Re: devfs vs udev, thoughts from a devfs user

Mike Bell
2004-02-10T19:24:35Z

On Tue, Feb 10, 2004 at 12:52:51PM -0500, Chris Friesen wrote:
> What names would you use for your device files? This is the key
> difference. With udev it gets a notification that says "I have a new
> block device", it then looks it up, applies the rules, and creates a new
> entry. The whole point is to move the naming scheme into userspace for
> easier management.

Why does it make management easier to have no predictable name for a
device?

> You could have the kernel export a simple devfs with a hardcoded naming
> scheme based on similar ideas as what is in sysfs (which would then make
> sysfs and the daemon optional for tiny embedded setups), but the only
> advantage over just exporting the information in sysfs is to save a few
> bytes at the cost of yet another filesystem to maintain.

I think the space savings are a pretty good reason alone. Add to that
the fact I think devfs would be a good idea even if it cost MORE
memory... You can mount a devfs on your RO root instead of needing to
mount a tmpfs on /dev and then run udev on that. A devfs gives
consistant names for devices in addition to the user's preferred
user-space dictated naming scheme. A devfs means even with dynamic
majors/minors, even if you have new hardware in your system, your /dev
at least has the devices it needs.