the Tab key to auto-complete commands, file names, or directory names. Press Tab twice to see all available options if there's more than one.
  • Arrow Keys: Use the Up and Down arrow keys to cycle through your command history. This saves typing and helps recall previous commands.
  • Ctrl+R (Reverse Search): Press Ctrl+R and start typing to search your command history for a specific command. It's incredibly useful for finding a command you ran a while ago.
  • Read the Manual (man): If you're unsure about a command or its options, use man <command_name> for detailed documentation. Press q to quit the manual.
  • Be Careful with sudo: Always double-check your commands before pressing Enter when using sudo. Commands run with root privileges can make significant, irreversible changes to your system if executed incorrectly.
  • Backup Regularly: Make a habit of backing up important files and configurations, especially before performing major system changes or software installations. This can save you from potential data loss.