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Date:      Sun, 7 Nov 1999 03:54:54 +0100
From:      Juergen Lock <nox@jelal.kn-bremen.de>
To:        Mike Smith <mike@smith.net.au>
Cc:        zzhang@cs.binghamton.edu, freebsd-stable@FreeBSD.ORG
Subject:   Re: easyboot far into disk
Message-ID:  <19991107035454.B59629@saturn.kn-bremen.de>
In-Reply-To: <199911062040.MAA07163@dingo.cdrom.com>
References:  <199911061143.MAA35365@saturn.kn-bremen.de> <199911062040.MAA07163@dingo.cdrom.com>

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On Sat, Nov 06, 1999 at 12:40:47PM -0800, Mike Smith wrote:
> > >Also, Linux can boot from a floppy.  Can FreeBSD does similar things (boot
> > >from a floppy and then use data on the hard drive)? 
> > 
> > Seems so, use a modified kern.flp with your kernel and change its
> > loader.rc: remove the loading of the mfsroot image and add a line
> > that sets currdev to point to your root fs (you can use lsdev in
> > the loader to find it), and you should be ready to go.  (I first
> > tried setting rootdev instead but that seems to be getting ignored
> > completely at least when booting from a floppy.)
> 
> Rootdev ought to work, actually.  But if you get it wrong, the loader 
> will fall back to using currdev.a

Hmm then thats strange.  I first tried rootdev, which didn't work, and
then later currdev, which did work, and i believe i used the same value
both times!  Or was rootdev fixed only recently, the boot floppies i
had lying around and tested this on weren't the latest...
> 
> >  Btw i remember reading in a commitlog that the concept of a `current
> > device' in loader is about to go, so maybe now this no longer works in
> > -current...
> 
> The model I'm currently looking at tries to hide the way the loader 
> thinks about devices as much as possible simply because it's too 
> confusing.

 Well its just the BIOS' way to think about devices, isn't it?

>  In -current the "best" way to tell your loaded kernel where 
> to find its root filesystem is with the vfs.root.mountfrom tunable.

 But since the kernel isn't using the BIOS to mount its root that
of course still makes much more sense.  (no need to fiddle with
root_disk_unit if the disk is on the second IDE channel and there
aren't two more on the first, or if there are both IDE and SCSI
disks...)
> 
> >  (Maybe this should be added to the FAQ as a method of last resort when
> > the BIOS boot code can't see above cyl 1024?)
> 
> From what I've been hearing from people lately, in most cases it's 8GB 
> that's the new sound barrier,

 Yea, probably true with later boards. (anyone know if there's a
real technical reason for that, or just again short-sightedness of
the BIOS writers?  I mean first 32M if i remember right, then 512M,
then 2G, now 8G...  shouldn't everyone know by now that disks are
getting bigger all the time?)

>  but yes, a FAQ entry is probably worth 
> writing.  Go to it!

 Thats what i get for saying such things... :)  Well OK, once i know
why `rootdev' didn't work i should have a try.

 Regards,
-- 
Juergen Lock <nox.foo@jelal.kn-bremen.de>
(remove dot foo from address to reply)


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