Re: How to copy the binary image of a dos floppy ?
on Fri, May 04, 2001 at 04:30:50PM -0400, Jonathan D. Proulx ([EMAIL PROTECTED]) wrote: On Fri, May 04, 2001 at 02:48:35PM -0500, B Thomas wrote: :Hi, :I have dos and debian installed on my system . I would like to backup the ddevice drivers that came on dos floppies with my system. I know I need to use the dd command to make a binary image of the floppy. But I do not know the exact parameter to pass . Could you please show me a sample command line . :sincerely :b.thomas [EMAIL PROTECTED] dd if=/dev/fd0 of=floppy.img bs=72k I'm not sure where you're getting your bs= value. I tend to use: $ dd if=/dev/fd0 of=floppy.img bs=1024 count=1440 ...though you may not want to set a count if you aren't sure of the size of the image. Though most 3.5 floppies are 1.4MB, other sizes are possible. -- Karsten M. Self kmself@ix.netcom.comhttp://kmself.home.netcom.com/ What part of Gestalt don't you understand? There is no K5 cabal http://gestalt-system.sourceforge.net/ http://www.kuro5hin.org pgpmY3ukrS6wF.pgp Description: PGP signature
Re: How to copy the binary image of a dos floppy ?
On Fri, May 04, 2001 at 10:17:13PM -0700, Karsten M. Self wrote: : [EMAIL PROTECTED] dd if=/dev/fd0 of=floppy.img bs=72k : :I'm not sure where you're getting your bs= value. Ok, I admit it's just what we use here, I don't know if there's any particular reason for it. To an extent the larger the block size the quicker the dd goes, though floppies are so slow anyway, I don't think it matters much. BTW bs=72k results in a count=20 on a 1.44 floppy That is the inverse of the command I use to make boot floppiesa and it's worked well. This is not to say anything against bs=1440 :) -Jon
Re: How to copy the binary image of a dos floppy ?
On Fri, May 04, 2001 at 10:17:13PM -0700, Karsten M. Self wrote:
on Fri, May 04, 2001 at 04:30:50PM -0400, Jonathan D. Proulx ([EMAIL
PROTECTED]) wrote:
On Fri, May 04, 2001 at 02:48:35PM -0500, B Thomas wrote:
:Hi,
:I have dos and debian installed on my system . I would like to backup the
ddevice drivers that came on dos floppies with my system. I know I need to
use the dd command to make a binary image of the floppy. But I do not know
the exact parameter to pass . Could you please show me a sample command
line .
:sincerely
:b.thomas
[EMAIL PROTECTED] dd if=/dev/fd0 of=floppy.img bs=72k
I'm not sure where you're getting your bs= value.
I tend to use:
$ dd if=/dev/fd0 of=floppy.img bs=1024 count=1440
...though you may not want to set a count if you aren't sure of the size
of the image. Though most 3.5 floppies are 1.4MB, other sizes are
possible.
I was always taught to use a block size of 512 when {read,writ}ing to
floppies, and double the kByte size of the floppy to obtain the count
e.g.
dd if=/dev/fd0 of=floppy.img bs=512 count=2880
I'll poke around to see if I can discover _why_ I've been doing it
this way for the last 5 years ... I believe the physical block size of
a floppy is 512 however.
Cheers,
--
Nathan Norman - Staff Engineer | A good plan today is better
Micromuse Ltd. | than a perfect plan tomorrow.
mailto:[EMAIL PROTECTED] | -- Patton
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Re: How to copy the binary image of a dos floppy ?
on Sat, May 05, 2001 at 02:14:20PM -0500, Nathan E Norman ([EMAIL PROTECTED])
wrote:
On Fri, May 04, 2001 at 10:17:13PM -0700, Karsten M. Self wrote:
on Fri, May 04, 2001 at 04:30:50PM -0400, Jonathan D. Proulx ([EMAIL
PROTECTED]) wrote:
On Fri, May 04, 2001 at 02:48:35PM -0500, B Thomas wrote:
:Hi,
:I have dos and debian installed on my system . I would like to backup
the ddevice drivers that came on dos floppies with my system. I know I
need to use the dd command to make a binary image of the floppy. But I do
not know the exact parameter to pass . Could you please show me a sample
command line .
:sincerely
:b.thomas
[EMAIL PROTECTED] dd if=/dev/fd0 of=floppy.img bs=72k
I'm not sure where you're getting your bs= value.
I tend to use:
$ dd if=/dev/fd0 of=floppy.img bs=1024 count=1440
...though you may not want to set a count if you aren't sure of the size
of the image. Though most 3.5 floppies are 1.4MB, other sizes are
possible.
I was always taught to use a block size of 512 when {read,writ}ing to
floppies, and double the kByte size of the floppy to obtain the count
e.g.
dd if=/dev/fd0 of=floppy.img bs=512 count=2880
I'll poke around to see if I can discover _why_ I've been doing it
this way for the last 5 years ... I believe the physical block size of
a floppy is 512 however.
The only place I've found blocksize _really_ matters is in writing to
tape. I've had endless problems in my former existence as a data
analyst, usually working with data sourced from mainframes, in which
blocking factors were critical. Also more recently when I'd managed to
change the blocking factor while producing some backups to SCSI tape
(DDS), but hadn't changed them for the following read/restore attempt.
