On Mon, Nov 07, 2011 at 03:54:14PM +0100, Benny Lofgren wrote:
> On 2011-11-06 21.42, David Vasek wrote:
> > On Sun, 6 Nov 2011, Benny Lofgren wrote:
> >> On 2011-11-06 18.00, Bambero wrote:
> >>> Thanks, but without skip=1 dd will copy partition table and mbr too
> >>> (first block 521b).
> >>> So it may damage my partition table on second machine. I'm I wrong ?
> >>
> >> No, you will not copy the partition table with your command, since
> >> you are using wd0a. That partition starts after the boot sector(s)
> >> and partition table, so what you're in fact doing is skipping the
> >> first blocks of the file system that is on partition a of wd0. Which
> >> you don't want to do. (If you had used wd0c on the other hand, you
> >> would have gotten the disk partition metadata as well. But you don't
> >> want that either.)
> >>
> [...]
> >
> > Benny, with this you will overwrite the disklabel of whole target disk,
> > as the disklabel in a typical case indeed resides at the beginning of
> > the wd0a. See disklabel(5).
>
> Ah, you are absolutely correct, thanks. Please ignore my previous advice!
>
> (Except the part about seek= and skip= not operating on 512 byte block
> sizes but on the block size set by bs=/ibs=/obs=, that one will bite
> anyone not paying attention to detail.)
>
> Sorry for spreading FUD. (Although I can't really seem to find this out
> from just reading disklabel(5) (I did check prior to my last comment), but
> then again my brain's English language center might very well be somewhat
> deficient...)
>
> The best bet is probably to either go the dump/restore route like someone
> suggested or simply save the target disk's label to file using something
> like "disklabel wd1 >/tmp/disklabel.wd1" and then restoring it after dd
> with "disklabel -R wd1 /tmp/disklabel.wd1" (since the in-core copy of the
> original disk label will keep the working layout, there is no risk involved
> with temporarily overwriting the label as long as it is restored prior to
> the new disk's partitions being used).
There's also /etc/daily, you can get some inspiration from the
ROOTBACKUP part of it.
-Otto
>
>
> Regards,
> /Benny
>
> --
> internetlabbet.se / work: +46 8 551 124 80 / "Words must
> Benny Lofgren / mobile: +46 70 718 11 90 / be weighed,
> / fax: +46 8 551 124 89 / not counted."
> / email: benny -at- internetlabbet.se
