linux-intro.pdf

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What is Linux?

The Origins Of Linux

Started by Linus Torvalds in 1991

Caught on in hacker community

Exploding in popularity today

Linux is Unix

Designed from scratch to be multi-user and multi-tasking

Very mature design

Thousands of applications

Linux is Open-Source

The source code is public

Supported by thousands

Widely available

Why Use Linux?

Linux Is Robust And Stable

inux Presentation Outline

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Linux has fewer bugs (than anyone)

Linux Is Powerful

Linux is high-performance

Linux will network with almost anything

The X Factor

Linux Is Flexible

Customizable hardware support

Totally customizeable software

Linux runs on multiple platforms

Linux Is Well-Supported

Best tech support anywhere

Linux Is Stunningly InexpensiveNo license fees!

Powerful software bundled with the system

Rough Spots

Linux can be picky about PC hardware

Limited support for proprietary formats

Linux requires a paradigm shift




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urther information

Last updated Sunday, May 9th, at 10:30pm




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Linus Torvalds Started Linux

Linus started writing Linux as a hobby project in 1991

Followed the design of Unix

Released as open-source

he Origins Of Linux

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Linux Caught On In The HackerCommunity

Linux attracted developers quickly

Became useful quickly

Grew steadily for years

he Origins Of Linux



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Linux Popularity Is Exploding Today

Linux has about 10 million users today

Used by companies large and small

Drawing increasing attention from technology community

User base is increasing dramatically - up 212% for 1998

Linux usage is expected to increase by at least 25%

compounded annually for the next four years.

he Origins Of Linux



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Designed from scratch to be multi-userand multi-tasking

You can run multiple apps without hampering stability

Multiple simultaneous users are no problem

You can run apps on one machine and display on another

inux is Unix



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Very mature design

Sane handling of DLL's

Better memory management than Win 98 or NT

Advanced filesystem

Remote administration

Reboot only for some kernel or hardware upgrades

Great networking - the OS of the Internet

Solid security

Doesn't crash - runs for years

inux is Unix



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Linux Has Thousands Of UnixApplications Available

Most Unix applications are portable between Unix brands

Most Unix applications are open-source

Commercial applications (including games) are available for

Linux, too

inux is Unix



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t's Open-Source

The source code must always be available

If you modify the source code, you must make your changes

available

Just because you develop on Linux does notmean you have t

make your programs free

Plenty of commercial applications are available (StarOffice,

WordPerfect, Informix, Oracle, etc.)

You can (and many many do) run your business on Linux

Check out http://www.opensource.org/ for details

inux is Open

http://www.opensource.org/http://www.opensource.org/


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Linux is a (large) group effort

Thousands of developers all over the world collaborate on Lin

development

Anyone can contribute

Linus Torvalds, the original author, supervises

inux is Open-Source - Development Community



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Linux Is Available For (Nearly) Free!

Many organizations assemble "distributions" of the Linux kern

and other applications

You can download distributions for free

You can buy Linux distributions on CD

You can pay for value-added items like commercial software

inux is Open-Source - Widely Available



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Linux kernel and applications are solid

People write Linux code because they want or need it

People write Linux code for fun and recognition

Other people can and doread, critique and fix

Bugs are fixed quickly

Linux is demonstrably stable and nearly bug-free.

Advantages of Linux - Fewer Bugs



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Unix philosophy is first stable, then fast

Linux takes advantage of decades of Unix design work

Linux makes even low-end hardware useful

Benchmarks show Linux to be very fast

Advantages of Linux - High Performance



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Linux Is A Promiscuous Networker

Linux talks with Windows

Linux talks with Macintosh

Linux talks with Novell

IP Masquerading

Web servers, FTP servers, IRC, MUD, mail servers, and much

more!

Advantages of Linux - Networking



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Linux Is A Hacker's Dream

Gain experience with low-level programming

Unusual types of networking

High-end parallel processing

Software RAID

Emulation software

Advantages of Linux - The X Factor



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Make Your Hardware Do What YouWan

Correct hardware performance - work around hardware bugs o

deficiencies

Improve hardware performance - use allof its potential

Dynamically change hardware support - use only what you ne

when you need it

Run without normal hardware like a keyboard or mouse, or ev

a disk drive

Advantages of Linux - Customizing Hardware



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Very Customizeable Software

Most software is highly configurable

Everything is scriptable

When all else fails, do it yourself!

Advantages of Linux - Customization



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There are many, many Linux ports:

Intel 386+ (of course) with support for ISA, EISA, PCI, VLB, andMCA (and Merced)

Alpha (Linux is 64-bit now)

Motorola 68030+

Power PC

ARM

SPARC

MIPS

SGI (in progress)

VAX (in progress)

PalmPilot (in progress)

8086-80286 (in progress)

And more!

Advantages of Linux - Multiplatform

http://www.zdnet.com/intweek/daily/980910b.htmlhttp://www.azstarnet.com/~axplinux/http://www.azstarnet.com/~axplinux/http://www.azstarnet.com/~axplinux/http://www.linux-m68k.org/http://www.linuxppc.org/http://www.arm.uk.linux.org/~rmk/armlinux.htmlhttp://www.geog.ubc.ca/s_linux.htmlhttp://lena.fnet.fr/http://www.linux.sgi.com/http://ucnet.canberra.edu.au/~mikal/vaxlinux/home.htmlhttp://ryeham.ee.ryerson.ca/uClinux/http://www.uk.linux.org/ELKS-Home/http://www.ctv.es/USERS/xose/linux/linux_ports.htmlhttp://www.ctv.es/USERS/xose/linux/linux_ports.htmlhttp://www.uk.linux.org/ELKS-Home/http://ryeham.ee.ryerson.ca/uClinux/http://ucnet.canberra.edu.au/~mikal/vaxlinux/home.htmlhttp://www.linux.sgi.com/http://lena.fnet.fr/http://www.geog.ubc.ca/s_linux.htmlhttp://www.arm.uk.linux.org/~rmk/armlinux.htmlhttp://www.linuxppc.org/http://www.linux-m68k.org/http://www.azstarnet.com/~axplinux/http://www.zdnet.com/intweek/daily/980910b.html


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Most Linux Software Has No LicenseFees!

Install on as many computers as you like with one CD

Support as many users as you need

Sharing with others is encouraged

Advantages of Linux - Inexpensive



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Hundreds Of Applications Bundled ForFree

Every network application you could want

More compilers than you can shake a stick at

Spreadsheets, databases, scientific simulation and visualizati

games, and more!

Advantages of Linux - Inexpensive



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Some oddball or proprietary hardwarehas limited support

Winmodems, Winprinters not supported

UDMA/33 under development

ISA Plug and Play can be complicated (PCI is fine)

Somevideo cards, SCSI cards, and so on

Almost always alternatives available

Disadvantages of Linux - Less PC Hardware Support



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Proprietary protocols and formats aredifficult to support

No AOL client, or MSN, or Compuserve, or...

Office '97 support took a while

No Internet Explorer, most use Netscape

Disadvantages of Linux - Proprietary Formats



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Linux represents a different philosophyrom Windows or even Mac

There is a learning curve

...but there are ways to ease the journey

You have to look under the hood a bit

...but you will be more productive

Disadvantages of Linux - Paradigm Shift



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More Linux Resources

This Presentation

he full text of this presentation (along with all of these links) is available online attp://www.tir.com/~sorceror/mdlug/preso.html. Each bullet point is a link to a page with explanation

ore detail, and links to further information. The Metro Detroit Linux Users Group's home page is atp://www.mdlug.org/.

Linux for Free

he Linux Giveaway List is at http://visar.csustan.edu/. Linux users from around the world offer to m

ou their Linux CDs if you pay for the postage. You don't usually get the most recent stuff that way, s nearly free.

A partial list of businesses that sell Linuxmaterials:

Linux Central, at http://www.linuxcentral.com/. (Operated by Brad Glonka, an MDLUG memb

Linux Systems Labs, at http://www.lsl.com/.

Infomagic, at http://www.infomagic.com/.

CheapBytes, at http://www.cheapbytes.com.

Walnut Creek CDROM, at http://www.cdrom.com/

Linux Documentation & Information

he Linux Documentation Project at http://sunsite.unc.edu/LDP/has huge amounts of information on

ings Linux. One page to visit is the Linux INFO-SHEET attp://sunsite.unc.edu/LDP/HOWTO/INFO-SHEET.html, which contains a thorough summary of Lin

atures. The Linux Myth Dispeller at http://www.KenAndTed.com/KensBookmark/linux/index.htm

d the Linux Anti-FUD FAQ at http://www.geocities.com/SiliconValley/Hills/9267/fud2.htmladdrmmon myths and misconceptions about Linux.

ther sites to visit include http://www.linux.org/, http://www.linuxresources.com/,

tp://www.debian.org/, and http://www.redhat.com/.

