Date: Fri, 11 Aug 2000 11:41:54 -0700 (PDT) From: John Baldwin <jhb@pike.osd.bsdi.com> To: John Reynolds~ <jreynold@sedona.ch.intel.com> Cc: questions@FreeBSD.org Subject: Re: diff between fdisk, boot0cfg, and disklabel -B? (was Re: recompiling boot blocks & serial console) Message-ID: <200008111841.LAA22766@pike.osd.bsdi.com> In-Reply-To: <14740.12435.310805.691257@hip186.ch.intel.com> from John Reynolds~ at "Aug 11, 2000 09:57:55 am"
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John Reynolds~ wrote:
>
> > On Thu, 10 Aug 2000, Mike Smith wrote:
> >
> > You need to recompile the bootblocks to change the baudrate; set
> > BOOT_COMCONSOLE_SPEED in /etc/make.conf, then do:
> >
> > # cd /sys/boot
> > # make clean cleandepend
> > # make depend && make && make install
> > # disklabel -B <boot device>
>
> Good information!
>
> Question: What is the difference between the "-B" option of disklabel, fdisk,
> and boot0cfg? They seem to do the same thing from reading the man pages but
> recently I was not able to use "disklabel -B" when using the "fixit"
> floppy. jhb said "use boot0cfg -B". I did and it worked.
>
> I'm just wondering why there are 3 programs with seemingly the same option and
> if they are not the same, how do they differ?
They don't all do the same thing. :) fdisk -B and boot0cfg -B do do the
same thing in that they both install MBR boot loaders, which are only
present on x86 machines. This is the code that chooses which slice to
boot from. disklabel -B sets the FreeBSD boot loaders, which are inside
the FreeBSD slice itself. Maybe this diagram can help:
disk start disk end
--------------------------------------------------------------------------
| MBR | FreeBSD slice | Windows slice |
--------------------------------------------------------------------------
| boot0 | boot1 | FreeBSD data | FAT | Windows data |
--------| disklabel | |-------------------------------
| boot2 | |
-----------------------------------
The reason that both boot0cfg and fdisk have -B, is that fdisk -B is a
general tool for configuring the slice table in the MBR and installing
MBR boot loaders. boot0cfg is a tool for installing and configuring
boot0, which is a specific MBR boot loader. The -B option is the one
place in which those two programs' functionality overlap.
HTH.
> Thanks,
>
> -Jr
--
John Baldwin <jhb@bsdi.com> -- http://www.FreeBSD.org/~jhb/
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