OPERATING SYSTEMS
(BIT-202)
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Dr. Rahul Sachdeva
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INFORMATION
MANAGEMENT
INTRODUCTION
▪ Information management in operating systems involves the systematic collection,
organization, storage, and maintenance of data.
▪ It is a core function of the OS, enabling efficient access, reliable storage, and secure
handling of system and user data.
▪ The operating system manages various types of information, including:
▪ System configurations
▪ User files
▪ Application data
▪ System logs and temporary files
▪ Effective information management helps maintain:
▪ System stability by ensuring smooth data handling during operations
▪ Performance optimization through organized storage and fast access
▪ Security and protection against unauthorized data access
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KEY COMPONENTS OF INFORMATION
MANAGEMENT
▪ Storage Management
▪ Manages physical storage devices and memory allocation.
▪ Handles allocation and deallocation of storage space.
▪ Ensures data consistency, integrity, and optimal performance.
▪ File Systems
▪ Provide a logical structure to store and organize data.
▪ Define how files and directories are created, accessed, and indexed.
▪ Support various features like large file handling, reliability, and fault tolerance.
▪ Access Control Mechanisms
▪ Manage user permissions and access policies.
▪ Include authentication (user identity verification) and authorization (access level control).
▪ Protect critical data from unauthorized access or modification.
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A SIMPLE FILE SYSTEM (SFS)
• A Simple File System (SFS) is a basic file system designed to manage and
organize data on a storage device efficiently.
• It uses a hierarchical structure where data is organized in a tree-like format of
directories and files.
• The topmost directory is the root directory, which contains all other
subdirectories and files.
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A SIMPLE FILE SYSTEM (SFS)
Structure and Organization
• Subdirectories can contain additional subdirectories or files, creating a nested
hierarchy.
• Files can be of any type: text, images, audio, or binary data.
• Each file is associated with a set of file attributes, including:
• File name
• Creation date
• Size
• Ownership and permissions
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A SIMPLE FILE SYSTEM (SFS)
File Access and Management
• SFS uses file descriptors—unique identifiers assigned to each file for access and
tracking.
• A File Allocation Table (FAT) is used to manage:
• Allocation and deallocation of storage space
• Tracking the physical location of file data on the disk
• When a file is created or deleted, the FAT is updated accordingly by the OS.
Key Features and Use Cases
• Simple to implement and maintain
• Efficient for small systems with limited storage needs
• Serves as a foundational concept for learning more advanced file systems
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KEY GENERAL MODEL OF A FILE SYSTEM
▪ Storage Space
• Physical memory on the storage device where files and directories reside.
▪ Files
• Basic units of data storage.
• Can contain text, images, audio, or program data.
• Have attributes like name, size, type, and creation/modification dates.
▪ Directories
• Special files that hold references to other files and subdirectories.
• Allow hierarchical organization of data (folders within folders).
• File Names
• Unique identifiers for each file.
• Can be simple (file.txt) or hierarchical (/docs/images/file.png).
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KEY GENERAL MODEL OF A FILE SYSTEM
• File Metadata
• Descriptive data about a file such as its size, ownership, timestamps, and access
permissions.
• File Access Methods
• Mechanisms for reading and writing data.
• Common methods: sequential access, direct access, indexed access.
• Allocation Methods
• Techniques used to allocate space to files on disk.
• Common types: contiguous, linked, and indexed allocation.
• The general file system model offers a structured framework to ensure data is
organized, accessible, and manageable.
• It supports essential operations for both users and system processes in managing
stored information effectively. 9
SYMBOLIC FILE SYSTEM (SYMLINK)
• A Symbolic File System refers to the use of symbolic links (symlinks), which are
special files that act as references or pointers to other files or directories.
• Unlike hard links, which directly reference the file's physical data, a symlink
stores a path to another file or directory.
How Symbolic Links Work
• When a program or user accesses a symbolic link, the operating system
automatically redirects to the target file or directory.
• The link behaves as if the original file is being accessed directly, even though
the symlink is a separate file.
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COMMON USES OF SYMBOLIC LINKS
▪ Creating Aliases
▪ Allows access to the same file or directory from multiple paths without
duplication.
▪ Example: Linking a configuration file from /etc/config to
/home/user/app/config.
▪ Redirecting Locations
▪ If a file/directory is moved, a symlink can be placed at the original location to
maintain compatibility with existing programs.
▪ Building File Hierarchies
▪ Used to simulate or simplify complex directory structures, helping organize
large systems efficiently.
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KEY ADVANTAGES OF SYMBOLIC LINKS
Key Advantages
• Saves disk space by avoiding duplicate files.
• Offers flexibility and convenience in system navigation and resource access.
• Simplifies maintenance when paths or structures change.
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BASIC FILE SYSTEM
• A file system is a method used by the operating system to organize, store, retrieve,
and manage digital data on storage devices (e.g., HDD, SSD, USB).
• It defines how data is named, accessed, allocated, and protected.
Key Responsibilities of a File System
• Space Allocation
• Assigns free storage blocks to files and directories.