NET has recently set up an introductory site on Linux attp://home.cnet.com/category/topic/0,10000,0-3721-7-279437,00.html.

Resources

le:///D|/Linux Presentation/resources.html (1 of 2) [08\23\2002 4:47:39 PM]
http://www.tir.com/~sorceror/mdlug/preso.htmlhttp://www.mdlug.org/http://visar.csustan.edu/http://www.linuxcentral.com/http://www.lsl.com/http://www.infomagic.com/http://www.cheapbytes.com/http://www.cdrom.com/http://sunsite.unc.edu/LDP/http://sunsite.unc.edu/LDP/HOWTO/INFO-SHEET.htmlhttp://www.kenandted.com/KensBookmark/linux/index.htmlhttp://www.geocities.com/SiliconValley/Hills/9267/fud2.htmlhttp://www.linux.org/http://www.linuxresources.com/http://www.debian.org/http://www.redhat.com/http://home.cnet.com/category/topic/0,10000,0-3721-7-279437,00.htmlhttp://home.cnet.com/category/topic/0,10000,0-3721-7-279437,00.htmlhttp://www.redhat.com/http://www.debian.org/http://www.linuxresources.com/http://www.linux.org/http://www.geocities.com/SiliconValley/Hills/9267/fud2.htmlhttp://www.kenandted.com/KensBookmark/linux/index.htmlhttp://sunsite.unc.edu/LDP/HOWTO/INFO-SHEET.htmlhttp://sunsite.unc.edu/LDP/http://www.cdrom.com/http://www.cheapbytes.com/http://www.infomagic.com/http://www.lsl.com/http://www.linuxcentral.com/http://visar.csustan.edu/http://www.mdlug.org/http://www.tir.com/~sorceror/mdlug/preso.html


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ome helpful tips on installation can be found at http://heather.cs.ucdavis.edu/~matloff/linux.html.

Unix / Windows NT Comparisons

http://citv.unl.edu/linux/LinuxPresentation.htmlis a website made from a presentation on why

university switched from NT to Linux.

http://www.unix-vs-nt.org/is an oft-cited paper by a Microsoft Certified Engineer comparing

Linux and Windows NT.

http://mercury.chem.pitt.edu/~angel/LinuxFocus/English/May1998/article16.htmlis an article

from LinuxFocus magazine comparing Windows to Linux.

http://www.isdmag.com/Editorial/1998/CoverStory9807.html

Resources

le:///D|/Linux Presentation/resources.html (2 of 2) [08\23\2002 4:47:39 PM]
http://heather.cs.ucdavis.edu/~matloff/linux.htmlhttp://citv.unl.edu/linux/LinuxPresentation.htmlhttp://www.unix-vs-nt.org/http://mercury.chem.pitt.edu/~angel/LinuxFocus/English/May1998/article16.htmlhttp://www.isdmag.com/Editorial/1998/CoverStory9807.htmlhttp://www.isdmag.com/Editorial/1998/CoverStory9807.htmlhttp://mercury.chem.pitt.edu/~angel/LinuxFocus/English/May1998/article16.htmlhttp://www.unix-vs-nt.org/http://citv.unl.edu/linux/LinuxPresentation.htmlhttp://heather.cs.ucdavis.edu/~matloff/linux.html


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Begun By Linus Torvalds In 1991

1991, a Finnish computer science student acquired a 386 PC and decided to study operating systemogramming with it. He was dissatisfied with the DOS that came with the system and wished for atter alternative.

e played with a special educational operating system called Minix that was a small version of Unixtoo, had limitations, including a restrictive license that he felt stifled improvement. After a while, hcided to write a new operating system that would take better advantage of his hardware. His statedthe time was to "write a better Minix than Minix".

or more information on Linus Torvalds, look here.

he Origins Of Linux

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Linus Decided To Follow The Design OfUnix

ecause of the long history of Unix, the elegance of its basic design, the wide variety of softwareailable for it, and his own familiarity with the system, Linus decided to write a version of Unix. Sie basic design was widely documented and used, he had plenty of information to work with.

he existence of the GNU Projecthelped out a great deal. This was (and is) a set of programs written

nix-like operating systems that was freely available with source code. Once the operating system w

en marginally functional, he had unitilities and applications available, both to test the system with make use of the system once tested. This was, of course, a tremendous help in gaining acceptance nux early on.

he Origins Of Linux

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http://www.gnu.org/http://www.gnu.org/


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Linux Was Open From The Start

order to encourage the wide dissmination of Linux, and in the spirit of cooperation and communityat characterizes most computer programmers, Linus released the code under the GNU Public Licen

hich meant that anyone could use and improve linux however they liked, as long as they made theirntributions available to the rest of the world.

his meant that anyone who wanted a new feature for Linux, or had an idea for a possible improvemuld try it out for themselves. They could request help, or work by themselves, or organize a projecng as they made their changes or developments available. This led to a snowballing effect, becausenux became more useful, it also became more interesting to new programmers, and as it became mteresting to new programmers, it became more useful.

he Origins Of Linux

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Linux Attracted Developers Quickly

y the end of the first year of development, there were around 100 developers working on Linux. Byd of the second year, there were over a thousand. Because of Linux's flexibility, familiarity, andrformance, developers found themselves enjoying working on Linux just for the fun of it.

ecause of its open nature, unusual sophistication, and cooperative spirit, lots of experimentalvelopment was done on Linux. New ideas, and twists on successful old ideas, were added by peopho had interests in specific areas. Developers who wanted powerful home networks added networkde. Those with experience in memory management worked on virtual memory, code sharing, and srth.

y tradition, Linus got the final say about what was "officially" part of the Linux kernel and what was been generally agreed that his guidance has been outstanding for sheperding the project. Somehoom the work of thousands of developers spread all over the world, communicating almost entirelyrough the Internet, a remarkably cohesive and organized structure has emerged.

he Origins Of Linux

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Linux Became Useful Quickly

side from an enjoyable way to experiment with operating system programming, Linux quickly becavery useful tool for general computing. Unix applications were easily ported to the new variant, andople began using Linux for more than toy experiments.

s it became more useful, developers became more ambitious. "Wouldn't it be nice if Linux did..." wmmon question, and someone (often the person who'd asked the question) went ahead and

mplemented the needed feature.

he Origins Of Linux

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Linux Kept Growing

nux use grew steadily. Engineers who wanted to quickly test a piece of hardware or students whouldn't afford commercial software were able to adopt Linux for their needs. Linux has at least doubuser base every year of its existence.

nce 1994 the growth has been particularly impressive. Attention was paid to making Linux easier tstall, use, and maintain. People began putting together "distributions" of the Linux kernel bundled weful applications and utilities. The Linux Documentation Project was begun, ensuring that newcomould be able to find the information they needed to get the most out of the platform. And commercimpanies began paying more attention to Linux, making sure that driver information was avialable

rdware and specifications were available for software.

he Origins Of Linux

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Linux Has Millions Of Users

ecause Linux is open-source, it's hard to tell just how many Linux users there are. When a single CD

n be used to install hundreds of copies of Linux, when people can download a distribution over theternet and install it, it's just about impossible to keep an accurate count.

stimates based on website reports, CD sales, and voluntary registration are necessarily incomplete, ey support a figure of between 7 and 15 million Linux users worldwide, and that number appears to

oubling every twelve months. For more information, visit the Linux Counter Home Page. Also chec

ut this article in InfoWorld.

nux is the onlynon-Microsoft OS that is gaining market share.

he Origins Of Linux

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http://counter.li.org/http://www.infoworld.com/cgi-bin/displayNew.pl?/reed/reed.htmhttp://www.infoworld.com/cgi-bin/displayNew.pl?/reed/reed.htmhttp://counter.li.org/


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Linux Is Used By Many Businesses

nux is known to be used at Corel, Boeing, NASA, and other organizations large and small. Diamonultimedia, Adaptec, and many other hardware vendors officially support Linux and many provide tivers for their hardware.

ou may use Linux at work for print or file services, or for your Intranet or Internet website, and noten know it. As a reporter for Inter@ctive Week noted, (May 11 1998) "I talked to the chief financificer at a bank in New York, and he said they weren't using Linux... Then I talked to the IS staff, aney said they had 100 servers running Linux."

this announcement, Salon magazine proudly announces that its new site is powered by Linux.

