17 May
2015
17 May
'15
10:50 a.m.
The only reason I guess is that they're bootable disks. Otherwise a simple filecopy is
more than enough :)
-------- Messaggio originale --------
Da: Fred Cisin <cisin at xenosoft.com>
Data:17/05/2015 16:40 (GMT+01:00)
A: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Oggetto: Re: 3.5 floppy imaging
If they are just plain old dos format (DD or HD) dd
under linux will do
IF they are just plain old DOS format (DD or HD), then COPY will do.
IF they are just plain old DOS format (DD or HD), then there is no reason
to "image"!
IF they are just plain old DOS format (DD or HD), then the files are all
that matters.
IF they are NOT just plain old DOS format (DD or HD), THEN there might be
reason to image, such as if they are some unknown and not understood
format, and the files can not be extracted, or there is reason to believe
that there is some form of information in the structure and format of the
disk that should be preserved, such as system tracks on CP/M disks, etc.
Or, if they are copy-protected, and stuff other than the files needs to be
preserved to be able to use the files.? 'Course then, your "imaging"
methods are not likely to work, anyway.
But, IF they are just plain old DOS format (DD or HD),
then there is NO information other than the file content on the disks.
If you format a 3.5" disk in a DOS/Windoze machine, and copy some file
onto it, . . .
Could you please explain to me WHY you would want an "image" of that disk?
17 May
17 May
11:38 a.m.
New subject: 3.5 floppy imaging
I'll second the suggestion of dd, that's how I always take disk images,
personally.Lots of support for these RAW files on other UNIX machines or on
DOS/Windows ... I guess if you have a Mac it makes more sense to try and
make Disk Copy images, but for most platforms I find dd is the way to go.
If you're having some trouble with the media, try something like:
dd if=... of=... bs=... conv=notrunc,noerror,sync
This will cause dd to persist if media errors occur; it will try to just
fill them in with NULs while still getting your image written out and
squared up to proper size; you can then often go back after the fact and
use filesystem repair utilities to clean up the holes, or often an at least
get a fair majority of files off the media with the holes in place... I've
used this to great effect more than once to image failing drives before
replacement.
Best,
Sean
On Sun, May 17, 2015 at 10:50 AM, supervinx <supervinx at libero.it> wrote:
The only reason I guess is that they're bootable
disks. Otherwise a simple
filecopy is more than enough :)
-------- Messaggio originale --------
Da: Fred Cisin <cisin at xenosoft.com>
Data:17/05/2015 16:40 (GMT+01:00)
A: "General Discussion: On-Topic and Off-Topic Posts" <
cctalk at classiccmp.org>
Oggetto: Re: 3.5 floppy imaging
If they are just plain old dos format (DD or HD)
dd under linux will do
IF they are just plain old DOS format (DD or HD), then COPY will do.
IF they are just plain old DOS format (DD or HD), then there is no reason
to "image"!
IF they are just plain old DOS format (DD or HD), then the files are all
that matters.
IF they are NOT just plain old DOS format (DD or HD), THEN there might be
reason to image, such as if they are some unknown and not understood
format, and the files can not be extracted, or there is reason to believe
that there is some form of information in the structure and format of the
disk that should be preserved, such as system tracks on CP/M disks, etc.
Or, if they are copy-protected, and stuff other than the files needs to be
preserved to be able to use the files. 'Course then, your "imaging"
methods are not likely to work, anyway.
But, IF they are just plain old DOS format (DD or HD),
then there is NO information other than the file content on the disks.
If you format a 3.5" disk in a DOS/Windoze machine, and copy some file
onto it, . . .
Could you please explain to me WHY you would want an "image" of that disk?
12:06 p.m.
On Sun, 17 May 2015, supervinx wrote:
The only reason I guess is that they're bootable
disks. Otherwise a
simple filecopy is more than enough :)
If they are bootable DOS disks (and normal, not weird), then there is one
part that won't come across with a filecopy. That is Track 0, side A,
sector 1. If they are some version of DOS for which you don't have a copy
of the boot-sector, that might be worth saving. Using DEBUG, you can copy
that into RAM, and save it as a 512 byte file.
DEBUG
L 100 0 0 1 ; load sector from A: L 100 1 0 1 for B:
R CX ; set byte count
200 ; 512
N BOOT.DAT ; filename
W ; write
Q ; quit out of DEBUG "most important command of DEBUG"
NOTE: do NOT type in the comments!
There were a few boot-sector viruses, such as Alameda/Yale, Stoned, and a
Stoned derivative that was passed off as Michelangelo. Copying the
sector using DEBUG does not expose your machine, but attempting to boot
with them does.
BTW, if they are bootable, then there will be two hidden files:
IO.SYS & MSDOS.SYS for MS-DOS, IBMBIO.COM & IBMDOS.COM for PC-DOS.
When recreating the disks, those must be the first files on the disk,
in the first contiguous sectors.
Plus COMMAND.COM. The filedate of COMMAND.COM is
normally sufficient to identify the DOS version.
On PC-DOS and "generic" MS-DOS, 720K started with V3.20
But some OEMs started using 720K as early as 2.11, often uniquely
non-standard (Gavilan, etc.)
1.4M started with V3.30
NEC had their own version of an MS-DOS HD format.
and, there were some 3.5" CP/M machines. THOSE should be imaged.
--
Grumpy Ol' Fred cisin at xenosoft.com
8:10 p.m.
On Sun, 17 May 2015, Fred Cisin wrote:
Why bother? As most people suggest `dd' is the most straightforward way,
and on a reasonable OS you can then mount the filesystem directly from
such an image of a floppy via a loop device. You can then copy individual
files out from there if really needed. You can copy the boot sector
separately with `dd' too if required, also from that image rather than the
original.
With defect-free media, which is usually the case with properly stored
diskettes made up to mid 1990s, in addition to what has already been
written I'd suggest the block size of 32768 with `dd' to get a decent read
performance. The performance of individual floppies may vary depending on
how they have been formatted, i.e. if any sector staggering has been used.
Also, from experience, with marginal media you may still be able to read
data out eventually with a linear dump such as `dd' performs, while
copying files out individually that involves random seeks may not be as
successful.
Maciej
The only
reason I guess is that they're bootable disks. Otherwise a simple
filecopy is more than enough :)
If they are bootable DOS disks (and normal, not weird), then there is one part
that won't come across with a filecopy. That is Track 0, side A, sector 1. If
they are some version of DOS for which you don't have a copy of the
boot-sector, that might be worth saving. Using DEBUG, you can copy that into
RAM, and save it as a 512 byte file.
8:48 p.m.
Mostly, I got request based on "these disks have my source code, my
dissertation, my accounting spreadsheets, my legal correspondence, . . . "
On Mon, 18 May 2015, Maciej W. Rozycki wrote:
You can then copy individual
files out from there if really needed.
If your need is for "disk images" instead of files,
and file contents are "if really needed",
then you should most certainly stick with DD.
3425
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4 comments
4 participants
participants (4)
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cisin＠xenosoft.com -
macro＠linux-mips.org -
scaron＠umich.edu -
supervinx＠libero.it