Last-modified: 14 Mar 94
Linux Information Sheet
0.1 Introduction to Linux
Linux is a completely free reimplementation of the POSIX spec,
with SYSV and BSD extensions (which means, it looks like unix,
but does not come from the same source code base), which is
available in both source code and binary form. It is copyrighted
by Linus B. Torvalds (torva...@kruuna.helsinki.fi) and other
contributors and is freely redistributable under the terms of
the GNU Public License. Linux runs only on 386/486 machines with
an ISA or EISA bus. MCA (IBM's proprietary bus) is not currently
supported because there is little available documentation. VLB
and PCI local busses are both supported, although the NCR SCSI
chip that is used in many PCI machines is not yet supported, but
is currently in development.
Porting to other CPU's is likely to be difficult, as the kernel
makes extensive use of 386 memory management and task
primitives. However, this is becoming easier as the kernel
becomes more general, and there is a port in progress for
multiple Motorola 680x0 platforms, and ports are being
considered to other platforms as well. Don't hold your breath,
but if you are interested and able to contribute, you may find
other developers who wish to work with you.
Linux is no longer considered to be in beta testing, as version
1.0 was released on March 14, 1994. There are still bugs in the
system, and new bugs will creep up and be fixed as time goes on.
Because Linux follows the ``open development model'', all new
versions will be released to the public, whether or not they are
considered ``production quality''.
Linux is still free as of version 1.0, and will continue to be.
Because of the nature of the GNU copyright which Linux is
subject to, it would be illegal for it to be made not free.
If you wish to make sure that you have a stable version of
Linux, you may get version 1.0, or may wait a few weeks from the
release of a version which has attained the reputation of being
stable among the bleeding edge who already use it, or may wait
for another version which is officially released as a stable
release, like version 1.0.
Most versions of Linux, beta or not, are quite stable, and you
can keep using those if they do what you need and you don't want
to be on the bleeding edge. One site had a computer running
version 0.97 patchlevel 1 (dating from last summer) for over 136
days without an error or crash. (It would have been longer if
the backhoe operator hadn't mistaken a main power transformer
for a dumpster...)
One thing to be aware of is that Linux is developed using an
open and distributed model, instead of a closed and centralized
model like much other software. This means that the current
development version is always public (with up to a week or two's
delay) so that anybody can use it. The result is that whenever a
version with new functionality is released, it almost always
contains bugs, but it also results in a very rapid development
so that the bugs are found and corrected quickly, often in
hours, as many people work to fix them. Furthermore, the bugs
are generally discovered within hours of a kernel release,
especially those which might endanger a user's data, so it is
easy for an end-user to avoid these bugs.
In contrast, the closed and centralized model means that there
is only one person or team working on the project, and they only
release software that they think is working well. Often this
leads to long intervals between releases, long waiting for bug
fixes, and slower development. Of course, the latest release of
such software to the public is often of higher quality, but the
development speed is generally much slower.
As of March 14, 1994, the current version of Linux is 1.0!
0.2 Linux Features
* multitasking: several programs running at once.
* multiuser: several users on the same machine at once (and NO
* runs in 386 protected mode.
* has memory protection between processes, so that one program
can't bring the whole system down.
* demand loads executables: Linux only reads from disk those
parts of a program that are actually used.
* shared copy-on-write pages among executables. This means that
multiple process can use the same memory to run in. When one
tries to write to that memory, that page (4KB piece of
memory) is copied somewhere else. Copy-on-write has two
benefits: increasing speed and decreasing memory use.
* virtual memory using paging (not swapping whole processes) to
disk: to a separate partition or a file in the filesystem, or
both, with the possibility of adding more swapping areas
during runtime (yes, they're still called swapping areas). A
total of 16 of these 128 MB swapping areas can be used at
once, for a theoretical total 2 GB of useable swap space.
* a unified memory pool for user programs and disk cache (so
that all free memory can be used for caching, and the cache
can be reduced when running large programs).
