Understanding Linux Network Internals - Case Study Example

Linux MUOS Report Introduction An operating system (OS) is a set of basic programming instructions to computer hardware, forming a layer of instructions on which other applications and functions of the computer are built. The programming code that is the core of the operating system is called the kernel. Code is a general term that refers to instructions written in a computer programming language. A multiuser system is one that supports multiple users who are accessing the computer’s and operating system’s hardware and software facilities. Servers, such as a Linux or Windows Server, 2009, can provide real-time access to numerous users on a network. Most multiuser systems use preemptive, multitasking technology. These systems are intended to handle up to about 10 simultaneous users before they buckle under the load. A server system can typically handle hundreds of users at once. Linux is a UNIX look-alike system that is popular as a server operating system in business, education, and government and is rapidly replacing UNIX (Benvenuti 2006). Linux operating systems are particularly popular for servers because they take advantage of a huge open source software community. Open source software is typically developed by thousands of volunteers, relies on peer review, contains code in the public domain, and is typically distributed free. The principle features of a multi-user operating system Resource Sharing One of the critical responsibilities of an OS is to manage the available resources such as memory, or processor time. Multiuser systems must implement an execution setting in which several processes can be active concomitantly and compete for system resources, mainly the CPU (Bovet and Cesati n.d.). Even though a computer has two or more CPUs, it is still important that one user does not dominate all of the time on a CPU; the computer might appear to hang and possibly crashing the computer. The operating system uses specialized programs called resource managers to ensure that memory is used properly without any memory conflicts (Palmer and Walters n.d., p. 12). The operating system will give each user a time slice on the CPU. Each user does a little work during its time slice and then hands the CPU access over to the next user for its time slice. Multi-tasking Multitasking is another crucial feature of a multiuser operating system. A multitasking OS can handle more than one processor, as the jobs are executed different processors. (Buchanan 1999, p. 42). The running state of the program is called a process or task. A multitasking OS supports two or more simultaneously executing processes. A multiuser OS allows concurrent admittance to a computer system via two or more terminals. Although commonly associated with multiprogramming, multiuser OS does not imply multitasking. A multiuser system usually breaks the disk space up into user directories, so that each user has his data files in a separate place (Baldwin 1986, p. 271). Background Processing In a multiuser operating system, two or more active processes are permits. During the execution of such processes, the OS protects the memory space reserved for one process from other processes. Out of multiple processes, most of these systems only process and recognize input from mouse, keyboard, or other input devices (Yadav 2010, p.146). This process is known as the foreground processes. The rest of the processes are said to be background processes. Background processes cannot accept interactive participation from a user, but they can access information stored on a disk, ready to write it to the video display. In a large multiuser OS, the number may be hundreds of processes running, with each having several active services at once. In fact, even though no users use the system that is running, dozens of background processes, called daemons (Liu, Yue, & Guo 2011, p. 82), are executing. Types of multi-user operating system Multi-processor There are many types of multiuser operating systems, which work in different ways, intended for completely different purposes. One of these is the multiprocessing system. This is one that executes many processes concurrently. In a unit-process system, when the lone system executes a wait operation, the processor would sit idle and waste time until the process comes out of the wait state. The objective of multiprocessing is to have a process running on the processor at all times (Haldar & Aravind 2010, p.82). Multiprocessing can be done in two ways called asymmetric and symmetric multiprocessing. In asymmetric multiprocessing, different jobs may be allocated to different processors. The disadvantage of asymmetric multi-processing is that some processors may be overloaded while other processors remain idle (World 1990, p.84). In symmetric multiprocessing, the same job may be executed simultaneously at different processors. Time-sliced In a time-sharing system, several users can share the computer resources concurrently. Given that each action and command in a time-shared system takes an extremely minute fraction of time, only a tiny CPU time is desired for each user. As the CPU toggles rapidly from one user to another, each gets the notion that he has his own computer, while in actuality it is one computer being shared among many users. Most time-sharing systems use time-slice or round robin scheduling of CPU. By using this approach, programs are carried out with rotating priority