File:  [GPL Stacker compression] / dmsdos / INSTALL.TXT
Revision 1.1.1.3 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 16:38:42 2018 UTC (22 months ago) by root
Branches: MAIN, DMSDOS
CVS tags: dmsdos092322, dmsdos092232, HEAD
DMSDOS 0.9.2.3-pre2

DMSDOS + CVF-FAT installation
-----------------------------

*** These are installation instructions for use under LINUX. If you want to
    install dmsdos in a Dos/Win32 environment see file PORT_TO_WIN32. ***


If you want to install dmsdos without bothering all the details, please
read at least the chapter 'Easy Installation'. If that does not work for
you, try 'Manual Installation'.

*** FAT DRIVER BUG WARNING: 

    * FAT32 kernels earlier than 2.0.36 have a serious rmdir bug
      that causes filesystem corruption in a msdos filesystem.
      See file patches/DIFFS.TXT where to find a patch to fix this
      (patches/msdos-rmdir-bugfix.diff).

    * All kernels from the 2.0, 2.1 and 2.2.x(x<3) series have a bug that 
      can do write access to a FAT filesystem though it is mounted read-only.
      Though it only occurs in a rare situation, this bug can especially be
      triggered by dmsdos. Also see file patches/DIFFS.TXT where to find a 
      patch to fix this (patches/fat-truncate-bugfix.diff).

    * All 2.2.x(x<3) kernels (and maybe late 2.1 
      kernels too) have a serious bug in the vfat driver that can cause 
      system hang ("kernel panic: VFS: LRU list corrupted") due to filesystem 
      buffer list corruption. Also see file patches/DIFFS.TXT where to find a 
      patch to fix this (patches/vfat-brelse-bugfix.diff). IT IS VITAL FOR
      USING DMSDOS IN A VFAT PARTITION TO HAVE THIS BUG FIXED.

    * At least kernel 2.2.13 and 2.2.14 have a bug in CVF write access support
      (you always get "no space left on decive" and "DMSDOS: fat_add_cluster
      failed" messages). See file patches/DIFFS.TXT for a patch.

    These bugs are not fixed automatically during installation. If you are
    in doubt, please check the diff files and your kernel source. You can use
    dmsdos without these bugfixes, but you may crash or hang your system or
    lose data. YOU HAVE BEEN WARNED.

WARNING: Support for 2.3.99 and newer is currently highly experimental and
may not work for you. If you want a stable dmsdos subsystem, use a 2.2.x
kernel.

A. Easy Installation
====================

  Dmsdos comes with a set of scripts for automatic installation. If you do not 
  like some scripts poke around in your system, see chapter 'Manual 
  Installation' :)

  Okay, just a small warning: automatic installation can never be perfect.
  For a 2.0.xx kernel I recommend to make a backup copy of your kernel sources
  if you cannot restore it easily. Dmsdos needs to patch the 2.0.xx kernels
  a bit. This is not a problem if you are using unmodified kernel sources
  from 2.0.29 to 2.0.36 (others are currently not tested), but if your kernel
  is highly hacked or patched the patch might go wrong and need manual 
  correction. If you are not familiar with hacking around in failed patches,
  I think, you will be lucky to restore the old state :)

  2.1 and 2.2 kernels do not need a patch, but you may choose to update the
  CVF-FAT interface (though it still works with the old one). The updated 
  files have been included into the official kernel 2.2.3. A 
  description of how and what to update can be found in patches/cvf.c.README.

  And, of course, you should ensure you have fixed the kernel FAT driver bugs 
  listed above :)


  1. Prepare automatic installation:
  ----------------------------------

    You need, of course, full kernel sources in /usr/src/linux (which may be a
    symbolic link to the real kernel source directory). No discussion here, 
    I say you _need_ or automatic installation refuses to start. You should 
    also ensure that the kernel version that you are currently running and the
    sources in /usr/src/linux do match. Dmsdos may install the module at a
    wrong place if they don't match, which does no harm but somewhat confuses
    both the module subsystem and the system administrator :)

    * If you have installed a previous dmsdos version:

    Check the version number. If it's 0.8.x or lower you have a problem.
    You must completely uninstall that version before. How to do so, see the
    documentation of that old version (it should have some sripts for that
    purpose). If you really can't uninstall it, throw away your old kernel
    sources and get fresh ones and remove the old dmsdos binaries that may
    be lying around in directories in your path.