* dynamically linked shared libraries (DLL's)(static libraries
too, of course).
* does core dumps for post-mortem analysis, allowing the use of
a debugger on a program not only while it is running but also
after it has crashed.
* mostly compatible with POSIX, System V, and BSD at the source
* all source code is available, including the whole kernel and
all drivers, the development tools and all user programs;
also, all of it is freely distributable. There are some
commercial programs being provided for Linux now without
source, but everything that has been free is still free.
* POSIX job control.
* pseudoterminals (pty's).
* 387-emulation in the kernel so that programs don't need to do
their own math emulation. Every computer running Linux
appears to have a math coprocessor. Of course, if your
computer already contains an FPU, it will be used instead of
the emulation, and you can even compile your own kernel with
math emulation removed, for a small memory gain.
* support for many national or customized keyboards, and it is
fairly easy to add new ones.
* multiple virtual consoles: several independent login sessions
through the console, you switch by pressing a hot-key
combination (not dependent on video hardware).
* Supports several common filesystems, including minix-1,
Xenix, and all the system V filesystems, and has an advanced
filesystem of its own, which offers filesystems of up to 4
TB, and names up to 255 characters long.
* transparent access to MS-DOS partitions (or OS/2 FAT
partitions) via a special filesystem: you don't need any
special commands to use the MS-DOS partition, it looks just
like a normal Unix filesystem (except for funny restrictions
on filenames, permissions, and so on). MS-DOS 6 compressed
partitions do not work at this time.
* read-only HPFS-2 support for OS/2 2.1
* CD-ROM filesystem which reads all standard formats of
* TCP/IP networking, including ftp, telnet, NFS, etc.
0.3 Hardware Issues
0.3.1 Minimal configuration
The following is probably the smallest possible configuration
that Linux will work on: 386SX/16, 2 MB RAM, 1.44 MB or 1.2 MB
floppy, any supported video card (+ keyboards, monitors, and so
on of course). This should allow you to boot and test whether it
works at all on the machine, but you won't be able to do
In order to do something, you will want some hard disk space as
well, 5 to 10 MB should suffice for a very minimal setup (with
only the most important commands and perhaps one or two small
applications installed, like, say, a terminal program). This is
still very, very limited, and very uncomfortable, as it doesn't
leave enough room to do just about anything, unless your
applications are quite limited. It's generally not recommended
for anything but testing if things work, and of course to be
able to brag about small resource requirements.
0.3.2 Usable configuration
If you are going to run computationally intensive programs, such
as gcc, X, and TeX, you will probably want a faster processor
than a 386SX/16, but even that should suffice if you are
In practice, you need at least 4 MB of RAM if you don't use X,
and 8 MB if you do. Also, if you want to have several users at a
time, or run several large programs (compilations for example)
at a time, you may want more than 4 MB of memory. It will still
work with a smaller amount of memory (should work even with 2
MB), but it will use virtual memory (using the hard drive as
slow memory) and that will be so slow as to be unusable.
The amount of hard disk you need depends on what software you
want to install. The normal basic set of Unix utilities, shells,
and administrative programs should be comfortable in less than
10 MB, with a bit of room to spare for user files. For a more
complete system, get Slackware, MCC, TAMU, or (soon) Debian or
Linux/PRO, and assume that you will need 60 to 200 MB, depending
on what you choose to install and what distribution you get. Add
whatever space you want to reserve for user files to these
totals. With today's prices on hard drives, if you are buying a
new system, it makes no sense to buy a drive that is too small.
Get at least 200 MB, and you will not regret it.
Add more memory, more hard disk, a faster processor and other
stuff depending on your needs, wishes and budget to go beyond
the merely usable. In general, one big difference from DOS is
that with Linux, adding memory makes a large difference, whereas
with dos, extra memory doesn't make that much difference. This
of course has something to do with DOS's 640KB limit.
