Udev rules and the management of the plumbing layer

Posted Aug 13, 2008 0:14 UTC (Wed) by jreiser (subscriber, #11027)
Parent article: Udev rules and the management of the plumbing layer

"Increasingly, the operation of the kernel is being tied to a set of low-level user-space applications; there is not much which can be done with a bare kernel."

It is sad that our esteemed editor travels in such a small world and with such limited vision. Make the quantifiers explicit: perhaps those comments apply to personal desktop and workgroup server installations that are prevalent today in first-world environments. But Linux has more uses than just these, and would be unfortunate if adapting to such uses were to exclude other uses, or make those other uses noticeably more cumbersome.

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Udev rules and the management of the plumbing layer

Posted Aug 13, 2008 1:54 UTC (Wed) by mattdm (subscriber, #18) [Link] (4 responses)

I think you misunderstand the comment. It has nothing to do with desktop or server software.
Rather, important functionality is increasingly required from user-space (not linked into the
kernel) daemons that run at the system level.

Udev rules and the management of the plumbing layer

Posted Aug 13, 2008 8:56 UTC (Wed) by gnb (subscriber, #5132) [Link] (3 responses)

> It has nothing to do with desktop or server software.
 But it has to do with desktop/server deployments. Embedded systems with 
a fixed set of hardware can often still be built with all the drivers 
built-in, a fixed /dev containing the correct nodes, and no need for 
early userspace or udev or probably most of the daemons you had in mind.     
There is plenty that can be done with a bare kernel and a minimal 
userpsace to push config. into it, just not in the desktop space.

Udev rules and the management of the plumbing layer

Posted Aug 14, 2008 22:24 UTC (Thu) by deleteme (guest, #49633) [Link] (1 responses)

Well at somepoint it's going to be cheaper to just run udev than mapping everything on your
own, even in embedded.

Udev rules and the management of the plumbing layer

Posted Aug 15, 2008 0:17 UTC (Fri) by madscientist (subscriber, #16861) [Link]

On my embedded systems, which are busybox-based, I use mdev instead.  Same basic idea though.

Udev rules and the management of the plumbing layer

Posted Aug 15, 2008 0:01 UTC (Fri) by quotemstr (subscriber, #45331) [Link]

Isn't it fair to assume the desktop space by default and make it explicit if you're talking
about embedded Linux?

Huh?

Posted Aug 13, 2008 2:10 UTC (Wed) by corbet (editor, #1) [Link] (3 responses)

I guess my vision is even more limited than you think; I must confess that I don't understand your comment at all. What does first-world have to do with anything?

The point is that the thing we think of as the "kernel" increasingly involves a layer of surrounding software which mediates between the kernel and the rest of user space.

Huh?

Posted Aug 13, 2008 8:51 UTC (Wed) by dlang (guest, #313) [Link] (2 responses)

I think that this poster is referring to the embedded problem. for embedded systems udev is
not an admantage, it's something to remove. currently they can get along just fine with an
old-stule /dev/directlry (populated only with the devices that actually exist)

as long as these things are kept optional I don't see this as a big problem (although the
authors of these tools do tend to forget that not every system is going to use them)

In my mind the bigger problem is that these tools are a middle ground between the kernel and
userspace, sometimes they are tied to one and sometimes to the other. this can cause surprises
when upgrading, and it's all to easy to get into a bind where you can't upgrade one piece
without having to upgrade a lot more, or where once you upgrade you can't go back.

Huh?

Posted Aug 13, 2008 14:11 UTC (Wed) by pj (subscriber, #4506) [Link] (1 responses)

Indeed, the Openmoko guys found tat removing udev and prepopulating /dev saved them over 5s of
boot time - something very desirable in a cellphone!

Huh?

Posted Aug 14, 2008 6:48 UTC (Thu) by deleteme (guest, #49633) [Link]

Doesn't OpenMoko take about 1.5 minutes to boot up?

Udev rules and the management of the plumbing layer

Posted Aug 13, 2008 6:05 UTC (Wed) by bvdm (guest, #42755) [Link]

Whiskey Tango Foxtrot?