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  • 1. INFO 320 Server Technology I Week 1 Server operating system and hardware concepts INFO 320 week 1
  • 2. Overview
    • This course covers basic operating system (OS), server, and architecture concepts
    • Here we’ll mainly focus on server operating systems, though much of their functionality is done by any OS
    INFO 320 week 1
  • 3. Linux and UNIX
    • Much of our emphasis will be on Linux and UNIX, since that’s the OS in most servers
      • The labs will use the Ubuntu distribution of Linux
      • What other kinds of server operating system are there?
      • What kind of operating systems are there, other than server OS’s?
    INFO 320 week 1
  • 4. What does an OS do?
    • An OS lets applications use server hardware
    INFO 320 week 1 User Application OS Hardware CLI or GUI API or system calls Interrupts or device drivers
  • 5. Server hardware
    • So the point of an operating system is to be able to access hardware
    • What hardware does a server have?
      • What hardware characteristics do we care about from the selection or management perspective?
    INFO 320 week 1
  • 6. Possible traits of an OS
    • What are these terms?
      • Multi-user OS
      • Multiprocessing OS
      • Multitasking OS
    • Which of these can a server OS perform?
    INFO 320 week 1
  • 7. Resources and Sharing
    • One way to look at a computer is as a set of resources
      • The CPU of a computer is a resource
      • The memory of a computer is a resource
      • The keyboard of a computer is a resource
      • The hard disk drive of a computer is a resource
    INFO 320 week 1
  • 8. Why consider this way of looking at computers?
    • Since the CPU of a computer operates at extremely high speeds, and since there is a speed differential between the CPU and other resources
    • When the CPU is waiting for another resource, it is essentially wasting time – if the only thing that it is doing is waiting
    INFO 320 week 1
  • 9. Resources and sharing
    • On the other hand if we can have the CPU do something else while it is waiting for a resource we can make better use of the CPU resource – we won’t waste as much of the capability of the resource
    • If we were to do this then we would be able to share the CPU resource among more than a single task
    • The term multitasking derives from this approach
    • Multitasking allows us to share computer resources
    • The sharing of one or more computer resources is controlled by scheduling
    INFO 320 week 1
  • 10. What does an OS do?
    • Process management
    • Interrupts
    • Memory management
    • Storage management and disk access
    • Device drivers
    • Networking
    • Security
    INFO 320 week 1
  • 11. Process management
    • Executing a process means creation of a process by the OS
    • A task is a collection of processes
    • The OS kernel creates a process by assigning it memory, and defining its priority
    • Then the program is loaded into memory, and executed by the (a?) CPU
    INFO 320 week 1
  • 12. Process management
    • In order to multitask, we need a mechanism to share all of the computer resources among the tasks that require it
    • The sharing requires a manager, called the kernel of the operating system
    INFO 320 week 1
  • 13. Process management
    • A process can be in three possible states
    INFO 320 week 1 ready waiting executing Needs data Gets data Needs data Gets data and CPU Gets CPU Is preempted
  • 14. Process management
    • Having multiple processes leads to the need for scheduling
    • Processes are assigned priorities
    • CPU time goes to highest-priority process that is ready
    INFO 320 week 1
  • 15. Interrupts
    • An interrupt is a signal informing a program that an event has occurred
      • Interrupts are handled by the OS kernel, and may come from software or hardware
    • When an interrupt is received, the hardware suspends whatever program is running, and might take other actions
    INFO 320 week 1
  • 16. Interrupts
    • Hardware interrupts might include
      • Keystrokes
      • Inputs from other devices (mouse, printer, etc.)
