Linux: Free Unix Information Sheet 0.1 Introduction to Linux Linux is a completely free cl

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Linux: Free Unix Information Sheet 0.1 Introduction to Linux Linux is a completely free clone of the unix operating system which is available in both source code and binary form. It is copyrighted by Linus B. Torvalds (, 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. However, support for MCA is being added at this time. Porting to other architectures is likely to be difficult, as the kernel makes extensive use of 386 memory management and task primitives. However, despite these difficulties, there are people successfully working on a port to the Amiga. Linux is still considered to be in beta testing. There are still bugs in the system, and since Linux develops rapidly (new versions come out about once every two weeks), new bugs creep up. However, these bugs are fixed quickly as well. Most versions 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 has 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 17, 1993, the current version of Linux is 0.99 patchlevel 7. 0.2 Linux Features * multitasking: several programs running at once. * multiuser: several users on the same machine at once (and NO two-user licenses!). * 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. * 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 16 MB swapping areas can be used at once, for a total 256 MB 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 (using a debugger on a program after it has crashed). * mostly compatible with POSIX, System V, and BSD at the source level. * 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. * 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. * 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 and Xenix, 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). * CD-ROM filesystem which reads all standard formats of CD-ROMs. * 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 anything useful. 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 patient. 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, SLS reports that a full base system without X fits into 45 MB, with X into 70 MB (this is only binaries), and a complete distribution with everything takes 90 MB. Add the whatever space you want to reserve for user files to these totals. 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 (you still need an ISA-bus hard disk controller, though). MCA (aka PS/2) does not work. Local bus works. RAM: Theoretically up to 1 GB, but using more than 16 MB requires that the kernel be recompiled. 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) need a special driver which is not currently part of the standard kernel. Supported SCSI adaptors: Adaptec 1542 (but not 1522), 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, and Western Digital wd7000. SCSI and QIC-02 tapes are also supported. Video: VGA, EGA, CGA, or Hercules (and compatibles) work in text mode. For graphics and X, there is support for (at least) EGA, normal VGA, some super-VGA cards (most of the cards based on ET3000, ET4000, Paradise, and some Trident chipsets), some S3 cards (not Diamond Stealth, because the manufacturer won't tell how to program it), 8514/A, and hercules. (Linux uses the Xfree86 X server, so that determines what cards are supported.) Other hardware: SoundBlaster, AST Fourport cards (with 4 serial boards), 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, gprof. Graphical environments: X11R5 (Xfree86), MGR. Editors: GNU Emacs, Lucid Emacs, MicroEmacs, jove, epoch, elvis, joe, pico. Shells: Bash, zsh (include ksh compatiblity mode), tcsh, csh, rc, ash. Telecommunication: Taylor (BNU-compatible) UUCP, kermit, szrz, minicom, pcomm, xcomm, term/slap (runs multiple shells over one modem line), and Seyon. News and mail: C-news, trn, nn, tin, smail, elm, mh. Textprocessing: TeX, groff, doc. Games: Nethack, several Muds and X games. All of these programs (and this isn't even a hundredth of what is available) are freely available. 0.5 Getting Linux 0.5.4 Anonymous FTP At least the following anonymous ftp sites carry Linux. This list is taken from the Meta-FAQ list, which is posted every week to the comp.os.linux newsgroup (the Meta-FAQ is updated more often than this information sheet, so the list below may not be the most current one). Textual name Numeric address Linux directory ============================= =============== =============== /pub/linux /pub/Linux /pub/OS/Linux /pub/linux /pub/linux /pub/Linux /pub/linux /pub/Linux /pub/linux /pub/OS/Linux /systems/unix/linux mirrors/linux /pub/linux /pub/linux /Linux /pub/os/linux /pub/Linux /pub/OS/linux and are the official sites for Linux' GCC. Some sites mirror other sites. Please use the site closest (network-wise) to you whenever possible. 0.5.5 Other methods of obtaining Linux There are many BBS's that have Linux files. A list of them is maintained by Zane Healy; he posts it to the comp.os.linux newsgroup around the beginning and middle of the month, please see that post for more information. comp.os.linux is echoed on the LINUX echoid on fidonet. This list is available as, and is mirrored on fine mirrors everywhere. There is also at least one organization that distributes Linux on floppies, for a fee. Contact Softlanding Software 910 Lodge Ave. Victoria, B.C., Canada V8X-3A8 +1 604 360 0188 FAX: 604 385 1292 for information on purchasing. There is also an organization which sells Linux on CD-ROM --- contact Yggdrasil Computing, Incorporated CDROM sales PO Box 8418 94707--8418 510--526--7531 for information on purchasing the CD-ROM. Also, don't forget about friends and user's groups, who are usually glad to let you make a copy. 0.5.6 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 most important one is currently the SLS release. SLS is put together by Peter MacDonald, and is the more full-featured one. It contains much of the available software, and includes X. I really recommend SLS to anyone who's serious about getting started with Linux. 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. 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). 0.6 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 have each their own copyright, although much of it uses the GPL as well. All of the software on the FTP site is freely distributable (or else it shouldn't be there). 0.7 News About Linux There is a Usenet newsgroup, comp.os.linux, 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). For the current status of the Linux kernel and a summary of the most recent versions, finger There is also a more or less weekly ``newsletter,'' Linux News, which summarizes the most important announcements and uploads, and has occasional other articles as well. Look in comp.os.linux.announce for a sample issue. 0.8 Future Plans Work is underway on Linux version 1.0, which will close some of the gaps in the present implementation. The major functionality shortcomings are advanced interprocess communication (semaphores, shared memory), closer compatibility with POSIX, and a lot of tweaking. Documentation is also sorely missing, but is being worked on by those on the ``Linux Documentation Project'' (the DOC channel of the mailing list). By April 1993 there should be a complete installation and getting started manual for Linux. 0.9 This document This document is maintained by Michael K. Johnson, 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 current copy of this document can always be found as, and a .dvi version can be found as INFO-SHEET.dvi, in the same directory. 0.10 Legalese 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.


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