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

Michael Sperber sperber at
Fri Sep 17 13:35:34 UTC 2010

"Marat N.Afanasyev" <amarat at> writes:

> Michael Sperber wrote:
>> 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!
> beware of drago^Wchanging of adX numbers each time you add/remove
> drive ;) It's better to label filesystems, imho ;)

This is a rented server, so I no drive will ever be removed or added.
On the other hand, if I understand it correctly, I'll need to unmount
the root partition in order to label it - right?


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