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Linux@assignment ppt
- 1. Shri Mata VaishnoDevi University Katra Jammu & Kashmir
- 2. SUBMITTED BY:RAMA ENTRY NO.:15MCA005 COURSE:MCA3rd SEMESTER SUBMITTED TO : Mrs. SONIKA GUPTA
- 3. What isOpen Source. Linux Operating System History of linux Linux distributors Features of linux Linux kernel Process management in linux Input/output in linux Memory management in linux Advantages of linux
- 4. whose sourcecode is available. People improve it, people adapt it, people fix bugs. The freedom to run the program for any purpose The freedom to study how the program works, and adapt it to your needs The freedom to redistribute copies The freedom to improve the program
- 6. 7-Zip Eclipse GIMP Chromium Blender Mozilla Firefox Open Office
- 7. Linux FreeBSD ReactOS Android Haiku FreeDOS
- 8.
- 11. In 80’s,Microsoft’s DOS was mostly used OS for PC UNIX was much better, but much more expensive. Only for minicomputer for commercial applications Apple MAC OS was better, but was also expensive People were looking for an Operating system, which is cheaper and can easily run on PC All DOS, MAC and UNIX were proprietary, i.e., the source code of their kernel was protected No modification was possible without paying high License fees
- 12. Linus Torvalds wasa student at the University of Helsinki, he was using a version of the UNIX operating system called ‘Minix‘. When Linus and other users found that some modifications can make the OS even better he and the other users sent requests for modifications and improvements to Minix’s creator, Andrew Tanenbaum, but Andrew felt that these changes are not necessary and didn’t make the changes. That was the time when Linus decided to create his own operating system that would take into account user’s comments and suggestions for improvements. As Linus was a student of C Language he started writing the codes in C, around 95% of the Linux was written in C, and 2nd most used language for the Linux development was ‘Assembly‘ language i.e. around 2.8%
- 13. Linux isUNIX-based operating system. In Sept 1991, Linus Torvalds , a second year student of Computer Science at the University of Helsinki, developed the preliminary kernel of Linux, known as Linux version 0.0.1 Its was originally named as Freax It is licenced under GNU General Public licence.
- 14. Tux is apenguin character and the official mascot of the Linux kernel.
- 15. It wasoriginally developed for 32-bit x86-based PCs (386 or higher), but today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell, IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64, AXIS CRIS, Xtensa, Tilera TILE, AVR32 and Renesas M32R architectures.
- 17. Linux isfree i.e. open source Linux is portable to any hardware platform Linux is secure and versatile Linux is scalable The Linux OS and most Linux applications have very short debug-times It is case sensitive Multiuser multi-tasking ,multiprogramming Supports multi shell Modularity . In Linux everything is file.
- 18. Kernel isthe core part of linux operating system. Monolithic kernel is used in linux. Function of linux kernel:- Memory management Process management Device management Storage management Network management Architectural prespective of linux kernel
- 19.
- 20. The UserSpace is the space in memory where user processes run. This Space is protected. The system prevents one process from interfering with another process. Only Kernel processes can access a user Process.
- 21. The kernelSpace is the space in memory where kernel processes run. The user has access to it only through the system call.
- 23. The forksystem call creates an exact copy of the original process. The forking process is called the parent process. The new process is called the child process. Each process has a unique identifier (Process ID). Each process is represented by a task_struct data structure. The task_vector is an array of pointers to every task_struct data structure in the system. This means that the maximum number of processes in the system is limited by the size of the task vector.
- 24. Along withthe foreground processes, dozens of background processes are also running , known as daemons. A typical cron daemon is used in linux.
- 25. As a processexecutes it changes state according to its circumstances. Linux processes have the following states: 1. Running The process is either running or it is ready to run. 2. Waiting The process is waiting for an event or for a resource. Linux differentiates between two types of waiting process; interruptible and uninterruptible. Interruptible waiting processes can be interrupted by signals whereas uninterruptible waiting processes are waiting directly on hardware conditions and cannot be interrupted under any circumstances.
- 26. Cont…… 3. Stopped Theprocess has been stopped, usually by receiving a signal. A process that is being debugged can be in a stopped state. 4.Zombie This is a halted process which, for some reason, still has a task_struct data structure in the task vector. It is what it sounds like, a dead process.
- 29. Processes inLinux can communicate with each other using a form of message passing. Channels are created through pipes. Shell pipelines are implemented with pipes. When the shell sees a line like sort <f | head Another way of communication is : software interrupts. A process can send a signal to another process.
- 30. In linux schedulingis based on threads, not processes. Linux distinguishes three classes of threads for scheduling purposes: 1. Real-time FIFO. 2. Real-time round robin. 3. Timesharing.
- 31. A keydata structure used by the Linux scheduler is a runqueue. A runqueue is associated with each CPU in the system, and among other information, it maintains two arrays: active expired.
- 33. LINUX followsthe philosophy that every thing is a file. The I/O system in Linux looks much like that in any UNIX system. All device drivers appear as normal files. Users can open an access channel to a device in the same way they open any other file. Devices can appear as objects within the file system. A user can access a device in the same way as he opens any other file. The administrator can set access permission for each device.
- 34. Linux splits alldevices into three classes: 1) Block devices. 2) Character devices. 3) Network devices.
