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Re: What is the dd command ???

On Wed, May 03, 2006 at 11:29:31AM -0500, Mike McCarty wrote:
> Andrew Sackville-West wrote:
> >On Wed, May 03, 2006 at 10:24:00AM -0500, Mike McCarty wrote:
> >
> >>Andrew Sackville-West wrote:
> >>
> >>[snip]
> >>
> >>
> >>>bootable floppy disk with it. This is different than a windows/dos
> >>>made bootable floppy in that it doesn't have any windows or dos system
> >>>on it. You use any blank floppy and the rawrite program to copy the
> >>>disk image over to the floppy. make sense? 
> >>
> >>I believe that the disc must have been formatted. Unless a low-level
> >>format has been done to establish sectors, I don't think dd could
> >>write to the floppy. It must also have a BR with a BPB in it, I do
> >>believe, else how could it distinguish, e.g. 720K floppy from a 1.44M
> >>floppy? If I can find a floppy I am willing to degauss, I'll give it
> >>a try...
> >
> >
> >not to argue :) but the debian installer manual chapter 4.3 makes no
> I'm not, either. But the floppy drive has to be told whether
> to use high-coercion or low-coercion current drive. Using high-mu
> drive on a low-mu disc will likely ruin it. And how can the driver
> know what kind of disc is in there?

good point, and I don't know. suffice it to say that in my limited
experience, it Just Works(tm) on regular HD disks without my having to
do anything more that run the command. But, as I said, I'm not sure of
the state of some of the floppies I've used. Some were surely
formatted previously, though not as bootable media. LIkewise some may
not have been formatted.

> >reference to formatting the floppy. It does refer to make a "sector
> >copy" and writing in a raw format which tells me its bit-for-bit copy
> >of a disk including its boot sectors and fs. man dd is suitably
> >uninformative. 
> No, a sector copy is not a bit-for-bit copy, as sectors do not have
> to be arranged sequentially on the track. In fact, sectors used
> normally to be written with interleave to speed up access. I haven't
> looked into it lately, so I dunno whether sectors are now commonly
> written with interleave of 3 as used to be, or are now sequential.

yup. I only mean that Im interpreting the statements in the install
guide as indicating that the entire disk image, boot record and all is
being copied. I might have some truly blank floppies around... I'll
play with them and see what happens.


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