Trouble swapping bootdisk to different controller

[Joerg Sonnenberger]

On Mon, Jan 31, 2005 at 12:27:17PM +0100, Heinrich Rebehn wrote:
> After adjusting the BIOS boot config, the kernel asked me where to mount 
> the root fs from. After some probing, i figured out it was ufs:ad7s2a.
> Of course the kernel count not mount the remaining fs because fstab was 
> still referring to ad0s2*.

This means that the boot loader and the kernel can't figure the correct
mapping out. You can override it in at the loader prompt by setting
vfs.root.mountfrom to the correct slice. But playing a bit more with
the BIOS settings may fix it.

> Some of the obstacles i experienced:
> - /sbin not in PATH, why?

It's a fallback value built into the shell and that doesn't
include /sbin. Just add it.

> - vi not available

vi is on /usr, that's expected.

> - keyboard layout not set (i use german keyboard, luckily i am quite 
> familiar with the US layout)

kbdcontrol is on /usr, too. The normal rc scripts haven't been
run yet to customize the keyboard layout, so this is expected.

> - weird device numbering: why can't the first disk be assigned to ad0???

Because you have ATA_STATIC_ID in your kernel? Because the kernel doesn't
know which "the first disk" is? Normally "internal" controllers are probed
before "external" controllers, therefore "internal" disks are enumerated before
"external" disks. Combine this with ATA_STATIC_ID and you get the behaviour
you have.

> - I then decided to try and edit fstab with sed (of course sed was not 
> there), but it would not have helped me anyway, because the root fs was 
> mounted -ro.
> I then tried to remount the root fs -rw:
> 
> # mount -u -rw / ==> /dev/ad0s2a not configured
> # mount -u -rw /dev/ad7s2a / ==> /dev/ad7s2a: No such file or directory

Now you have a small problem :) We normally don't create device entries
for secondary slices. Workaround:
mount -t mfs swap /mnt
cp /dev/MAKEDEV /mnt/
cd /mnt
sh MAKEDEV ad7s2
mount -uw /dev/ad7s2a /
cd /dev
sh MAKEDEV ad7s2

Joerg