    • Software interrupts include
      • A program needs to get to hardware (save a file)
      • Program needs more memory
    INFO 320 week 1
  • 17. Memory management
    • The OS kernel includes a memory management unit (MMU)
      • This makes it possible for several processes to share main memory
      • An application deals with logical memory addresses
      • The MMU deals with physical addresses
    INFO 320 week 1
  • 18. Memory management
    • The kernel protects memory usage via swapping, paging, and segmentation
    • Swapping is when a process is temporarily moved to a backing storage location
      • The process is swapped out to storage, then back in
    INFO 320 week 1
  • 19. Memory management
    • Paging manages physical memory space
      • Physical memory is divided into frames
      • Logical memory is divided into pages
      • Frames and pages have the same size, defined by the hardware involved
    INFO 320 week 1
  • 20. Memory management
    • Segmentation is the mapping of logical address space for each process into segments
      • A segment table keeps track of each segment’s name, length, and the offset to find its physical memory location
    • Attempts to address other memory locations results in a segmentation fault interrupt
    INFO 320 week 1
  • 21. Storage management
    • All OS’s need a way to access stored data
    • Data is stored on devices using files and directories
    • Files are structured to allow fast access, improve reliability, and make efficient use of space
    • A file system is a method for storing and organizing data
    INFO 320 week 1
  • 22. Storage management
    • OS activities include
      • Create and delete files and directories
      • Manipulate files and directories
      • Back up files onto storage media
    • UNIX and Linux support Virtual File Systems (VFS)
      • Allows interoperability with Mac and Windows, transparent to the user
    INFO 320 week 1
  • 23. Storage management
    • File system examples
      • Solaris uses Unix file system
      • Linux uses extended file system (ext4)
      • MS-DOS used File Allocation Tables (FAT)
      • Mac OS used Hierarchical File System (HFS), and now supports Unix file systems
      • Windows NT/XP/Vista/7 use NT File System (NTFS)
    INFO 320 week 1
  • 24. Device drivers
    • Device drivers allow software to communicate with specific kinds of hardware
    • Each OS has drivers for each device
    • Hardware manufacturers develop drivers
    INFO 320 week 1
  • 25. Networking
    • Most OS’s support various networking protocols, both open source and proprietary formats
      • What networking protocols might you expect to be supported?
    • Various network architectures are also supported
      • Client/server, peer to peer, hybrid
    INFO 320 week 1
  • 26. Security
    • Within a network, the server OS is a critical security component
      • Controls access to processes, and data
    • Networking aspect also affects external security threats
      • Denial of service, worms, Trojan horses, etc.
    INFO 320 week 1
  • 27. Security
    • Within a network, security is controlled by user and group identification
      • User has a user ID
      • Belongs to a group which has a group ID
      • Anyone else is considered ‘other’ = outside your group
    INFO 320 week 1
  • 28. Security
    • Each file and directory can be controlled to have different privileges for user, group, and other (u-g-o)
    • The allowed privileges are
      • r ead
      • w rite (includes create, modify, or delete)
      • e x ecute (application or script)
    INFO 320 week 1
  • 29. OS Examples
    • Microsoft Windows
      • Huge worldwide market share
      • Windows NT is the basis for Windows 2000, XP, Vista, and 7, plus Windows Server 2003 and 2008
    INFO 320 week 1
  • 30. OS Examples
    • Unix
      • Now over 40 years old, the longest lived family of operating systems
      • Mainly used in business and academia
        • Sun  Solaris (was SunOS)
        • HP  HP/UX
        • IBM  AIX
        • SGI  IRIX (obsolete)
        • NeXT (obsolete, but basis for Mac OS X)
    INFO 320 week 1
  • 31. OS Examples
    • Unix-like variants
      • Linux
      • FreeBSD
      • openSolaris
    INFO 320 week 1
  • 32. OS Examples
    • Macintosh
      • System 1-9
      • OS X and OS X Server (based on BSD Unix)
    • Mainframe OS’s
      • OS/400 (IBM AS/400)
      • DEC VMS and openVMS
      • OS/360 (IBM mainframes e.g. RS/6000)
    INFO 320 week 1
  • 33. OS Examples
    • Google Chrome
      • To be fully released in late 2010?
      • Based on Linux
      • All apps other than the OS kernel will be delivered in a web browser
      • Apps and data are in the cloud, not locally
    INFO 320 week 1
  • 34. OS Examples
    • Real time OS’s
      • Typically used when time-predictable response to many inputs are needed
        • Video or audio processing, system control software, many complex hardware/software systems
      • There are real time versions of Linux, and many other custom OS’s
    INFO 320 week 1