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1 Page1 ALT_01_Ch1 : Introduction to Linux ideas and history The History of Linux starts with the earlier development of UNIX. UNIX In , Kenneth Thompson, Dennis Ritchie, and others at AT&T Bell Labs began developing a small operating system on a little-used PDP-7. The operating system was soon christened UNIX, a pun on an earlier operating system project called MULTICS. In the system was rewritten in the programming language C, an unusual step that was visionary: due to this decision, UNIX was the first widely-used operating system that could switch from and outlive its original hardware. Other innovations were added to UNIX as well, in part due to synergies between Bell Labs and the academic community. In 1979, the ``seventh edition'' (V7) version of UNIX was released, the grandfather of all extant UNIX systems. After this point, the history of UNIX becomes somewhat convoluted. The academic community, led by Berkeley, developed a variant called the Berkeley Software Distribution (BSD), while AT&T continued developing UNIX under the names ``System III'' and later ``System V''. In the late 1980's through early 1990's the ``wars'' between these two major strains raged. After many years each variant adopted many of the key features of the other. Commercially, System V won the ``standards wars'' (getting most of its interfaces into the formal standards), and most hardware vendors switched to AT&T's System V. However, System V ended up incorporating many BSD innovations, so the resulting system was more a merger of the two branches. The BSD branch did not die, but instead became widely used for research, for PC hardware, and for single-purpose servers (e.g., many web sites use a BSD derivative). The result was many different versions of UNIX, all based on the original seventh edition. Most versions of UNIX were proprietary and maintained by their respective hardware vendor, for example, Sun Solaris is a variant of System V. Three versions of the BSD branch of UNIX ended up as open source: FreeBSD (concentrating on ease-of-installation for PC-type hardware), NetBSD (concentrating on many different CPU architectures), and a variant of NetBSD, OpenBSD (concentrating on security). Free Software Foundation In 1984 Richard Stallman's Free Software Foundation (FSF) began the GNU project, a project to create a free version of the UNIX operating system. By free, Stallman meant software that could be freely used, read, modified, and redistributed. The FSF successfully built a vast number of useful components, including a C compiler (gcc), an impressive text editor (emacs), and a host of fundamental tools. However, in the 1990's the FSF was having trouble developing the operating system kernel [FSF 1998]; without a kernel their dream of a completely free operating system would not be realized. Linux In 1991 Linus Torvalds began developing an operating system kernel, which he named ``Linux'' [Torvalds 1999]. This kernel could be combined with the FSF material and other components (in particular some of the BSD components and MIT's X-windows software) to produce a freely-modifiable and very useful operating system. This book will term the

2 Page2 kernel itself the ``Linux kernel'' and an entire combination as ``Linux''. Note that many use the term ``GNU/Linux'' instead for this combination. In the Linux community, different organizations have combined the available components differently. Each combination is called a ``distribution'', and the organizations that develop distributions are called ``distributors''. Common distributions include Red Hat, Mandrake, SuSE, Caldera, Corel, and Debian. There are differences between the various distributions, but all distributions are based on the same foundation: the Linux kernel and the GNU glibc libraries. Since both are covered by ``copyleft'' style licenses, changes to these foundations generally must be made available to all, a unifying force between the Linux distributions at their foundation that does not exist between the BSD and AT&T-derived Unix systems. This book is not specific to any Linux distribution; when it discusses Linux it presumes Linux kernel version 2.2 or greater and the C library glibc 2.1 or greater, valid assumptions for essentially all current major Linux distributions. Open Source / Free Software Increased interest in software that is freely shared has made it increasingly necessary to define and explain it. A widely used term is ``open source software'', which is further defined in [OSI 1999]. Eric Raymond [1997, 1998] wrote several seminal articles examining its various development processes. Another widely-used term is ``free software'', where the ``free'' is short for ``freedom'': the usual explanation is ``free speech, not free beer.'' Neither phrase is perfect. The term ``free software'' is often confused with programs whose executables are given away at no charge, but whose source code cannot be viewed, modified, or redistributed. Conversely, the term ``open source'' is sometime (ab) used to mean software whose source code is visible, but for which there are limitations on use, modification, or redistribution. This book uses the term ``open source'' for its usual meaning, that is, software which has its source code freely available for use, viewing, modification, and redistribution; a more detailed definition is contained in the Open Source Definition. In some cases, a difference in motive is suggested; those preferring the term ``free software'' wish to strongly emphasize the need for freedom, while those using the term may have other motives (e.g., higher reliability) or simply wish to appear less strident. For information on this definition of free software, and the motivations behind it, can be found athttp:// Those interested in reading advocacy pieces for open source software and free software should see and There are other documents which examine such software, for example, Miller [1995] found that the open source software were noticeably more reliable than proprietary software (using their measurement technique, which measured resistance to crashing due to random input). Comparing Linux and UNIX Mostly we will use the term ``Unix-like'' to describe systems intentionally like UNIX. In particular, the term ``Unix-like'' includes all major UNIX variants and Linux distributions. Note that many people simply use the term ``UNIX'' to describe these systems instead. Originally, the term ``Unix'' meant a particular product developed by AT&T. Today, the Open Group owns the UNIX trademark, and it defines UNIX as ``the worldwide Single UNIX Specification''. Linux is not derived from UNIX source code, but its interfaces are intentionally like UNIX. Therefore, UNIX lessons learned generally apply to both, including information on security. Most of the information in this book applies to any Unix-like system. Linux-specific