he Origins Of Linux

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http://www.newsalert.com/bin/story?StoryId=CnWG1qbWbsfnnmdiXhttp://www.newsalert.com/bin/story?StoryId=CnWG1qbWbsfnnmdiX


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Linux Usage Is Exploding Today

ternational Data Corporation, which does annual surveys of operating system usage among their mher statistical services, has noted that Linux usage increased by 212% in 1998, making it thestest-growing operating system, period. Please see the report for yourself.

nother report has Linux use increasing by 25% each year for the next four years.

or some information on the recent history of Linux, please see the 1998 Linux timelineat the Linux

eekly News.

s worth noting that, currently, overall Windows usage dwarfs Linux usage by a large margin (perha00 to one or more). However, in the high-end market, where Microsoft's Windows NT / "Windows000" competes, Linux and Windows arefarcloser.

s also worth noting the reasons cited for NT's growth...

he Origins Of Linux

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http://www.news.com/News/Item/0,4,30027,00.html?st.ne.fd.gif.ahttp://www.idc.com/Data/Software/content/SW033199PR.htmhttp://lwn.net/1999/features/1998timeline/http://lwn.net/http://lwn.net/http://lwn.net/http://lwn.net/http://lwn.net/1999/features/1998timeline/http://www.idc.com/Data/Software/content/SW033199PR.htmhttp://www.news.com/News/Item/0,4,30027,00.html?st.ne.fd.gif.a


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True, stable multitasking

ll applications in Linux run in their own private memory space. This means that a poorly-writtenplication cannot tamper with the memory of another application (or the kernel). If an application d

y to access memory it doesn't own, it is immediately halted by the operating system, without disturby other process on the system.

he Windows family of operating systems implement this type of protection imperfectly. Even WindT, the most protected Microsoft operating system, does not by default enforce as strict a separationtween processes, and deliberately allows some ability to tamper with the kernel. This often leads to

ndesired interations, which can impair the stability of the system.

addition, all programs under Linux are preemptively multitasked. This means that the OS handles heduling of processes (and kernel threads). No application can hog the resources of the system unlee system administrator specifically defines it as high-priority. This leads to smoother performance tter load balancing.

What Is Linux? - Linux is Unix

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Multiple simultaneous users

nix was designed with the notion that multiple people would be sharing use of the system at the samme. Several people can log into a Linux machine and each of them can run whatever programs theyke. Because of the nature of the Linux GUIs (see the nextdetail) these users don't all have to be in f

the machine to fully use it.

ach user has their own individual preference files that allow them to cusomize their use of the systeithout affecting others. Unix applications are written from scratch with the idea that multiple peopleill be using them, and each may have entirely different preferences. One user of a mail-reader mighefer to read and send in full HTML, while another might want to read and send text-only. In Linuxey both can have their way, even if each of them is running the mail-reader at the same time!


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Remote operation

ecause of the fundamental design of Unix, every application can be run on one machine and displayterface on another machine. For graphical applications, you probably want to use a high-speed netwke Ethernet, but even a serial connection will work. Programs don't have to be designedto run remoey just do. It takes extra effort to write a program that can only be used on one machine.

ost Linux users use the X Window system, which is designed to transparently export graphics overtwork. A user on machine1 can fire up X-Windows and connect to machine2, and run programs, sees, and so onjust as if they were directly in front of machine 2, even if machine1 is in California anachine2 is in Switzerland.

ven if all you have is a terminal emulator (e.g. Hyperterminal, Procomm Plus, or one of the manyrminal programs for Linux) you can log in remotely and run non-graphical, command-line tools jusyou were at the command line of the remote machine.

his is extremely useful for remote administration. If you're a webmaster and your webserver is havi

oblems, you don't have to go in to work, you can dial in to the server from home and do everythingou could do if you were in front of the machine. (Well, okay, you can't swap hardware, but just abouerything else.)

the Windows world, these capabilities are imperfectly emulated with things like PC Anywhere orinFrame. Each of these has limitations and applications that don't work with this model, and requirreful setup, because the applications were never intended to run in such a manner. Also, Windowsten needs a reboot for even some trivial changes to take effect, which is in sharp contrast to Linux booting).

ote that there are X systems available that run under Windows, so even Windows boxes on the samtwork can run Linux programs. At least one X program is free.


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Sane Handling Of DLL's

indows allows the use of DLLs (Dynamic Link Libraries) to modularize applications and reuse codhe idea is that, when an application is starting up, it locates the DLL and calls functions inside it. Ths several theoretical advantages. The application does not need to contain the code itself, otherplications can reuse the same code, and different people (even different companies) can providemponents that other people can link to and use.

he problem with this in Windows is that there is no version control on DLLs. When you installplication1, it installs version 1 of "frog.dll". Then you install app2, which uses version 2 of "frog.d

he new version overwrites the old version. The next time you start app1, it opens "frog.dll" and find

mething other than version 1, leading to unpredictable results. It might work fine (if you're lucky). ight immediately crash. It might look like it's working but really be slowly corrupting your data.

ven worse, the operating system uses the same DLLs, and can be subject to the same problems. Maindows users have installed an application (even one written by Microsoft) and had it break otherograms that were working fine, or even render the machine unbootable, requiring a full reinstall ofindows.

here are third-party applications that help to deal with this problem, but they don't allow you to runplications that require conflicting DLLs at the same time.

nux (among other operating systems) does not have this problem. Linux uses DLLs, too (in Unix teey are called "shared objects"), but the OS keeps track of the versions. When you run app1, Linux nat it needs version 1 of "frog.so", and automatically links it in. When you run app2, Linuxtomatically links version 2 of "frog.so". This happens even if app1 and app2 are running at the sam

me.


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Memory Management

nux is oustanding in the area of memory management. Linux will use every scrap of memory in astem to its full potential. For example:

he Linux kernel itself is much smaller and more efficient than the NT kernel. On my 64MB box atork, NT typically takes up about 18MB. On my 64MB box at home, the Linux kernel takes up less MB. That means 16MB of extra memory can be used by applications instead of just holding the OS

nux uses a copy-on-write scheme. If two or more programs are using the same block of memory, one copy is actually in RAM, and all the programs read the same block. If one program writes to that

ock, then a copy is made for just that program. All other programs still share the same memory. Whading things like shared objects, this is a major memory saver.

emand-loading is very useful, as well. Linux only loads into RAM the portions of a program that artually being used, which reduces overall RAM requirements significantly. At the same time, when

wapping is necessary, onlyportionsof programs are swapped out to disk, not entire processes. Thislps to greatly enhance multiprocessing performance.

nally, any RAM not being used by the kernel or applications is automatically used as a disk cache. eeds access to the disk so long as there is unused memory.


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Linux Supports An Advanced Filesystem

he DOS/Windows FAT file system was designed in the days of 320K floppy disks, and has not worell now that drives commonly hold well over ten thousand times as much data. It works by dividingsk up into chunks of a fixed size, and keeping a table (the File Allocation Table, or FAT) of whichunks belong to which files. This wastes space (even a file that is one byte in size takes up one fullunk, which could be 64K or more) and quickly leads to disk fragmentation.

ven worse, there is no error-checking when the FAT is modified, and filesystem errors can accumuading to disk corruption. Most Windows users have learned through experience to run SCANDISKen DEFRAG once a month to keep these problems under control, or eventually the disk becomes

nusable, perhaps losing important data.

nux normally uses its own high-performance filesystem, which uses disk space much more efficienptimizes for speed on reading and writing, and automatically prevents fragmentation. The Linuxesystem literally does not need a defragmenter, though one is available. The operating system notichen programs make errors writing to the disk and automatically prevents them, so there is usually ned to run a disk checker unless you notice a problem.

ecause of the automatic disk cacheingthat Linux uses, programs don't have to wait for the disk to f

riting data before they can can continue operations, so programs visibly run faster. About the only

sadvantage, if you can call it that, is that you shouldn't just shut the power off on the computer. Yorongly advised to shut down the system first, so that any unsaved data can be written out to disk.

ven if the power fails or you accidentally switch off the system before shutting down, Linux usuallytomatically recover the filesystem without problems. Although I have heard of people losing data tay, my system personally has survived a couple power losses without and data loss. (Of course, I wd added a UPSand now I don't have to worry about it...)

f course, Linux can also read and write all FAT variants (from FAT12 to FAT32 and VFAT), WindT's NTFS, OS/2's HPFS, and many others you've never heard of. Often it can use them faster than t

tive operating system can.


