Write Raw Sectors to a Disk
Usage: dskwrite [-abcdEfFhHLSTvxz-] [-Z!] [-n name] [-N sectors]
[-s size] [-t tracks] [-V volid]
[ disk: ] [ <sectorlist> ]
dskwrite copies stdin to the low-level raw sectors on the disk
you specify.
In conjunction with dskread, dskwrite is most useful as a quick
diskette duplication utility: you can read a whole diskette
image into a file with dskread, then write it back out with
dskwrite to a new diskette. But it's also useful for dumping
a long stream of data across a series of diskettes, formatting
and filling each with as much as possible before requesting
the next one.
The disk is given as a single alphabetic drive letter plus a
colon. If no disk is specified, the first logical drive is
assumed. (In most machines, this is the a: drive.)
Operation:
dskwrite normally starts at cylinder 0, head 0, sector 0 and
walks through the whole disk, writing all the sectors on a track
under one head and then all tracks in a cylinder before
repositioning the heads to the next cylinder. You can also
cause dskwrite to write to just specific sectors by giving it
a sector list.
dskwrite always writes whole sectors and, if requested,
formats whole tracks. If the last sector is only partially-
used, dskwrite fills it out with binary zeros.
To avoid conflicts with other applications, dskwrite always
locks a drive before actually writing to it.
Basic Options:
-a Autoformat. If the disk appears to be unformatted,
automatically do a low-level format of the entire
disk.
-f Low-level format the entire disk as data is copied
to it from stdin.
-F Low-level format the entire diskette and create an
empty FAT filesystem. Do not read anything from
stdin.
-S Share the drive for read/write access by other
processes.
-v Verify. Read back and verify each write.
-h Help. (This screen.)
-- End of options.
Options for using the disk as a serial media:
-b Boot record. Write a simple non-system disk
boot record and parameter block corresponding to
the particular media into sector 0. If writing
the entire disk, continue with the next sector.
-c Continuation. If there's more data on stdin
after an entire disk has been written, prompt
for a new disk to be inserted and continue. If
-d is specified also, the filename extension on
each disk will be the disk number, i.e., 001,
002, 003, etc.
-d Dummy filesystem. Write a boot record and a FAT
filesystem into the initial sectors allocating
whatever is written to a single file.
-n <name> The filename to be given to any data written
onto the disk if the -d (dummy filesystem) option
is used. Default is 'bindata'.
Formatting:
Default is to let Windows NT try to determine how the media
has been formatted and not to reformat the disk.
If the disk isn't already formatted and the -a (autoformat)
option is selected or if formatting is explicitly requested
with the -f or -F options, dskwrite will do a low-level
format of the media.
Dskwrite takes its specification of the format (e.g., low- or
high-density) from the following sources, in decreasing priority:
1. Explicit specifications on the command line.
2. The Windows NT kernel's guess at the media format, assuming
the disk is already formatted and not being re-formatted.
3. The format parameters in the boot sector copied from stdin,
assuming neither the -b nor the -d options is given.
4. The previous format of the media, assuming it's already
formatted in a standard configuration but being reformatted.
5. The highest-density format supported by the drive.
Unless you specify -b or -d, dskwrite will expect to copy a
compatible disk image from stdin including a suitable boot
sector, etc. That happens automatically when dskread'ing
a whole disk is paired with dskwrite'ing a whole disk but
not otherwise.
Explicit Format Specification Options:
-E Extended density (2.88M) format.
-H High density format.
-L Low density format.
-N <sectors> Sectors per track.
-s <size> Sector size. Normally only 512 is supported but,
depending on your hardware, you may also be able
to create 128, 256 or 1024-byte sectors.
-t <tracks> Number of tracks.
Other Advanced Options:
-T Low-level format the media track-at-a-time as
the disk is written. Only as much of the disk
as is being written to will be formatted.
-V <volid> The volume identifier to be written into the
dummy filesystem header if -F or -d is used.
(Ignored otherwise.)
