GUIDE TO (mostly) HARMLESS HACKING

Vol. 2 Number 2

Linux!

    Unix has become the primo operating system of the Internet. In fact,

Unix is the most widely used operating system in the world among computers

with more power than PCs.

True, Windows NT is coming up fast as a common Internet operating system,

and is sooo wonderfully buggy that it looks like it could become the number

one favorite to crack into. But today Unix in all its wonderful flavors

still is the operating system to know in order to be a truly elite hacker.

    So far we have assumed that you have been hacking using a shell

account that you get through your Internet Service Provider (ISP). A shell

account allows you to give Unix commands on one of your ISP's computers. But

you don't need to depend on your ISP for a machine that lets you play with

Unix. You can run Unix on your own computer and with a SLIP or PPP

connection be directly connected to the Internet.

Newbie note: Serial Line Internet Protocol (SLIP) and Point-to-Point

Protocol (PPP) connections give you a temporary Internet Protocol (IP)

address that allows you to be hooked directly to the Internet. You have to

use either SLIP or PPP connections to get to use a Web browser that gives

you pictures instead on text only. So if you can see pictures on the Web,

you already have one of these available to you.

    The advantage of using one of these direct connections for your

hacking activities is that you will not leave behind a shell log file for

your ISP's sysadmin to pore over. Even if you are not breaking the law, a

shell log file that shows you doing lots of hackerish stuph can be enough

for some sysadmins to summarily close your account.

    What is the best kind of computer to run Unix on? Unless you are a

wealthy hacker who thinks nothing of buying a Sun SPARC workstation, you'll

probably do best with some sort of PC. There are almost countless variants

of Unix that run on PCs. Most of them are free for download, or

inexpensively available on CD-ROMs.

    The three primary variations of Unix that run on PCs are Sun's

Solaris, FreeBSD and Linux. Solaris costs around $700. Enough said. FreeBSD

is really, really good but doesn't offer a lot of support. Linux, however,

has the advantage of being available in many variants (so you can have fun

mixing and matching programs from different Linux offerings). Most

importantly, Linux is supported by many news groups, mail lists and Web

sites. If you have hacker friends in your area, most of them probably use

Linux and can help you out.

Historical note: Linux was created in 1991 by a group led by Linus Torvalds

of the University of Helsinki. Linux is copyrighted under the GNU General

Public License. Under this agreement, Linux may be redistributed to anyone

along with the source code. Anyone can sell any variant of Linux and modify

it and repackage it. But even if someone modifies the source code he or she

may not claim copyright for anything created from Linux. Anyone who sells a

modified version of Linux must provide source code to the buyers and allow

them to reuse it in their commercial products without charging licensing

fees. This arrangement is known as a "copyleft."

    Under this arrangement the original creators of Linux receive no

licensing or shareware fees. Linus Torvalds and the many others who have

contributed to Linux have done so from the joy of programming and a sense of

community with all of us who will hopefully use Linux in the spirit of good

guy hacking. Viva la Linux! Viva Torvalds!

    Linux consists of the operating system itself (called the "kernel")

plus a set of associated programs.

    The kernel, like all types of Unix, is a multitasking, multi-user

operating system. Although it uses a different file structure, and hence is

not directly compatible with DOS and Windows, it is so flexible that many

DOS and Windows programs can be run while in Linux. So a power user will

probably want to boot up in Linux and then be able to run DOS and Windows

programs from Linux.

    Associated programs that come with most Linux distributions may include:

• a shell program (Bourne Again Shell -- BASH -- is most common);
• compilers for programming languages such as Fortran-77 (my favorite!), C,

C++, Pascal, LISP, Modula-2, Ada, Basic (the best language for a beginner),

and Smalltalk.;

• X (sometimes called X-windows), a graphical user interface
• utility programs such as the email reader Pine (my favorite) and Elm

Top ten reasons to install Linux on your PC:

1. When Linux is outlawed, only outlaws will own Linux.

2. When installing Linux, it is so much fun to run fdisk without backing up

first.

3. The flames you get from asking questions on Linux newsgroups are of a

higher quality than the flames you get for posting to alt.sex.bestiality.

4. No matter what flavor of Linux you install, you'll find out tomorrow

there was a far more 3l1te version you should have gotten instead.

5. People who use Free BSD or Solaris will not make fun of you. They will

offer their sympathy instead.

6. At the next Def Con you'll be able to say stuph like "so then I su-ed to

his account and grepped all his files for 'kissyface'." Oops, grepping

other people's files is a no-no, forget I ever suggested it.

7. Port surf in privacy.

8. One word: scripts.

9. Installing Linux on your office PC is like being a postal worker and

bringing an Uzi to work.

10. But - - if you install Linux on your office computer, you boss won't

have a clue what that means.

    What types of Linux work best? It depends on what you really want.

Redhat Linux is famed for being the easiest to install. The Walnut Creek

Linux 3.0 CD-ROM set is also really easy to install -- for Linux, that is!

My approach has been to get lots of Linux versions and mix and match the

best from each distribution.

    I like the Walnut Creek version best because with my brand X

hardware, its autodetection feature was a life-saver.

    INSTALLING LINUX is not for the faint of heart! Several tips for

surviving installation are:

1. Although you in theory can run Linux on a 286 with 4 MB RAM and two

floppy drives, it is much easier with a 486 or above with 8 MB RAM, a

CD-ROM, and at least 200 MB free hard disk space.

2. Know as much as possible about what type of mother board, modem, hard

disk, CD-ROM, and video card you have. If you have any documentation for

these, have them on hand to reference during installation.

