How to predict drive number change for 7.3->8.1 upgrade?

Michael Sperber sperber at
Fri Sep 17 12:57:41 UTC 2010

Oliver Fromme <olli at> writes:

> Michael Sperber <sperber at> wrote:
>  > I just upgraded my desktop system from 7.3 to 8.1, and the main hard
>  > drive, which was /dev/ad6 before is now /dev/ad10.  Consequently, the
>  > initial boot failed when trying to mount the root file system from ad6.
>  > 
>  > The desktop system is now fixed, but I also have a rented server with
>  > only a serial console, and I worry that the upgrade is going to leave me
>  > with a dead machine.  Is there any way to predict how the drive number
>  > changes?  (Why does it change at all?)  If so, what's the proper way to
>  > tell the system the initial root device *before* rebooting?
> Remove "options ATA_STATIC_ID" from your kernel config
> before building the new kernel and rebooting.  Then your
> first disk will be ad0, no matter what controller and
> channel it is connected to.  Be sure to update your
> /etc/fstab file.

Ah, excellent - that's what I was looking for.  Thanks!


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