    Dmsdos 0.9.0 and newer need not be uninstalled prior to an upgrade.


  2. Beginning installation:
  --------------------------

    Go into the directory where the dmsdos sources untarred and enter a
    'make'. That should do it. The installation script will ask some
    questions. The script always waits for your confirmation before it
    changes anything in your kernel sources or your system. You can exit
    with CTRL-C at any stage (and continue with manual installation).
    Be also prepared that the script calls kernel configuration and 
    recompiles your kernel (that depends on your system setup).

    * If problems arise:

      Automatic installation stops if it finds that something has gone wrong
      (i.e. a patch failed). 

    * If the script calls kernel configuration:

      This means something that is necessary for dmsdos to work correctly
      has been turned off in your kernel configuration. For dmsdos you need:

        - Module support
        - Loopback block device (may be compiled as module)
          *** NOTE: This one can be found under 'Additional block devices'.
              It has nothing in common with the network loopback interface
              so please don't mix them up :)
        - FAT filesystem (may be compiled as module)
        - MSDOS or VFAT filesystem (may be compiled as module)
        - since 2.0.34 also NLS support (but this is already required by FAT)

    * If the sript stops and asks for kernel and module installation and
      for reboot:

      Well I hate scripts that install new kernels and reboot automatically.
      So the dmsdos installation refuses to do that. Usually, the script wants
      you to do

            cd /usr/src/linux
            make zlilo
            make modules_install
            reboot

      or similar commands that have the same effect. You can do that 
      immediately, but you can also continue without rebooting. But, please
      remember to do that before _using_ dmsdos the first time :)

      YOU SHOULD KNOW WHAT YOU ARE DOING. If not, read for example
      the KERNEL-HOWTO or related documentation.

      Note that dmsdos installation is not complete yet. Rerun 'make' in the
      directory where the dmsdos sources untarred.

    * If it asks strange questions about dmsdos configuration:

      Consult the "online" help or accept the default settings if you don't
      understand what you are doing. You can rerun the dmsdos configuration 
      script again at any time later if you want to play with the options. 
      See 'Manual instalation' section 'Compiling the sources' for details.

      IMPORTANT NOTE FOR 2.3 and 2.4 kernels:
      Go into "dmsdos expert configuration", there select "misc options"
      and disable "writable mmap support". Otherwise the code fails to
      compile.

  3. Completing installation
  --------------------------

    Okay, if all has completed without errors, it's time for the first test.
    If the script asked for kernel and modules installation and for reboot
    but you haven't done it yet, please do it now.

    The first test and everything beyond that is described in part 
    'C. The first test'.


B. Manual Installation
======================

  1. Preparing installation
  -------------------------

    * Upgrade from dmsdosfs 0.8.x(.y) or earlier: *** WARNING ***

    If you have an earlier version of the dmsdos filesystem installed (i.e. 
    dmsdos 0.8.x), you'd better throw away your kernel sources and get fresh 
    ones. You must remove all old dmsdos sources, especially header files, and 
    executables or modules. The new code doesn't install the dmsdos module in 
    the kernel source tree, so this is very important. To be sure, do a 
    'find / -name "*dmsdos*" -print', or check your path for old executables 
    and your /lib/modules/* directories for old modules. Okay, I promise that 
    this kind of cleanup will no longer be necessary for further upgrades :)

    * Upgrade from 0.9.0(.x) or higher:

    You don't need to reconfigure or recompile your kernel. You don't
    need to patch the kernel again. Just compile the new dmsdos module 
    and the updated dmsdos utilities.

    * Fresh installation:

    If you have never used an older version of dmsdos before, you don't
    have to remove anything :) But, depending on your kernel version, you
    may have to patch your kernel sources. You may also have to reconfigure
    and recompile your kernel even if there's no patch needed.

    *** Please ensure to have the kernel FAT driver bugs fixed (the bugs are
        listed at the beginning of this ducument).