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Remote Administration

nce Unix was designed to run continuously, for extended periods of time, in mission-critical capacith a minimum of downtime, administration was given a lot of attention. Almost any maintenance tn be done remotely on a Unix system.

s noted before, essentially all applications can be run remotely from another machine on a network

en over a dialup line. When you consider that almost every feature of Linux and its applications canfigured without rebooting, it's clear why Unix systems are favored by many administrators.

emote maintenance is often not very important to the home user, but to a business user of Linux it c

critical. If the pager goes off in the middle of the night because the file server is full, it's nice to bele to just dial in and take care of it from home instead of having to drive in to work to sit down in fthe machine. Using kernel modules, even relatively major upgrades can be done remotely.

bout the only things that can't be done remotely are hardware updgrades and full kernel upgrades.Actually, even kernel upgrades can be done remotely if you're confident that nothing will go wrong.


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Reboots Are For Upgrades

nux enforces a strict separation between the kernel and other applications. Most services like mail,d print serving, web serving and so on are applications, and can usually be changed dynamically. Aorst, a specific application may need to be stopped and restarted, but not the whole system. This meat Linux only needsto be rebooted for kernel updates and hardware changes, and often not then. (Ta great boon for remote administration.)

or example, the Linux kernel is designed to use loadable modules whenever possible. If you hook uD-ROM drive to your SCSI bus, you can insert a CD-ROM device driver module into the kernel whe kernel is runningand immediately begin using the CD drive. Of course, if you remove hardware n also remove modules and reclaim the memory those modules were using.

hile it is notrecommended, there are reports of people swapping internal cards and drives withoutbooting. Again, this is extremely risky, but it's possible under Linux. In Windows, installing a deviciver alwaysrequires a reboot. (Once installed, some device drivers can be stopped and restarted.)

nux provides the ability to dynamically increase swap space and then reduce itlater without a rebohis is in sharp contrast to Windows, where the swapfile can only increase in size, and never decreasntil the next reboot.


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The OS Of The Internet

CP/IP networking and the Internet was originally developed on Unix systems, and most of thegh-power networking in the world is done on Unix systems. The OSI++ Counterindicates that abo

% of the web servers on the net are Unix boxes. In fact, Linux has the largest market share for thetire Internet, running 25.7% of the news servers, 26.9% of the web servers, and 33.7% of the FTPrvers in the world. (If you combine Windows 95/98 with Windows NT, Windows is second to Linu

oth web and FTP servers. Solaris, a Unix variant, is the number two news server.)

nux provides not only extremely fast and reliable networking, but dozens of major and minor netwrvices are usually provided when you get Linux. Web servers, file and print servers, ftp servers, timrvers, NIS servers, IRC servers, News servers, compute servers, and more are available for free or tle cost. This includes Apache, the most widely-used webserver on the planet (with over 50% mark

are).

uch of the development of the new IPv6 specification is being done on Linux systems, because of be low cost and the ease of development of the system code. See The Linux IPv6 Pagefor further

formation.

fact, a large fraction of all experimental networking, perhaps most, is done on Linux, in no small pue the the open source code. Linux provides a wide variety of uniquenetworking methods.


le:///D|/Linux Presentation/1-2/network.html [08\23\2002 4:48:37 PM]
http://www.leb.net/hzo/ioscount/index.htmlhttp://www.apache.org/http://www.bieringer.de/linux/IPv6/http://www.bieringer.de/linux/IPv6/http://www.apache.org/http://www.leb.net/hzo/ioscount/index.html


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Solid Security

iruses are unknown in Linux

nux is a very secure operating system, much more so than Windows 9x, and at least the equal ofindows NT. So far as anyone has been able to tell, exactly one virus has ever been written for Unixatforms. And as viruses go, it's pretty anemic. It's worth it to examine why this is the case. To do sove to take a quick look at how viruses work.

virus spreads when an infected application is run. The virus then looks for other running applicatiofor applications on disk, and copies its own code into the other applications, thereby infecting themhen the newly-infected applications are run, they will try to infect other applications, and so on.

oth of these avenues of infection are severely limited or impossible under Linux. Since each applica

ns in its own protected memory space, it is not possible for a virus to infect another application run

memory. And Linux implements a file permission structure that greatly limits the damage that a vin do.

Unix systems, there are three main kind of permission for a file - read, write, and execute. There aree kinds of users this can apply to - the file's owner, users in the same group as the owner, andthers".

practical terms, when a user runs a program infected with a virus, the virus can only infect theplications that the user has permission to write to. In the typical Linux system, this is very fewplicaitons, and none of them are critical to the operation of the system.

here isone type of virus that can infect a Linux system - a boot-sector virus. This kind of virus doese an operating system at all, but instead runs using the BIOS. When the boot-sector virus runs, Linn't even running yet, so it can't intercept it. However, no known boot-sector virus is written to workith Linux, and so as soon the machine is infected with such a virus, it probably won't boot. At thisoint, all you need to do is boot from a Linux floppy and erase the virus. In this sense, Linux is a gre

rus-detector!

reventing remote takeovers and denial-of-service

nce viruses are difficult and not terribly impressive in the Linux world, crackers tend to try other mcompromising systems. There are two ways to approach this - "getting root" and "denial-of-servicthe first case, the cracker tries to get "root" or "superuser" access - more or less the same as

Administrator" under Windows NT. In the second, the cracker tries to impair the operation of themputer in some like, like a SYN flood or a WinNuke.


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nux is less prone to these sorts of attacks than most operating systems. This is partly because of itssign and partly because of the open-sourcenature of Linux development. For example, Linux is

signed so that the "sechole.exe" program (which gives any user Administrator access under WindoT) is not possible - at least, by that method. The permissions structure described above means that ea bug in one process is found, it does not affect other processes. Very few services run with a lot ofrmissions, and most of the bugs in those services have been found and removed. (Remember, Unixen around for almost 30 years - performance and security problems have been continuously addres

at entire time.)nd because Linux is open-source, security bugs are fixed quickly, often within hours. Having the so

pen is a lot like having thousands of programmers audit the security of the system continuously.

enial-of-service (DOS) attacks are also more limited under Linux. If you give users write permissioshare under Windows NT, those users can fill up the entire disk if they like, which can cause NT tocome unstable. Linux supports disk quotas, which limit the amount of space a malicious or mistaker can take up.

nux also supports limits on other resources, to prevent users running too many processes, or openin

o many network connections, or whatever.

or more information, check out the Linux Security HOWTO.

the way of a testimonial, check out this storyabout an ISP that upgraded to Linux to improve secu


le:///D|/Linux Presentation/1-2/security.html (2 of 2) [08\23\2002 4:48:38 PM]
http://sunsite.unc.edu/LDP/HOWTO/Security-HOWTO.htmlhttp://www.zdnet.co.uk/news/1999/4/ns-6857.htmlhttp://www.zdnet.co.uk/news/1999/4/ns-6857.htmlhttp://sunsite.unc.edu/LDP/HOWTO/Security-HOWTO.html


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Crashes are extremely rare

nce Linux is designed not to require rebooting, it is very important that the system be stable enoug

ndle running for extended periods of time without crashing.

ecause Linux has fewer bugsthan other platforms, and is designed to run in demanding environmen

r long periods of time, many Linux users run their systems 24/7 for months on end. This is particulmmon among businesseswho use Linux on their servers.

nux users have reported uptimes of well over a year, on active, heavily-loaded systems. Uptimes loan that are rare, not because of crashes, but because few users can resist upgrading their hardware f

ore than a year. Even so, the Linux kernel was recently modified to allow logging of uptimes beyon97 days without wraparound. Compare this to the known problem that Windows 95 and Windows 9

nnot run more than 49.7 days, ever.

icrosoft admits that Windows NT is only about twice as reliable as Windows 95. A Unix server wo

ashamed to post numbers like these.

ne common hobby of some Linux users is running the "crashme"program for long periods of time.

sually they run until they give up. When a kernel bug isdiscovered, it is found and fixed.


le:///D|/Linux Presentation/1-2/nocrash.html [08\23\2002 4:48:38 PM]
http://www.zdnet.com/zdhelp/stories/main/0,5594,2238939-3,00.htmlhttp://www.zdnet.com/zdhelp/stories/main/0,5594,2238939-3,00.htmlhttp://www.microsoft.com/ntworkstation/basics/features/reliability/default.asp?site-ntwhttp://www.microsoft.com/ntworkstation/basics/features/reliability/default.asp?site-ntwhttp://www.zdnet.com/zdhelp/stories/main/0,5594,2238939-3,00.htmlhttp://www.zdnet.com/zdhelp/stories/main/0,5594,2238939-3,00.html


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Unix Applications Are Portable

ecause all the variants of Unix share almost all their major design features, programs written for onand or variation of Unix are usually easily portable to other types of Unix. All Unix programs are aore portable between Unix brands than programs are between, say, Windows 98 and Windows NT

his means that programs written for some other brand of Unix can almost always be ported to Linuxther easily. Linux didn't even exist when Sendmail (which carries over 80% of Internet e-mail), BIN

which handles almost all DNS services) and the other critical Internet applications were written, butere easily ported to Linux.

ven commercial software is available for Linux. Oracle, Sybase, and other commercial softwarendors have already ported or are in the process of porting their products to Linux. The large amounmmon ground among the various strains of Unix simplifies this task enourmously.


