1.1. What is Linux?

Linux is the kernel of operating systems that look like and perform as well or better than the famous operating system from AT&T Bell Labs. Linus Torvalds and a loosely knit team of volunteer hackers from across the Internet wrote (and still are writing) Linux from scratch. It has all of the features of a modern, fully fledged operating system: true multitasking, virtual memory, shared libraries, demand loading, shared, copy-on-write executables, proper memory management, and TCP/IP networking.

Most people, however, refer to the operating system kernel, system software, and application software, collectively, as "Linux," and the convention is used in this FAQ as well.

Linux ran originally on 386/486/586-based PC's, using the hardware facilities of the 80386 processor family (TSS segments, et al.) to implement its features. There are now many ports to other hardware platforms. (``What Ports to Other Processors Are There?'')

Linus Torvalds is working on a Linux distribution specifically designed for mobile computers and the Crusoe Smart Microprocessor developed by Transmeta. There is a API specification and developer's kit that are available from Transmeta. There is more information at http://www.transmeta.com/. The Crusoe is a microprocessor chip that provides low power consumption, power management features, workstation performance, and in-software configuration, but it's not a complete system, so it's probably mostly harmless.

See the Linux INFO-SHEET for more details. (``Where Can I Get the HOWTO's and Other Documentation?'')

The Linux kernel is distributed under the GNU General Public License. (``Is Linux Public Domain? Copyrighted?'')

There is a historical archive of all versions of the Linux kernel at http://ps.cus.umist.ac.uk/~rhw/kernel.versions.html.

1.2. Where Do I Start?

There are a handful of major Linux distributions. For information about them, and how they are installed, see Matthew Welsh's Installation and Getting Started, or IGS for short. It's located at the Linux Documentation Project Home Page, http://www.linuxdoc.org/, and on the Linux FAQ home page, http://www.mainmatter.com/

The information in IGS is somewhat dated now. More up-to-date information about first-time Linux installation is located in the LDP's Installation HOWTO, also located at the LDP Home Page.

Commercial distributions have begun to appear on the shelves of many book and electronics stores in the last six months, at least in the U.S., and some hardware vendors now ship systems with Linux pre-installed.

There is a very thorough installation guide on line at http://heather.cs.ucdavis.edu/~matloff/linux.html.

Some distributions can still be installed via anonymous FTP from various Linux archive sites, but in many cases, the size of the distribution makes this impractical. (``Where Can I Get Linux Material by FTP?'') There are also a large number of other releases which are distributed less globally that suit special local and national needs.

1.3. What Software Does Linux Support?

Linux supports GCC, Emacs, the X Window System, all the standard Unix utilities, TCP/IP (including SLIP and PPP), and all of the hundreds of programs that people have compiled or ported to it.

There is a DOS emulator, called DOSEMU. The latest stable release is 0.98.3. The FTP archives are at ftp://ftp.dosemu.org/dosemu The Web site is http://www.dosemu.org.

The emulator can run DOS itself and some (but not all) DOS applications. Be sure to look at the README file to determine which version you should get. Also, see the DOSEMU-HOWTO (slightly dated at this point--it doesn't cover the most recent version of the program), at ftp://metalab.unc.edu/pub/Linux/docs/HOWTO.

Work has been progressing on an emulator for Microsoft Windows binaries. (``Can I Run Microsoft Windows Programs under Linux?'')

iBCS2 (Intel Binary Compatibility Standard) emulator code for SVR4 ELF and SVR3.2 COFF binaries can be included in the kernel as a compile-time option. There is information at ftp://tsx-11.mit.edu/pub/linux/BETA/ibcs2/README.

For more information see the INFO-SHEET, which is one of the HOWTO's (``Where Can I Get the HOWTO's and Other Documentation?'' and ``How Do I Port XXX to Linux?'')

