Date: Tue, 30 Mar 2004 12:27:24 +0100 From: Matthew Seaman <matthew@cryptosphere.com> To: Roberto Nunnari <roberto.nunnari@supsi.ch> Cc: freebsd-questions@freebsd.org Subject: Re: # bsdlabel -w /dev/amrd1 auto Message-ID: <20040330112724.GG68464@happy-idiot-talk.infracaninophile.co.uk> In-Reply-To: <40694B6B.5010708@supsi.ch> References: <40694B6B.5010708@supsi.ch>
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On Tue, Mar 30, 2004 at 12:26:51PM +0200, Roberto Nunnari wrote:
> hello.
>=20
> What does the auto argument mean?
>=20
> # bsdlabel -w /dev/amrd1 auto
Hmmm... Interesting. It seems that the description of 'auto' has
vanished from the bsdlabel(8) man page, although it is present in the
disklabel(8) man page from 4.x (disklabel was renamed bsdlabel between
4.x and 5.x):
http://www.freebsd.org/cgi/man.cgi?query=3Ddisklabel&apropos=3D0&sektio=
n=3D0&manpath=3DFreeBSD+4.9-stable&format=3Dhtml
According to disklabel(8), 'auto' means that {disk,bsd}label should
try and create a "virgin" disklabel on the slice -- that (if I
remember correctly) is essentially a 'c' partition spanning the whole
slice, and nothing else. bsdlabel(8) either works the same way, or it
will search for an entry marked 'auto' in disktab(5) -- see
/etc/disktab -- and there is no such entry in the default
/etc/disktab.
Assuming bsdlabel(8) still works the same way as disklabel(8): note
that the auto behaviour doesn't work on all media -- only those where
{disk,bsd}label can find the parameters it needs without having to
read the thing it's labelling directly. However, that includes all
SCSI or IDE hard drives, vnodes and regular files.
=20
> Is it possible that the command above configures amrd1
> as the default boot partition and modifies amrd0 not the
> be the active? And even modifies the partition table on
> amrd0 so that it starts at sect 0 instead of sect 63 as before?
No. bsdlabel(8) is all about BSD partitioning -- the final 'a' in a
device name like /dev/amr1s1a It's fdisk(8) that sets /slices/ (the
's1' part in the device name) as bootable/non-bootable by altering the
master boot record (MBR) on the drive (the 'amr1' part of the device
name).
If you're using fdisk(8) on a different drive to the one you usually
boot from, then it won't be able to affect the usual booting process
in the way you are asking about. If you used fdisk(8) to turn of the
bootable flag on all slices on your boot drive, then yes, there would
be an effect. However, I'm sure you would remember doing something
like that. It's easy to reverse if you did -- just use fdisk(8)
again.
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks
Savill Way
PGP: http://www.infracaninophile.co.uk/pgpkey Marlow
Tel: +44 1628 476614 Bucks., SL7 1TH UK
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