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Most Common Unix Applications AreOpen-Source

nce most of the common or important Unix applications or utilites are also open-source, this meanat Linux automatically has thousands of applications to choose from. These include everything frommmon utilities to large-scale applications like Apache, the most popular webserver on the planet.

lmost all new development explicitly includes a Linux port, so more are available all the time. In faost new Unix programs are developed on Linux first, or at least in parallel. Even commercialvelopers tend to run Linux on their PC's at home, so they can use the same tools, compilers, andvironment they have with their commercial Unix workstations at work.


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Plenty Of Commercial ApplicationsAvailable

articularly in recent months, commercial developers have flocked to the Linux platform. Oracle,

ybase, and many other commercial database providerseither have released or announced software f

nux.

he StarOffice and Applixware office suites offer Microsoft Office compatibility and a full set of offplication functions.

any Linux games exist. Notably, over half the Quake servers in the world run under Linux. The Lin

amessite has plenty of information on games for Linux.


le:///D|/Linux Presentation/1-2/commapps.html [08\23\2002 4:48:45 PM]
http://www.linuxgames.com/http://www.linuxgames.com/http://www.linuxgames.com/http://www.linuxgames.com/


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The GNU Public License

nux is developed under the GNU Public License. This is sometimes referred to as a "copyleft", tostinguish it from a copyright.

he gist of the GPL is that the source code is available to anyone who wants it, and can be freelyodified, developed, and so forth. There are only a few restrictions on the use of the code.

you make changes to the kernel, you have to make those changes available to everyone. This basiceans you can't take the Linux source code, make a few changes, and then sell your modified versionithout making the source code available, for no more than your cost of providing it.

f course, you can't just copy source code from the Linux kernel and just use it your own programs.opying ideasis fine, but cutting and pasting chunks of source is forbidden. (Well, actually, you canour program will then be covered by the GPL too. Often this is not a problem.)

his practical effect of this is that you can't charge much for the Linux source code. When you buy antaining the Linux binaries and source code, you're buying the convenienceof installing from CDstead of downloading it off the net, and the convenience of having the code pre-compiled for you.ou're not really paying for the software itself.

oftware released under public licenses (like the GPL and others) has often been called "free softwar

his has led to some confusion. When Linux is referred to as "free", it means "liberated", not necessaero-cost". Becuase of this confusion, the term "open-source" has been coined. For details, please taok at the open-source home page.

ote that there is no restriction on how the kernel is used. You can use it at home, at work, inovernment computers and church computers and anything else. (See the nextdetail for more

formation.)

he GPL has a lot of ramifications and is too broad a subject to cover in this overview. You can readpy of the GPL here.

What Is Linux? - Linux is Open

le:///D|/Linux Presentation/1-3/gpl.html [08\23\2002 4:48:52 PM]
http://www.opensource.org/http://www.opensource.org/gpl-license.htmlhttp://www.opensource.org/gpl-license.htmlhttp://www.opensource.org/


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Commercial Development

you develop a program that runs under Linux, even if you use the free, high-performance GNUmpilers (also under the GPL), you don't have to make it open-source, too. Just because you usethe

rvices of the kernel doesn't mean you have to be under the same license as the kernel.

here are a wide variety of programs and applications available for Linux, under a wide variety ofcenses. These range from public domain to postcard-ware to shareware to commercial, with all sortmbinations, too.


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Commercial Applications

any commercial vendors either have released or are developing applications for Linux, including:

Corel

Informix

Oracle

Netscape

Even Microsoftis porting the Windows Media Player to Liunx

And more!ecently Intel announcedthat it was working on a Uniform Driver Interface so that all Unix variants

tel platforms would use the same driver model. To quote direct from the horse's mouth: "Linux wilid Quick, key to the adoption of the UDI initiative. A reference platform will be distibributed aseeware for Linux, and the Project UDI members will be counting on the Linux community to workvice drivers." In other words, Intel is basing a key business plan on Linux and the Linux developmmmunity.

enty of Linux games exist. Notably, over half the Quake servers in the world run under Linux. Thenux Gamessite has plenty of up-to-date information on games for Linux.


le:///D|/Linux Presentation/1-3/commavail.html [08\23\2002 4:48:53 PM]
http://www.corel.com/news/1998/may/linux.htmhttp://www.informix.com/cyb-cgi/Webdriver?MIval=cyberzine_view_Story&ID=1634http://www.oracle.com/cgi-bin/press/printpr.cgi?file=980721.26767.html&mode=corp&td=1&tm=8&fd=1&fm=07&status=Search&ty=98&limit=50&fy=98http://www.mozilla.org/http://www.microsoft.com/http://www.zdnet.co.uk/news/1998/37/ns-5501.htmlhttp://www.linuxgames.com/http://www.linuxgames.com/http://www.zdnet.co.uk/news/1998/37/ns-5501.htmlhttp://www.microsoft.com/http://www.mozilla.org/http://www.oracle.com/cgi-bin/press/printpr.cgi?file=980721.26767.html&mode=corp&td=1&tm=8&fd=1&fm=07&status=Search&ty=98&limit=50&fy=98http://www.informix.com/cyb-cgi/Webdriver?MIval=cyberzine_view_Story&ID=1634http://www.corel.com/news/1998/may/linux.htm


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Linux In Business

large number of business are using Linux (see this linkfor an incomplete list) in a wide variety of

elds, ranging from ISP to manufacturing to government to retailers and more. (It seems that an ama% of ISP's use Linux!)

ecause of Linux's 24/7 reliability, scalability, performance, and configurability, it can make a poweresource for any company. When you consider Linux's low cost(zero per-user license fees are jus

mple) Linux systems are even more attractive.

partial list of Linux business resources is maintained at http://www.linux.org/business/index.html,

a good place to look for more information.

recent example in the press is Total Travel Management, in Troy, Michigan. You can read about thnversion to Linux here.


le:///D|/Linux Presentation/1-3/business.html [08\23\2002 4:48:53 PM]
http://www.m-tech.ab.ca/linux-biz/http://www.ci.infobeads.com/INSIDER/PAGES/TOPICS/INTERNET/ISP_HW_0505/Default.asphttp://www.linux.org/business/index.htmlhttp://www.infoworld.com/cgi-bin/displayNew.pl?/wonnacott/990215lw.htmhttp://www.infoworld.com/cgi-bin/displayNew.pl?/wonnacott/990215lw.htmhttp://www.linux.org/business/index.htmlhttp://www.ci.infobeads.com/INSIDER/PAGES/TOPICS/INTERNET/ISP_HW_0505/Default.asphttp://www.m-tech.ab.ca/linux-biz/


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The Linux Development Community

ecause the source code is available to anyone who wants it, many many programmers have examine source, and thousands have been interested enough to contribute bugfixes, improvements, newatures, and more.

very popular description of the open-source development model can be found in Eric Raymond'sper, The Cathedral And The Bazaar. This compares and contrasts the traditional, closed-source

velopment model with the open-source means of development.


le:///D|/Linux Presentation/1-3/bazaar.html [08\23\2002 4:49:05 PM]
http://locke.ccil.org/~esr/writings/cathedral.htmlhttp://locke.ccil.org/~esr/writings/cathedral.html


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Linux Torvalds Supervises Developmen

thousands of people develop Linux from all over the world, how does their work get distributed toer community? The answer is simple. By popular acclamation, Linus Torvalds gets to decide what

oes into the Linux kernel and what doesn't. If a developers have some new code, they submit it to Lho decides whether or not to accept it, reject it, or request modifications before accepting it.

f course, this is a bit of an oversimplification. In actuality, several developers have more-or-lesspreme control over their particular subsections. There is a networking chief, a driver chief, and sorth. While Linus has ultimate authority, he seldom rejects a decision made by one of theseb-administrators.

o far, Linus has done an excellent job managing the development of Linux. However, even if he wee, or quit, or take the Linux kernel in a direction that no one else wanted to go, he himself could noep others from taking over the job, thanks to the GPLthat Linux is controlled by. Even Linus can't

event others from developing Linux.

ometimes things don't make it into the kernel but are still useful to some group of users. For exampmetimes optimizing for one kind of hardware would break support for other hardware. Some usersquire paranoid security. Some developments are too experimental to inflict on everyone. In this casople can (and do) provide their own patches to the kernel, available separately. These allow even

eater customization without risking support for the vast majority.


