Standard File Hierarchies

Standard File Hierarchies

Introduction

• Topic 2.3 focuses on the two most common standard file hierarchies: Microsoft Windows and POSIX (Linux).
• These standards dictate the location of important files for the respective operating systems.
• The standardization ensures that the OS and applications can locate essential libraries and data.
• Standardized locations group similar data in known directories, simplifying the system.
• Application developers know where to place and find ancillary components.
• System administrators know where to look for log files and other critical data.
• Even regular end-users benefit from knowing the standard locations of applications and configurations.

Microsoft Windows File Hierarchy

• Users can explore the file system by opening the file browser and navigating to the C drive.
• Key directories:
  • Program Files and Program Files (x86): Store executable system files and end-user applications.
    • 32-bit applications are stored in Program Files (x86) due to Windows' ability to emulate older architectures.
  • Users: Contains home directories/folders for user accounts on the Windows machine.
  • Windows: Contains all operating system resources.
    • Should be treated as read-only.
    • Subdirectories:
      • System32: Contains utilities and libraries.
      • System32\Drivers: Contains drivers for hardware devices.
  • Temp: Contains temporary files created by applications.
    • Files may persist after a reboot and can be cleaned by the OS or user.
• Key differences from POSIX file systems:
  • Devices/hard disks are referenced by a letter followed by a colon (e.g., C:).
  • Paths are separated by backslashes (e.g., Windows\System32).
  • Other operating systems and web browsers use forward slashes in paths (URLs).

POSIX (Linux) File Hierarchy

• POSIX systems are older than Windows and have evolved organically since the 1970s.
• Backward compatibility is crucial, so the structure remains largely unchanged.
• The root of the file system is denoted by a forward slash (/).
• Any other mounted file systems reside within this hierarchy.
• Key directories:
  • /home: User home directories (equivalent to the 'Users' directory in Windows).
  • /tmp: Temporary files.
  • /bin: Important system programs (binary files).
  • /sbin: Important system administration tools.
  • /var: Log files. Subdirectories exist for different services (e.g., web server logs).
  • /etc: System and program configuration files.
    • Configuration files are typically text files, unlike Windows, which uses a registry.
  • /usr: Executable programs, structured text, library files, and documentation used by end-users but not part of the core OS.
    • /usr/bin: Programs created/stored by users.
    • /usr/lib: Library files for user-oriented programs.
    • /usr/share: Documentation, including man pages.

POSIX File System Example

• Demonstration of navigating the POSIX file system using a terminal.
• Commands:
  • pwd: Present working directory. Displays the current directory.
  • cd: Change directory. Used to navigate the file system (cd / goes to the root directory).
  • ls: Lists files and directories in the current directory.
  • ls -l: Long listing, provides more information about files and directories (permissions, size, modification date, etc.).
  • tree: Displays the file system in a tree-like diagram.
    • tree -d -L 1: Restricts the output to directories only and limits the depth to one level below the current directory.
• File types indicated in the long listing:
  • d: Directory.
  • l: Symbolic link.
  • -: Regular file.

Common Files in Linux Root Directories

• /etc: Contains system and application configuration.
  • fstab: Table of file systems mounted at boot.
  • Password files.
  • Network information.
  • Time zone configuration.
• /bin: Essential command binaries.
  • ls: Lists directory contents.

Additional Resources

• Slide 33 lists additional references for learning more about standard file locations for Linux and macOS.