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Information about linux

Published on April 1, 2009

Author: vigneshpsgtech


Slide 1: A mini- project on linux operating system Slide 2: CONTENTS INTRODUCTION HISTORY OF LINUX VERSIONS BOOTING PROCES LINUX KERNEL ARCHITECTURE SEMAPHORES PROCESS MANAGEMENT PROCESS STATES PROCESS SWITCHING KERNEL THREAD MEMORY MANAGEMENT Slide 3: INTRODUCTION OF LINUX To over come the disadvantages and break troughs of windows & Windows vista the first version of LINUX (LINUX 1.0) is been bought up in 1991 Lets see the architecture of LINUX and its various features ---? Slide 4: LINUX Developed by LINUX TORVALDS in 1991 .1st version – Linux 1.0. Freely distributed- open source. FUNCTIONALITY,ADAPTABILITY & ROBUSTNESS –main alternative to UNIX & MICROSOFT OS. Slide 5: VERSIONS: Debian based. Ubuntu based official distributions. Red-hat –enterprise LINUX- based. Slide 6: BOOTING PROCESS Computer power- BIOS procedure. BOOT LOADER- invokes BIOS to load OS kernel into RAM Slide 8: LINUX KERNELS: Linux kernel is monolithic. Traditional UNIX kernels are compiled & linked statistically. Kernel threading. Multilevel application support. LINUX is a non-pre emptive kernel. Multiprocessor support. Slide 9: ARCHITECTURE Kernel layer is integrated & runs in kernel mode. Slide 10: SEMAPHORES: Used to implement threads. A counter DS. Two methods 1.drop(): decrements the semaphore value. 2.up(): increments the semaphore value. Slide 11: PROCESS MANAGEMENT PROCESS: Fundamental to multiprogramming os. Instance of program in execution Creation of process-fork(). Termination of process-exit(). Slide 12: PROCESS STATES TASK_RUNNING TASK_INTERRUPTIBLE TASK_UNINTERRUPTIBLE TASK_STOPPED TASK_ZOMBIE Slide 13: PROCESS SWITCHING: Also called CONTEXT SWITCHING. To control the execution of process ,kernel suspends execution of process RUNNING and resumes the execution of some other process previously suspended Slide 14: KERNEL THREAD –DISTINGUISHING FACTORS: Executes single specific kernel function. Whereas others through system call Kernel threads run only in kernel mode. Whereas others through in kernel & user mode Slide 15: MEMORY MANAGEMENT VIRTUAL MEMORY: Abstraction acts as logical layer between Application request and MMU. Slide 16: ADVANTAGES: Several processes can be executed concurrently. Possible to run application whose memory needs >available memory Relocatablity i.e. can be placed any where in MM. Programmers need to write only machine- independent code DISADVANTAGES: Memory fragmentation. Slide 17: MEMORY ADDRESSING Uses three addresses: Logical address. Linear addresses. Physical addresses. SEGMENTATION UNIT TRANSFORMS Logical address --? linear address PAGING UNIT TRANSFORMS Linear address-? physical address Slide 18: SEGMENTATION UNIT: Logical address- Segment register holds segment selector or identifier. Slide 19: TRANSLATION LOOKASIDE BUFFERS (TLB): To speed linear address translation. Linear address when used for one time, physical address is computed through page tables and stored in TLB. Further references can be quickly found. Slide 20: PAGE TABLES: Page global directory Page middle directory Page Table Paging ensures efficient protection against addressing error. Distinguish pages from page frames (Basic ingredient of VM mechanism). Slide 21: MEMORY AREA MANAGEMENT: Classification: CONTIGIOUS: Better use of cache. Lower average memory access times. Suffers internal fragmentation. NON-CONTIGIOUS: Avoids external fragmentation Disadvantage is fiddle through page tables. Slide 22: DEMAND PAGING: Denotes a dynamic memory allocation techinque that of differing page frame allocation until the last possible moment. Page fault occurs when we attempt to address a page that is not in RAM. Only a small subset of the process pages are referenced. ADVANTAGE: Preferable to global allocation. Increases average number of free page frames. Better throughput. Slide 23: SYNCHRONISATION TECHNIQUES: To avoid race conditions among processes. Non preemptability of processes in kernal mode. Atomic operations. Interrupt disabling. Locking.. Slide 24: SWAPPING: Kernel uses some space on disk as an extension of RAM. It is transparent to the programmer. Abstraction of availability of physical memory. Extends amount of addressable memory at the expense of access speed Slide 25: SWAPPING BENEFITS: To extend the address space that is effectively usable by a process To expand the amount of dynamic RAM to load process. Slide 26: ISSUES TO BE CONSIDERED DURING SWAPPING: Which kind of page to swap out. How to distribute pages in the swap area. How to select the page to be swapped out. When to perform the swap out. Slide 27: I/O MANAGEMENT: Data paths are provided for information flow between CPU,RAM, &I/O devices. Data paths are collectively known as bus, which are the primary