CIS 240 Introduction to UNIX Instructor: Sue Sampson

CIS240 – Unix Overview 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).

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, without a kernel their dream of a completely free operating system would not be realized. In 1991 Linus Torvalds began developing an operating system kernel, which he named ``Linux'' 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 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. CIS240 – Unix Overview

Terminology  Kernels = memory resident part of the OS; manages CPU scheduling, memory management, process management, etc. 4.3BSD = 4.3BSD is a modern UNIX operating system distributed by University of California at Berkeley in TCP/IP was introduced into the UNIX world for the first time by 4.2BSD which preceded 4.3BSD. LINUX = Linux is a kernel originally created by Linus Torvalds. He began to write it since he was a student at the University of Helsinki. Now, Linux is used all over the world as part of GNU/Linux operating system.  Shells = Shell is a Unix term for the interactive user interface with an operating system. The shell is the layer of programming that understands and executes the commands a user enters. In some systems, the shell is called a command interpreter. A shell usually implies an interface with a command syntax (think of the DOS operating system and its "C:>" prompts and user commands such as “dir”. Bourne (sh) - original Unix shell that was developed at AT&T. Prompt -> $ C (csh) - created by Bill Joy at the University of California at Berkeley as an alternative to UNIX's original shell. Prompt -> % Korn (ksh) - developed by David Korn of Bell Labs as a comprehensive combined version of other major UNIX shells. Prompt -> $ CIS240 – Unix Overview

CIS240 – Administering Users Root is a ‘superuser’ (aka Admin for system)  Add and delete users  Change user passwords  Change ownership of files  Add and remove users to or from groups  Create and remove directories  Configure the operating system  Shutdown the computer

Adding a user –  Use adduser or useradd  Different command formats for different UNIX varieties  Plan your new user before you add CIS240 – Administering Users

Planning for a User  Name  ID  Groups  Home directory  Password CIS240 – Administering Users

Creating/Modifying User Password  Must be superuser  Enter passwd  Don’t forget the username or you will be changing the password for the superuser account  You will be prompted to enter the password twice CIS240 – Administering Users

Deleting a user =  Enter userdel and the username  userdel will not delete the home directory in some distributions Checking to see if a user exists  Users are added, by default to the \home directory CIS240 – Administering Users

Pre-assessment CIS240 – Unix Overview

CIS Using Red Hat in the Lab You will be loading Red Hat Linux on your removable hard drive. Once it has been loaded, Red Hat will boot automatically when you turn on your computer. You should shut your computers down prior to leaving each class to prevent damage to the file system. You need to sit in the same place for each class period so that you’ll have the same hard drive. Please let me know if you don’t have a hard drive and I’ll get you one.

Lab Worksheet 1 (not graded) Installing Red Hat CIS Using Red Hat in the Lab