[NTFSDOS Logo]
Copyright © 1996-1997 Mark Russinovich and Bryce Cogswell
Last Updated December 5, 1997, Version 2.0R+
Introduction NTFSDOS.EXE is a read-only network file
system driver for DOS/Windows that is able to
recognize and mount NTFS drives for
transparent access. It makes NTFS drives
appear indistinguishable from standard FAT
drives, providing the ability to navigate,
view and execute programs on them from DOS or
from Windows, including from the Windows 3.1
File Manager and Windows 95 Explorer.
Please read this entire file before
contacting us for help.
Enhancements over V1.30 Version 2.0 has the following enhancements
over V1.30:
* Several significant bug fixes.
* An option for tolerating directories
containing files with unicode names.
* Support for disks with many partitions.
* Greatly improved robustness.
* An add-on, NTFSDOS Tools, is available
for NTFSDOS 2.0R+ that provides limited
write capability aimed at disaster
recovery. See Read-Write NTFSDOS for
details.
Contents of the Package The NTFSDOS package (see the bottom of this
page) contains the following files:
* README.TXT: This file
* README.TXT: This file
* NTFSHLP.VXD: Helper VxD needed only for
long filename support in Windows 95
Installation and Use To use NTFSDOS, simply execute it from the
DOS command line (DOS 5.0 or greater is
required), or from your AUTOEXEC.BAT.
Executing NTFSDOS before Windows is started
will create NTFS drives that are visible
globally once inside Windows. Executing
NTFSDOS in a DOS box means that the NTFS
drives only exist within the DOS box where
NTFSDOS was executed.
When NTFSDOS starts, it will scan all
hard-disk partitions on your system to look
for NTFS drives. It will mount all NTFS
drives it finds as unique DOS logical drive
letters, and will inform you as it does so.
If you run NTFSDOS under DOS 7.0, NTFS drives
will support long filename calls even before
Windows starts. To propagate this support
into Windows 95, NTFSDOS automatically has
Windows run the NTFSHLP.VXD VxD device
driver. No changes to SYSTEM.INI or the
registry are necessary for this to occur -
NTFSDOS will detect when Windows 95 starts
and load the driver without
user-intervention. You need NTFSHLP.VXD only
if you will be running NTFSDOS with Windows
95.
NTFSDOS implements its own caching, and uses
one of two types of memory, depending on how
your system is configured. Its first choice
is to use XMS memory for caching, as this
minimizes demands placed on conventional
memory. If you start NTFSDOS before Windows,
then HIMEM.SYS, which can be found in the
WINDOWS directory under Windows 95 or the DOS
directory under Windows 3.1, or its
equivalent, must be started before NTFSDOS.
If NTFSDOS does not detect an XMS server, it
will resort to allocating 64KB of
conventional memory for its cache. In either
case, it will inform you of its action.
NTFSDOS takes six command line parameters.:
* The /L parameter lets you specify which
drive letters NTFSDOS should attempt to
use as it mounts NTFS drives.
* The /C option lets you override the
default XMS cache size.
* The /V option directs NTFSDOS to print
some messages detailing the drives it
looks at and the memory it allocates.
* The /X switch forces NTFSDOS to use
standard BIOS Int 13 services. Use this
if NTFSDOS has problems with your
computer's extended Int 13 services.
* The /U option has NTFSDOS correctly sort
through files with unicode names. You
should only use this if a NTFSDOS
directory listing enters an infinite
loop within directories that contain
files with unicode names.
* Finally, the /N switch can be used to
disable NTFSDOS support for compression.
Much of the conventional memory that
NTFSDOS normally uses is for compression
buffers, so if you will be accessing
drives or files that are not compressed
and would like to optimize NTFSDOS use
of memory, use this switch.
The syntax for these parameters is:
/L:<letter> Specifies drive letter to
start mounting at
/C:<size> Specifies size of XMS cache
in KB
/V Verbose
/X Disable extended int 13
support
/U Tolerate unicode file names
/N Disable support for
compression
If You Have Problems This section lists and addresses various
Running NTFSDOS issues that may arise when you run NTFSDOS.
* NTFSDOS does not recognize my NTFS drive
NTFSDOS does not handle cluster sizes >
4K on NT 4.0 formatted drives. This is
rare, since NTFS compression does not
handle these cluster sizes either.
NTFSDOS requires that disks be
accessible via BIOS, using the INT 13 or
extended INT 13 services. In some cases,
SCSI drives may not be fully accessible
without a DOS device driver (see your
SCSI adapter documentation).
* NTFSDOS uses too much conventional
memory
Some people have complained that NTFSDOS
is a memory hog. Unfortunately, this
fact is largely imposed on us by the
architecture of NTFS itself (sorry, but
its a little more complicated than FAT,
and much more memory intensive), coupled
with our desire to provide reasonable
performance across a wide variety of
NTFS installations. In general, the
footprint of NTFSDOS increases largely
with the clustersize of the largest NTFS
partition, and slightly with the number
of NTFS volumes mounted.
* Accessing an NTFSDOS drive causes a hang
or crash
NTFSDOS does not support disk striping.
Further, it cannot handle drives that
are on partitions extending beyond the
2GB boundary, or that are larger than
2GB in size, UNLESS the computer's BIOS
has extended INT 13 support for the
drives in question. The latter
restrictions are due to limitations in
standard disk BIOS code that prevent it
from addressing sectors 2GB or more from
the start of a disk.
NTFSDOS has not been thoroughly
bullet-proofed against corrupt NTFS
drive data structures, so it may cause
Windows to crash or hang when it runs
into problems. To insure that a crash or
hang is due to a problem with NTFSDOS
rather than your NTFS drive, be sure to
chkdsk the drive from Windows NT and try
NTFSDOS again.
