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Lecture 10

Operating System Fundamentals

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Operating System Basics

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Overview of PC Operating Systems

Desktop microcomputers became popular in the early 1980s.

Users of these PCs put their systems to work performing a variety of tasks, including word processing, home accounting, and computer gaming.

Workplace productivity was limited by their inability to share information easily with other systems.

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The Kernel Kernel is the most common term for the core of the operating system. It is a small piece of code that is loaded into memory when the computer boots. The kernel manages and controls memory allocation, system processes, and other programs.Application software and other parts of the operating system rely on the kernel to provide basic scheduling services and access to the computer hardware and peripherals.

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The User Interface (UI)

The UI is the component of the OS that the user interacts with. The UI is like an interpreter, translating user keystrokes, mouse clicks, or other input for the appropriate programs. A graphic user interface (GUI) allows the user to manipulate software using visual objects such as windows, pull-down menus, pointers, and icons. A CLI (command line interface) is a user interface to a computer's operating system or in which the user responds to a visual prompt by typing in a command on a specified line, receives a response back from the system, and then enters another command, and so forth.

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The File System The file system of an OS determines the way files are named and how and where they are placed on storage devices, such as hard disks. Windows, Macintosh, UNIX, and Linux OSs all employ file systems that use a hierarchical structure In a hierarchical file system, files are placed in logical containers that are arranged in an upside-down tree structure.

UNIX and Linux call these containers “directory” and “subdirectory”.

Windows and Macintosh OSs use the term "folder" and "subfolder“.

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The File System (Cont …)

The file system of an OS determines more than just how files and folders are logically organized.

The type of file system used by the computer determines whether or not files can be secured from other users or programs.

The file system also defines how data is physically arranged on the storage media (such as a hard drive).

Some file systems use disk space more efficiently than others

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OS and File Systems

Different operating systems use different file systems, and some operating systems can use more than one file system. For example, although Windows 3.x can use only the FAT16 file system, Windows 2000/XP can use FAT16, FAT32, or the New Technology File System (NTFS).

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OS and Their File Systems

OS Native File Systems

Windows 3.x FAT16

Windows95, 98, ME FAT32

WindowsNT, 2000 NTFS

Windows XP NTFS (or NTFS5)

IBM OS/2 HPFS (High Performance File System)

Linux ext2/ext3,

Note: Filesystem for CDROM is ISO9660.

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Common Desktop Operating Systems

Microsoft Disk Operating System (MS-DOS) is an obsolete OS that is still used to support legacy business applications. Microsoft Windows includes Windows 95, 98, ME, NT, 2000, and XP.Apple Macintosh OS (Mac OS) includes OS 8, OS 9, and OS X (OS 10).Linux includes distributions from various companies, such as Red Hat, Caldera, Santa Cruz Operation (SCO), SuSE, and others.UNIX includes HP-UX, Sun Solaris, and others.

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Networking Operating System Overview

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Common Network Operating Systems

The limitations of early desktop OSs led to the development of more powerful NOS softwareNOSs provide built-in networking components and network services, multiuser capability, and sophisticated file security and file sharing technologies. Common NOSs in use today include:

Microsoft Windows 2000/2003 Server

Novell NetWare Linux Unix

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Windows and Linux NOS Comparison Windows has been marketed as a user-friendly, graphical interface (GUI), desktop operating system.The roots of Linux begin with UNIX and with that modular design made Linux a very popular choice among system administrators to run their servers.

Text-mode interface functionalityCostObtaining the OSAbility to run from a CDAvailable application software and obtaining application softwareVirus vulnerabilitySecurity featuresSupporting multiple users

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The Client-Server Model Most network applications, including Internet-related applications such as the World Wide Web (WWW) and e-mail, are built around a client/server relationship.A server offers network services, such as e-mail to other programs called clients. Once enabled, a server program waits to receive requests from client programs. If a legitimate request is received, the server responds by sending the appropriate information back to the client.

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The Client-Server Model

Any computer can act as a server as long as it is connected to the network and is configured with the appropriate software.

Most organizations put all of their key network services on high-end computers called servers running NOSs optimized for servicing remote clients.

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Network/NOS Services Networking operating systems are designed to provide network processes to clients and peers. Network services include the World Wide Web (WWW), file sharing, mail exchange, directory services, remote management, and print services. Most popular network processes rely on the TCP/IP suite of protocols.

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Directory Services

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What is a Directory Service? A directory service is a software application that stores and organizes information about a computer network's users and network resources, and that allows network administrators to manage users' access to the resources.

