[LUG.ro] Distribucion buteable desde CD-ROM (Minix)

Pablo lugro@lugro.org.ar
Fri, 28 Nov 2003 13:20:32 -0300


Les paso este mail que recibi, no es otra opcion a GNU/Linux
pero puede ser interesante.


          Saludos. Pablo.


[This is posted for Aleksander Korzynski <minixNOSPAM@elka.pw.edu.pl> and
his colleagues at Warsaw University of Technology, Poland. It was
originally posted on the comp.os.minix newsgroup. The newsgroup headers
have been moved to the end of the article. -- ASW]

From: Aleksander Korzynski <minixNOSPAM@elka.pw.edu.pl>
Newsgroups: comp.os.minix
Subject: CD-based Minix distribution
Date: Thu, 27 Nov 2003 22:32:03 +0100

Hello,

I would like to announce the availability of an unofficial CD-based
Minix 2.0.3 distribution. One of its advantages is the possibility
to boot Minix directly from CD-ROM.

The distribution is the result of a project the aim of which was
to create a convenient working environment for teaching Operating
Systems on the example of Minix. The environment was expected to fulfill
the following conditions:

    1. The computer on which the distribution is running should be easily
       restorable to its initial state, no matter what (potentially
       catastrophic) changes a student makes to the operating system.
       This is the reason why it has been chosen to store the filesystem
       into RAM disk.

    2. The distribution should be easily portable to students' personal
       computers. It should not be required to alter in any way the hard
       drive of the computer it is running on. This is the reason why it
       has been chosen to load its filesystem entirely from CD-ROM.

    3. It should be possible to boot the distribution using a custom
       kernel. This is the reason why it has been chosen to start the
       booting process from a floppy disk, from where the kernel is loaded.

*Note:* the provided CD-ROM image can be booted directly with a standard
kernel, although this method results in at least one known problem (see
Known Issues). In any case, in order to load a custom kernel the booting
process has to be started from a floppy disk.


         Download:

The CD image that is the result of this project, compressed with gzip
(28MB), is available at the following locations:

     * <http://studia.elka.pw.edu.pl/prog/minix/download/m203CD08iso.gz>
     * <http://minix1.hampshire.edu/pub/contrib/m203CD08iso.gz>
     * <http://minix1.bio.umass.edu/pub/contrib/m203CD08iso.gz>

How to create a bootable floppy disk suitable for use with this
distribution is described in the README.TXT file stored in the root
directory on the CD.


         Summary of the CD-ROM contents:

    1. The original Minix 2.0.3 interim release is stored in the /MINIX
       directory.

    2. The source code patch that enables Minix to load a filesystem
       image from CD-ROM into RAM disk is stored in the directory
       /MINIX/ADDONS/BOOTCD. The code is designed to access a filesystem
       image that is stored on the CD-ROM as described in the El Torito
       Bootable CD Specification. Because of that, the patch also enables
       Minix to be booted directly from CD-ROM. The directory also
       contains a README.TXT file which refers to the patch.

    3. A general README.TXT describing the distribution is stored in the
       root directory of the CD.


         What happens when the distribution is booted with the usage of
a
         floppy disk:

    1. The bootmonitor and the kernel are loaded from the floppy disk.

    2. The kernel, using the ATAPI driver, accesses a filesystem image,
       which is stored on the CD-ROM as described in the El Torito
       Bootable CD Specification, and copies it into RAM disk. The size
       of the image is 1.44MB but the file system is prepared in such a
       way that on load to RAM disk it is stretched to 32MB.

    3. By the /etc/rc script, the archives USR.TAZ and SRC.TAZ are read
       from the CD-ROM using the isoread tool and they are uncompressed
       on the fly into the RAM disk.

    4. The sources are then patched with the CD-booting patch, which is
       also read from the CD-ROM using isoread.

    5. The script /usr/src/tools/mkboot (which is needed for installing
a
       freshly compiled, custom kernel) is also patched in order to make
       it compatible with the changes introduced by the CD-booting patch
       (more information about the changes to this script is available at
       /MINIX/ADDONS/BOOTCD/README.TXT).

    6. All the IDE device nodes in the /dev directory, except the one
       pointing to the CD-ROM device, are removed, in order to minimize
       the risk of accidental damage to hard drives when a student is
       experimenting with the kernel or shell commands. If the device
       nodes are needed they can be recreated at run-time with the
       command MAKEDEV (see the MAKEDEV.8 manual page for usage
       information).

    7. It is then possible to make changes to the kernel source code,
       compile the kernel with 'make fdboot', which will store the custom
       kernel on a floppy disk, and then boot the floppy disk with the
       custom kernel. The boot parameters on the floppy disk will be
       automatically set so that the filesystem will be loaded from CD-ROM.


         What happens when the distribution is booted directly from CD-ROM:

    1. BIOS recognizes the CD-ROM as bootable and emulates the filesystem
       image, which is stored on the CD-ROM in the way described in the
       El Torito Bootable CD Specification, as drive A:

    2. The bootmonitor is loaded into memory from the emulated drive.
       Using BIOS commands, the bootmonitor accesses the filesystem on
       the emulated drive and loads the kernel.

    3. The kernel, using the ATAPI driver, accesses the filesystem image
       stored on the CD-ROM and copies it into RAM disk. The size of the
       image is 1.44MB but the file system is prepared in such a way that
       on load to RAM disk it is stretched to 32MB.

    4. Same as in the previous section, beginning at point 3.


         Known issues:

     * Occurs only if the distribution has been booted directly from
       CD-ROM. Upon shutdown the system freezes immediately after
       returning to the bootmonitor. Another symptom of, most likely, the
       same bug is that if in the beginning of the boot process the
       command /ls/ is issued in the bootmonitor, the system freezes
       immediately after displaying on the screen the contents of the
       current directory on the emulated A: drive. If the command is not
       issued the system can be successfully booted. It is currently
       thought that this behaviour is the result of bootmonitor's
       incompatibility with the BIOS-emulated drive. The problem does not
       occur if the booting process is started from a floppy disk.


         The project team would like to thank:

     * The developers of Minix: Andrew Tanenbaum, Kees Bot and
       Albert Woodhull, for creating an operating system excellent for
       educational purposes.

     * Albert Woodhull for various help and webspace.

     * Kees Bot for the tip on how to create a small filesystem that could
       be stretched to 32MB on load to RAM disk.

     * The numerous contributors to Minix.


Feedback on the distribution would be welcome.


Warsaw University of Technology, Poland
Main maintainer: Alexander Korzynski
Project idea: dr Tomasz J. Kruk
Project's main webpage: <http://studia.elka.pw.edu.pl/prog/minix>
Additional webpages:
     <http://minix1.hampshire.edu/faq/minixcd08.html>
     <http://minix1.hampshire.edu/pub/contrib/m203CD08.txt>
     <http://minix1.bio.umass.edu/faq/minixcd08.html>
     <http://minix1.bio.umass.edu/pub/contrib/m203CD08.txt>
Contact address: <minixNOSPAM@elka.pw.edu.pl>

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From: Aleksander Korzynski <minixNOSPAM@elka.pw.edu.pl>
Newsgroups: comp.os.minix
Subject: CD-based Minix distribution
Date: Thu, 27 Nov 2003 22:32:03 +0100
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reposted to minix-l by:
+----------------------------------+
| Albert S. Woodhull               |
| Hampshire College, Amherst, MA   |
| awoodhull@hampshire.edu          |
| http://minix1.hampshire.edu/asw/ |
+----------------------------------+


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