0.3.3 Supported hardware
CPU: Anything that runs 386 protected mode programs (all models
of 386s and 486s should work; 286s don't work, and never will).
Architecture: ISA or EISA bus. MCA (mostly true blue PS/2's)
does not work. Local busses (VLB and PCI) work.
RAM: Theoretically up to 1 GB. This has not been tested. Some
people (including Linus) have noted that adding ram has slowed
down their machine extremely without adding more cache at the
same time, so if you add memory and find your machine slower,
try adding more cache.
Data storage: Generic AT drives (IDE, 16 bit HD controllers with
MFM or RLL) are supported, as are SCSI hard disks and CD-ROMs,
with a supported SCSI adaptor. Generic XT controllers (8 bit
controllers with MFM or RLL) are now also supported. Supported
SCSI adaptors: Adaptec 1542, 1522, and 1740 in extended (not
1542 compatible) mode, Seagate ST-01 and ST-02, Future Domain
TMC-88x series (or any board based on the TMC950 chip) and
TMC1660/1680, Ultrastor 14F, 24F and 34F, and Western Digital
wd7000. SCSI and QIC-02 tapes are also supported. Support for
QIC-80 tapes is now in ALPHA testing. Several CD-ROM devices are
also supported, including Matsushita/Panasonic, Mitsumi, Sony,
Soundblaster, Toshiba, and others. For exact models, check the
hardware compatability HOWTO.
Video: VGA, EGA, CGA, or Hercules (and compatibles) work in text
mode. For graphics and X, there is support for (at least) normal
VGA, some super-VGA cards (most of the cards based on ET3000,
ET4000, Paradise, and some Trident chipsets), S3 (except for
Diamond Stealth cards, because the manufacturer won't tell how
to program it), 8514/A, ATI MACH8, ATI MACH32, and hercules.
(Linux uses the Xfree86 X server, so that determines what cards
Networking: Western Digital 80x3, ne1000, ne2000, 3com503,
3com509, Allied Telliesis AT1500 (said to be some of the
fastest, as well as quite cheap), d-link pocket adaptors, SLIP,
CSLIP, PLIP (Parallel Link IP), and more I have forgotten at the
Other hardware: SoundBlaster, ProAudio Spectrum 16, Gravis
Ultrasound, AST Fourport cards (with 4 serial ports), several
models of Boca serial boards, the Usenet Serial Card II, several
flavours of bus mice (Microsoft, Logitech, PS/2).
0.4 An Incomplete List of Ported Programs and Other Software
Most of the common Unix tools and programs have been ported to
Linux, including almost all of the GNU stuff and many X clients
from various sources. Actually, ported is often too strong a
word, since many programs compile out of the box without
modifications, or only small modifications, because Linux tracks
POSIX quite closely. Unfortunately, there are not very many
end-user applications at this time. Nevertheless, here is an
incomplete list of software that is known to work under Linux.
Basic Unix commands: ls, tr, sed, awk and so on (you name it,
we've probably got it).
Development tools: gcc, gdb, make, bison, flex, perl, rcs, cvs,
Graphical environments: X11R5 (Xfree86), MGR.
Editors: GNU Emacs, Lucid Emacs, MicroEmacs, jove, epoch, elvis
(GNU vi), vim, vile, joe, pico, jed.
Shells: Bash (POSIX sh-compatible), zsh (include ksh
compatiblity mode), pdksh, tcsh, csh, rc, ash (mostly
sh-compatible), and many more.
Telecommunication: Taylor (BNU-compatible) UUCP, kermit, szrz,
minicom, pcomm, xcomm, term/slap (runs multiple shells over one
modem line), Seyon (popular X-windows communications program),
and several fax (using class 2 modems) and voice-mail (using
ZyXEL modems) packages are available. Of course, remote serial
logins are supported.
News and mail: C-news, innd, trn, nn, tin, smail, elm, mh.
Textprocessing: TeX, groff, doc.
