Re: Re: Undersanding bootable media
Quoting Ries van Twisk (rvt@dds.nl):
The reply given below tells you plenty about how computers boot, but
I thought I'd add a couple of points to the original question (and
I don't have the original to reply to).
>
> At 11:16 AM 7/3/1999 -0800, you wrote:
> >In my quest to understand booting/LILO/MBR's I've come a cross
> >a phenomenon I dont understand. Friend of mine (linux guru-ish)
> >said that to make a linux bootable floppy you had to use a lowlevel
> >tool like dd as opposed to just copying the files over to the floppy.
Yes, that's right. dd will copy the whole filesystem and the
boot sectors.
> >But dos floppies boot just fine by making copies of other dos boot disks.
Well, that depends how they are copied. If you take a virgin disk,
FORMAT A: and then COPY the files, you won't be able to boot that.
But if you copy the files onto a floppy that was formatted in the
past to make it bootable by typing, say, FORMAT /S A: then it will
remain bootable (also as long as the hidden files have not been
deleted).
If you use DISKCOPY A: A: to copy a disk, the bootability or
otherwise will be transferred from the first disk to the second along
with the files. (About the only change is the volume serial number.)
This is roughly equivalent to using dd.
> >BUT I tried to copy the files from a dos boot disk onto an CDR, and guess
> >what? It wont boot. Despite the fact that it contains the exact same files
> >as the floppy. I understand that in order for media to be bootable it's
> >MBR needs to contain a "program" to point to the OS, so how does a copied
> >dos-boot disk work? Thanks, marlon
[snipped the explanation]
Cheers,
--
Email: d.wright@open.ac.uk Tel: +44 1908 653 739 Fax: +44 1908 655 151
Snail: David Wright, Earth Science Dept., Milton Keynes, England, MK7 6AA
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official stationery. Views expressed here are either my own or plagiarised.
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