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

[Oliver Fromme]

Michael Sperber <sperber at deinprogramm.de> 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.

Best regards
   Oliver

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