how to assure that a certain device (e.g. /dev/pass1) always is /dev/pass1 on subsequent reboots?

Matthew Seaman matthew at
Thu Aug 27 11:18:23 UTC 2015

On 2015/08/27 11:38, Raimund Sacherer wrote:
> I need to make sure that certain devices always have their
> corresponding device names (like /dev/pass1) assigned. I need this for
> auto changers in our backup server (but not only there).
> I have vastly more linux knowledge and there you can for example
> create udev rules which rename the device to what you need. What is
> the equivalent way on FreeBSD? Loader hints?

You probably don't need to worry about this: for permanently wired
peripherals, the device names will generally be stable across reboots.

For something like an autochanger -- given they're always plugged into
the system and you can assume they're powered on -- then the devices
will be numbered in the order the kernel probes for them at boot.

That's repeatable: so long as you aren't changing connections you can be
satisfied that /dev/pass1 will refer to the same device before and after
a reboot.

However, if you do need it:

For SCSI / SAS / SATA devices see:


To obtain the bus, device, etc. parameters you'll need, see:


Otherwise, if your devices are connected via USB, then:



USB device mappings etc. are assumed to change at run time, as devices
are plugged in and out, and may not even be present at boot, which makes
it tricky to ensure the same physical device always gets the same device
number.  For your requirement to work, the devices would have to be
permanently wired into the system.



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