  2. Check kernel for CVF-FAT and install it if it is missing
  -----------------------------------------------------------

    Make sure you have a kernel version 2.0.29 or newer from the 2.0 series
    or a kernel version 2.1.94 or newer from the 2.1 development series or
    any 2.2.x kernel. Older kernels may work too, but this has never been 
    tested. If you are using older kernels and run into problems please don't
    expect me to fix them - it's too much work to keep a multi-kernel dmsdos 
    package work with all old and new kernels :)

    Dmsdos version 0.9.0 and higher depend on the CVF-FAT interface in the
    kernel. This interface is already present in kernels 2.1.80 and newer,
    and it is also compatible with UMSDOS in 2.1.xx since 2.1.94.
    So if you have 2.1.80 or newer you do not need a patch. But you may want
    to update the CVF-FAT interface. The new interface has been suggested to 
    be included in newer kernels, but at the time of writing this it has not 
    yet gone in. See patches/cvf.c.README for instructions how and what to 
    update. Note that you do _not_ have to update - the old interface still
    works (but it has a minor bug and lacks kerneld or kmod support).

    For 2.0.xx kernels you need to apply at least one of the CVF-FAT patches. 
    Dmsdos comes with a collection of patches for different setups. If you 
    are brave you can enter a 'make patch'. This starts a script that tries 
    to find out automatically whether you need a patch and which one, and it 
    installs the patches it thinks you need. Be warned, the script is not 
    perfect. It is known to work if you do not have an unusual setup (well, 
    it works for a plain 2.0.33 kernel, also with a fat32 patched 2.0.33 
    kernel and with the newer 2.0.34 up to 2.0.36).

    If automatic patching fails or if your setup is a highly patched or hacked 
    kernel you might want to take a look at further instructions. Please read 
    the file patches/DIFFS.TXT to find out which patch you need and how to 
    install it. 


  3. Check kernel configuration
  -----------------------------

    For dmsdos you need:

      - Module support
      - Loopback block device (may be compiled as module)
        *** NOTE: This one can be found under 'Additional block devices'.
            It has nothing in common with the network loopback interface
            so please don't mix them up :)
      - FAT filesystem (may be compiled as module)
      - MSDOS or VFAT filesystem (may be compiled as module)
      - since 2.0.34 also NLS support (but this is already required by FAT)

    If you don't know whether all of them are present you can enter a
    'make kernelconf'. This calls a script that checks your kernel
    configuration and calls the interactive kernel 'Configure' script if
    something is missing. In that case, just go through the questions,
    mostly accepting the defaults, but be sure to say Y for module support,
    Y or M for loopback block device, Y or M for FAT filesystem support, 
    and Y or M for the MSDOS or VFAT filesystem. Then the script tries to
    compile your kernel. In some cases the script tends to recompile your
    kernel though it isn't really necessary. So don't be surprised - it's 
    a dumb script. :) Note that the script does not *install* the new kernel 
    and the new modules.

    Refer to the kernel documentation for details about kernel configuration.

    If you do not want to let the dmsdos Makefile call the script but you 
    want to do it 'by hand' you can do something like this:

        cd /usr/src/linux
        make config (or 'make menuconfig' if you prefer)
        make dep
        make clean
        make zImage (or 'make bzImage' if you need it)
        make modules

    When the kernel and the modules have been compiled, they must be
    installed. This is usually done with these commands:

        cd /usr/src/linux
        make zlilo
        make modules_install
        reboot


  4. Compile the dmsdos sources
  -----------------------------

    Go into the directory where the dmsdos package untarred and do
  
        cd src
        make config (or 'make menuconfig' if you prefer)

    Yes, there's a configuration script that asks some questions now.
    You very likely know this procedure from the Linux kernel. In fact,
    the scripts have been copied from the kernel and a bit hacked :-)
    Well, there's no xconfig (I think this is overkill).

    If you have no clue what to answer to the questions, consult the online
    help or accept the defaults (which should be safe and work for all
    systems). As I have received a lot of mail about that, the dmsdos
    configuration has now a normal and an expert mode. In normal mode,
    only the most important questions (which should be understood by a
    novice without problems) show up.

    For convenience, there are some pre-configured files which can be loaded 
    with the 'Load an Alternate Configuration File' menu item during
    'make menuconfig'. Currently, these files are available:

    config.small-module       - for a small dmsdos module (e.g. for bootdisk)
    config.low-traffic-write  - for low-traffic write access to a CVF
    config.high-traffic-write - for high-traffic write access to a CVF
    config.debug              - for safe low-level dmsdos debugging

    After loading the alternate config file you'd better check the settings
    (just walk through all the menus). Especially if you want a small module 
    exclude the CVF format drivers you don't need.

