Re: Announcing Trapfs: a small lookup trapping filesystem, like autofs and devfs

[Jamie Lokier <jamie@shareable.org>]

Adam J. Richter wrote:
> Trapfs can also be used to provide create-on-demand device file
> functionality for some non-devfs systems.

I understand udev is the "new" way to create device files when devices
are attached.

It works fine for real devices.  However, udev's weak point is that it
won't create devices like "/dev/ppp" and "/dev/net/tun0" until you
load their respective modules...  and you usually want an attempt to
load those devices to cause the modules to be loaded.

That's why on my laptop, when I want to run pppd, I have to do
"modprobe ppp_async" first.

There's an ugly workaround where the entire contents of /dev are
stored in a .tar.bz2 file which is restored at boot, including those
kinds of device nodes, but it is very ugly because that file
invariably ends up containing a lot of devices that you don't want,
and duplicating a lot of the settings in udev's config files.  When
using that .tar.bz2, there isn't a lot of point in using udev at all.

It would be nice if opening a non-existent file in /dev would trigger
a hotplug/udev event - but otherwise have a perfectly normal
tmpfs-like filesystem.  IMHO that would fix udev nicely.

Is trapfs suitable for that?

-- Jamie