* Starting programs or loading files seems
very slow
Access of large compressed files may be
noticeably slower than of their
non-compressed versions.
* File times are not correct when running
under DOS 7.0 without Windows 95
This problem is due to the fact that
NTFS and LFN FAT time stamps are stored
in Coordinated Universal Time (UTC),
which is based on Greenwich Mean Time,
and Windows 95 automatically converts
times stamps returned by LFN calls to
local time. Since local time zone
information is not accessible outside of
Windows 95, running NTFSDOS under DOS
7.0 without Windows 95 results in the
display of unadjusted times.
* Programs complain about not being able
to find files when they are there
A directory listing of files that have
no short filename will result in the
short filename field of the listing
being blank. Changing the current
directory to a path where any component
of the pathname does not have a short
filename will result in all short
filename calls failing while in the
directory. This makes most Windows 3.1
and DOS programs and many DOS commands
(e.g. MORE) inoperative in these
directories. However, LFN calls are
supported in these directories.
* Data read from a file appears to be
corrupt
Since this work is based on
reverse-engineering rather than official
Microsoft specifications (which are
reportedly available under special
circumstances for large amounts of
money), we do not guarantee data
integrity of NTFSDOS drives. This is
especially important if you are
considering using NTFSDOS as a file
backup utility.
* Files or directories seem to be missing
Remember that files and directories that
were created with no DOS 8.3 short
filenames will not be visible if you are
running DOS versions earlier than 7.0.
* You get the message "No drive letter to
mount NTFS partition..."
If NTFSDOS complains that it cannot
mount a drive because there are no
available drive letters, you must find
the line in your CONFIG.SYS that begins
with "LASTDRIVE=". If you do not find
one, then add one. Set the LASTDRIVE
variable to a letter that is greater, by
the number of NTFS drives on your
system, than the largest drive letter
you normally have under DOS/Windows. For
example, if the highest drive letter
normally in use is E: and you have two
NTFS drives, set LASTDRIVE to G: with a
statement in CONFIG.SYS like:
LASTDRIVE=G:
If you still get the message then
increment the letter and try again.
Remember to reboot after every change to
CONFIG.SYS.
* You get the message "Could not allocate
XMS or conventional cache"
Memory usage on your machine is so high
that NTFSDOS could not allocate 64KB for
a conventional cache. Try removing
unnecessary TSRs and drivers and/or
running a DOS memory optimizer or
manager.
* XCOPY does not work in a DOS box
XCOPY will not work on NTFS drives that
are mounted in DOS boxes under Windows
95 (e.g. running NTFSDOS in a DOS box).
This is because you cannot run Windows
programs off of non-global drives, and
under Windows 5, XCOPY starts the
Windows console program XCOPY32.EXE.
Reporting Bugs When you report a bug please provide the
following information about your system:
* disk types (IDE, etc.)
* disk and partition sizes
* BIOS version
* drive sizes and formats
* version of NT that was used to format
NTFS drives
* version of NTFSDOS you are using
* an output dump of NTFSDOS run with the
/V (verbose) option
* version of DOS and/or Windows you are
running NTFSDOS on
Implementation NTFSDOS scans the system's partition tables
looking for partitions that have the NTFS
attribute byte. When it finds one, it looks
for an unused DOS driver letter and registers
a network drive on it. After it completes the
drive search it hooks the network redirector
interrupt and goes resident. Requests come
into NTFSDOS as full path names, or
continuations of a previous directory
traversal (as with findnext), so it proceeds
to determine where, based on NTFS internal
data structures, the target file is located.
When it retrieves the header for the target
file it can determine where the file's data
is located, and read it when it receives
requests to do so.
To provide long filename support (LFN),
NTFSDOS hooks INT 21/AH=0x71 calls and
implements LFN functionality when it sees an
LFN call. Under Windows 95, NTFSHLP.VXD is
required to send LFN calls down to the
NTFSDOS for it to process; otherwise NTFSDOS
would not see LFN calls since Windows assumes
DOS redirected drives do not provide LFN
support.
NTFSDOS also uses the INT 2F/11 and INT 13
APIs. In addition, it contains memory and
cache management plus interpretation of the
NTFS on-disk structures.
Read-write NTFSDOS A full read-write version of NTFSDOS will not
be released.
If you have a dead system that you would like
to recover data from or repair, and you have
access to a second NT machine, you may want
to try NTRecover, another utility we have
written. A read-only NTRecover is available
for free download, and with it you can access
the drives on the dead system from the
working system using native NT file systems
and utilities. In fact, to NT the drives
appear as if they were local drives on the
working system. With the read/write version,
you can copy/edit/delete files.
An add-on package called NTFSDOS Tools will
be available for sale in the next week at the
Winternals site. If you require limited write
access for disaster recovery purposes,
NTFSDOS Tools may help. It consists of two
utilities, NTFSCopy and NTFSRen, that work
with NTFSDOS 2.0R+. NTFSCopy allows you to
overwrite a NTFS file with a fresh copy in
cases where one has become corrupt and is
preventing NT from booting. NTFSRen will give
a specified file a new name. This is useful
in cases where a new driver or application is
installed and is preventing NT from booting.
With NTFSRen an offending file can be renamed
so that NT will not load it.
Acknowlegements We thank everybody that e-mailed us with bug
reports and other feedback.
Significant understanding of the NTFS file
system layout was derived by studying the
Linux-based NTFS driver code maintained by
Martin von Loewis. We acknowledge his
indirect contribution to this endeavor.
Andrew Schulman, et. al.'s, book,
Undocumented DOS 2nd Edition
(Addison-Wesley), was invaluable in providing
network redirector information necessary for
implementing NTFSDOS.
------------------------------------------------------------------------
Download NTFSDOS (39KB)
[Image]