• Tracking Used and Free Space
• Maintains a record of used vs. available space (via bitmaps, tables).
• Data Recovery and Reliability
• Organizes data to allow recovery after crashes or failures.
• System Integration
• Provides a standard interface for the OS to access, read, write, and manage data.
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COMMON TYPES OF FILE SYSTEMS
▪ FAT (File Allocation Table)
▪ Early file system used in DOS and older Windows systems.
▪ Simple but limited; mainly used in legacy systems and small storage devices.
▪ NTFS (New Technology File System)
▪ Default file system for modern Windows OS.
▪ Supports file permissions, encryption, compression, and large volume sizes.
▪ exFAT (Extended FAT)
▪ Designed for USB drives and SD cards.
▪ Combines FAT’s simplicity with NTFS-like capabilities (large file support, portability).
▪ HFS / HFS+ (Hierarchical File System)
▪ Used in Apple macOS.
▪ Offers features like journaling and metadata support.
▪ Ext2/Ext3/Ext4 (Extended File Systems)
▪ Common in Linux environments.
▪ Ext4 is the latest and most efficient, offering journaling, faster file access, and high reliability. 14
ACCESS CONTROL VERIFICATION
• Access control verification is the process of ensuring that a user is properly
authorized to access a particular file, directory, or system resource.
• It plays a crucial role in maintaining the security, integrity, and confidentiality of
sensitive data within an operating system.
Key Components
• Authentication
• Verifies the identity of the user.
• Common methods include passwords, biometrics, smart cards, or multi-factor
authentication.
• Authorization
• Determines what actions the authenticated user is permitted to perform.
• Controls read, write, execute, or delete access based on policies.
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TYPES OF ACCESS CONTROL MODELS
▪ Role-Based Access Control (RBAC)
▪ Users are grouped by roles (e.g., admin, user, guest).
▪ Permissions are assigned based on the user's role.
▪ Rule-Based Access Control
▪ Access is granted or denied based on predefined conditions or rules, such as time of
access or device used.
▪ Discretionary Access Control (DAC)
▪ The owner of the resource decides who can access it and what actions are allowed.
▪ Common in Unix/Linux using file permission bits (r/w/x).
▪ Mandatory Access Control (MAC)
▪ Access is determined by system-enforced security labels on both users and resources.
▪ Often used in military or government systems.
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LOGICAL FILE SYSTEM (LFS)
• A Logical File System (LFS) provides an abstract and user-friendly view of
physical storage devices.
• It allows users and applications to interact with files and directories without
needing to understand the underlying physical structure.
Key Features of LFS
• Treats physical storage (e.g., HDDs, SSDs) as a collection of files and directories.
• Organizes data into a hierarchical structure using directories and
subdirectories.
• Supports essential file operations:
• Create, read, write, delete files
• Create and remove directories
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LOGICAL FILE SYSTEM (LFS)
User-Friendly Interface
▪ Allows access to files using file names and paths (e.g., /home/user/file.txt).
▪ Makes file navigation intuitive and logical for users and programs.
▪ Enables easy location, retrieval, and organization of data.
Advanced Capabilities
• Tracks file changes, such as modifications or deletions.
• Manages access control to enforce permissions and security policies.
• Supports file metadata (e.g., timestamps, ownership, file type).
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LOGICAL FILE SYSTEM (LFS)
Examples of Logical File Systems
• NTFS – Windows OS
• Ext4 – Linux systems
• HFS+ / APFS – Apple macOS
• Logical File Systems are a core part of modern operating systems.
• They provide a high-level abstraction over physical storage, making
data management easier, secure, and efficient.
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PHYSICAL FILE SYSTEM & FILE SYSTEM
INTERFACE
What is a Physical File System (PFS)?
• A Physical File System is the lowest layer of the file system architecture.
• It directly interacts with physical storage devices like HDDs, SSDs, and flash
drives.
• Responsible for actual data reading/writing, storage block allocation,
fragmentation handling, and wear leveling.
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ROLE OF PHYSICAL FILE SYSTEM
▪ Manages raw storage blocks and ensures correct data placement.
▪ Translates logical file system requests into low-level device operations.
▪ Performs error detection and correction on storage hardware.
▪ Handles device-specific optimizations such as TRIM commands for SSDs.
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PHYSICAL FILE SYSTEM INTERFACE
• Set of operations and data structures used by the OS to interact with physical
media.
• Facilitates essential functions like:
• Read/write blocks of data
• Format and partition drives
• Monitor device health
• Manage free space and perform maintenance operations
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IMPLEMENTED BY STORAGE CONTROLLERS
• Storage controllers act as intermediaries between the OS and the hardware.
• Optimize access speed and ensure reliable data transfer.
• Interface includes utilities for:
• Formatting
• Partition management
• Disk error checking
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IMPORTANCE OF A ROBUST PFS
INTERFACE
▪ Enhances performance by reducing overhead and latency.
▪ Improves system reliability and stability.
▪ Enables efficient storage utilization and long-term device health.
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THANK YOU
Any QUESTIONS?
