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Member "pcemu/programs/lredir.readme" (22 Jan 2001, 4922 Bytes) of package /linux/privat/old/pcemu-1.2.tar.gz:


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    1 From Tim Bird (Tim_R_Bird@Novell.COM) :
    2 (altered slightly by DH - changed 'LINUX\FS' to 'PCEMU\FS')
    3 
    4 LREDIR is a general purpose DOS redirection utility, specifically
    5 implemented for use with the Linux DOS emulator DOSEMU.
    6 
    7 In general, DOSEMU provides emulation of a DOS disk redirector via the
    8 MFS (Mach File System) module of the emulator.  This support was originally
    9 derived from the redirector for the DOS emulator for Mach.
   10 
   11 DOS supports installable file systems by issueing callouts to a "redirector"
   12 on any functions it receives for files or drives that are registered
   13 with it as being non-local.  The installable file system support is intended
   14 mainly for use by CD-ROM drivers and network clients, so that these file
   15 systems may be presented to the DOS user as additional drives.  In DOSEMU, 
   16 MFS uses this mechanism to present a section of the Linux file system to
   17 the DOS which is running in the emulator.  This means that any subtree in
   18 the Linux file system may be redirected and designated as a drive letter
   19 under DOS for use in the emulator.
   20 
   21 In order for DOS to use redirected drives, it must be configured for
   22 additional drives.  This is done by putting a "LASTDRIVE=Z" statement in
   23 the CONFIG.SYS that is used by the emulator upon loading DOS.  You can set
   24 the LASTDRIVE to any letter of the alphabet.  The default is F if none is
   25 specified, which means that DOS can only use letters A-F for drives.  The
   26 example above configures all possible drive letters, A through Z, to be
   27 available for use by DOS (and is what I recommend).  There is a slight
   28 memory penalty for configuring this many drives (about 1K of the
   29 conventional memory inside the emulator).
   30 
   31 To use LREDIR, MFS must first have been enabled using EMUFS.SYS.  To do
   32 this, load EMUFS.SYS in your CONFIG.SYS, with a line like:
   33 
   34     device=C:\EMUFS.SYS /usr/src
   35     
   36 This will initialize the MFS redirector, and create one redirection 
   37 automatically on the first available drive letter (usually D:).  Although
   38 EMUFS.SYS can be loaded multiple times to get additional drives, I
   39 recommend that you only load it once, and use LREDIR to redirect more
   40 drives to other places in the Linux file system as needed.
   41 
   42 LREDIR can be used to create new redirections, get a list of the current
   43 redirections, or to delete a redirection.  To create a new redirection,
   44 specify the drive letter to use, and the Linux file system path which
   45 will become the root of that drive.  Since LREDIR is a general-purpose
   46 redirection utility, it has a generic syntax which allows it to be used
   47 with other redirectors besides MFS (like the NetWare Lite client, or
   48 DOS VLM NetWare client).  The syntax is:
   49        
   50     LREDIR drive: server\volume\path
   51     
   52 For use with the Linux file system, we use PCEMU as the server name,
   53 FS as the volume name, and then specify a path from the root of the
   54 Linux file system as the location to redirect the drive to.  For example:
   55 
   56     LREDIR F: PCEMU\FS\USR\SRC
   57     
   58 would create a new redirection for drive F:, where the contents of
   59 /usr/src would appear at the root of drive F:.  Note that this establishes
   60 a root for drive F: which will be enforced by DOS.  ie, drive F: cannot
   61 be used to access files in /usr or /usr/bin, because those Linux directories
   62 are not in the subtree under /usr/src.
   63 
   64 LREDIR allows you to redirect any drive available to DOS, including one
   65 that is currently a physical drive.  This means that you can replace one of
   66 your startup drives with a redirection.  When you delete the redirection,
   67 the physical drive will become visible again.  This can be used so that
   68 the boot diskimage disappears, and is replaced by the mounted MSDOS
   69 file system in Linux, with the drive letter and root the same as before
   70 Linux was installed.  For example on my system, I have a partition
   71 with a DOS file system on it.  If I boot my machine with a DOS boot
   72 diskette, this partition is my C: drive in DOS.  When I boot Linux, I mount
   73 this partition, using the msdos file system type, at location /dos/cdrive.
   74 
   75 For this to work right, you actually need two AUTOEXEC.BAT files, one on
   76 the boot diskimage, and one in the directory that will become the root
   77 of the redirected drive.
   78 
   79 In the AUTOEXEC.BAT in the boot diskimage I put the line:
   80 
   81     LREDIR C: PCEMU\FS\DOS\CDRIVE
   82     
   83 and when DOS runs in DOSEMU, it redirects drive C: to be replaced with
   84 the drive C: I booted from.  Also, parsing of the AUTOEXEC.BAT file
   85 will continue with the AUTOEXEC.BAT (if any) on the redirected drive.
   86 
   87 People who use LREDIR in this way should be careful because COMMAND.COM
   88 will continue parsing the AUTOEXEC.BAT from the redirected drive at the
   89 same file offset where it left off in the AUTOEXEC.BAT on the original
   90 C: drive.  For this reason, it is best to have the LREDIR command on the
   91 first line of the original (diskimage) AUTOEXEC.BAT, and have the line
   92 be identical in the AUTOEXEC.BAT on the redirected drive.  Is this clear
   93 as mud?
   94