Introduction to

Linux

Introduction to Linux

➲ What is Linux, and Who Created it?➲ GNU and the GPL➲ Unix/GNU, What is the Difference?➲ POSIX Compliance➲ Other POSIX Operating Systems➲ Uses of Linux➲ Advantages and Disadvantages

What is Linux

➲ Linux is a UNIX clone● It can run on 32 bit and 64 bit hardware

● Linux is a true multitasking environment

● Fully capable of taking advantage of multiple

processors

● Can address up to 64 GB of RAM

● Partial POSIX Compliance

Penguin Power

➲ Linux is free

● Anyone can download and compile the source

● The code can be modified by anyone provided

the modifications are released to the community

History

➲ The history of Linux began with Unix in 1969

● Unix was created at Bell Labs with the goals:● Simplicity● Recycleable code● Written in C as opposed to assembly

➲ Development started in 1991● Linus Torvalds wanted to create a free

implementation of UNIX● By 1993 there were 12000 Linux users● Today Linux rivals UNIX in stability and

scalability

The Kernel

➲ Linux is not an Operating System

➲ Linux is a kernel

➲ Linux Distrobutions use the Linux kernel together with the GNU Operating System

➲ A kernel is a program that allocates and controls hardware resources in a system

The Linux Kernel

➲ The Linux kernel is currently maintained by Linus Torvalds and a few hundred other developers

➲ Releases are numbered in a very ordered fashion.

● Major.minor.patchlevel● Odd minor numbers are development kernels● Thus

● 2.4.20 latest stable kernel● 2.5.67 latest development kernel

● Will become the 2.6 kernel

Design➲ The Linux kernel has a monolithic design➲ The other approach is the microkernel

design➲ Both have their upsides and downsides

● Monolithic kernels● Easier to build and design● Generally faster● More recompiles● Less object oriented

● Micro kernels● Considered safer● Easier to develop drivers for● Only recompile for upgrades● Generally slower● Much harder to build and design

Other *NIX Kernels

➲ The BSD kernel● This is the kernel used by the open source

BSD's● FreeBSD, OpenBSD, NetBSD

● It is neither GNU nor GPL➲ The GNU HURD

● Hird of Unix Replacing Daemons● Hurd of Interfaces Representing Death● The world's first doubly recursive acronym● Micro kernel● Not very functional

Isn't a GNU an Animal?

➲ GNU stands for GNU Not Unix

➲ The goal of GNU ● Create a free and complete UNIX-like operating

system● This has been in development since 1984

● Towards this goal the GNU project has released:● GCC, GNU Emacs, Bash, to name a few

● For more information see the GNU Manifesto● http://www.gnu.org/gnu/manifesto.html

What is the GNU GPL?

➲ The GNU General Public License● Ensures that GNU software stays free

● This is done through Copy Lefting

● Any modification to GPL software is required to

be released to the public

● Linux is released under the GPL

● Due to its restrictive nature the GPL has recently

come under fire

● http://www.linux.org.uk/GPL.html

Does the GPL Matter?

➲ Depends on your point of view● Not as important for users

● Very important for developers● Any GPL code that is incorportated into a program

makes the entire program GPL

● No closed source software can use any GPL software

So Unix Costs Money and GNU/Linux is Free

➲ Essentially this is the case● Both have the goals of POSIX compliance● Commercial UNIXes are in general closer

● This is generally in implementation, not in use➲ Commercial UNIXes generally perform

better in large systems● But even this is difference is shrinking

➲ The biggest difference is that UNIX is trademarked and must be commericial—not free

POSIX? Another Operating System?

➲ Nope, its yet another acronym● Portable Operating System Interface

➲ POSIX is a set of specifications ● Describes how the operating system should

behave● Both to the user, and to other programs

➲ POSIX was created to combat the plethora of UNIXes that popped up in the 1980, all of which had a different look and feel

POSIX cont...

