INFO 320 Server Technology I

INFO 320Server Technology I Week 1 Server operating system and hardware concepts INFO 320 week 1

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

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

What does an OS do? An OS lets applications use server hardware User CLI or GUI Application API or system calls Interrupts ordevice drivers OS Hardware INFO 320 week 1

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

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

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

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

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

What does an OS do? Process management Interrupts Memory management Storage management and disk access Device drivers Networking Security INFO 320 week 1

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

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

Process management A process can be in three possible states executing Needs data Is preempted Gets data and CPU Gets CPU Gets data waiting ready Needs data INFO 320 week 1

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Security Each file and directory can be controlled to have different privileges for user, group, and other (u-g-o) The allowed privileges are read write (includes create, modify, or delete) execute (application or script) INFO 320 week 1

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

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

OS Examples Unix-like variants Linux FreeBSD openSolaris INFO 320 week 1

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

OS Examples Google Chrome 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

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

INFO 320 Server Technology I