3. It works better to use hardware that is name-brand and somewhat out of

date on your computer. Because Linux is freeware, it doesn't offer device

drivers for all the latest hardware. And if your hardware is like mine --

lots of Brand X and El Cheapo stuph, you can take a long time experimenting

with what drivers will work.

4. Before beginning installation, back up your hard disk(s)! In theory you

can install Linux without harming your DOS/Windows files. But we are all

human, especially if following the advice of 3).

5. Get more than one Linux distribution. The first time I successfully

installed Linux, I finally hit on something that worked by using the boot

disk from one distribution with the CD-ROM for another. In any case, each

Linux distribution had different utility programs, operating system

emulators, compilers and more. Add them all to your system and you will be

set up to become beyond elite.

6. Buy a book or two or three on Linux. I didn't like any of them! But they

are better than nothing. Most books on Linux come with one or two CD-ROMs

that can be used to install Linux. But I found that what was in the books

did not exactly coincide with what was on the CD-ROMs.

7. I recommend drinking while installing. It may not make debugging go any

faster, but at least you won't care how hard it is.

    Now I can almost guarantee that even following all these 6 pieces of

advice, you will still have problems installing Linux. Oh, do I have 7

advisories up there? Forget number 7. But be of good cheer, since everyone

else also suffers mightily when installing and using Linux, the Internet has

an incredible wealth of resources for the Linux-challenged.

    If you are allergic to getting flamed, you can start out with Linux

support Web sites.

    The best I have found is http://sunsite.unc.edu:/pub/Linux/. It

includes the Linux Frequently Asked Questions list (FAQ), available from

sunsite.unc.edu:/pub/Linux/docs/FAQ.

    In the directory /pub/Linux/docs on sunsite.unc.edu you'll find a

number of other documents about Linux, including the Linux INFO-SHEET and

META-FAQ,

    The Linux HOWTO archive is on sunsite.unc.edu:/pub/Linux/docs/HOWTO.

The directory /pub/Linux/docs/LDP on sunsite.unc.edu contains the current

set of LDP manuals.

    You can get ``Linux  Installation and Getting Started'' from

sunsite.unc.edu in /pub/Linux/docs/LDP/install-guide. The README file

there describes how you can order a printed copy of the book of the same

name (about 180 pages).

    Now if you don't mind getting flamed, you may want to post questions

to the amazing number of Usenet news groups that cover Linux. These include:

comp.os.linux.advocacy Benefits of Linux compared

comp.os.linux.development.system Linux kernels, device drivers

comp.os.linux.x Linux X Window System servers

comp.os.linux.development.apps Writing Linux applications

comp.os.linux.hardware Hardware compatibility

comp.os.linux.setup Linux installation

comp.os.linux.networking Networking and communications

comp.os.linux.answers FAQs, How-To's, READMEs, etc.

linux.redhat.misc

alt.os.linux Use comp.os.linux.* instead

alt.uu.comp.os.linux.questions Usenet University helps you

comp.os.linux.announce Announcements important to Linux

comp.os.linux.misc Linux-specific topics

    Tobin Fricke has also pointed out that "free copies of Linux CD-ROMs

are available the Linux Support & CD Givaway web site at

http://emile.math.ucsb.edu:8000/giveaway.html. This is a project where

people donate Linux CD's that they don't need any more. The project was

seeded by Linux Systems Labs, who donated 800 Linux CDs initially! Please

remember to donate your Linux CD's when you are done with them. If you live

near a computer swap meet, Fry's, Microcenter, or other such place, look for

Linux CD's there. They are usually under $20, which is an excellent

investment. I personally like the Linux Developer's Resource by Infomagic,

which is now up to a seven CD set, I believe, which includes all major Linux

distributions (Slackware, Redhat, Debian, Linux for DEC Alpha to name a few)

plus mirrors of tsx11.mit.edu and sunsite.unc.edu/pub/linux plus much more.

You should also visit the WONDERFUL linux page at

http://sunsite.unc.edu/linux, which has tons of information, as well as the

http://www.linux.org/. You might also want to check out

http://www.redhat.com/ and http://www.caldera.com/ for more information on

commercial versions of linux (which are still freely available under GNU)."

    How about Linux security? Yes, Linux, like every operating system,

is imperfect. Eminently hackable, if you really want to know. So if you want

to find out how to secure your Linux system, or if you should come across

one of the many ISPs that use Linux and want to go exploring (oops, forget I

wrote that), here's where you can go for info:

ftp://info.cert.org/pub/cert_advisories/CA-94:01.network.monitoring.attacks

ftp://info.cert.org/pub/tech_tips/root_compromise

http://bach.cis.temple.edu/linux/linux-security/

    Last but not least, if you want to ask Linux questions on the Happy

Hacker list, you're welcome. We may be the blind leading the blind, but what

the heck!

Want to see back issues of Guide to (mostly) Harmless Hacking? See

http://www.feist.com/~tqdb/evis-unv.html. Want to subscribe to this list?

Email majordomo@edm.net with the message "subscribe happyhacker." Want to

share some kewl stuph with the Happy Hacker list? Send your messages to

hh@edm.net. To send me confidential email (please, no discussions of

illegal activities) use cmeinel@techbroker.com. Please direct flames to

dev/null@techbroker.com. Happy hacking!

Copyright 1996 Carolyn P. Meinel. You may forward the GUIDE TO (mostly)

HARMLESS HACKING as long as you leave this notice at the end..

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Carolyn Meinel

M/B Research -- The Technology Brokers