- 35. provide themain interface to all disk devices in a system. It include all devices that allow random access to completely independent, fixed-sized blocks of data, including hard disks and floppy disks , CD- ROMs and Blu-ray discs, and flash memory. used to store file systems The request manager manages the reading and writing of buffer contents to and from a block device driver.
- 36. • Used inversion 2.6 • Associates a deadline with each request ,thus addressing the starvation issue • Maintains three queues: • Sorted queue • Read queue • Write queue • By default the deadline for read request is 0.5 seconds and for write requests is 5 seconds
- 37. A devicedriver which does not offer random access to fixed blocks of data. A character device driver must register a set of functions which implement the driver’s various file I/O operations. The kernel performs almost no preprocessing of a file read or write request to a character device, but simply passes on the request to the device. The main exception to this rule is the special subset of character device drivers which implement terminal devices, for which the kernel maintains a standard interface. e.g. keyboards, mouse, serial ports
- 38. Users can’tdirectly transfer data to network devices They communicate indirectly by opening a connection to the kernel’s networking subsystem. Networking in the Linux kernel is implemented by three layers of software: 1. The socket interface 2. Protocol drivers 3. Network-device drivers
- 39. User applicationsperform all networking requests through the socket interface. It looks like the BSD socket layer, so that any programs designed to make use of Berkeley sockets will run on Linux without any source- code changes. The BSD socket interface is sufficient to represent network addresses for a wide range of networking protocols.
- 40. o It isthe second layer of software . o When data arrive at this layer, either from an application’s socket or from a network-device driver , the data are expected to have been tagged with an identifier specifying which network protocol they contain. o Functions of protocol layer: 1. rewrite packets 2. create new packets 3. split or reassemble packets into fragments 4. discard incoming data.
- 41. o communication betweenthe layers of the networking stack is performed by passing single skbuff (socket buffer) structures. o A skbuff set of pointers into a single continuous area of memory , representing a buffer inside which network packets can be constructed. o The networking code either add or trim data from the end of packets. o The most important set of protocols in the Linux networking system is the TCP/IP protocol suite.
- 42. IP protocolimplements routing between different hosts anywhere on the network. On top of the routing protocol are the UDP, TCP, and ICMP protocols. The UDP protocol carries arbitrary individual datagram between hosts. The TCP protocol implements reliable connections between hosts. ICMP protocol carries various error and status messages between hosts.
- 43. Cont….. Incoming IPpackets are delivered to the IP driver. this layer performs routing. After deciding where the packet is to be sent, the IP driver forwards the packet to the appropriate internal protocol driver to be delivered locally or injects it back into a selected network-device- driver queue to be forwarded to another host. The routing can be done using two tables: 1. forwarding information base (FIB). 2. cache of recent routing decisions.
- 44. Cont…… Large outgoingpackets are split up into smaller fragments. At the receiving host, these fragments are reassembled. Incoming fragments are matched against each known ipq. If a match is found, the fragment is added to it ; otherwise, a new ipq is created. Once the final fragment has arrived for a ipq , a completely new skbuff is constructed to hold the new packet, and this packet is passed back into the IP driver.
- 46. Memory management underLinux has two components: 1. The first deals with allocating and freeing physical memory-pages, groups of pages, and small blocks of memory. 2. The second handles virtual memory, which is memory mapped into the address space of running processes.
- 47. Linux separatesphysical memory into three different zones, or regions: ZONE_DMA ZONE_NORMAL ZONE_HIGHMEM
- 48. Zone_DMA (0-16MB):Permanently mapped into the kernel address space. . Zone_Normal (16MB-896MB): Permanently mapped into the kernel address space. ZONE_HIGH_MEM (896MB-above): not permanently mapped into the kernel's address space.
- 49. The pageallocator allocates and frees all physical pages; it can allocate ranges of physically-contiguous pages on request. The allocator uses a buddy-heap algorithm to keep track of available physical pages. Each allocatable memory region is paired with an adjacent partner. Whenever two allocated partner regions are both freed up they are combined to form a larger region. If a small memory request cannot be satisfied by allocating an existing small free region, then a larger free region will be subdivided into two partners to satisfy the request. Memory allocations in the Linux kernel occur either statically (drivers reserve a contiguous area of memory during system boot time) or dynamically (via the page allocator).
- 50. Splitting of memoryin the buddy system
- 51. The VMsystem maintains the address space visible to each process: It creates pages of virtual memory on demand, and manages the loading of those pages from disk or their swapping back out to disk as required. The VM manager maintains two separate views of a process’s address space: A logical view describing instructions concerning the layout of the address space. The address space consists of a set of non overlapping regions, each representing a continuous, page-aligned subset of the address space.
- 52. The pagingsystem can be divided into two sections: Policy algorithm: decides which pages to write out to disk and when to write them. Paging mechanism: carries out the transfer and pages data back into physical memory when they are needed again.
- 53. Linux iseasy to install! Errors in the code itself are far more likely to be caught and quickly fixed under the watchful eyes of peers. Kernel of the Linux can be customized to user’s needs. Under Linux user can run any program allowed by the system administrator on server without having to redesign that program. Under the GPL system programmers can release code without the fear of being used
- 54. Linux isless vulnerable to computer malware! Because most computer malware are designed to attack Windows (often through Active X which is not typically found in Linux) the odds are considerably less for Linux to be infected with a virus than Windows The same holds true with spyware, trojans, and worms. While Linux malware does exist, they are relatively few in number and none have become widespread so far