    The text-based 'make config' can also use a pre-configured file. Just copy
    the config.what-you-like to .config and run 'make config'.

    IMPORTANT NOTE FOR 2.3 and 2.4 kernels:
    Go into "dmsdos expert configuration", there select "misc options"
    and disable "writable mmap support". Otherwise the code fails to
    compile.

    Then continue with these steps:

        make dep
        make clean
        make

    The last line starts compiling the sources.

    There were problems with some old versions of binutils reported (it's a
    bug in old GNU assembler versions). Have a look at the Makefile for some 
    hacks.

    If you want a shared dmsdos library instead of a static one you have
    to edit the Makefile. Using the shared library is currently strongly
    discouraged (well _not_ because of bugs). See the documentation for 
    the reasons.

    If you run into strange problems, you can try to compile each part of
    dmsdos separately:

      make dmsdos.o       - compiles the dmsdos module dmsdos.o (required)
      make dutil          - compiles the dmsdos utility dutil (useful)
      make dmsdosd        - compiles the external dmsdos daemon (nice)
      make libdmsdos.a    - compiles the dmsdos library
      make dcread         - compiles a sample program using libdmsdos
      make dmsdosfsck     - Ahh... it's there :) 
      make mcdmsdos       - compiles a mc external fs interface tool

    If you can't get the external daemon compiled try the internal daemon
    (though most people never need the daemon). It can be enabled during 
    configuration ('make config').

    If you can't get it compiled at all, have a look at the Makefile in the
    src directory. It has some switches to work around some problems (gas
    bugs, unusual systems, switch off cpu specific optimization, switch off
    inline assembler statements, etc). This should not be necessary, but some
    systems might need it.

    If you still can't get it compiled, please send a bug report including a
    detailed description of your system (version of kernel, gcc, binutils etc)
    and what error messages are shown. If you know how to fix the problem
    please also let me know :) A checklist about the details I usually need
    for tracing down a problem can be found in doc/dmsdos.doc.


C. The first test
=================

  1. Check whether the module loads correctly:
  --------------------------------------------
  
    Try a

        insmod -m dmsdos > /tmp/dmsdos.map

    Check the file /tmp/dmsdos.map for error messages.
    Depending on your modutils version, you may have to use depmod or
    modprobe instead of insmod. (Please forgive me, I never understood the 
    difference. Maybe I should read the documentation some day :) )

    If the module fails to load, make sure you are using the right insmod
    version (there are lots of modutils versions for 2.1.xx - most don't
    work correctly under all kernel versions; some are even said not to work 
    at all). If it still fails, try to load the fat module (and since kernel 
    2.0.34 also the nls module) before. If it complains about a missing symbol,
    try to find out which part of the kernel the symbol belongs to, and load
    the appropriate module before or compile that part into your kernel.
    If it continues to fail this is a bug. If it prints out strange errors
    like "kernel_version needed ...blah..." and you are using a 2.2.x kernel
    get the latest module utilities for 2.1.xx kernels (I ran into this
    problem too :) ).

    Note that, for a mixed 2.0/2.2 system, I need modutils-2.1.121 (compiled
    against 2.2.x headers) but I must keep the kerneld binary from 
    modutils-2.0.0 (compiled against 2.0.x headers). Ughly, but the newer
    kerneld provided with modutils-2.1.121 breaks my 2.0.x system :(

    Please always load the module with the -m flag and redirect the
    output, which contains a symbol table, to a file. This file is needed
    in case there is a crash with a register dump. Please use this symbol 
    table to find the function where the problem occured. (Unfortunately, 
    this table usually differs from one insmod time to another depending on 
    actually free memory pages, so you can't just create the table once and 
    then use it for all dumps later.) If you don't know how to interpret a
    register dump, please have a look at Linus' excellent instructions for 
    that in the file README in /usr/src/linux. It is really important that 
    *you* try to interpret the register dump since it is absolutely system 
    dependent. THIS IS NOT DIFFICULT. YOU DO NOT HAVE TO KNOW C PROGRAMMING 
    FOR THAT.

    Let me repeat this. I just cannot track down register dumps since they
    are just some numbers, even to me :) Those numbers only make sense in 
    conjunction with the symbol table that was printed by insmod when the 
    module was loaded the last time before the crash. Thus, bug reports 
    without your interpretation by means of the symbol table are Really 
    Worthless and will be ignored.


