Operating Systems

Operating Systems CCNA Discovery 1– Chapter 2

Purpose of an OS • The purpose of an Operating System is to manage the computer system’s data, hardware, software and resources • The OS provides an interface between the user and the computer hardware • The OS acts like a translator between the hardware and user applications

Parts of an Operating System • All Operating Systems share these 3 components: • Kernel • Shell • File System

Parts of an OS: The Kernel • The kernel is the part of the OS code that interacts directly with the computer hardware • It is the core of the OS • The kernel consists of a piece of code that is loaded into memory after boot-up • The kernel code tells the computer how to manage hardware, memory, system processes and applications • On Linux and Unix, there is often a file named kernel • Windows systems have many files with name kern or kernel, which are part of the kernel

Parts of an OS: The Shell • The shell is the part of the OS code that interacts with users and applications • The shell is like a bridge between the user, applications and the kernel, it interprets keyboard strokes, mouse clicks, and other input from the user • The shell also organizes and displays output for the user • There are 2 types of Shells GUI: graphical user interface CLI: command line interface

The GUI vs. the CLI • GUI Characteristics: • The user interacts with graphical elements, like windows, menus and icons, using a keyboard, and mouse • makes tasks easier for the user • takes up more disk space • uses more memory and processing power • CLI Characteristics • The user interacts with a text-based screen using text commands • NOS’s rely mostly on the CLI

Parts of an OS: The file system • The file system determines how and where files are saved on the disk (hard drive) • Windows and Linux both use a hierarchical file system • Files are put in logical containers, and stored in an upside-down tree structure • The containers in Windows are called folders and subfolders • The containers in Linux are called directories and subdirectories • The type of file system used also determines: • Whether files can be secured from other users or programs • How data is physically arranged on a drive • How files are named (ex. Maximum length, illegal characters) • The format for specifying a path, or route, to a file’s destination

FAT File Systems • FAT (file allocation table) is one common type of file system used by OS’s • A FAT table is like a map of files on the hard drive • The FAT table references disk clusters • A cluster is the basic unit of measurement for file storage • A file can be stored on many different clusters, but a cluster can only contain data from 1 cluster • There are 3 different types of FAT file systems: FAT FAT 16 FAT 32

File System Types FAT: the early DOS systems used the original FAT system • Only 8 character filenames are supported, and there is no support for large drives FAT 16:for use on disk partitions up to 4 GB • If you use FAT 16 on larger disks, it just creates larger clusters • Windows 3.x used FAT 16 FAT 32: for use on partitions up to 2 terabytes, it uses smaller cluster sizes • FAT 32 was created to minimize the wasted space of FAT 16 • Windows 9.x can use FAT 16, or FAT 32 • Windows XP can use FAT 32 or NTFS • Windows NT, Windows 2000 can use FAT16, FAT32 or NTFS NTFS – new technology File System is a newer, more secure file system, which can be used by Windows 2000, NT, XP, Vista and Server

Operating System Functions • Operating Systems are designed to have complete control of local hardware resources • They are designed to work with one user at a time. • In order to work with Network Resources an OS needs a redirector • Special software that lets the OS manage network resources • It can be part of the OS or installed as a network client

OS Evolution • Originally, OS’s were designed for stand-alone PCs, so they only allowed 1 user to access files and resources • Desktop computers grew in popularity in the 80’s, and companies began to install LANs (local area networks) to connect these desktop PCs, in order to share data and resources • As networks grew in popularity, there became a need to provide file security, user privileges, and shared resources on LANs • Specialized operating systems were created to meet these needs: the Network Operating System (NOS) • With the growth of networking and the Internet, the line has blurred between a strict OS and a true NOS, many modern OS’s have NOS characteristics

OS vs. NOS • A NOS is a specialized OS that is designed to: • Provide file security • Allow multiple user access to resources • Provide for user privileges • Allows network resources to be treated as local • A NOS is usually run on a server, due to its higher processing and memory requirements • The server provides a centralized point for file storage, shared resources, and security • Users access the server from client machine, which run a regular OS

Operating System Capabilities Most Modern OS’s share these capabilities • Multitasking– more than one application running at the same time • Multiuser – more than one user sharing applications or hardware at the same time • Multithreading – a program that is broken down into smaller parts and run at the same time Some OS’s also support: • Multiprocessing – more than one processor working at the same time

OS Types There are many different OS’s available: • Microsoft Windows: XP, Vista, 2003 Server • UNIX-Based: IBM AIX, Hewlett Packard HPUX, and Sun Solaris • BSD - Free BSD • Linux-Based (Many varieties) • Macintosh OS X • Non-Unix Proprietary: IBM OS/400, z/OS

OS Licensing • Most OS’s require the user to purchase and agree to a commercial license, which allows you to install it on only 1 computer • Users are not allowed to modify the code in any way • Structure support is available for a fee • Development is very structured and changes occur slowly • Some OS’s, like Linux and BSD, operate under the GNU Public licensing • GNU OS’s operate using free software • The GPL allows end-users to modify and enhance the code, if they desire, to better suit their environment. • The OS can evolve and change quite quickly

OS Requirements • Each OS has specific hardware requirements that are needed to run it • RAM amount • Hard drive support • Processor speed and type • Video Resolution • Most OS’s will specify both a minimum and a recommended hardware requirement list • System performance at the minimum hardware requirement is usually poor and only sufficient to support the OS and no other functionality • The recommended hardware is usually the better option and is more likely to support standard additional applications and resources.

