OS - Operating System
- 1. Understanding Operating System Yasir Hussain Yasir Hussain BCA , MCA/ NIT SRINAGAR (Gold Medalist)
- 2. Operating System • An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. ... Other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. • An operating system (OS) is the program that, after being initially loaded into the computer by a boot program, manages all of the other application programs in a computer.The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface such as a command line or a graphical user interface (GUI).
- 3. Computer system can be divided into four components Hardware – provides basic computingresources CPU, memory, I/O devices
- 4. • An operating system or OS is a software program that enables the computer hardware to communicate and operate with the computer software.Without a computer operating system, a computer and software programs would be useless. • An operating system is a software which acts as an interface between the end user and computer hardware. Every computer must have at least one OS to run other programs. An application likeChrome, MSWord, Games, etc needs some environment in which it will run and perform its task. Need of an Operating System • Operating system goals: • Execute user programs and make solving user problems easier • Make the computer system convenient to use • Use the computer hardware in an efficient manner
- 5. Loading of an operating system (Booting)
- 6. Booting • Booting of a computer refers to the process of powering on the computer and starting the operating system. The operating system is the program that makes all your software applications and hardware work together, so once you hit the power button, it's all automatic from there. The boot process loads the operating system into main memory or the random access memory (RAM) installed on your computer
- 7. Boot Process • When you push the power button, power is sent to a small bootloader program, which loads the computer's operating system.The bootloader is located in the cache memory. The cache memory is a portion of your RAM that is directly attached to the central processing unit (CPU). • Once the bootloader program gets power, it starts the process of activating the operating system. If you were to see this happening, it would show a black screen with the text of the boot up processes.
- 8. How operating system Load • Bootstrapping is the process of loading a set of instructions when a computer is first turned on or booted. During the startup process, diagnostic tests are performed, such as the power-on self- test (POST), that set or check configurations for devices and implement routine testing for the connection of peripherals, hardware and external memory devices.The bootloader or bootstrap program is then loaded to initialize the OS. • bootstrapping, bootloader, or boot program, a bootstrap loader is a program that resides in the computer's ROM, or another non-volatile memory. It is automatically executed by the processor when turning on the computer.The bootstrap loader reads the hard drives boot sector to continue the process of loading the computer's operating system. • When the computer is turned on or restarted, the bootstrap loader first performs the power-on self-test, also known as POST. If the POST is successful and no issues are found, the bootstrap loader will load the operating system for the computer into memory.The computer will then be able to quickly access, load, and run the operating system.
- 9. History Of OS •Operating systems were first developed in the late 1950s to manage tape storage •The General Motors Research Lab implemented the first OS in the early 1950s for their IBM 701 •In the mid-1960s, operating systems started to use disks •In the late 1960s, the first version of the Unix OS was developed •The first OS built by Microsoft was DOS. It was built in 1981 by purchasing the 86-DOS software from a Seattle company •The present-day popularOSWindows first came to existence in 1985 when a GUI was created and paired with MS-DOS. What is a Kernel? The kernel is the central component of a computer operating systems. The only job is to the manage the communication between the software and the hardware. A Kernel is at computer. It makes the communication between the hardware and software possible. While innermost part of an operating system, a shell is the outermost one.
- 10. •A Mobile / computer Operating System •An Embedded operating system •A Network operating system (NOS) •A Real-time operating system (RTOS) Types of Operating System
- 11. A Mobile / computer Operating System • A mobile OS allows smartphones, tablet PCs and other mobile devices to run applications and programs. Mobile operating systems include Apple iOS, GoogleAndroid, BlackBerry OS andWindows 10 Mobile.
- 12. An Embedded operating system • An embedded operating system is specialized for use in the computers built into larger systems, such as cars, traffic lights, digital televisions,ATMs, airplane controls, point of sale (POS) terminals, digital cameras, GPS navigation systems, elevators, digital media receivers and smart meters.
- 13. A Network operating system (NOS) • A network operating system (NOS) is a computer operating system that is designed primarily to support workstation, personal computer, and, in some instances, older terminals that are connected on a local area network (LAN).
- 14. Examples of Operating System with Market Share
- 15. A real-time operating system (RTOS) • A real-time operating system (RTOS) is an operating system that guarantees a certain capability within a specified time constraint. For example, an operating system might be designed to ensure that a certain object was available for a robot on an assembly line.
- 16. Objectives of Operating System • The objectives of the operating system are − • To make the computer system convenient to use in an efficient manner. • To hide the details of the hardware resources from the users. • To provide users a convenient interface to use the computer system. • To act as an intermediary between the hardware and its users, making it easier for the users to access and use other resources. • To manage the resources of a computer system. • To keep track of who is using which resource, granting resource requests, and mediating conflicting requests from different programs and users. • To provide efficient and fair sharing of resources among users and programs.