  2. Test whether dmsdos can read a CVF
  -------------------------------------

    For the first test be sure to have the loop module, the fat module,
    the dmsdos module and the msdos or vfat module loaded. If you are using
    kerneld you might not have to care about most of them. Just the fat
    module may have to be loaded manually in that case in order to load
    the dmsdos module.
  
    Mount your Dos/Win95 partition that is the host for a compressed drive
    as usual (if you haven't done this already).

    Assuming the large Compressed Volume File (CVF) is /DOS/dblspace.001 and
    in doublespace format and you want to mount it under /mnt, try this 
    (it mounts READ-ONLY):

       mount -t msdos -o ro,loop,cvf_format=dblspace /DOS/dblspace.001 /mnt

    Please also use the "cvf_format=dblspace" option for drivespace drives.
    If the drive is in stacker format and the CVF is /DOS/stacvol.001 the
    command looks like this:

       mount -t msdos -o ro,loop,cvf_format=stacker /DOS/stacvol.001 /mnt

    If the _compressed_ filesystem contains long filenames, you may want 
    to use the VFAT driver instead of the MSDOS driver:

       mount -t vfat -o ro,loop,cvf_format=dblspace /DOS/dblspace.001 /mnt

    Note that you can leave out the "cvf_format=xxx" option. In that case,
    dmsdos automatically detects the CVF format. But it is recommended to
    specify always a "cvf_format=xxx" option.

      (If you leave out the "cvf_format=xxx" option there can be a strange
      error condition that is not immediately visible and causes awful 
      trouble some time later:

      If you leave out the "cvf_format=xxx" option and the dmsdos module 
      has not been loaded the plain FAT driver gets the compressed 
      filesystem, which it cannot handle. Unfortunately, a compressed FAT 
      filesystem looks very similar to an uncompressed one, so the FAT 
      driver may not refuse to mount the filesystem with an error message.

      *** This means, the mount command may succeed even if the dmsdos 
          module is not present. In that case, the FAT driver - wrongly - 
          assumes the mounted filesystem is _not_ compressed and it can 
          crash, hang or destroy the filesystem later when you try to 
          access it.

      So, *please*, always specify a "cvf_format=xxx" option for safety, 
      as it just prints an error if the dmsdos module is not loaded.)

    Now you can go into the /mnt directory and do some read access tests.
    If there are some problems, the dmsdos driver becomes very noisy and logs
    a lot of messages in the syslog. Not all of them are real errors, though.
    Some are just information about the kind of CVF detected and the results
    of some probing functions. Yes, there are different kinds of CVF formats
    throughout the Dos/Win95 versions :)

    Note that, at mount time, for all doublespace and drivespace format CVFs
    one (and only one) loop device error like "access beyond end of device"
    or similar appears. This is normal and results from dmsdos working around
    a limitation in the loop driver. This is *not* a dmsdos bug.


D. Permanent installation
=========================

  *** WARNING ***
  If you are upgrading from a dmsdos release in the range 0.9.0 to 0.9.1.1, 
  be sure to remove the old dmsdos module from the module path. The default
  location has changed from /lib/modules/misc/ to /lib/modules/`uname -r`/fs/.
  So the old module will not be overwritten and insmod may load the wrong 
  module if there are more than one dmsdos module lying around :)
  Note that the default location where the module is installed may be a bad
  choice if you switch kernel versions often. You may have to compile a
  seperate module for each kernel version. If you prefer the module to be
  installed at a different location feel free to edit the Makefile :)

  If you are sure it works, you can install it permanently on your system
  by doing

      make install

  This copies the module, binaries and manpages to standard system
  directories (usually under /lib/modules and /usr/local/[bin|man] - check 
  the Makefile for the locations). All the files that are copied by 
  'make install' are removed by 'make uninstall'.


