LINUX Information sheet.

Rob Harper Rob.Harper at csc.fi
Wed May 12 09:09:57 EST 1993


Linux, the free Unix-like OS for 386 and 486 computers, is primarily 
available at two sites, sunsite.unc.edu and tsx-11.mit.edu.
And of course the first site to receive it is nic.funet.fi this side
of the atlantic.

I reccomend reading the Usenet newsgroup comp.os.linux for more information;
also, I am attacing the Linux info-sheet, which answers many questions.

                             Linux 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 (torvalds at kruuna.helsinki.fi), 
        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 



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