Some companies have commercial software available, including Motif, WordPerfect, and Framemaker. They often announce their availability in comp.os.linux.announce-- try searching the archives. (``Are the News Groups Archived Anywhere?'')

1.4. Does Linux Run on My Computer? What Hardware Is Supported?

Giving Linux a try requires a machine with an Intel '386, '486, or '586 processor with at least 2Mb of RAM and a single floppy drive. To do anything useful, more RAM and disk space is needed. (``How Much Memory Does Linux Need?'')

VESA Local Bus and PCI are supported.

MCA (IBM's proprietary bus) and ESDI hard drives are mostly supported. There is further information on the MCA bus and what cards Linux supports on the Micro Channel Linux Web page, http://www.dgmicro.com/mca. See also (``Where Should I Look on the World Wide Web for Linux Stuff?'')

Linux runs on most current laptops, with a decent X display. Refer to How do I know if my notebook runs Linux? For details of exactly which PC's, video cards, disk controllers, etc. work see the INFO-SHEET and the Hardware-HOWTO. (``Where Can I Get the HOWTO's and Other Documentation?'')

There is a port of Linux to the 8086, known as the Embeddable Linux Kernel Subset (ELKS). This is a 16-bit subset of the Linux kernel which will mainly be used for embedded systems. See http://www.linux.org.uk/Linux8086.html for more information. Linux will never run fully on an 8086 or '286, because it requires task-switching and memory management facilities not found on these processors.

Linux supports multiprocessing with Intel MP architecture. See the file Documentation/smp.tex in the Linux kernel source code distribution.

See the question below for a (probably incomplete) list of hardware platforms Linux has been ported to.

1.5. What Ports to Other Processors Are There?

There is a reasonably complete list of Linux ports at http://www.ctv.es/USERS/xose/linux/linux_ports.html, and at http://www.linuxhq.com/dist-index.html.

A project has been underway for a while to port Linux to suitable 68000-series based systems like Amigas and Ataris. The Linux/m68K FAQ is located at http://www.clark.net/pub/lawrencc/linux/faq/faq.html. The URL of the Linux/m68k home page is http://www.linux-m68k.org.

There is a m68k port for the Amiga by Jes Sorensen, which is located at ftp://sunsite.auc.dk/pub/os/linux/680x0/redhat/. The installation FAQ for the package, by Ron Flory, is at http://www.feist.com/~rjflory/linux/rh/.

There is also a linux-680x0 mailing list. (``What Mailing Lists Are There?'')

There is (or was) a FTP site for the Linux-m68k project on ftp.phil.uni-sb.de/pub/atari/linux-68k, but this address may no longer be current.

Debian GNU/Linux is being ported to Alpha, Sparc, PowerPC, and ARM platforms. There are mailing lists for all of them. See http://www.debian.org/MailingLists/subscribe

One of the Linux-PPC project pages has moved recently. Its location is http://www.debian.org/MailingLists/subscribe. http://www.linuxppc.org, and the archive site is ftp://ftp.linuxppc.org/linuxppc.

There is a Linux-PPC support page at http://www.cs.nmt.edu/~linuxppc/. There you will find the kernel that is distributed with Linux.

Apple now supports MkLinux development on Power Macs, based on OSF and the Mach microkernel. See http://www.mklinux.apple.com.

There are two sites for the Linux iMac port: http://w3.one.net/~johnb/imaclinux, and http://www.imaclinux.net:8080/content/index.html.

A port to the 64-bit DEC Alpha/AXP is at http://www.azstarnet.com/~axplinux/. There is a mailing list at vger.rutgers.edu. (``What Mailing Lists Are There?'')

Ralf Baechle is working on a port to the MIPS, initially for the R4600 on Deskstation Tyne machines. The Linux-MIPS FTP sites are ftp://ftp.fnet.fr/linux-mips and ftp://ftp.linux.sgi.com/pub/mips-linux. Interested people may mail their questions and offers of assistance to mailto:linux@waldorf-gmbh.de.

