Hi,

Years ago Jude Nelson announced that he was going to migrate his production machine
to using eventfs with libudev-compat [*]. Once he was satisfied that it worked as expected,
he would begin packaging all of vdev's components for devuan. But finally he left this
eventfs integration pending to do, or at least untracked on the project's Github.

As he explained in the mailing list, eventfs is a specialized userspace filesystem that
replaces the udev-to-libudev event multicast protocol, which is currently based on netlink.
Eventfs fulfills an equivalent role, but it does so in a portable manner in userspace, and
it abstracts dealing with message multicast groups as dealing with files and directories
with a few extra rules.

If you look in /dev/metadata/udev/events, you'll see that libudev-compat processes will
have created a bunch of directories into which vdev's udev-compat.sh helper writes device
events. Currently there is no straightforward and automatic way to clean this directory out.
By having libudev-compat clients write to eventfs, we can ensure that these directories are
automatically removed after the process that created them dies. This is the way libudev-compat
benefits from using eventfs.

All this is explained in detail here:

https://www.gnuinos.org/libudev-compat/

As you can see, I didn't complete the documentation at that time because I've been using
libudev-compat without eventfs thus far, as it can be considered a soft dependency.

But that's something I've managed to deal today, and shortly I'll build new images of gnuinos
with this new feature and complete the documentation related to libudev-compat and eventfs, as
part of the vdev documentation.

Cheers,

Aitor.

[*] You can read the complete thread here:

https://lists.dyne.org/lurker/thread/20150922.004416.63712820.nl.html#20150922.004416.63712820