➲ The Open Group controls the UNIX trademark

● They also release their own UNIX specification➲ The latest POSIX specification has been

merged with the Open Group's UNIX specification

➲ For more information see:● http://www.pasc.org● http://www.opengroup.org/

Other POSIX OSes

➲ IBM AIX

➲ Sun Solaris

➲ SGI IRIX

➲ HP HP--UX

➲ Compaq TRU64 UNIX

So Why Should I Use Linux?

➲ As a server platform ● few other operating systems can match Linux in:

● Performance● Price● Stability

➲ For Developers● Resources:

● Linux has a tremendous number of tools available for developers. And they are all free.

➲ For the Desktop● It's fun

Advantages

➲ Linux is free● Can't say that enough● It's great for poor college students

➲ Learning Linux means learning UNIX, and UNIX is the largest server platform in the world

➲ Community● The Linux community is very active and helpful● This makes support very rapid

But it's hard to learn

➲ Linux is much harder than Windows

➲ It's harder to use than Windows

➲ It lacks all those great automated

installation tools

➲ You have to manually configure hardware

➲ There is lots of hardware out there that just

won't run in Linux

So You Are Ready to Take the Plunge

➲ What do I need to know?● Not all distros are the same

● Linux From Scratch is a bad starting place● Internet Resources

● www.linux.org● www.tldp.org● www.justlinux.org● www.desktoplinux.org

➲ What distro should I start with?● Redhat● Mandrake● Suse

Some Linux Basics

➲ File System● Linux is much more hierarcal than Windows

● Everything starts at the root● /

● Boot -- contains the kernel and system map● Bin -- contains the basic system binaries● Dev -- all the device entries● Etc -- can't think of any other place to put it● Home -- where all the users live● Lib -- system libraries● Mnt -- place to mount filesystems● Proc -- system information● Root -- the root user's home● Sbin -- system binaries● Usr -- where user accessible programs go● Var -- logs and such

Basics cont...

➲ CLI● The command line interface● Bash is the most common shell● The CLI in Linux is quite useable

➲ Navigation● ls -- lists files and directories● cd -- changes directories● rm -- removes files● Navigation switches

● Most programs have options that you can pass to them via switches, for ex. ls -h gives you all the options that ls can take and what they do

6 Runlevels

➲ Level 0● Halt

➲ Level 1● Single User mode

➲ Level 2● Reserved

➲ Level 3● Full Mulituser

➲ Level 4● Reserved

➲ Level 5● Xwindows

➲ Level 6● Reboot

XWindows

➲ Linux Graphical Environment

➲ Invoked via the startx command● Two major environments

● KDE

● Gnome

● The difference is primarily in philosophy● Redhat trys to erase the differences with Bluecurve

➲ Does everything Windows does and more

A Few Good Distros

➲ Redhat

➲ Mandrake

➲ Suse

➲ Lycoris

➲ Gentoo

➲ Knoppix

Hat's off

➲ Redhat● Pros

● Easy install● Tons of graphical tools● Great hardware support● One of the most mature distros

● Cons● It's slow● Their stock kernel is somewhat bloated● Installs files in non-standard directories● Not customizeable

Drako

➲ Mandrake● Based on Redhat

● Modified to suit desktop systems more than

Redhat

● Supports that funky DVD Decoder Card you

have to use

● More on the edge than Redhat

● Uses a modified kernel

Tame the Lizard

➲ Suse● Pros

● Avoids much of the bloat of Redhat and Mandrake

● Great hardware support

● The easiest Linux installation I have ever had

● Cons● Still hard to customize

Perfection

➲ Gentoo● Pros

● Builds Linux from scratch, optimizing for the architecture of your PC

● Blazing speed● Highly customizeable● User Forums are a great place for support● Runs Quake and Unreal Tournament 2003 out of the

box● Has a kernel specifically modified for gamers

● Cons● Can be overwhelming● Takes a long time to build● Do not trip over the power cable while it is building

Knoppix

➲ Self contained

➲ Can boot almost any pc that supports cdrom

booting

➲ Settings can be stored locally or on USB

pen drive

➲ Great to learn on

➲ Does not require resizing partions or wiping

drives