Overview of Linux Dr. Michael L. Collard 1

Linux A Unix-like operating system that uses the Linux kernel A premiere example of “open source” Center of the world’s largest collaborative software effort 2

Parts of “Linux” Linux kernel - manage hardware, run program, provide security GNU Project – utilities: bash, gcc, emacs, etc. X.org – X Window system GNOME & KDE – desktop environments Many other sources 3

Where Linux Comes From 1970: Unix Operating System – Thomson & Ritchie 1978: BSD (Berkeley Standard Distribution) 1983: GNU Project – Richard Stallman, goal of a free Unix-like operating system, GPL (General Public License) written in : MINIX – Unix-like operating system for education by Andrew Tannenbaum 4

Problems with Unix-like O.S.’s for x86 GNU Project had many utilities, but no kernel (GNU Hurd) BSD based on 6 th edition of AT&T Unix, and lawsuits limited development MINIX development was lacking, and limited distribution No good solution for running a Unix-like system on a PC 5

Linus Torvalds Computer Science student at University of Helsinki, Finland in 1991 Started to write a terminal emulator (independent of the operating system) for his PC Developed using MINIX and the GNU C Compiler Grew into the Linux kernel Announced what he had started in the newsgroup comp.os.minix in August,

Linux kernel Timeline 1991: Linux kernel 0.11 – self-hosted 1992: “Linux is Obsolete” – Tannenbaum 1992: Linux kernel 0.12 – released under GNU GPL license 1992: Linux kernel 0.95 – capable of running X Windows 1994: Linux kernel 1.0 – i386 only – 176,250 LOC 1995: Linux kernel 1.2 – additional CPU’s – 310,950 LOC 7

Linux Timeline (cont) 1996: Linux kernel : Linux kernel – 1,800,147 LOC 2001: Linux kernel – 3,377,902 LOC 2003: Linux kernel – 5,929,913 LOC 2008: Linux kernel

Development Model Previous Model – Stable: 1.0, 1.2, 2.0, 2.2, 2.4, 2.6 – Unstable (development): 1.1, 2.1, 2.3, 2.5, 2.7 Current Model: – – releases – 2.7 unstable never forked – Plan was a new release every 2-3 months 9

Current Development Average of – : – 2.7 months between releases – 2.83 patches per hour – 3,621 LOC added, 1,550 LOC removed, and 1,425 LOC changed per day Total of – : – 3,678 developers – 271 companies, e.g., RedHat, Novell, IBM, Intel 10

Why do companies support Linux? Make sure it runs on their hardware, e.g., Intel Distributors of Linux, e.g., RedHat, Novell Embedded devices, e.g., Sony Platform for technical development, e.g., Volkswagen 11

GNU Project “GNU’s Not Unix” Started by Richard Stallman (rms) in 1983 Start of the Free Software Movement, and the corresponding FSF (Free Software Foundation) 12

GNU Four Freedoms 0: The freedom to run the program for any purpose 1: The freedom to study how the program works, and adapt it to your needs 2: The freedom to redistribute copies so you can help your neighbor 3: The freedom to improve the program, and release your improvements to the public, so that the whole community benefits 13

GNU GPL General Public License “CopyLeft” Copyright retained by the author GPL Software must be available for free Source code must be made available If other developers make changes, they must distribute it with the original source 14

GPL Issues Cannot directly use in proprietary code What about programs developed using GPL editors, compilers, o.s.? – Not a problem What about programs that call a function library, e.g., GNU C library? – LGPL (Lesser General Public License) 15

Open Source Licenses Variety including BSD license, Apache License, Mozilla Public License GPL Version 2 in 1991 GPL Version 3 in 2008 Linux (GPL v2) - individuals hold copyright – All indications are that Linux will stick with v2 GNU Project – individuals assign copyright to FSF 16

GNU/Linux Distribution Installation program General configuration Packages of compatible software Handles dependencies Support (technical and legal) Updates Security fixes 17

Differences between Distributions Community-based versus commercial Hardware and device support Number of packages (different software) available Use of proprietary packages Package management Size, software typically installed Security Frequency of updates/releases Support 18

Debian Non-commercial, holding to strict free software guidelines 26,000 packages for 11 architectures APT package management Basis for other distributions MEPIS, Damn Small Linux, Xandros, Knoppix, etc. Debian GNU/Linux 4.0 (Etch) 19

Ubuntu Most popular desktop distribution (~30%) Canonical Ltd. Based on Debian unstable packages APT package management New versions every 6 months, Ubuntu 8.04 LTS (Hardy Heron) Best desktop Linux installation program (?) 20

RedHat A major commercial server and desktop Linux distributor RedHat Linux 1.0 (Mother’s Day) (1994) – Linux RPM Package Manager RedHat Enterprise Linux 5 (Tikanga) (2007) Community-Based Distribution: – Fedora 9 (Sulphur) (2008) – Basis for commercial edition 21

SUSE A major commercial server Linux distributor “Software and System Development” (German) S.u.S.E. Linux 1.0 (1994) – based on Slackware Novell, Inc. SUSE Linux Enterprise Server 10 (2006) Community-based distribution: – openSUSE Linux 11.0 (2008) – Basis for commercial edition 22

Other Distributions: Slackware – one of the first in 1993 Gentoo – typically built from source CentOS – based on Red Hat Enterprise Linux 23