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Linux Comes Packaged InDistributions"

he Linux kernel by itself, is not useful. It provides services for applications to take advantage of, buithout applications there are only a few things it can do. Fortunately, a wide variety of groups,ganizations, and companies have combined Linux with other applications in the form ofistributions".

"distribution" is a combination of the Linux kernel, applications to run with it, utilities to install it mputer, and utilities to manage the system once it's installed. Distributions vary in the options theyfer, the utilities they provide, what commercial software comes bundled, price, and so forth.

few of the more popular distributions are:

Red Hat- popular for its ease-of-use, graphical utilities, software management system, and

bundled commercial software.

Debian- a non-commercial distribution, Debian concentrates on using open-source software

whenever possible. Popular also for its advanced software management system.

S.U.S.E.- produced in Germany, this distribution is very well liked by some for its administra

tools, comprehensive application set and thorough documentation.

Slackware- one of the oldest distributions, it is popular for its easy maintenance.

s worth noting that, for all their differences, the Linux distributions are all pretty much interoperablhere is a standard for how directories are set up, and standards for things like shared libraries (DLL

d so forth. This means that almost all Linux programs can run on any distribution.

dividual applications usually come in "packages", much like ZIP files. The most popular packagermat is "RPM", developed by Red Hat. Almost all distributions either use this format natively, or ools to automatically translate and install RPM files. Choosing a distribution is really a matter of tas

inux is Open-Source - Low Cost

le:///D|/Linux Presentation/1-3/distribution.html [08\23\2002 4:49:14 PM]
http://www.redhat.com/http://www.debian.org/http://www.suse.com/http://www.slackware.com/http://www.slackware.com/http://www.suse.com/http://www.debian.org/http://www.redhat.com/


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You Can Download Linux (AndApplications) For Free

ecause of the open-source nature of Linux, almost all distributions are available for free over theternet. There are limits to this, since most distributions fill up at least one CD (650MB) and some t

p as many as five. You need a pretty fast net connection to make this practical.

owever, you can also downloadpartsof distributions as well. You can download a usable, if minimstem without tying up your modem for weeks. This also allows you to upgrade parts of your system

ncluding the kernel) without having to buy another CD. The Debiandistribution, for example, is

signed to be upgraded automatically in just this manner. This can dramatically reduce the cost ofaintaining a system.


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You Can Buy (Or Beg, Borrow, or Steal)Linux On CD

nux is almost always installed from CD, like most modern software. You can buy Linux CDs fromide variety of vendors, for a wide variety of prices. If you buy from the original vendor, you can expay from $20.00 to $100.00, for one to five (or more) CDs. You can order by mail by phone orrough the Web, or purchase packages at most computer stores. One popular way to start with Linuxbuy a book that includes a distribution on CD.

hat do you get for that $20-$100 price tag? Quite a lot. You get the kernel, dozens of compilers anbuggers, hundreds of applications (ranging from image processing to word processing to servers toients to productivity applications to office suites to scientific applications to database applications tmes to editors and much more), installation utilities, system management utilities, and lots of

ocumentation, plus at least some tech support from the distributor.

hy is everything so cheap? Because it's almost all open-source. If someone charges too much, somse can take the source code and make it available for less. The competition isfierce. You aren't buye software so much as you're buying the convenience of not having to download it and compile it

ourself. There are companies that resell distributions like this for as little as $1.99. The only thing yon't get from them is commercial tech support from the distributor. (For many people, the free, publ

ch supportis plenty.

nd almost all of this software comes with no license fees. You can borrow a CD from a friend and sou like it before you buy your own. (Or just upgrade for freeover the net.) There's even a websitew

ople offer old Linux CD's they don't want anymore. You just mail them a postage-paid envelope aney'll send you their CDs for free. You don't get the most recent stuff like that, but the price is right.


le:///D|/Linux Presentation/1-3/cd.html [08\23\2002 4:49:14 PM]
http://visar.csustan.edu/http://visar.csustan.edu/


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You Can Pay For Value-Added Features

everal major distributions, such as Red Hatand Calderaoffer several value-added features like bun

mmercial applications (such as office suites or full Netware suites, for example) and commercial te

pport.

ou can't always get these types of extras if you just download the distribution, or buy it from a reselhop around a bit and ask questions before you make up your mind what distribution to get.


le:///D|/Linux Presentation/1-3/valueadded.html [08\23\2002 4:49:15 PM]
http://www.redhat.com/http://www.caldera.com/http://www.caldera.com/http://www.redhat.com/


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People Write Linux Code To Fill A Need

any Linux developments are begun because the programmer had a personal need for it, and had torite their own support. Most device drivers are written this way, because a developer had the hardwd wanted to use it under Linux. Some of these developments distributed with Linux are useful onlyw people - but they are veryuseful indeed, sometimes, to the people who use them.

he programming community has always had a very cooperative attitude - as Richard Stallman, founthe Free Software Foundationsaid, "Sharing code is the fundamental act of friendship between

ogrammers." This attitude has served Linux, and all programmers, very well.

one is writing code for fun, for one's own personal enjoyment, and is planning on sending that codto the world, one has plenty of motivation to make sure that the code is correct and performs well.ne's reputation as a programmer may be at stake. Which brings us to our next point.


le:///D|/Linux Presentation/2-1/need.html [08\23\2002 4:49:22 PM]
http://www.fsf.org/http://www.fsf.org/


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People Write Linux Code For Fun

lthough it may not seem like it to some, many programmers greatly enjoy working on difficultoblems in computer programming theory, simply for the mental excercise and sense of enjoyment ings. Programming is their passion, and they love to expand their horizons working on new andciting developments. It has been said of programming, like playing arcade games, that the reward f

oing it well is the chance to do it again.

ogrammers like to show off, and Linux development has become perhaps the premier means to do oming up with more efficient ways to do things, supporting new modes of old hardware, exploringtirely new ways to use computers, and doing it well, enhances one's reputation in the eyes of other

ogrammers. This is often far more rewarding than commercial enticements.

ecause one of the goals of Linux development is often to enhance one's reputation, the developers aghly motivated to avoid bugs in their code. Nothing is more embarrassing than to have someone em

ou with a report of bugs in your software.

ic Raymond has written several accessible and thought-provoking articles about the Linuxvelopment community. for more information, read The Cathedral And The Bazaar, and then perha

omesteading the Noosphere.

s important to note the difference between a desire for fame and adulation, and a desire for the earnd considered respect of one's peers. Again, Eric Raymond has clarified this distinctionvery well.


le:///D|/Linux Presentation/2-1/fun.html [08\23\2002 4:49:22 PM]
http://locke.ccil.org/~esr/writings/cathedral.htmlhttp://earthspace.net/~esr/writings/homesteading/http://earthspace.net/~esr/writings/homesteading/fame.htmlhttp://earthspace.net/~esr/writings/homesteading/fame.htmlhttp://earthspace.net/~esr/writings/homesteading/http://locke.ccil.org/~esr/writings/cathedral.html


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Code Is Subject To Peer-Review

ource code in Linux terms is aggressively tested by many users. Even development code not intendr mission-critical systems is widely used and tested. Some testers are motivated by a desire to helpthors produce the best possible code, and some by the notoriety of finding bugs in code where bugre. (Yes, programmers are really motivated by such things.)

hatever the motivations, a simple glance at the Linux newsgroups and mailing listsshows the proc

action. It's the clearest validation of the Linux development model.

s an example, to test the Linux kernel, the "crashme" program was written. It torture-tests systems b

nerating random OS calls (either with valid or invalid data) or even generating random garbage anying to execute it as code. No application is supposed to be able to crash the kernel, and if crashmends a way to do so, it is an affront to the pride of the Linux kernel developers. Such bugs are fixed vuickly.

here is another side-effect to having the source code open - it is subject to careful scrutiny by a widriety of people for security problems. Security problems arefound from time to time, but they areosed as soon as they are found. (If the discoverer doesn't tell others about the problem but instead trexploit it, he can do so for only as long as no one notices the break-ins. Once it's noticed, an alert i

osted and the fix is soon available, often within hours.)