communication channel. Bus types: ISA,EISA.PCI,MCA. Bus classification: DATA BUS ADDRESS BUS CONTROL BUS Slide 28: I/O PORTS & INTERFACES: Every device connected to I/O bus has its own set of I/O address, which are I/O ports. Interface is a circuit inserted between a group of I/O ports and the corresponding device controller. Acts as an interpreter to translate value in I/O ports into commands. Slide 29: DEVICE CONTROLLERS: A complex device may require a device controller to drive it. It interprets the highly-level commands and executes specific actions. Converts and properly interprets the electrical signals received from the device. Slide 30: DMA-DIRECT MEMORY ACCESS Auxillary processor to transfer data between RAM and I/O device. Once activated , takes its own control to transfer. Memory arbiter controls the conflicts occuring when both CPU & DMCA need to access the same memory location. Slide 31: LEVEL OF KERNAL SUPPORT: No support at all. Minimal support. Extended support. TECHNIQUES TO MONITOR I/O OPERATION: Polling mode. Interrupt mode. Slide 32: FILE MANAGEMENT A UNIX file is an info container structured as a sequence. Length of file system is 255 characters. Directory corresponding to root is root directory denoted by /. Same name cannot be used for different directories. Pathname is used to identify a specific file. Slide 33: Difference from other os: Linux is free of cost Fully customizable Runs on low-end ,cheap platforms. Powerful. High standard. Kernel is very small & compact. Highly compatible. Well supported. Slide 34: FILE TYPES Regular file. Directory Symbolic link. Block oriented device file. Pipe & named pipe (also called FIFO) socket Slide 35: FILE HANDLING SYSTEM CALLS: A process in user mode cannot directly interact with low –level h/w components. Therefore each actual file operation must be performed In kernel mode. To prevent this UNIX os defines system call. Is used & file pathname is passed as parameter. Eg: To access a file ,open the file using system call. fd=open(path ,flag ,mode) path ?denotes path name of opened file flag ?specifies how file must be opened mode ?specifies the access rights of created file. Slide 36: VIRTUAL FILE SYSTEM : VFS Linux manages to support multiple disk type in same way as UNIX variants do ,through a concept called VFS VFS is a kernel software layer that handles all system calls related to standard UNIX file system. Its main strength is providing a common interface to several kind of file systems. It allows you to transparently mount different file systems at same time. On implementing Linux VFS ,access to the files is as fast & efficient as possible. Slide 37: VFS INODE Every file & directory in VFS is represented by only one VFS inode. The info in each VFS node is built from information. In file system by specific file system routines. It exists only in kernel’s memory & uses cache. It contains following fields: Device Inode number Mode User id’s Block size Inode operations Count Lock Dirty Slide 38: NETWORK MANAGEMENT IN LINUX Mission maintaining availability of resources such as ROUTERS, HUBS,SERVERS and Etc.. Network of an organization includes WAN or INTERNET. Other links, link point to point or frame relay are charged on a flat rate. Slide 39: SNMP-SIMPLE NETWOK MANAGEMENT PROTOCOL Aim was to integrate the management of different n/w with simple design that causes very little stress on the n/w. Uses TCP/IP transport protocol. ELEMENTS IN SNMP: AGENT-SERVER: Performs deal with fetch & store paradigm. MANAGER-CLIENT Request or set value of variable in MIB of the agent. Slide 40: SECURITY: Supports two password schema called communities. PUBLIC: Allows manager to request value of variables. PRIVATE: Allows these values to be set. DISADVANTAGES: If IP Routing between two devices fails , its impossible to reach the target to monitor or reconfigure it. Slide 41: A SIMPLE PROCESSSING OF FILES IN LINUX This is how the process is moduled and scheduled and this diagram shows the simple path of processing Slide 42: SECRET OF LINUX LOGO Once Linus went to the southern hemisphere on a vacation. There he encountered a penguin, not unlike the current logo of Linux. As he tried to pat it, the penguin bit his hand. This amusing incident led to the selection of a penguin as the logo of Linux sometime later Slide 43: SEE THE USER SCREEN OF LINUX PALM TOP ----? Slide 45: WHY TO USE THE LINUX AS YOUR OPERATING SYSTEM….? HACKING IS NOT ALL POSSIBLE WHEN A SYSTEM IS RUNNING IN LINUX OPERATING SYSTEM DATA SECURITY AND SYSTEM SECURITY IS WELL CONCERNED FREE OF COST NO MALWARE OR VIRUS THREATS COULD BE FOUND IN LINUX Slide 47: QUERRIES……..? Slide 48: Mini – Project on operating system BY 1.) K.PREETHI 2.) V.VIGNESH KUMAR 3.) R.PORKODI 4.) K.M.SARAVANA PRABHU 4th SEM B.Sc CT-G1

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