Games: Nethack, several Muds and X games, and lots of others.
One of those games is looking through all the games available at
tsx-11 and sunsite.
All of these programs (and this isn't even a hundredth of what
is available) are freely available.
0.5 Who uses Linux?
Linux is freely available, and no one is required to register
their copies with any central authority, so it is difficult to
know how many people use Linux. Several businesses are now
surviving solely on selling and supporting Linux, and very few
Linux users use those businesses, relatively speaking, and the
Linux newsgroups are some of the most heavily read on the
internet, so the number is likely in the hundreds of thousands,
but hard numbers are hard to come by. However, one brave soul,
Harald T. Alvestrand, has decided to try, and asks that if you
use Linux, you send a message to linux-coun...@uninett.no with
one of the following subjects: ``I use Linux at home'', ``I use
Linux at work'', or ``I use Linux at home and at work''. He is
also counting votes of ``I don't use Linux'', for some reason.
He posts his counts to comp.os.linux.misc.
0.6 Getting Linux
0.6.4 Anonymous FTP
New information: Matt Welsh has released a new version of hiw
Installation and Getting Started guide. Also, the Linux
documentation project (the LDP) has put out several other books
in various states of completion, and these are available at
sunsite.unc.edu:/pub/Linux/docs/LDP. Stay tuned to
At least the following anonymous ftp sites carry Linux.
Textual name Numeric address Linux directory
============================= =============== ===============
tsx-11.mit.edu 18.104.22.168 /pub/linux
sunsite.unc.edu 22.214.171.124 /pub/Linux
ftp.funet.fi 126.96.36.199 /pub/OS/Linux
net.tamu.edu 188.8.131.52 /pub/linux
ftp.mcc.ac.uk 184.108.40.206 /pub/linux
src.doc.ic.ac.uk 220.127.116.11 /packages/linux
fgb1.fgb.mw.tu-muenchen.de 18.104.22.168 /pub/linux
ftp.informatik.tu-muenchen.de 22.214.171.124 /pub/Linux
ftp.dfv.rwth-aachen.de 126.96.36.199 /pub/linux
ftp.informatik.rwth-aachen.de 188.8.131.52 /pub/Linux
ftp.ibp.fr 184.108.40.206 /pub/linux
kirk.bond.edu.au 220.127.116.11 /pub/OS/Linux
ftp.uu.net 18.104.22.168 /systems/unix/linux
wuarchive.wustl.edu 22.214.171.124 mirrors/linux
ftp.win.tue.nl 126.96.36.199 /pub/linux
ftp.stack.urc.tue.nl 188.8.131.52 /pub/linux
ftp.denet.dk 184.108.40.206 /pub/OS/linux
NCTUCCCA.edu.tw 220.127.116.11 /Operating-Systems/Linux
nic.switch.ch 18.104.22.168 /mirror/linux/sunsite
monu1.ccmonash.edu.au 22.214.171.124 /pub/linux
cnuce_arch.cnr.it 126.96.36.199 /pub/Linux
tsx-11.mit.edu and fgb1.fgb.mw.tu-muenchen.de are the official
sites for Linux' GCC. Some sites mirror other sites. Please use
the site closest (network-wise) to you whenever possible.
At least SunSite.unc.edu and ftp.informatik.tu-muenchen.de offer
ftpmail services. Mail ftpm...@sunsite.unc.edu or
f...@informatik.tu-muenchen.de for help.
If you are lost, try looking at
SunSite.unc.edu:/pub/Linux/distributions/, where several
distributions are offered.
0.6.5 Other methods of obtaining Linux
There are many BBS's that have Linux files. A list of them is
occasionally posted to comp.os.linux.announce. Ask friends and
user groups, or order one of the commmercial distributions. A
list of these is contained in the Linux distribution HOWTO,
posted regularily to the comp.os.linux.announce newsgroup.