- 17. Functions of an Operating System
- 18. •Memory Management The operating system manages the Primary Memory or Main Memory. Main memory is made up of •a large array of bytes or words where each byte or word is assigned a certain address. •Main memory is a fast storage and it can be accessed directly by the CPU. For a program to be executed, •it should be first loaded in the main memory. An Operating System performs the following activities for •memory management: It keeps tracks of primary memory, i.e., which bytes of memory are used by which user program. The memory addresses that have already been allocated and the memory addresses of the memory that has not yet been used. In multi programming, the OS decides the order in which process are granted access to memory, and for how long. It Allocates the memory to a process when the process requests it and deallocates the memory when the process has terminated or is performing an I/O operation.
- 19. Memory Management Virtual Memory: This is a technique used by the operating systems which allow the user can load the programs which are larger than the main memory of the computer. In this technique the program is executed even if the complete program can not be loaded inside the main memory leading to efficient memory utilization. Virtual Memory is a storage allocation scheme in which secondary memory can be addressed as though it were part of main memory.
- 20. Swapping Swapping is a mechanism in which a process can be swapped temporarily out of main memory (or move) to secondary storage (disk) and make that memory available to other processes. At some later time, the system swaps back the process from the secondary storage to main memory. Though performance is usually affected by swapping process but it helps in running multiple and big processes in parallel and that's the reason Swapping is also known as a technique for memory compaction.
- 21. Pagingis a method of writing data to, and reading it from, secondary storage for use in primary storage, also known as main memory. ... In a memory management system that takes advantage of paging, the OS reads data from secondary storage in blocks called pages, all of which have identical size. In a memory management system that takes advantage of paging, the OS reads data from secondary storage in blocks called pages, all of which have identical size.The physical region of memory containing a single page is called a frame.
- 22. Processor Management In a multi programming environment, the OS decides the order in which processes have access to the processor, •and how much processing time each process has.This function of OS is called process scheduling. An Operating •System performs the following activities for processor management. Keeps tracks of the status of processes.The program which perform this task is known as traffic controller. Allocates the CPU that is processor to a process. De-allocates processor when a process is no more required.
- 23. • Multitasking: Operating System manages memory and allow multiple programs to run in their own space and even communicate with each other through shared memory. Multitasking gives users a good experience as they can perform several tasks on a computer at a time this deals with management of the Central ProcessingUnit (CPU).The operating system takes care of the allotment of CPU time to different processes.When a process finishes its CPU processing after executing for the allotted time period, this is called scheduling.There are various type of scheduling techniques that are used by the operating systems: 1.Shortest Job First(SJF): Process which need the shortest CPU time are scheduled first. 2.Round Robin Scheduling: Each process is assigned a fixed CPU execution time in cyclic way. 3.Priority Based scheduling (Non Preemptive): In this scheduling, processes are scheduled according to their priorities, i.e., highest priority process is schedule first. If priorities of two processes match, then schedule according to arrival time
- 24. Device Management An OS manages device communication via their respective drivers. It performs the following activities for device management. Keeps tracks of all devices connected to system. designates a program responsible for every device known as the Input/output controller. Decides which process gets access to a certain device and for how long.Allocates devices in an effective and efficient way. Deallocates devices when they are no longer required. Buffering: In this technique, input and output data is temporarily stored in Input Buffer and Output Buffer. Once the signal for input or output is sent to or from the CPU respectively, the operating system through the device controller moves the data from the input device to the input buffer and for the output device to the output buffer. In case of input, if the buffer is full, the operating system sends a signal to the program which processes the data stored in the buffer.When the buffer becomes empty, the program informs the operating system which reloads the buffer and the input operation continues.
- 25. File management is one of the basic and important features of operating system. Operating system is used to manage files of computer system.All the files with different extensions are managed by operating system. • File Management A file system is organized into directories for efficient or easy navigation and usage.These directories may contain other directories and other files.An Operating System carries out the following file management activities. It keeps track of where information is stored, user access settings and status of every file and more…These facilities are collectively known as the file system. The following are some of the tasks performed by file management of operating system of any computer system: 1.It helps to create new files in computer system and placing them at the specific locations. 2.It helps in easily and quickly locating these files in computer system. 3.It makes the process of sharing of the files among different users very easy and user friendly. 4.It helps to stores the files in separate folders known as directories.These directories help users to search file quickly or to manage the files according to their types or uses. 5.It helps the user to modify the data of files or to modify the name of the file in the directories.
