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Date:      Tue, 22 Nov 2011 03:50:04 +1100 (EST)
From:      Ian Smith <smithi@nimnet.asn.au>
To:        Bruce Cran <bruce@cran.org.uk>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: 9.0 and bsdinstall - avoiding updating the MBR
Message-ID:  <20111122030531.U72022@sola.nimnet.asn.au>
In-Reply-To: <20111121101201.6336C10656E5@hub.freebsd.org>
References:  <20111121101201.6336C10656E5@hub.freebsd.org>

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In freebsd-questions Digest, Vol 390, Issue 1, Message: 18
On Mon, 21 Nov 2011 01:47:27 +0000 Bruce Cran <bruce@cran.org.uk> wrote:
 > I'm planning to install FreeBSD alongside a whole range of Windows 
 > builds for testing. In 8.x it's possible to tell the installer not to 
 > bother updating the MBR so you can use something like EasyBCD to boot it 
 > via the Windows bootloader instead. Is it still possible on 9.0-RC2 
 > using bsdinstall? I don't seem to remember seeing any option to avoid 
 > writing out the new boot code.

Hi, I gather not (yet?)  Can save the MBR with (eg) 'boot0cfg -f ~/mymbr 
adaX' for safety, dd it back if need be, and/or use fdisk(8) -p, -t and 
-f flags to save, test and restore just the slice table.

At least they're precautions I'm taking, really not wanting to clobber 
win2k (for BIOS updates :), 8.2-RELEASE or a shared UFS partition when 
next trying to install 9.0-RC2 to slice 2, currently 7.4-RELEASE ..

% boot0cfg -v ad0
#   flag     start chs   type       end chs       offset         size
1   0x00      0:  1: 1   0x0b   1023:  5:63           63      8385867
2   0x00   1023:255:63   0xa5   1023: 13:63      8385930    125821080
3   0x00   1023:255:63   0xa5   1023: 15:63    134207010     33543342
4   0x80   1023:255:63   0xa5   1023: 14:63    167750730     66685815

version=2.0  drive=0x80  mask=0xf  ticks=182  bell=# (0x23)
options=packet,update,nosetdrv
volume serial ID a8a8-a8a8
default_selection=F4 (Slice 4)

% fdisk -p ad0
# /dev/ad0
g c232581 h16 s63
p 1 0x0b 63 8385867
p 2 0xa5 8385930 125821080
p 3 0xa5 134207010 33543342
p 4 0xa5 167750730 66685815
a 4

cheers, Ian



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