Choosing an OS • Many factors must be considered when choosing an appropriate OS: • Does it support the user’s requirements • Does it support the applications that will be run • Does the computer have the necessary hardware to run the OS • What resources and support will be needed to support the OS • You should always consider the TCO (total cost of ownership) when purchasing an OS. This includes: • Cost to buy and install it • All costs required to support it

Disk Partitions • An OS is installed in a defined section of the hard disk, called a disk partition. • Partitioning: involves dividing a disk into sections or logical divisions • Each partition has its own File System • Each partition CAN have its own OS • A disk can have 1 or more partitions

Disk Partitioning • One of the techniques available to help protect data is to divide the hard drive into multiple partitions: • 1 partition for data • 1 separate partition for the OS • Typically a network server is configured with multiple partitions before installing a NOS • Provides for more security and fault tolerance • Data and system files should be kept on separate partitions • Creating a separate swap partition will speed up a server’s performance • Enables an OS to be upgraded without the risk of losing data • Simplifies backup and recovery of data files

Partition Types • Primary partition – the 1st main partition • The active partition, or bootable partition that contains a bootable OS • Always labeled with a C on a windows system • Only the primary partition on a hard drive can be bootable • Win 2000 supports more than 1 primary partition per disk • There can up to 4 primary partitions in a windows/Linux PARTITION TABLE • This would require 4 separate disks • Extended partition – an additional partition, which uses all of the available disk space not used by the primary partition • its really just a placeholder for logical drives • There can only be 1 extended partition in a windows/Linux Partition table • Logical Drives: • a section created inside an extended partition, which can store data • There can be up to 23 logical drives in an extended partition • each logical drive gets its own a drive letter • Separates information, makes data retrieval faster • Can install multiple OS on the same computer

Partition Table • The partition table is stored in the MBR of a hard disk, and contains partition information • Linux and Windows both use a DOS type partition table • Stored in the MBR, in the boot sector of the hard disk • The 1st sector of a hard disk with an OS on it • MBR has a program that finds the 1st sector of a bootable OS and turns control over to that OS • Contains information about which partitions are bootable • Windows and Linux partition Tables Support • Up to 4 primary partitions • In Linux, Numbered 1 to 4 (1 to 3 reserved for Primary) • 1 extended partition • In Linux, Numbered 4 • 23 logical drives • In Linux numbered 5 and up • Unix uses a partition table called a VTOC, which supports up to 8 partitions

Installing an OS • There are various methods for installing an OS. • The method selected for installation is based on : • system hardware • OS being installed • user requirements There are 4 basic options for installing an OS: • Clean Install • Upgrade Install • Multi-boot • Virtualization

Clean Install • Done a new system or when an upgrade is not possible • deletes all data on the partition where the OS is installed and requires application software to be reinstalled

Upgrade Install • Can be done when you stay with the same OS platform • system configuration settings, applications and data are preserved • old OS files are replaced with the new OS files

Multi-Boot • Each OS is contained within its own partition and can have its own files and configuration settings • A start-up menu let the user select the desired OS to boot • Only one OS can run at a time and it has full control of the hardware.

Virtualization • Enables multiple copies of an OS to be run on a single set of hardware (creates virtual machines) • A technique that is often deployed on servers • Each virtual machine can be treated as a separate computer • Enables a single physical resource to appear to function as multiple logical resources.

Pre-Installation Checklist A pre-installation checklist helps ensure that the installation process is successful. • Verify that all hardware is certified to work with the selected OS. • Verify that the hardware resources meet or exceed the published minimum requirements. • Confirm that the appropriate installation medium is available – ex. CD or DVD • If doing an Upgrade: • Use system diagnostic tools and utilities to ensure the current OS installation is in good condition, free of malicious or damaging files and codes • Complete a full backup of all important files. • If performing a clean-install, verify that all application software is available for installation.

Configuring a Computer for the Network • A network is a group of devices, such as computers, that are connected to each other for the purposes of sharing information and resources. • To physically connect to a network, a computer must have: • a network interface card (NIC) • a IP network configuration • An IP address – a unique address that identifies the computer on a network. • Subnet mask- a number used to identify the network on which the computer is connected. • Default gateway- the IP address for the device that the computer uses to access the Internet or another network.

Configuring IP • IP addresses can be assigned in 2 different ways: • Dynamically • The computer requests an address from a pool of addresses assigned by another device within the network • When the computer is finished with the address it is returned to the pool for assignment to another computer • Usually this is done with DHCP services (a DHCP server running DHCP software) • Manually • The IP address is entered into the properties of the NIC by the network administrator • This is a static address and is permanently assigned to that computer.

Installation of an Operating System • Prepare your computer to participate in the network DHCP server

Computer Naming • Some network operating systems and network services use names instead of IP addresses • Each computer on the network should also have a unique name • A computer name provides a user friendly name, making it easier for users to connect to shared resources such as folders and printers • Names must be manually assigned to each device, although some tools do exist to help automate the naming process

Maintaining the OS • Once an operating system (OS) or application is installed, it is important to keep it up to date with the latest patches. • A patch is a piece of program code that can correct a problem or enhance the functionality of an application program or OS • Patches are provided by the manufacturer to repair a known vulnerability or reported problem. • Computers should be continually updated with the latest patches unless there is a good reason not to do so.

Windows Updates • Updates to Windows can be configured in several different ways: • Automatic Install • Updates are automatically downloaded and installed • Prompt for Permission • Updates are automatically downloaded, but the user must choose whether or not to install them • Manual • Major patches, like Service Packs should be manually downloaded and installed

Operating Systems