Creating /dev links to dynamic devices

Warren Block wblock at
Sun Oct 25 03:19:44 UTC 2009

On Sat, 24 Oct 2009, Justin Hibbits wrote:

> On Sat, Oct 24, 2009 at 10:00 PM, Warren Block <wblock at> wrote:
>> devfs.conf allows creating static device links:
>> link    acd0    cdrom
>> This only runs on devfs startup, so it's useless for creating a link to a
>> dynamic device.
>> The specific example is for scanners.  My scanner is ugen2.3, but only as
>> long as it is plugged into the same USB hub/port each time.  I can manually
>> create a uscanner0 link in /dev with devd.conf:
>> attach 20 {
>>        device-name "ugen[0-9]+";
>>        match "vendor" "0x04b8";
>>        match "product" "0x010a";
>>        action "/bin/ln -sf /dev/$device-name /dev/uscanner0; /sbin/devfs
>> rule applyset";
>> };
>> Using /dev/uscanner0 then works in place of ugen2.3.
>> Now the second part of the example: I want devd to recognize the attach or
>> creation of uscanner0.  But it's not a true devfs device; devd doesn't see
>> an attach event, or a notify CDEV/CREATE event.
>> Is there a method to create a true devfs link to a dynamic device?
> Check devfs.rules(5)

I did, but maybe missed the relevant information.  There are conditions 
to match and modify (perm/owner) a node, but none to create or delete 
one.  Maybe something with unhide?  Could you post an example?

-Warren Block * Rapid City, South Dakota USA

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