There is (or was) also a MIPS channel on the Linux Activists mail server and a linux-mips mailing list. (``What Mailing Lists Are There?'')

There are currently two ports of Linux to the ARM family of processors. One of these is for the ARM3, fitted to the Acorn A5000, and it includes I/O drivers for the 82710/11 as appropriate. The other is to the ARM610 of the Acorn RISC PC. The RISC PC port is currently in its early to middle stages, owing to the need to rewrite much of the memory handling. The A5000 port is in restricted beta testing. A release is likely soon.

For more, up-to-date information, read the newsgroup comp.sys.acorn.misc. There is a FAQ at http://www.arm.uk.linux.org.

The Linux SPARC project is a hotbed of activity. There is a FAQ available from Jim Mintha's Linux for SPARC Processors page, http://www.geog.ubc.ca/sparclinux.html. The SPARC/Linux archives are at ftp://vger.rutgers.edu/pub/linux/Sparc.

The Home Page of the UltraSPARC port ("UltraPenguin") is located at http://sunsite.mff.cuni.cz/linux/ultrapenguin-1.0/.

There is also a port ("Hardhat") to SGI/Indy machines. The URL is http://www.linux.sgi.com/.

1.6. How Much Hard Disk Space Does Linux Need?

About 10Mb for a very minimal installation, suitable for trying Linux, and not much else.

You can fit an installation that includes X into 80Mb. Installing Debian GNU/Linux takes 500Mb--1GB, including kernel source code, some space for user files, and spool areas.

Installing a commercial distribution that has a desktop GUI environment, commercial word processor, and front-office productivity suite, will claim an additional 1 GB of disk space, approximately.

1.7. How Much Memory Does Linux Need?

At least 4MB, and then you will need to use special installation procedures until the disk swap space is installed. Linux will run comfortably in 4MB of RAM, although X Apps will run slowly because they need to swap out to disk.

Some recent applications, like the later versions of Netscape, require as much as 64MB of physical memory.

There is a distribution, "Small Linux," that will run on machines with 2MB of RAM. Refer to Where can I get Linux material by FTP?

1.8. How Much Memory Can Linux Use?

A number of people have asked how to address more than 64 MB of memory, which is the default upper limit. Place the following in your lilo.conf file:

append="mem=XXM"

Where "XX" is the amount of memory, specified as megabytes; for example, '128M'. For further details, see the lilo manual page.

1.9. Does Linux Support the USB Bus?

Linux supports a few dozen USB devices at present, and work is underway to develop device drivers for additional hardware devices. There is a Web page devoted to the subject, at http://www.linux-usb.org/. In addition, there is a LDP HOWTO. See also, (``Where Should I Look on the World Wide Web for Linux Stuff?'')

1.10. Is Linux Public Domain? Copyrighted?

The Linux trademark belongs to Linus Torvalds. He has placed the Linux kernel under the GNU General Public License, which basically means that you may freely copy, change, and distribute it, but you may not impose any restrictions on further distribution, and you must make the source code available.

This is not the same as Public Domain. See the Copyright FAQ, ftp://rtfm.mit.edu/pub/usenet/news.answers/law/copyright, for details.

Full details are in the file COPYING in the Linux kernel sources (probably in /usr/src/linux on your system).

The licenses of the utilities and programs which come with the installations vary. Much of the code is from the GNU Project at the Free Software Foundation, and is also under the GPL.

Note that discussion about the merits or otherwise of the GPL should be posted to the news group gnu.misc.discuss, and not to the comp.os.linux hierarchy.

For other legal questions, see (``Where Are Linux Legal Issues Discussed?'')

1.11. Is Linux *nix?

Not officially, until it passes the Open Group's certification tests, and supports the necessary API's. Even very few of the commercial operating systems have passed the Open Group tests. For more information, see http://www.unix-systems.org/what_is_unix.html.

[Bob Friesenhahn]