-x Force use of a non-standard format or writing of
non-standard format parameters to the boot sector.
-z Zero-length files written with -d option should
still be added to the directory. (Otherwise,
they're ignored.)
-Z! Force write to a hard disk. Warning! Very risky
unless you know exactly what you're doing.
Sector lists:
Optionally, you can specify a list of sectors you want written.
Sectors are given in
(cylinder, head, sector)
coordinates with parentheses around and commas or white space
to separate the numeric values you write. Cylinders, heads and
sectors are counted from zero and can be specified in decimal,
hex or octal.
A single sector specified alone means just that sector.
Listing several separated by commas or spaces means each one
individually.
A pair of sectors joined by a hyphen means a range: all the
consecutive sectors beginning with the first and running
through to the second.
Specifying a negative number as an ordinate means use the
highest possible value for that disk.
If any of the ordinates of a sector are omitted, they're assumed
to be zero except when it closes a range, in which case it means
use the highest possible value.
Examples:
1. To duplicate a whole diskette image, autoformatting the
output media if it's not already formatted:
dskread a: > dskimage.a
dskwrite -av a: < dskimage.a
2. To use dskwrite to format a disk with an empty FAT file
system, use either:
dskwrite -F a:
or:
dskwrite -df a: < nul
3. To rewrite just the boot sector to make it a non-system
disk:
dskwrite -b a: < nul
4. To use a diskette as a serial archive media:
The -d option allows you to request just enough dummy file
system "envelope" around the otherwise arbitrary data you
intend to write to ensure the disk can still be used with
other Windows NT utilities. Here's an example writing the
result of a tar'ing (archiving) a whole directory to a series
of diskettes, again autoformatting:
tar -cs mydir | dskwrite -avcd -n mydir a:
It's restored with
dskread -dc -n mydir a: | tar -xs
The diskettes used do not all have to be the same density;
any mix of high and low is okay. But remember that if a disk
isn't already formatted, there's no way for dskwrite to tell
whether it should be high or low density; any disks it has
to format will all be formatted the same way.
5. Reading or writing tar-format floppies:
Many UNIX machines support the use of a floppy as a tar
archive media, just as if it were a tape. Every sector
contains data; there's no filesystem and no boot record
at all. This allows the greatest possible amount of data
to be written to the disk and it does allow interchange
with a UNIX machine, but tar-format floppies are not
readable by any ordinary utilities.
Here's an example, tar'ing mydir to a single tar-format
floppy:
tar -cs mydir | dskwrite -vx a:
It's restored with
dskread a: | tar -xs
If the amount of data you're archiving is more than will
fit on one diskette, use the -c option with dskread and
dskwrite. But since there's no labeling recorded on
the diskettes and the data just runs continuously from
one diskette to the next, you will need to pay attention
to the order in which they're written or read.
Non-standard Diskette Formats:
If you write anything but a standard boot record into the boot
sector, you will not be able to read it with anything but
dskread and even then only if you tell it explicitly what
format was used. Without a standard parameter block in the
boot sector, the Windows NT diskette device driver just can't
tell on its own how the diskette was written.
Similarly, it's possible you may be able to write a non-
standard format (e.g., a sector size other than 512 bytes,
etc.) depending on your hardware. But doing that may make
the diskette impossible to read on other machines.
For that reason, dskwrite normally won't let you write a boot
record that doesn't match the actual format of the diskette
nor will it let you write anything other than one of the
standard format. To override these checks, you must use the
-x option.
Writing to a Hard Disk:
Deliberately, dskwrite normally only lets you write to diskettes.
Writing to a hard disk is very risky since the chance of
catastrophic loss of information is so high. Also, only ESDI
and SCSI disk controllers routinely map out bad blocks, so
reading the disk image from one drive and writing it to another
is unlikely to work if there are bad blocks on either one.
To force dskwrite to write to a hard disk, you must specify
the -Z! option, meant to be hard to accidentally type. In
effect, the -Z! option means you understand the risk you're
taking.
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