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Bugs Are Fixed Quickly

ecause the development process is so open, and so manyprogrammers are at work, even major bugnd to be fixed quickly.

or example, it turned out that the Pentium had a problem where the CPU could be locked up byecuting a particular kind of instruction. The actual instruction began with the bytes "F00F" and thu

ug was christened the foof-bug.

nce any application, even a non-privileged one, could thus crash the system, this was considered aajor problem by the Linux developers. Working directly with Intel, Linus Torvalds and other

velopers were able to modify Linux to be immune to the foof-bug, with exactly zero loss inrformance.

s another example, it was discovered that a particular invalid set of IP packets could be used to craside variety of operating systems, including Windows and Linux. The patch to protect against this atas available for Linux within hours. It took several days for Microsoft to produce patches for Wind

he fix for Linux actually protected against several variations on the so-called 'teardrop' attack.nfortunately, the original Windows patch did not, and a modified WinNuke program was quickly mailable. Microsoft had to come out with a second patch to handle the new varieties of 'teardrop'.


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Linux has been demonstrated morestable than other systems

esides the anecdotal stories and the devotion of Linux fans, there are other types of evidence that Lstems have fewer bugs. One report found that Linux was more stable than all other commercial Unriants.

he researchers used the simple method of giving programs random streams of input (the so-called "st"). They found that while the commercial Unix systems had failure rates of over 18%, Linux had ilure rate of 7-9%. As the authors say:

t is reasonable to ask why a globally scattered group of programmers, with no formal testing suppoftware engineering standards can produce code that is more reliable (at least, by our measure) thanmmercially produced code..."

he paper is avaliable attp://www.cs.wisc.edu:80/Dienst/UI/2.0/Describe/ncstrl.uwmadison/CS-TR-95-1268.

a 1995 interview with Bill Gates, the German magazine FOCUS appears to have uncovered an

teresting attitude towards bugs on the part of Microsoft's chairman. Whether his attitude has chang

nce then is an open question.

Advantages of Linux

le:///D|/Linux Presentation/2-1/proof.html [08\23\2002 4:49:24 PM]
http://www.cs.wisc.edu/Dienst/UI/2.0/Describe/ncstrl.uwmadison/CS-TR-95-1268http://www.cantrip.org/nobugs.htmlhttp://www.cantrip.org/nobugs.htmlhttp://www.cs.wisc.edu/Dienst/UI/2.0/Describe/ncstrl.uwmadison/CS-TR-95-1268


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Linux Has An Advanced, Mature Design

nce Linux is an open-source version of Unix, it takes advantage of the three decades of operatingstem design and testing that has gone into Unix. Most new operating system concepts have been tr

ut in Unix first, or co-opted when invented somewhere else. See the previous sectionon Unix for so

chnical reasons why Unix is so respected.

nix has been used for advanced computer science work since its inception. Cray computers run arsion of Unix. Almost all workstations, computer design tools, engineering systems, and so forth hn Unix variants for decades. (There is currently a trend toward Windows NT for workstations, but

end is being resisted by the technical people who have to actually use these systems.)he recent resurgence of open-source software (which is how most software was written for a long tis breathed new life into the Unix world, and also made Unix available to people who have not hadcess to this powerful operating system until now.


le:///D|/Linux Presentation/2-2/advanced.html [08\23\2002 4:49:31 PM]
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Even Obsolete Hardware Can Be Made

Useful Again With Linuxecause of Linux's ruthless efficiency in use of memory and disk space, it can run effectively on hardwarensidered obsolete by some other modern operating systems. Even a 386 can be made useful again with L

ecause applications can be run remotely under Linux, a 386 can be used as a graphical terminal forplications running on a more advanced system elsewere. All the tough computing is done on the serverachine, and the 386 just handles displaying the results and forwarding user input to the server. By booting

e network, the terminal doesn't even need to contain a hard disk.

r real work, a 386 makes a fine print server, and even an acceptable filserver for a small department or hofice. Since Linux can run without a monitor or keyboard, you don't even need a full system for this kind o

tivity.

386 is perfectly adequate as a router for a network. Attach a modem to it and use IP Masquerading, and a

e systems on a network can surf the Internet through the 386 at the same time, using only one IP address e ISP. Take a look at http://bopper.wcbe.org/, which is run on a 386 w/16MB of RAM.

he following quote is too good to resist putting in here:

rom: "Michael Appelt"ewsgroups: comp.os.linux.hardware

ubject: Re: 486DX33 as a firewall?

ate: Wed, 12 Aug 1998 13:19:01 +0200

rganization: NETPLEX Internet Services - http://www.ntplx.net/

believe, it will do.

e are using a 386/40 with ethernet & isdn & modem interface as firewall

hcp, dns, bootp, sendfax, pppd, smtp, smb, laser printer, to serve a to

f 8 internal and 1 dial-in clients:

PCs (games & internet), 2 PCs (MS-Office & Scanner/Fax/Copier),

uVAX2000 with NetBSD booting from the net, 1 uVAX II with VMS/UXC

nd 2 more Vaxstation2000 using basically DNS

o, Xfree86 is not included, and a telnet is sometimes a bit slower

hen heavy printing load has been queued.

ut that causes no impact on internet access, we get whatever our

rovider can serve close to the isdn-limits of about 7.2 kByte/sec.


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he system has been stable over more than 1 year.

always several weeks between reboots - caused by config changes

he wrong direction)

needed the keyboard and monitor just about 3 or 4 times to recover fro

erious disk

roblems (disk is gone...hope same with the problems) durcing that long

ime.

o what, take NT to get fun...., get Linux to get the functions

egards, Michael

486 system is even more powerful. On my 486-100, I can websurf, serve files, compile code, edit files, rail, transfer files, and more, all at the same time. At the same time, my wife can surf the web on her Wind11 PC through my Internet connection.

ecause the operating system is so efficient, I can do things on the 486 that are impossible under Windowsn play full-stereo, 44.1KHz .mp3 files on my 486 and read mail at the same time. Under Windows, you c

ay full .mp3's on a 486 at all.

magine what you can do with a more modern PC...


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Benchmarks Show Linux Very Favorabl

nux compares well when benchmarked against other operating systems, often surprisingly well. Foample, the InfoWorld Java Benchmarksshow that a 166MHz Pentium running Linux turns in num

ceedingly close to a 180MHz Pentium Pro running Windows NT.

collection of scores on the Byte Unix Benchmarksshow that Linux turns in numbers comparing ve

ell to commercial Unix boxes costing tens of thousands of dollars.

ecently, MSNBC did some tests of Linux performance versus Windows NT. To quote: "AccordingDLabs' results, each of the commercial Linux releases ate NT's lunch." See the full article here.

y own experience has shown that, for my own programs, on my own (admittedly somewhat obsolerdware, Linux is at least 15% faster than Windows 3.11, even when I optimize them for the respecatforms.


le:///D|/Linux Presentation/2-2/benchmarks.html [08\23\2002 4:49:32 PM]
http://www.infoworld.com/cgi-bin/displayTC.pl?/970915sb7-bench1.htmhttp://www.silkroad.com/linux-bm.htmlhttp://www.msnbc.com/news/244979.asphttp://www.msnbc.com/news/244979.asphttp://www.silkroad.com/linux-bm.htmlhttp://www.infoworld.com/cgi-bin/displayTC.pl?/970915sb7-bench1.htm


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Samba Allows Linux To Talk To Window3.1x, 9x, and NT

he Sambasoftware package allows Linux to share files, printers, and other kinds of data with Wind

oxes on the same network. It can act as a Primary Domain Controller for a Windows NT network. Oe same hardware, it beats Windows NT as a Windows file server in some benchmarks!

f course, Linux can read files from Windows shares and print files to shared Windows printers. Mausinesses use Linux as a file and print server system (like Cisco). You may be using Linux where y

ork as a file server and not even know it!


le:///D|/Linux Presentation/2-2/samba.html [08\23\2002 4:49:41 PM]
http://sunsite.unc.edu/LDP/HOWTO/SMB-HOWTO.htmlhttp://www.cisco.com/http://www.cisco.com/http://sunsite.unc.edu/LDP/HOWTO/SMB-HOWTO.html


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Linux Speaks To Macs, Too!

sing the Netatalkpackage, Linux can connect to Macintosh computers as well, and share files and

inters with Macs. So far as the Macs are concerned, it looks just like a Macintosh file and/or printrver. Of course, Linux can talk to Windows, Macintosh, and other boxes all at the same time.


le:///D|/Linux Presentation/2-2/appletalk.html [08\23\2002 4:49:41 PM]
http://thehamptons.com/anders/netatalk/http://thehamptons.com/anders/netatalk/