D. Other things to notice
=========================

  1. Some BUG WARNINGS important to know for installation
  -------------------------------------------------------

    * UMSDOS related bugs:

    a) *** IN SOME 2.1.XX KERNELS UMSDOS SUPPORT IS COMPLETELY BROKEN ***
      Please avoid kernels from 2.1.0 to 2.1.93. Use 2.1.94 or newer.
      Even better: Upgrade to 2.2.

    b) If the UMSDOS module fails to load and complains about two
      missing symbols 'fat_readpage' and 'fat_dir_ioctl':
      I forgot to add some symbols to the export list in older cvf.diffs for 
      kernel 2.0.33. This bug also went in 2.1.80 when CVF-FAT was included. 
      In order to fix the problem, edit file linux/fs/fat/fatfs_syms.c and 
      append the missing symbols 'fat_readpage' and 'fat_dir_ioctl' to the 
      export list. Look how the other symbols are listed there and put in the 
      missing ones in the same way. (You don't need to know C programming for 
      that. Just use your common sense. You'll know what to do when you see 
      what's in that the file.) Then recompile the fat module (or the kernel 
      if your fat support isn't modular).

      I have seen that the problem is fixed in 2.1.128, but I did not verify
      older kernels. Well that shouldn't matter as you always should use the
      latest kernel if you want a development kernel :))

    * FAT driver bugs: 

      See the list above at the beginning of this document.


  2. Using kerneld or kmod to load dmsdos
  ---------------------------------------

    This is an installation tip for the convenient system hacker. It is
    not the default installation, and it is only recommended for dmsdos
    versions that are known to be stable.

    Please note that in latest 2.1.xx kernels kerneld has been replaced by
    kmod. This does not make a difference for dmsdos.

    In dmsdos-0.9.2.0 kerneld-autoload behaviour again has been changed. The
    new behaviour is now believed to be the "right" way :-) If you are using
    a CVF-FAT patch from an older dmsdos version (0.9.2.0-pre-3 and older) or
    a kernel 2.2.2 or older you should update the CVF-FAT interface
    (see patches/cvf.c.README) - otherwise it may not work. The updated files
    have been suggested to be included into the kernel, but have not yet
    gone in.

    If you do not know what kerneld or kmod is and what it does, please read 
    the KERNELD-MINI-HOWTO, for example, or refer to the documentation that
    comes with the Linux kernel sources (for kmod).

    CVF-FAT now triggers kerneld or kmod to load missing CVF modules 
    according to the following rules:

       1. If a fat based filesystem is mounted with the mount option
          "cvf_format=autoload", a module with the name "cvf_autoload" is
          requested. Well, such a module never exists. This does however
          make sense together with a special modules configuration.

       2. If a fat based filesystem is mounted with the mount option
          "cvf_format=xxx" (where xxx has to be replaced with the name of
          the format) a module "xxx" is requested.

    Usually there is a difference between the CVF format name and the
    module name. This can be corrected with 'alias' statements in the
    modules configuration file /etc/modules.conf (or /etc/conf.modules,
    both file names are common). 

    For dmsdos, you need the lines

        alias stacker dmsdos
        alias dblspace dmsdos
        alias cvf_autoload dmsdos

    in the configuration file. Note that kerneld needs a signal SIGHUP in 
    order to re-read the configuration file. Also note that this setup 
    directly loads the module and does not generate a symbol table (which is 
    required for debugging, for example to analyse a crash somewhere in the 
    module).

    If you need a symbol table from CVF module loading, you are out of luck.
    Load the modules manually in that case, please.

    If you want to add support for loading other CVF modules (do they exist?
    Let me know) with auto-detection (cvf_format=autoload), add "pre-install" 
    lines for them, e.g.

        pre-install cvf_autoload insmod -k cvf_mod1 
        pre-install cvf_autoload insmod -k cvf_mod2
        ...
    (untested, should work in theory. I do not know other CVF modules.).

    Problems with automatic loading of CVF modules should be solved by
    hacking /etc/modules.conf. It is not recommended to fix them by changing
    the dmsdos or kernel sources. If it does not work at all try another
    kerneld version. Not every kerneld version runs correctly under
    every kernel version. (Well this was probably one of the inofficial
    reasons to replace it with kmod in latest 2.1.xx kernels...)


  3. Using dmsdos as external filesystem for Midnight Commander
  -------------------------------------------------------------

    Dmsdos comes with an interface utility that accepts standard Midnight
    Commander commands for reading archive files. The utility is named
    'mcdmsdos' and is compiled during usual dmsdos compile process.
    The utility is currently read-only. It follows the specification of
    Midnight Commander version 3.0.

    Please refer to the documentation of Midnight Commander for further
    information on how to configure an external filesystem.

