[TUHS] Device special files

Dave Horsfall dave at horsfall.org
Wed Feb 7 15:39:08 AEST 2018

On Tue, 6 Feb 2018, Bakul Shah wrote:

>> Wasn't that "devfs" (which Penguin/OS calls "udev")?  I've never 
>> grokked that concept.
> In the old days where a limited types of devices were
> available for a particular kind of machine, they could be
> statically assigned a major dev number (matching their index
> in the {b,c}devsw table). To make them accessible to users you
> did
>    mknod <name> <b or c> <major> <minor>


Umm, I've known that since Edition 5; I'm not exactly new to Unix, you 


> So the point of devfs is to avoid having to do mknod manually and yet 
> provide access to all found devices from the userland. As a side effect 
> you can also use it for programs that run in their own sandbox or for 
> jails and require access to a device.

That makes sense; bit of a pain when a USB device suddenly disappears just 
I unplugged it, though...

Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."

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