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Novell? No Problem!

nux speaks IPXjust fine, and can act as an IPX router, as well as an NCP client, so you can get file

om a Novell server and print to Novell print queues, and/or an NCP server, and serve files to Novelorkstations. Again, Linux can talk to Windows, Mac, and Novell clients all at the same time.


le:///D|/Linux Presentation/2-2/novell.html [08\23\2002 4:49:41 PM]
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P Masquerading - Let Everyone On YouNetwork Access The Internet

nux supports IP Masquerading, which allows any number of machines to surf the Internet through achine, using only one IP address. With IP Masquerading and a network, every computer at your hbusiness can share the Internet connection, even if you only have one IP address assigned by youren if the software doesn't support proxies

Masqeurading is not a proxy service. The way it works is simple. The Linux box connects to youry modem, ISDN, T1, whatever) and is assigned an IP address. When other clients on the network wtalk to the Internet, they send the packets to the Linux box (which is set up as the default gateway)

he Linux box rewrites the outgoing IP packets to look like they came from itself, and when the replme back, it rewrites them to look like they came directly to the client.

his way, lots of clients can share the connection at the same time, and the Linux box keeps track ofhich traffic goes where. This is usually a lot cheaper than getting multiple IP addresses from your Id even software that doesn't support proxies works fine with IP Masquerading. Read more about ite IP Masquerade mini-HOWTO.

f course, Linux also supports proxies like Squid, which can also cache files and optimize the use of

ndwidth.


le:///D|/Linux Presentation/2-2/ipmasq.html [08\23\2002 4:49:42 PM]
http://sunsite.unc.edu/LDP/HOWTO/mini/IP-Masquerade.htmlhttp://squid.nlanr.net/Squid/http://squid.nlanr.net/Squid/http://sunsite.unc.edu/LDP/HOWTO/mini/IP-Masquerade.html


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Everything Net, Linux Has

nux has just about every kind of network server there is, including web servers (like Apache, the m

opluar webserver ever), FTP servers, IRC, MUD, Sendmail(which carries about 80% of the mail on

ternet), and much, much more. If there's anything you've ever wanted to play with, or install for yousiness, Linux is the way to go.

f course, because of how inexpensiveLinux is, you can do all of the above without spending tens o

ousands of dollars. You can do it for less than $100!


le:///D|/Linux Presentation/2-2/allnet.html [08\23\2002 4:49:42 PM]
http://www.apache.org/http://www.sendmail.org/http://www.sendmail.org/http://www.apache.org/


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Operating Systems Programming MadeCheap And Easy

nux offers a unique opportunity to learn systems programming with hands-on experience. Since yove the source code available, and a worldwide network of advisors and collaborators, you can explmost any subject you care to.

arious aspects of Linux have been studied or developed as part of academic work such as graduateeses. A CS student can do serious, professional-level work, and examine serious, professional-leveurce code. Students who have assignments on Unix computers at school can do the work at home oeir PCs, and then confidently bring it it to the public labs (or just dial in from home) and be confideat very little, if any, modifications will need to be made.


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Linux Provides Some Unusual NetworkDevices

ne of the main use of Linux is in networking, and Linux shines in this category, as noted before. Li

en offers some atypical kinds of network devices:

PLIP- use TCP/IP over your parallel port - great for networking a laptop.

SCSI- if you want high speed networking, there's just about nothing faster. Great for Beowulf

supercomputers.

AX25- TCP/IP over ham radio. Often used for automatic GPS position reporting.

Skin- Research on wearable computers and information transfer by skin contact uses Linux.

single Linux box can use all of these network devices, as well as more traditional ones, and routetween them. (Linux boxes make great routers, especially boxes considered obsolete by other operastems.)

or more information, check out the Linux Networking Overview HOWTO.


le:///D|/Linux Presentation/2-2/funkynet.html [08\23\2002 4:49:50 PM]
http://sunsite.unc.edu/mdw/LDP/nag/node70.html#SECTION007750000http://www.msoe.edu/~sebern/courses/cs400/team1/design/net.htmhttp://sunsite.unc.edu/LDP/HOWTO/AX25-HOWTO.htmlhttp://lcs.www.media.mit.edu/projects/wearables/http://sunsite.unc.edu/LDP/HOWTO/Networking-Overview-HOWTO.htmlhttp://sunsite.unc.edu/LDP/HOWTO/Networking-Overview-HOWTO.htmlhttp://lcs.www.media.mit.edu/projects/wearables/http://sunsite.unc.edu/LDP/HOWTO/AX25-HOWTO.htmlhttp://www.msoe.edu/~sebern/courses/cs400/team1/design/net.htmhttp://sunsite.unc.edu/mdw/LDP/nag/node70.html#SECTION007750000


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You Can Make A Supercomputer FromThe Things You Find At Home!

sing Linux, NASA developed software that allows ordinary PCs, networked together, to form a reapercomputer capable of delivering impressive performance for a rock-bottom price. The software imed Beowulf, and has been turned into a product called Extreme Linux, distributed by Red Hat

oftware.

his concept has been used by many universities and corporations, due to the spectacular

ice-performance ratio. Other type of compute farms have been established using Linux, including oed to generate much of the special effects used in the movie Titanic.

his idea has been taken to something of an extreme in the CHAOSproject. CHAOS stands for "CH

rray of Obsolete Systems", and involves a man who built a parallel-processing array of 386 boxes.hile not terribly practical, it certainly illustrates the flexibility and scalability of Linux.


le:///D|/Linux Presentation/2-2/beowulf.html [08\23\2002 4:49:50 PM]
http://www.beowulf.org/http://www.redhat.com/http://www.redhat.com/http://www.msnbc.com/news/139296.asphttp://www.linuxgazette.com/issue30/vrenios.htmlhttp://www.linuxgazette.com/issue30/vrenios.htmlhttp://www.msnbc.com/news/139296.asphttp://www.redhat.com/http://www.redhat.com/http://www.beowulf.org/


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Software RAID - Stripe Your DrivesWithout Extra Hardware

AID (or Redundant Array of Independent Disks) is a set of technologies for spreading informationross multiple disks. This can be configured to provide increased fault-tolerance, increasedrformance, or both. Usually this is implemented with special hardware, almost always on SCSI dri

nux provides the ability to let the kernel create a "virtual" RAID system, spreading information acrultiple disks. It currently supports all major levels of RAID, from Level 0 to Level 5 and Level 0,1ecause it is implemented in software and not hardware, it is generally slower than a hardware-basedstem, but can be dramatically faster than not having any RAID at all. Also, Software RAID can be

mplemented on IDE disks as well as SCSI.

or more information, check out the Software RAID HOWTO.


le:///D|/Linux Presentation/2-2/softraid.html [08\23\2002 4:49:50 PM]
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Emulation Software - Turn Your PC IntoAlmost Anything

nux supports a wide variety of software emulators for all kinds of systems. These allow your PC toograms meant for other systems just as if it were running on its intended platform.

mulators exist for classic machines like the Atari 2600 and Commodore 64, so you can run theme-honored games and software you fondly remember.

n the more practical side, there is DOSEMU, an extremely good simulation of DOS that allows you

n almost any DOS program including games like Duke3d. (As of this writing, sound is not supportOSEMU, but it's being worked on and may be available soon.) Many people use this to run programke Wordperfect or other productivity apps without having to dual-boot to DOS. You can even runindows 95 under DOSEMU!

INEis a project that is attempting to emulate the Win32s API under Linux. While still a work in

ogress, it is usable for many applications. WABI from Caldera is a commercial program that doesuch the same thing.


le:///D|/Linux Presentation/2-2/emulators.html [08\23\2002 4:49:50 PM]
http://sunsite.unc.edu/LDP/HOWTO/DOSEMU-HOWTO.htmlhttp://www.winehq.com/http://www.winehq.com/http://sunsite.unc.edu/LDP/HOWTO/DOSEMU-HOWTO.html


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Linux Offers The Flexibility To WorkAround Hardware Problems

ecause Linux is by nature very flexible, and the source code is available for nearly everything, you apt the software to your particular hardware, even to the point of fixing bugs or deficiencies.

or example, my scanner (Mustek TwainScan II SP) is SCSI based, but is really designed to be the ovice on the SCSI bus. During a scan, it locks down the SCSI bus so that no other activity can happnder Windows, this often causes disk timeouts and other major problems. The only remedy is to gecond, dedicated SCSI card for the scanner.

wrote the author of my SCSI card driver and rec

Documents

linux-intro.pdf