The Linux System
- 1. The Linux System Presented by: Hadia Akhtar roll no: 016
- 2. Overview • Linux history • design principles • Kernel modules • Memory Management
- 3. Linux began in 1991 as a personal project by Finish student Linus Torvalds: • To create a new free operating system kernel because UNIX based system which uses before LUNIX were much expensive. • The resulting Linux kernel has been marked by constant growth throughout its history. • Since the initial release of its source code in 1991, it has grown from a small number of C files under a license prohibiting commercial distribution.
- 4. • Linus Torvalds had wanted to call his invention Freax , a portmanteau of "free", "freak", and "x" (as an allusion to Unix). • During the start of his work on the system, he stored the files under the name "Freax" for about half of a year. • Torvalds had already considered the name "Linux", but initially dismissed it as too egotistical.
- 5. linux In 1992, he suggested releasing the kernel under the GNU General Public License. 1 In the middle of December 1992 he published version 0.99 using the GNU GPL. 2 Linux and GNU developers worked to integrate GNU components with Linux to make a fully functional and free operating system. 3 Torvalds has stated, "making Linux GPLed was definitely the best thing I ever did." 4 Linux under the GNU GPL
- 6. • Various companies have also helped not only with the development of the kernels, but also with the writing of the body of auxiliary software, which is distributed with Linux. • The thousands of programmers around the world that use Linux and send their suggested improvements to the maintainers. The largest part of the work on Linux is performed by the community:
- 7. Linux Design Principles • Linux is a multiuser, multitasking system with a full set of UNIX compatible tools. • Its file system adheres to traditional UNIX semantics, and it fully implements the standard UNIX networking model. • Main design goals are speed, efficiency and standardization.
- 8. Linux Design Principles • Linux is designed to be compliant with the relevant POSIX documents, at least two Linux distributions have achieved official POSIX certification. • The Linux programming interface adheres to the SVR4 UNIX semantics, rather than to BSD behavior.
- 9. Linux SystemComponents The Linux system consists of three important code parts: It is a program that performs management work individually and specifically. System Utility Responsible for maintaining all important abstractions of the operating system, including things like processes and virtual memory. Kernel It defines a set of standard functions where applications can interact with the kernel, and implements almost all operating system functions that do not require full rights to the kernel. System library
- 10. Kernel • The Linux kernel forms the core of the Linux operating system. • It provides all the functions needed to run the process, and is provided with system services to provide settings and protection for access to hardware resources. • The kernel implements all the features needed to work as an operating system.
- 11. Kernel Modules • Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. • To create a kernel module, you can read The Linux Kernel Module Programming Guide. • In order to reduce the size of the Linux Kernel, it may be split into a 'core', and a large set of Kernel Modules. • They extend the functionality of the kernel without the need to reboot the system.
- 12. • In order to reduce the size of the Linux Kernel, it may be split into a 'core', and a large set of Kernel Modules. • A Kernel Module is a small file that may be loaded into the running Kernel, and unloaded, at will (the next generation of the Linux kernel will not allow unloading modules, unless told otherwise). • Many functions of the Kernel may either be compiled into the Kernel directly, or compiled as Modules.
- 13. • Modules are split into directories, based on categories: pcmcia - PCMCIA Drivers, for laptops. • kernel/net - network-related Modules (firewall, extra protocols support, etc.) • kernel/drivers - Drivers for various types of Hardware (including network Drivers). • kernel/fs - file-systems support (ext3, vfat, etc.) • kernel/arch - Architecture-specific support (e.g. Drivers to handle features of a a specific CPU or motherboard).
- 14. Memory Management TextTextTextText • This includes implementation of virtual memory and demand paging, memory allocation both for kernel internal structures and user space programs, mapping of files into processes address space and many other cool things. • Linux memory management is a complex system with many configurable settings.
- 15. Linux memory management The x86 memory management architecture uses both segmentation and paging. A segment is a partition of a process's address space that has its own protection policy. it is possible to split the range of memory addresses that a process sees into multiple contiguous segments, and assign different protection modes to each. Paging is a technique for mapping small (usually 4KB) regions of a process's address space to chunks of real, physical memory. Paging thus controls how regions inside a segment are mapped onto physical RAM.
- 16. 60% 40% In Linux, the OS desig ners decided to carve up the 32 bit address s pace of each process in the above way.
- 17. 01 Modern PowerPoint Presentation 02 Modern Presentation 03 Modern Presentation 04 Modern ppt 05Modern one segment (addresses 0x00000000 through 0xBFFFFF FF) for user-level, process-specific data such as the program's code, static data, heap, and stack. Every process has its own, independent user segment. 02 03 • All processes therefore have two segments (there are some details about additional segments that I'm hiding) 01 • The same kernel segment is mapped into every process, but processes can access it only when executing in protected kernel mode.
- 18. • Because kernel-critical data structures and the mapping to physical memory are contained in the kernel segment, it is imperative that the user-level process can't cause the kernel to unwittingly read or write memory locations in this segment • one segment (addresses 0xC0000000 through 0xFFFFFFFF), which contains kernel-specific data such as the kernel instructions, data, some stacks on which kernel code can execute, and more interestingly, a region in this segment is directly mapped to physical memory, so that the kernel can directly access physical memory locations without having to worry about address translation.
- 19. Conclusions While Linux has been around for a very long time, it has been ignored for mainstream desktop use for most of its existence. Linux is not like a Mac operating system. In fact, Linux will run on a wider range of hardware than even Windows.
- 20. Thank You