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Re: [vox-tech] backing up the master boot record
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Re: [vox-tech] backing up the master boot record

On Tue, 19 Jun 2001, Peter Jay Salzman wrote:

> begin: Mister Resistor <xxxxxx@uiuc.edu> quote
> > 
> > > also, a question about dd.  according to the man page, bs=BYTE tells dd to
> > > read and write BYTE bytes.  count=BLOCK tells dd to copy only BLOCK input
> > > blocks.
> > >
> > > what is a block?
> > 
> > Probably the equivalent of a sector.  Read the man pages. :-)
> i'd be glad to if you could tell me which man page to read...  :)

That would be nice, but it is in

 man dd

if you interpolate:

              copy only BLOCKS input blocks

              read BYTES bytes at a time
              write BYTES bytes at a time
              skip BLOCKS obs-sized blocks at start of output

              skip BLOCKS ibs-sized blocks at start of input

<hypothesizing>There is something historical about dd that I never quite
understood.  It was described to me as a tool for converting data from
storage on one type of device to storage on another, with 9-track tapes
from various sources being common examples at the time it was described to
me.  Of course, I have only used a 9-track tape once, and that was on a
VMS system, so I don't know much about them.  I imagine that if a device
driver could only support certain block sizes, a tool like dd would be
useful for extracting data from tapes with an odd block size and putting
it on tapes with a size more to your liking.  I don't know if such
restrictions remain in modern device drivers...</hypothesizing>

Jeff Newmiller                        The     .....       .....  Go Live...
DCN:<jdnewmil@dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live Go...
                                      Live:   OO#.. Dead: OO#..  Playing
Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
/Software/Embedded Controllers)               .OO#.       .OO#.  rocks...2k

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