3 Page3 information has been intentionally added to enable those using Linux to take advantage of Linux's capabilities. Unix-like systems share a number of security mechanisms, though there are subtle differences and not all systems have all mechanisms available. All include user and group ids (uids and gids) for each process and a filesystem with read, write, and execute permissions (for user, group, and other). See Thompson [1974] and Bach [1986] for general information on UNIX systems, including their basic security mechanisms. Linux /UNIX History Time Line Year 1957 Event Bell Labs found they needed an operating system for their computer center which at that time was running various batch jobs. The BESYS operating system was created at Bell Labs to deal with these needs Bell Labs was adopting third generation computer equipment and decided to join forces with General Electric and MIT to create Multics (Multiplexed Information and Computing Service). By April 1969, AT&T made a decision to withdraw Multics and go with GECOS. When Multics was withdrawn Ken Thompson and Dennis Ritchie needed to rewrite an operating system in order to play space travel on another smaller machine (a DEC PDP-7 [Programmed Data Processor 4K memory for user programs). The result was a system which a punning colleague called UNICS (UNiplexed Information and Computing Service)--an 'emasculated Multics' Summer 1969 Unix was developed Linus Torvalds is born First edition of Unix released 11/03/1971. The first edition of the "Unix PROGRAMMER'S MANUAL [by] K. Thompson [and] D. M. Ritchie." It includes over 60 commands like: b (compile B program); boot (reboot system); cat (concatenate files); chdir (change working directory); chmod (change access mode); chown(change owner); cp (copy file); ls (list directory contents); mv (move or rename file); roff (run off text); wc(get word count); who (who is one the system). The main thing missing was pipes Second edition of Unix released 12/06/ Ritchie rewrote B and called the new language C Unix had been installed on 16 sites (all within AT&T/Western Electric); it was publically unveiled at a conference in October Third edition of Unix released February Forth edition of Unix released November Fifth edition of Unix released June Thompson went to UC Berkeley to teach for a year; Bill Joy arrived as a new graduate student. Frustrated with ed, Joy developed a more featured editor em Sixth edition of Unix released May Bourne shell is introduced begins being added onto BSD released late BSD released mid 1978

4 Page Seventh edition of Unix released January BSD released late SCO founded by Doug and Larry Michels as Unix porting and consulting company BSD released October SGI introduces IRIX SCO delivers its first packaged Unix system called SCO XENIX System V for Intel 8086 and 8088 processor-based PCs Ultrix 1.0 was released Eighth edition of Unix released February The GNU manifesto is published in the March 1985 issue of Dr. Dobb's Journal. The GNU project starts a year and a half later HP-UX 1.0 released Ninth edition of Unix released September Sun and AT&T lay the groundwork for business computing in the next decade with an alliance to develop Unix System V Release HP-UX 2.0 released HP-UX 3.0 released SCO ships SCO Unix System V/386, the first volume commercial product licensed by AT&T to use the Unix System trademark HP-UX 7.0 released Tenth edition of Unix released October AIX short for Advanced Interactive executive was first entered into the market by IBM February Sun unveils Solaris 2 multiprocessing. operating environment, specially tuned for symetric Linux is introduced by Linus Torvalds, a student in Finland. Who post to the comp.os.minix newsgroup with the words: Hello everybody out there using minix - I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones HP-UX 8.0 released BSD/386 ALPHA First code released to people outside BSDI 12/xx/ HP-UX 9.0 released NetBSD 0.8 released 04/20/ FreeBSD 1.0 released December of Red Hat Linux is introduced Caldera, Inc was founded in 1994 by Ransom Love and Bryan Sparks NetBSD 1.0 released 10/26/ FreeBSD 2.0 released 01/xx/ SCO acquires Unix Systems source technology business from Novell Corporation (which had acquired it from AT&T's Unix System Laboratories). SCO also acquires UnixWare 2 operating system from Novell HP-UX 10.0 released.

5 Page BSD Lite Release 2 the true final distribution from the CSRG 06/xx/ KDE is started to be developed by Matthias Ettrich 1997 HP-UX 11.0 released Caldera ships OpenLinux Standard 1.1 May 5, 1997, the second offering in Caldera's OpenLinux product line 1998 IRIX 6.5 the fifth generation of SGI Unix is released July 6, SCO delivers UnixWare 7 operating system Sun Solaris 7 operating system released FreeBSD 3.0 released 10/16/ FreeBSD 4.0 released 03/13/ Caldera Systems Inc. announces that Caldera Systems has entered into agreement to acquire the SCO Server Software Division and the Professional Services Division Linus Torvalds releases version 2.4 of the Linux Kernel source code on January 4th Microsoft files a trademark suit against Lindows.com in December Lindows changes its name to Linspire April 14, 2004.

Introduction to Linux Overview and Some History

Introduction to Linux Overview and Some History Computational Science and Engineering North Carolina A&T State University Instructor: Dr. K. M. Flurchick Email: kmflurch@ncat.edu Operating Systems and