0.6.6 Getting started
As mentioned at the beginning, Linux is not centrally
administered. Because of this, there is no ``official'' release
that one could point at, and say ``That's Linux.'' Instead,
there are various ``distributions,'' which are more or less
complete collections of software configured and packaged so that
they can be used to install a Linux system.
The first thing you should do is to get and read the list of
Frequently Asked Questions (FAQ) from one of the FTP sites, or
by using the normal Usenet FAQ archives (e.g. rtfm.mit.edu).
This document has plenty of instructions on what to do to get
started, what files you need, and how to solve most of the
common problems (during installation or otherwise).
0.7 Legal Status of Linux
Although Linux is supplied with the complete source code, it is
copyrighted software, not public domain. However, it is
available for free under the GNU Public License. See the GPL for
more information. The programs that run under Linux each have
their own copyright, although many of them use the GPL as well.
X uses the MIT X copyright, and some utilities are under the BSD
copyright. In any case, all of the software on the FTP site is
freely distributable (or else it shouldn't be there).
0.8 News About Linux
A new magazine called Linux Journal was recently launched. It
includes articles intended for almost all skill levels, and is
intended to be helpful to all Linux users. Subscriptions are 19
USD worldwide. Subscription inquiries can be sent via email to
li...@fylz.com or faxed to (U.S.) 1-203-454-2582 or mailed to
Linux Journal, P.O. Box 3364, Westport, CT 06880-8364 USA.
Please do not send credit card numbers via email; the internet
is not secure, and it is entirely possible that a
technologically adept thief may steal your credit card number
and cost you a large sum of money if you do.
There are several Usenet newsgroups for Linux discussion, and
also several mailing lists. See the Linux FAQ for more
information about the mailing lists (you should be able to find
the FAQ either in the newsgroup or on the FTP sites).
The newsgroup comp.os.linux.announce is a moderated newsgroup
for announcements about Linux (new programs, bug fixes, etc).
The newsgroup comp.os.linux.admin is an unmoderated newsgroup
for discussion of administration of Linux systems.
The newsgroup comp.os.linux.development is an unmoderated
newsgroup specifically for discussion of Linux kernel
development. The only application development questions that
should be discussed here are those that are intimately
associated with the kernel. All other development questions are
probably generic UNIX development questions and should be
directed to a comp.unix group instead.
The newsgroup comp.os.linux.help is an unmoderated newsgroup for
any Linux questions that don't belong anywhere else.
The newsgroup comp.os.linux.misc is the replacement for
comp.os.linux, and is meant for any discussion that doesn't
In general, do not crosspost between the Linux newsgroups. The
only crossposting that is appropriate is an occasional posting
between one unmoderated group and comp.os.linux.announce. The
whole point of splitting comp.os.linux into many groups is to
reduce traffic in each. Those that do not follow this rule will
be flamed without mercy...
For the current status of the Linux kernel and a summary of the
most recent versions, finger torva...@kruuna.helsinki.fi
0.9 The Future
Now that Linux 1.0 has been released, work is already in
progress on several enhancements. Disk access speedups, TTY
improvements, and many more things are being worked on. Linux
1.0 is not the end of Linux, or is it even very important; it is
mostly intended to provide a stable version that people can use
without being afraid that they are using beta software, and that
can be standardized on to some extent.
There is plenty of code left to write, and even more
documentation. Please join the DOC channel of the mailing list
if you would like to contribute to the documentation.
0.10 This document
This document is maintained by Michael K. Johnson,
johns...@Sunsite.unc.edu. Please mail me with any comments, no
matter how small. I can't do a good job of maintaining this
document without your help. A more-or-less current copy of this
document can always be found as
tsx-11.mit.edu:/pub/linux/docs/INFO-SHEET, and a DVI version can
be found as INFO-SHEET.dvi, in the same directory.
Trademarks are owned by their owners. There is no warranty about
the information in this document. Use and distribute at your own
risk. The content of this document is in the public domain, but
please be polite and attribute any quotes.