Here's a quick one.

On a disk with partitions hda1 through hda4, will dd-ing 512 bytes of
hda and 512 bytes of hda1 produce the same file?

Regards,

r

"Reed Loefgren" <rloef@interfold.com> wrote:
> On a disk with partitions hda1 through hda4, will dd-ing 512 bytes of
> hda and 512 bytes of hda1 produce the same file?

The first 512 bytes of /dev/hda contains the master boot record and the
partition table. The first 512 bytes of /dev/hda1 might contain a boot
record. However, if so, this boot record differs from the master boot
record. The first 512 bytes of /dev/hda1 does not contain any partition
table unless /dev/hda1 is an extended partition. If you only have
/dev/hda1 to /dev/hda4 you don't have any logical partitions and probably
only primary partitions.

regards Henrik

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Reed Loefgren <rloef@interfold.com> wrote:
> On a disk with partitions hda1 through hda4, will dd-ing 512 bytes of
> hda and 512 bytes of hda1 produce the same file?

No.
The 512 bytes of hda is the MBR (also called master partition table),
the one for hda1 will get the boot block (block 0) OF that partition.

On _most_ disks the MBR will be cylinder 0, track 0, sector 1 and the
boot block for hda1 0, 1, 1 (so one track further).
The rest of track 0 is unused, except for boot managers.
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Thanks to both of you for the clarification. I lost the backup drive
to a mysteriously corrupted boot block on our reiserfs-ed mail server
and am trying to get a rescue scheme designed for future use, (the
disk has been replaced-ext3.)