Re: boot2 can't boot from USB?
- From: Oliver Fromme <olli@xxxxxxxxxxxxxxxxx>
- Date: Thu, 15 Mar 2007 12:11:09 +0100 (CET)
Fluffles <etc@xxxxxxxxxxxx> wrote:
Sorry if this is offtopic. Am i right to assume that:
- boot0 and boot1 both read from the disk via BIOS
- boot2 tries to read from the disk directly, without BIOS
?
No, only the kernel contains drivers that are independent
from the BIOS. Everything else (the boot* blocks and
/boot/loader) use BIOS calls.
If so, i may have found some bugs / problems with boot2. Long ago i
tried to make a bootable USB pendrive with FreeBSD 6.1 on it. It failed
to boot with the message "invalid slice" and i got a prompt like:
FreeBSD/i386 BOOT
Default: 0:ad(0,a)/boot/loader
boot:
Whatever i tried, it fails to load "Loader" or the kernel. Later, i
tried FreeNAS which enables the user to write an image to an USB
pendrive which contains a bootable FreeNAS installation. The copying
went ok, but i got the same boot problem. I then tried it on three
different systems with two different USB pendrives and they all had the
same problem. All of the systems supported USB boot, and it does
actually boot from USB how else could i see that FreeBSD boot prompt?
Some systems are brand new: dualcore SLI motherboards, etc.
It appears to me the boot2 program fails to read from USB. boot0 and
boot1 appear not to have this problem since it uses the BIOS to read
from the disk. Is this correct?
No, see above, they all use the BIOS. The difference is
that boot2 needs to understand UFS, locate the correct
slice and partition with /boot/loader in it and load it.
The earlier boot blocks are relatively dumb and only know
how to load boot2 from a fixed location on the media.
So, if boot2 doesn't work for you, it's probably unable
to locate your FreeBSD slice and/or partition. How did
you create them?
(Another difference is that boot2 enters protected mode
in order to be able to access memory above 1 MB, while
the earlier boot blocks use pure real mode. But that
should not be related to the problem that you see.)
Are USB boot problems by boot2 known, should i file a PR?
boot2 doesn't know about USB at all. It only knows about
BIOS-accessible drives (which may include USB drives if
that's enabled in the BIOS setup).
Best regards
Oliver
--
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FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd
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is not necessarily a good idea. It is hard to be sure where
they are going to land, and it could be dangerous sitting
under them as they fly overhead." -- RFC 1925
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