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1、Chapter 1 Introduction of the Linux Kernel History of Unix the creation of Unix in1969, Dennis Ritchie and Ken Thompson Unix grew out of Multics, a failed multiuser operating system project in Bell Lab Thompson implemented a PDP-7. In 1971, ported to PDP-11 In 1973, rewritten in C The first Unix wid
2、ely used outside Bell Labs was Unix System, Sixth Edition, called V6. Other companies ported Unix to new machines.Accompanying these ports were enhancements that resulted in several variants of the operating system. In 1977, Bell Labs released a combination of these variants into a single system, Un
3、ix System III; In 1982,AT&T released System V.(I readed Morris Bechs book in 1990) History of Unix The simplicity design, distributed source code, led to further development at external organizations. UC Berkeley Software Distributions, or BSD: 1BSD in 1977, a collection of patches and additional so
4、ftware on top of Bell LabsUnix. 2BSD in 1978, adding the csh and vi utilities 3BSD, The first standalone Berkeley Unix in 1979. virtual memory (VM) added. A series of 4BSD releases, 4.0BSD, 4.1BSD, 4.2BSD, 4.3BSD, followed 3BSD.These versions of Unix added job control, demand paging, and TCP/IP. In
5、1994, the university released the final official Berkeley Unix, featuring a rewritten VM subsystem, as 4.4BSD. Today the Darwin, FreeBSD, NetBSD, and OpenBSD systems. In the 1980s and 1990s, commercial versions of Unix based on AT&T or BSD, such as Digitals Tru64, Hewlett Packards HP-UX, IBMs AIX, S
6、equents DYNIX/ptx, SGIs IRIX, and Suns Solaris & SunOS. Characteristics of Unix The original elegant design , years of innovation and evolutionary has resulted in a powerful, robust, and stable operating system. Unix is simple: only hundreds of system calls ,straightforward, even basic, design. Ever
7、ything is a file. This simplifies the manipulation of data and devices into a set of core system calls: open(), read(), write(), lseek(), and close(). Written in C. Amazing portability to diverse hardware architectures and accessibility to a wide range of developers. Fast process creation time and t
8、he unique fork() system call. Simple yet robust interprocess communication (IPC) primitives that, when coupled with the fast process creation time, enable the creation of simple programs that do one thing and do it well. These single-purpose programs can be strung together to accomplish tasks of inc
9、reasing complexity. Characteristics of Unix Clean layering, with a strong separation between policy and mechanism. Supporting preemptive multitasking, multithreading, virtual memory, demand paging, shared libraries with demand loading, and TCP/IP networking. Scale to hundreds of processors, includin
10、g small, embedded devices. Continue to benefit from advances in operating system design while remaining a practical and general-purpose operating system. Lets remember: Dennis Ritchie, Ken Thompson Introduction of Linux 1991, Linus Torvalds a student at the University of Helsinki developed the first
11、 version of Linux on Intel 80386 microprocessor Minix, a low-cost Unix as a teaching aid with license limitation Began by writing a simple terminal emulatorused to connect to larger Unix systems Posted an early release to the Internet in late 1991. Introduction of Linux Swiftly evolved collaborative
12、 project Full-fledged OS running on Alpha, ARM, PowerPC, SPARC, x86-64 and many other architectures. From a watch to large as room-filling super-computer clusters. Powers the smallest consumer electronics and the largest Data centers. Many Companies provide Linux-based solutions for embedded, mobile
13、, desktop, and server needs. Unix-like system, but it is not Unix with Unix API It is not a commercial product but a collaborative project developed over the Internet. The Linux kernel is free or open source software. The Linux kernel is licensed under the GNU General Public License (GPL) version 2.
14、0. Linux system includes the kernel, C library, tool chain, and basic system utilities, such as a login process and shell, a modern X Window System, and GNOME. Overview of Operating Systems and Kernels OS is the parts of the system responsible for basic use and administration This includes the kerne
15、l and device drivers,boot loader, command shell or other user interface, and basic file and system utilities system, in turn, refers to the operating system and all the applications running on top of it The kernel is sometimes referred to as the supervisor, core, or internals of the operating system Relationship between applications, the kernel, and hardware In user-space, executing user code in a process In kernel-space, in process context, executing on behalf of a specific process In kernel-space, in interrupt context, not associated with a process, handling aninterrupt Linux Versus Cla
