/boot/ directory path

Joerg Sonnenberger joerg at britannica.bec.de
Tue Aug 10 04:06:12 PDT 2004

On Tue, Aug 10, 2004 at 12:19:39AM +0200, Barry Bouwsma wrote:
> [drop direct replies to me for your convenience]

I'm doing a list-reply in Mutt, which should send only one mail.

> > > I'd like to change the path /boot/ under which all sorts of
> > > things can be found to, well, something else like /dboot/ .
> > > Why?  Because I'd like to work around BIOS limitations of
> > Have you thought about mounting /boot from that disk directly and
> > place a symbolic link (/boot/boot -> ..) into it? It should be enough
> > to make loader(8) happy
> I'm not sure that I understand.  In order to mount /boot, I
> would already have needed to be booted into the OS, oder?
> Or is this something that can be done as part of the boot
> process, perhaps in loader?

Considering the firewire settup, we have:
ad0 as BIOS supported, small disk
da0 as firewire disk.

/boot resides on ad0 somewhere, da0s1a is the root filesystem.
You add a few symlinks as following:
/modules ==> /boot/modules
/kernel ==> /boot/kernel
/boot/boot ==> ..

The first two make e.g. savecore and kldload happy, the later is for

> If so, I believe that the boot0-2 and loader all depend on
> the BIOS to do disk access.  In my present case, my system
> drive is an external USB/firewire disk, and the BIOSen which
> I have at hand, among which I swap system disks, require me to
> settle for a lowest-common-denominator of CHS geometry, with
> 1024C limit.  At best I could access floppy, IDE drives, or
> with controller, SCSI, but I don't have any hardware with
> BIOS access to USB- or firewire-attached devices.
> I'd be happy to know if what you are suggesting would in fact
> be possible for me, but I'm pretty sure that I have a chicken-
> and-egg problem, in that the BIOS support needed doesn't
> cover the hardware I want to use, while as soon as loader
> gets the kernel running, I have no problems accessing any
> hardware the kernel supports.

With the above, you can either use boot2 on a slice on ad0 to
load the normal BSD loader or e.g. grub to load it directly.
You'll want to set the root device in loader.conf of course.

> Naturally, one has to keep the /dboot directory which
> is used at boot by the internal drive in sync with the
> /dboot or /boot directory on the actual root filesystem
> that gets mounted later from the external (or whatever)
> drive.

That's the advantage of the above setup, you just need a (sub)partition
to hold it.


> barry bouwsma

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