that amplifies when programs are waiting and reduces after the service is granted (Chaudhury 2010, p.32). In order to prevent a program from monopolizing the CPU, the OS interrupts a program that uses allocated processes longer than the multiuser system defined time-splice. Distributed The logical aggregation of several operating systems over an independent operational node is referred to as distributed. These operational nodes contain individual programs that can be shared across a network. The kernel and microkernel control the hardware on a low level, while functions of the microkernel manage the individual applications (Chaudhury 2010). Main components of a multi-user system Processor A vital part, without which the OS would not function, is the processor. Processors were originally developed with a single core. The core is the component of the processor that actually reads and executes instructions (Carswell, Shen, & Freese 2011, p. 48). Single-core processor can only carry out a single instruction at a time. Conversely, a multi-core processor system contains over two independent cores. It can be described as an IC (integrated circuit) to which more than two individual processors have been integrated. For instance, a dual-core processor family has two cores, whereas a quad-core processor has four embedded cores. The OS manages the memory by finding all available free space in the memory and allocating it to the processes. Every job under execution requires memory. In case, any job execution has to be suspended or terminated, the operating system combines the memory freed and allocated the memory to other processes (Bajpai 2007). The operating system, therefore, decides which process gets memory, when and how much and then allocates the memory when that process requires it. Data Storage Devices For the various devices in the computer system, the device manager provides an appropriate level of abstraction to handle system devices. For every device type, a device driver program is included in the OS. This includes input and output devices, and data storage devices. The device manager operates in combination with the resource manager and the file manager. The data storage devices act as the store for an information system. They store both processes and raw data. (Garrido, Schlesinger, & Hoganson 2011, p. 7). Terminals In the first few years of large multi-user computers, multiple terminals, such as keyboards and their associated monitors, were provided. The terminals sent commands to the central multi-user computer for processing, and the outcome was then displayed on the terminal monitor display. Terminals were hard-wired to the multi-user computer system. These days, these terminals are normally personal computers and employ a network to send and receive data to the multi-user computer. The OS to operate on a large multi-user computer system with a lot of terminals is much more intricate than a single-user OS; it must supervise and run all user requests, to prevent interference during operations. Input/ Output Devices (I/O) These are the external devices that enable communication between the processing unit and the users of the information system. Some of the I/O devices include mouse, keyboard, joystick, and touch screen. While the input devices send binary signals to the processing unit, the output devices on the other hand provide the user with human understandable information (Garrido, Schlesinger, & Hoganson 2011). Software components of a multi-user system Kernel Kernel is one of the vital components of the OS that works together directly with the computer hardware, through device drivers that are built into the kernel (Rosen, Host, and Klee 2006, p. 11). It offers sets of services that are used by programs, insulating these programs from the underlying software. The major purposes of the kernel are to direct computer memory, organize access to the computer, handle interrupts and errors, preserve the file organization system, execute input and output services, and to allocate resources of the computer among users. Device Handlers The I/O devices communicate with the operating system via device handlers. The file manager device handler provides for both sequential and random data access, as well as file management functions such as Rename, Erase, and Protect (Rosen, Host, and Klee 2006, p. 11). Spoolers The other vital element is the spooler, which is a program that carries out spooling. Spooling helps in simultaneous operations of peripheral by using a fast storing device as a buffer for data being transferred from primary storage to a slower device (Bhatnagar, 2010, p. 64). For example, if a large file of many pages has to be printed, then the spooler will not keep the entire file in the buffer, but will create the buffer for its use in the hard disk such that the RAM is available for other processing. User Interface The final part of the multiuser OS is the user interface. Users interact with the operating system using a kind of software user interface like typing commands or using a graphical user interface. For laptop and desktop computers, user interface is commonly considered an element of the operating system. On large multiuser operating systems, the user interface is usually implemented as an application program that runs outside the multiuser operating system. Reference List Bajpai S K 2007. Introduction To Computers And C Programming. 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