    You may want to write a small shell script as a wrapper around mcdmsdos
    in order to suppress output to stderr distorting the screen. For
    example, this (in the same directory where mcdmsdos resides), as it 
    does not need to know the absolute path:

       #!/bin/bash
       MCDMSDOS=`dirname $0`/mcdmsdos
       $MCDMSDOS $* 2>/dev/null


  4. Compiling dmsdos as a fix part of the kernel
  -----------------------------------------------

    For some purpose it may be desired to compile dmsdos as a fix part of
    the kernel (i.e. not as a loadable kernel module) so dmsdos is present
    immediately at bootup. This would probably be useful for a boot disk or 
    an emergency rescue disk, for example. (This saves you all the work to
    setup an initrd disk which is somewhat complex.)

    BE WARNED. This is not the default installation. This is not well tested.
    The patches for that setup have been created under Linux 2.0.35 and may
    fail for other kernels (that's unlikely because they are small, just a
    few lines, and it's easy to repair manually if they do fail.)

    Okay, if you really want to do this, just install dmsdos as usual. 
    Test whether it works. I'd also recommend to _write_ _down_ the dmsdos 
    configuration settings, especially if you use expert mode (because the 
    default values are not available later on when you might need them -
    due to my lazyness).

    After that, run the shell script 'in-kernel.sh' which just copies the
    dmsdos sources into the kernel source tree and patches some files to
    hang dmsdos in (have a look at the in-kernel*.diff if you want to know
    exactly what is changed). You _very_ likely want to create a backup of
    kernel sources before :)

    Then reconfigure your kernel. Answer 'Y' for loopback block device and
    for the fat filesystem (also for NLS since Linux 2.0.34). Then enable 
    DMSDOS support. You'll see the usual dmsdos configuration after that, but 
    you won't have any default values (this is a limitation of the 2.0.xx 
    configuration scripts and I am too lazy to create a workaround diff). 
    Don't forget to say 'Y' for the MSDOS or VFAT driver after that.

    Just some further warnings about that setup:
    
    * There's no easy way back. If you installed dmsdos as a fix part of the
      kernel the best way to get rid of it is getting fresh kernel sources.
      Well, you can disable it in kernel configuration. You can also try
      to run the script 'in-kernel-uninstall.sh', but no promise.
    
    * dmsdos may no longer compile in its own directory due to macro
      redefinitions in the kernel include files. But dmsdos can now be 
      compiled as module in the same way like all other kernel modules
      (i.e. run kernel configuration, answer 'M' to DMSDOS support, do
      'make modules' and 'make modules_install').

    * This setup is not recommended at all. YOU HAVE BEEN WARNED :)


  5. Mounting CVFs from /etc/fstab at boot time
  ---------------------------------------------

    It may be a bit tricky to get CVFs mounted at boot time. An /etc/fstab
    entry for a CVF usually looks like this:

         /DOS/drvspace.001  /DOSF  msdos   loop,cvf_format=dblspace  1  0
    or
         /DOS/stacvol.001  /DOSF  msdos   loop,cvf_format=stacker  1  0

    It is really important that the sixth field (the 'pass number') is zero
    in order to prevent the filesystem from being checked at boot time.
    (If you really want to check dos partitions *and* CVFs at boot time you
    very likely must hack your bootup scripts. This is not recommended,
    however, unless you are an experienced system administrator and know in
    detail how your bootup scripts work. This is not explained in the dmsdos
    documentation.)

    In the usual one-pass 'mount -a' procedure, I noticed a strangeness
    regarding the order in /etc/fstab: The filesystems seem to be
    mounted in reverse order. Thus

         /DOS/drvspace.001 /DOSF msdos     loop,cvf_format=dblspace  1  0
         /dev/hda1       /DOS    msdos     defaults   1  0

    works on my system while

         /dev/hda1       /DOS    msdos     defaults   1  0
         /DOS/drvspace.001 /DOSF msdos     loop,cvf_format=dblspace  1  0

    doesn't. So just be prepared to play around a bit with the fstab.


  6. Further information
  ----------------------

    The main dmsdos documentation is in doc/dmsdos.doc. Some other files in
    the doc directory may be useful, too. Take a look at them if you want to 
    know more details or technical information on how dmsdos works. Please 
    also take a look at the documentation if you run into problems before 
    sending a bug report. Yes, there is a list with common problems and their 
    solutions :)

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