- 26. System Security Plan A system security plan is a formal plan that defines the plan of action to secure a computer or information system. It provides a systematic approach and techniques for protecting a computer from being used by unauthorized users, guards against worms and viruses as well as any other incident/event/process that can jeopardize the underlying system’s security. A system security plan is primarily implemented in organizational IT environments. It can be a proposed plan to protect and control an information system, or a plan that is already in implementation Typically a system security plan includes: •List of authorized personnel/users that can access the system •Level of access/tiered access, or what each user is allowed and not allowed to do on the system •Access control methods, or how users will access the system (user ID/password, digital card, biometrics) •Strengths and weaknesses of the system and how weaknesses are handled •May also include system backup/restoration procedures
- 27. • OS security refers to specified steps or measures used to protect the OS from threats, viruses, worms, malware or remote hacker intrusions. OS security encompasses all preventive-control techniques, which safeguard any computer assets capable of being stolen, edited or deleted if OS security is compromised. Operating System Security OS security encompasses many different techniques and methods which ensure safety from threats and attacks. OS security allows different applications and programs to perform required tasks and stop unauthorized interference. OS security may be approached in many ways, including adherence to the following: •Performing regular OS patch updates •Installing updated antivirus engines and software •Scrutinizing all incoming and outgoing network traffic through a firewall •Creating secure accounts with required privileges only (i.e., user management)
- 28. Authentication Authentication refers to identifying each user of the system and associating the executing programs with those users. It is the responsibility of the Operating System to create a protection system which ensures that a user who is running a particular program is authentic. Operating Systems generally identifies/authenticates users using following three ways − •Username / Password − User need to enter a registered username and password with Operating system to login into the system. •User card/key − User need to punch card in card slot, or enter key generated by key generator in option provided by operating system to login into the system. •User attribute - fingerprint/ eye retina pattern/ signature − User need to pass his/her attribute via designated input device used by operating system to login into the system.
- 29. User Accounts •Limit the number of user accounts on the server computers.Unnecessary and legacy user accounts increase system complexity and may present system vulnerabilities. •Fewer user accounts reduces the amount of time administrators spend on account administration. •Ensure that only a few trusted users have administrative access to the server computers.Fewer administrators make it easier to maintain accountability.The administrators must be competent. •Assign the minimum required access permissions for the account that runs the application.If attackers obtain access to the application, they have the permissions of the user who runs the application.
- 30. System Patches •Run the latest, vendor-recommended patches for the operating system.The patches may be core OS patches, or patches required by additional applications. •Schedule regular maintenance of security patches.Logging and Monitoring •Log security-related events, including successful and failed logons, logoffs, and changes to user permissions. •Monitor system log files. •Use a time server to correlate time for forensics. •Secure the system log files by restricting access permissions to them.Logs are important for daily maintenance and as a disaster recovery tool. Therefore, they must be protected from system failures and user tampering. •Use IPF logging to build a more sophisticated logging system.To increase the security of the log file system, you can • place all log files in one location, on one serverThis simplifies the administration of log files. • set up multiple logging servers for redundancy • use a remote server for loggingThis protects the logs if the system is compromised and, for example, the hard drive is destroyed. • Because an IPF server is accessed through the network, it can be located anywhere in the world. •Secure the logging configuration file.The configuration file contains settings that, if changed, can compromise the reliability of the log system. For example, setting the log level incorrectly may cause some failures not to be logged.
- 31. Hardening of the OS is the act of configuring an OS securely, updating it, creating rules and policies to help govern the system in a secure manner, and removing unnecessary applications and services.This is done to minimize a computer OS's exposure to threats and to mitigate possible risk. Hardening Six OS Hardening Tips 1 Programs clean-up – Remove unnecessary programs. Every program is another potential entrance point for a hacker. Cleaning these out helps you limit the number of ways in. If the program is not something the company has vetted and "locked down," it shouldn’t be allowed. Attackers look for backdoors and security holes when attempting to compromise networks. Minimize their chances of getting through. 2 Use of service packs – Keep up-to-date and install the latest versions. It’s that simple. No one thing ensures protection, especially from zero-day attacks, but this is an easy rule to follow.
- 32. 3 Patches and patch management – Planning, testing, implementing and auditing patch management software should be part of a regular security regimen. Make sure the OS is patched regularly, as well as the individual programs on the client's computer. 4. Group policies – Define what groups can or can’t access and maintain these rules. Sometimes, it’s simply user error that leads to a successful cyber attack. Establish or update user policies and ensure all users are aware and comply with these procedures. For example, everyone should be implementing strong passwords, securing their credentials and changing them regularly. 5. Security templates – Groups of policies that can be loaded in one procedure; they are commonly used in corporate environments. 6. Configuration baselines – Baselining is the process of measuring changes in networking, hardware, software, etc.To create a baseline, select something to measure and measure it consistently for a period of time. Establish baselines and measure on a schedule that is acceptable to both your standard for maintaining security and meeting your clients' needs.