Shift ada device numbers?

Matthew Seaman matthew at
Tue Jun 27 08:07:02 UTC 2017

On 27/06/2017 00:01, Matthew Seaman wrote:
> On 26/06/2017 21:30, Trond Endrestøl wrote:
>> On Mon, 26 Jun 2017 21:20+0100, Mike Clarke wrote:
>>> On Mon, 26 Jun 2017 18:31:04 +0200
>>> Luciano Mannucci <luciano at> wrote:
>>>> I have a FreeBSD 10.3 RELEASE machine whith root on zfs on two discs
>>>> and a "standalone" SSD holding database data. I noticed that if I move
>>>> the SSD disk to another SATA controller it becomes ada0 and the members
>>>> of the zfs are shifted to ada1 and ada2, and the system doesn't work:
>>>> in fact it stops at boot because I've put the swap on the ssd and it
>>>> can't find it anymore.
>>>> Is there a way to control whichnumbers are assigned to the disks at
>>>> boot time?
>>> Some of the responses in
>>> might help. In particular the suggestion at the end to use "zpool import
>>> -d /dev poolname" to re-scan /dev to locate the devices.
>>> If your disk uses GPT partitions you could avoid this problem in the
>>> future by using gpart to add a label to each partition and then using
>>> "zpool import -d /dev/gpt". This worked for me but it was rather a long
>>> time ago and I might not have remembered the exact procedure correctly
>>> so do make sure you have reliable backups before attempting to make
>>> changes like this.
>>> It may be possible to do something similar for MBR partitions but I'm
>>> not sure if it's possible to safely assign a label to a live ZFS
>>> partition on a MBR disk.
>> Maybe this is what the OP is looking for:
>> I too recommend some form of labels, be it GPT, UFS, or glabel.
> The term the OP is looking for is 'wired devices' or 'wired down devices'
> See cam(4) and device.hints(5) -- search for this:
> in cam(4).  device.hints(5) is mostly used for legacy ISA stuff, but you
> can use it to control which of your drives is da0, da1 or da2.

Although on reflection, the best way to handle this problem is by using
gpart to label the devices and then using /dev/gpart/labelname as the
device name in /etc/fstab



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