I don't quite understand the whole thing myself. For dd, AFAICT,
blocking really only matters to the extent that you want to scale your
'count=' value to the blocksize, and the speed and buffering resulting.
512 was the traditional blocksize on a wide range of systems: DOS, VMS,
and many old Unix systems (OpenBSD still reports 'df' output in 512K
blocks).
It probably doesn't matter that you're reading in 512 byte increments so
long as whatever you're doing is in increments of 512 bytes, hence 1024,
2048, 4096, 8192, etc. The block factoring of a floppy is handled by
the filesystem itself -- when you're imaging the disk you're bypassing
this entirely. Sweet spot is probably determined by kernel disk
buffering, head speed, and memory.
Any hardware boffins here?
--
Karsten M. Self kmself@ix.netcom.comhttp://kmself.home.netcom.com/
What part of Gestalt don't you understand? There is no K5 cabal
http://gestalt-system.sourceforge.net/ http://www.kuro5hin.org
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Re: How to copy the binary image of a dos floppy ?
on Sat, May 05, 2001 at 01:10:01PM -0700, Karsten M. Self
(kmself@ix.netcom.com) wrote:
on Sat, May 05, 2001 at 02:14:20PM -0500, Nathan E Norman ([EMAIL PROTECTED])
wrote:
I was always taught to use a block size of 512 when {read,writ}ing to
floppies, and double the kByte size of the floppy to obtain the count
e.g.
dd if=/dev/fd0 of=floppy.img bs=512 count=2880
I'll poke around to see if I can discover _why_ I've been doing it
this way for the last 5 years ... I believe the physical block size of
a floppy is 512 however.
The only place I've found blocksize _really_ matters is in writing to
tape. I've had endless problems in my former existence as a data
analyst, usually working with data sourced from mainframes, in which
blocking factors were critical. Also more recently when I'd managed to
change the blocking factor while producing some backups to SCSI tape
(DDS), but hadn't changed them for the following read/restore attempt.
I don't quite understand the whole thing myself. For dd, AFAICT,
blocking really only matters to the extent that you want to scale your
'count=' value to the blocksize, and the speed and buffering resulting.
512 was the traditional blocksize on a wide range of systems: DOS, VMS,
and many old Unix systems (OpenBSD still reports 'df' output in 512K
blocks).
It probably doesn't matter that you're reading in 512 byte increments so
long as whatever you're doing is in increments of 512 bytes, hence 1024,
2048, 4096, 8192, etc. The block factoring of a floppy is handled by
the filesystem itself -- when you're imaging the disk you're bypassing
this entirely. Sweet spot is probably determined by kernel disk
buffering, head speed, and memory.
Any hardware boffins here?
Well, I ran a series of tests reading from a minix-formatted 1.4MB
floppy using different blocksizes, and flushing buffers by reading and
writing 140MB of data between tests.
Typical read was:
time dd if=/dev/fd0 of=/tmp/fd0 bs=1024 count=1440
Flush was accomplished with:
time dd if=/dev/zero of=/tmp/fdflush bs=1024 count=144000
Results are, um, suspiciously consistent. Times in seconds.
Blocksize Time
-
512 0:48.475
1024 0:48.517
2048 0:48.487
4096 0:48.482
8192 0:48.674
16384 0:48.472
32768 0:48.483
65536 0:48.475
131072 0:48.493
Even switching to a small and non-uniform blocksize (10) doesn't change
the results much -- a readtime of 48.517 seconds.
The odd man out is the 8192 blocksize timing, more than two standard
deviations from the mean (48.50644 seconds). Assuming that this is the
result of a single-trial deviation, I rerun the trial and get 48.476
seconds. A plot of time by ln(blocksize) shows no clear correlation.
[1] Correlation of time to log(blocksize) is -0.23. Negative and low.
As the 1024 blocksize value is now an outlier, I rerun it, get 48.472
and a correlation coefficient of 0.339. A boxplot shows all values
within two standard devations at this point.
I'm going to say that blocksize, in copying to/from floppy, probably
doesn't matter, from a performance perspective.
Stats via r-base package.
Notes:
1. I'm using ln(blocksize) to linearize this factor. It makes
interpretation of results somewhat simpler.
--
Karsten M. Self kmself@ix.netcom.comhttp://kmself.home.netcom.com/
What part of Gestalt don't you understand? There is no K5 cabal
http://gestalt-system.sourceforge.net/ http://www.kuro5hin.org
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How to copy the binary image of a dos floppy ?
Hi, I have dos and debian installed on my system . I would like to backup the ddevice drivers that came on dos floppies with my system. I know I need to use the dd command to make a binary image of the floppy. But I do not know the exact parameter to pass . Could you please show me a sample command line . sincerely b.thomas
Re: How to copy the binary image of a dos floppy ?
On Fri, May 04, 2001 at 02:48:35PM -0500, B Thomas wrote: :Hi, :I have dos and debian installed on my system . I would like to backup the ddevice drivers that came on dos floppies with my system. I know I need to use the dd command to make a binary image of the floppy. But I do not know the exact parameter to pass . Could you please show me a sample command line . :sincerely :b.thomas [EMAIL PROTECTED] dd if=/dev/fd0 of=floppy.img bs=72k -Jon
