What is Linux A Unix-like Operating System A famous open source project Free to use, distribute, modify under a compatible licence Produced by a large developer and user community A combination of many projects Cost of commercial development estimated at USD 7 billion Companies often make money by selling: Support Training Custom changes
How Linux can help us ? Full operating system Works well on a variety of hardware, including older hardware You can adapt it to fit your needs Thousands of programs available Secure by design LAMP stack Supports a wide range of programming languages Scalable
History 1965 - Bell Labs (AT&T), GE and MIT, Project to develop a new (multiuser, multitasking) operating system - MULTICS. (not successful) 1969 - Ken Thompson and Dennis Ritchie implemented the first UNIX system for the PDP-7. 1973 - The UNIX system was rewritten in the C programming language. 1982 - University of California, Berkeley (UCB), Developed BSD UNIX because new commercial UNIX releases no longer included the source code. 1984 - Richard Stallman started the GNU project to create a free operating system. 1991 they created a lot of the tools but no kernel. Professor Andrew Tanenbaum wrote the operating system MINIX from scratch to teach his students the inner workings of a real operating system. 1991 Apr - At age 21, Linus Torvalds starts working on a new operating system inspired by MINIX. 1991 September - Linux version 0.01 is released.
Some Linux Flavors http://en.wikipedia.org/wiki/List_of_Linux_distributions
Linux vs Windows Linux WindowsLinux was originally built by Linus Torvalds at Firstversion of Windows – Windows 3.1the University of Helsinki in 1991. released in 1992 by Microsoft.Linux is a Unix-like, Kernel-based, fully Windows is a GUI based operating systemmemory-protected, multitasking operating It has powerful networking capabilities, issystem multitasking, and extremely user friendlyIt runs on a wide range of hardware from PCs Many beginner users find Windows easer toto Macs. use than other operating systemsLinux has been primary used by advanced Windows is often known for a large amount ofcomputer users – programmers and developers loop holesLinux is more virus proof since viruses – User Interface is well known for Windowsmalicious programs either cannot be runautomatically on the Linux machine, or simplyare not capable of being executed on a 386architectureUser Interface in latest flavors like Ubuntu iscomparatively equal
User Space vs Kernel Space User Space Kernel SpaceUser space is the Kernel Space usmemory area where all strictly reserved foruser mode application running the kernel (OSwork and this memory background process),can be swapped out kernel extensions andwhen necessary most device driversUser space process Linux kernel spacenormally runs in its gives full access to theown virtual memory hardware, althoughspace and unless some exceptions runsexplicitly requested, in user space. (Thecannot access the graphic system mostmemory of other people use with Linuxprocesses. does not run in kernel in contrast to that found in Microsoft Windows)
What is a process ? Actual execution of passive collection of instructions Eg: Running Adobe acrobat reader Running word pad Running Printer application All the above are named as process in OS and this can be run parallel, methodology named as Multi-Tasking
What is Thread ? In Linux threads are initiated and executed inside a process (process specific area) Multiple threads can exist within the same process and share resource such as memory, while different process do not share these resource Eg: opening multiple instance of .pdf extension files in a adobe acrobat reader
Process/Threads state Diagram Process gets initiated from Creation state and ended with terminated state, depending on the logic of program other states are valid
Boot Flow diagram GRUB ( Grand Unified Bootloader) is Multi-boot boot loader A Master Boot Record is a 512 bye boot sector that is the first sector of a partitioned data storage such as hard disk Root filesystem is the file system that is contained on the same partition on which the root directory is located.
Open Community Links Linux kernel availability http://www.kernel.org/ http://www.linux.org/ Linux Drivers http://www.linux-drivers.org/ Grub http://www.gnu.org/software/grub/index.html File System http://www.busybox.net/ Google will be your best friend
This Document Release dateS.No Author Release Description Version/Date1 Suresh v0.1 / 08 Dec 2010 Initial Version Kalidasan