boot0: is booting from non-BIOS-recognized disk possible?

Lowell Gilbert freebsd-questions-local at
Tue Apr 18 14:17:07 UTC 2006

Amanda Babcock Furrow <alb at> writes:

> I have read the boot0cfg, disklabel (I have FreeBSD 4.9), and fdisk 
> manpages trying to figure out if boot0 can solve my problem.  I did
> not find the answer there, or in
> or the freebsd-questions archives.
> I would like to be able to boot from my Seagate ST3120814A, which is
> not compatible with my BIOS (Award Modular BIOS v4.51PG, BIOS string
> 08/21/97-580VPX-VIA83669-2A5LD000C-00, VT 580VX MMX motherboard).  
> The BIOS, for which no update was ever issued, will hang during disk
> detection unless I disable the Seagate by setting it to "None" in
> the BIOS (as opposed to "Auto" and "User", which hang).  However,
> once I boot FreeBSD from an older disk, the Seagate is detected as 
> /dev/ad3 and partitions from it can be mounted.
> I understand that boot0 can be configured to boot from a second disk
> using the -s 5 argument of boot0cfg.  However, the boot0cfg man page 
> does not go into great detail.  Can boot0 boot from a disk which is 
> disabled in BIOS but accessible from FreeBSD, or only from disks which 
> the BIOS is able to detect?

The latter.  It can, however, use the "packet interface" as well as
the old cylinder-based BIOS interface; perhaps that will work for you.

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