A directory service provides system administrators with centralized control of all users and resources across the entire network.

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What is a Directory Service?Shared resources are published to the directory

Users can locate and access them without ever knowing on which machine the resources physically reside.

The files, directories, and shares that users access from a single point can be distributed across multiple servers and locations using distributed directory and replication services.

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Directory Service Standards To operate within a NOS, different directory services need to have a common method of naming and referencing objects.

X.500 defines the Electronic Directory Service (EDS) standards.

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Windows 2000/2003 Active Directory

To use Active Directory, at least one server must be configured as a Domain Controller (DC).

It is recommended that there be at least two DCs in each domain, for fault tolerance.

Replication is the process of copying data from one computer to one or more other computers and synchronizing that data so that it is identical on all systems.

Active Directory uses multimaster replication to copy directory information between the domain controllers in a domain.

Each object in Active Directory has an Access Control List (ACL) that contains all access permissions associated with that object. Permissions can be either explicitly allowed or denied.

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Domains A domain is a logical grouping of networked computers that share a central directory or database. Domains have several advantages:

Centralized administration since all user information is stored centrally.

A single logon process that enables users to access network resources as well as specify permissions that control who can and cannot access these services.

The ability to expand a network to extremely large sizes throughout the world.

DomainWorkgroup

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Network Information Service (NIS) - LinuxLinux uses its own version of Directory Services called the Network Information Service (NIS).

The network consists of the NIS server, slaves, and clients.

The NIS Servers is where the NIS database is created and maintained.

The NIS slaves act the same way as NDS servers act in Novell.

The NIS databases are copied to all the NIS slave servers.

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Characteristics of a Network Operating System

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Overview of NOS Characteristics

Network operating systems (NOSs) distribute their functions over a number of networked computers.

It then adds functions that allow access to shared resources by a number of users concurrently.

NOS computers take on specialized roles to accomplish concurrent access to shared resources.

Client systems contain specialized software that allows them to request shared resources that are controlled by server systems responding to a client request.

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Differences Between PC and a NOS The NOS enhances the reach of the client PC by making remote services available as extensions of the local native operating system.

Although a number of users may have accounts on a PC, only a single account is active on the system at any given time.

NOS supports multiple user accounts at the same time and enables concurrent access to shared resources by multiple clients.

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Multiuser, Multitasking, and Multiprocessor Systems

A NOS server is a multitasking system. Internally, the OS must be capable of executing multiple tasks or processes at the same time.

Some systems are equipped with more than one processor, called multiprocessing systems.

They are capable of executing multiple tasks in parallel by assigning each task to a different processor.

The aggregate amount of work that the server can perform in a given time is greatly enhanced in multiprocessor systems.

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NOS Server Hardware NOS servers are large systems with additional memory to support multiple tasks that are all active, or resident, in memory at the same time.

Additional disk space is also required on servers to hold shared files and to function as an extension to the internal memory on the system.

Because a NOS depends on the continuous operation of its servers, the extra hardware components justify the additional expense.

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Microsoft Windows

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Windows 2000/XP Operating SystemXP also offers:

More extensive hardware and driver support. More user-friendly file-sharing and network configuration for setting up home networks. Enhanced wireless network features Increased security Remote Desktop control Overall improvements to the GUI, including the welcome screen additions, start menu improvements.Enhanced multimedia support for digital video, audio, and pictures.

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Windows 2000/XP Operating System The offline folders feature enables users to copy and synchronize documents from the network to the local system so that they can be accessed when the computer is not connected to the network. The Internet Printing Protocol (IPP) enables users to print to a URL and manage printers through a web browser interface. Built-in disk defragmenters and other tools and utilities help users maintain and manage the operating system. It supports Kerberos security (developing standard for authenticating network users), and the features of a Windows 2000 domain as an Active Directory client.

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Linux

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Linux Operating System

Linux is sometimes referred to as "UNIX Lite", and it is designed to run on Intel-compatible PCs. However, Linux will run on other machines as well. Linux brings the advantages of UNIX to home and small business computers. The following are a few of the most popular types:

Red Hat Linux Fedora Core Linux Mandrake Caldera eDesktop and eServer Debian GNU/Linux Corel Linux Turbo Linux Ubuntu CentOS SuSe

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Linux Clients / ServersWindows clients can access Linux servers without client software if the UNIX servers run Samba, which is a program that uses the Server Message Block (SMB) application layer protocol.

Windows computers use SMB for file access across the network.

Samba permits them to see the Linux file system.