Re: initial udev foray...successes and failures...

[Greg KH <greg@kroah.com>]

On Thu, Dec 18, 2003 at 01:13:27AM -0800, Tupshin Harper wrote:
> As a long time devfs user and MAKEDEV hater(mostly for aesthetic 
> reason), I decided to bite the bullet and see how close to usable udev is.
> 
> The platform:
> Debian Sid
> kernel 2.6.0-test11+
> hotplug that comes with sid
> udev 0.009 built for debian downloaded from: http://www.bofh.it/~md/debian/
> 
> The scenario:
> the Debian udev package creates everything in /udev. I moved /dev out of 
> the way, symlinked /udev to /dev and rebooted (ahhh...glorious optimism).

Wow, that's brave :)

> What worked:
> Most things, including (to my surprise) lvm2 which had been running on 
> the devfs setup.

Yeah, lvm2 uses block devices, so it all should "just work".  Glad to
see it does.

> What didn't:
> 1) anything that needed /dev/null
> 2) anything that needed /dev/random (and probably urandom...didn't check)

You need the misc sysfs patch that I posted to lkml and
linux-hotplug-devel a while ago.  That will create those nodes for you.

> 3) anything other that single user mode, since /dev/tty[0-9] were not 
> present ..just /dev/tty

That's odd.  Do you have any tty devices in /sys/class/tty/ ?  That's
what udev goes off of.

> What was odd:
> I have a number of ide hard drives in this machine(9). The first two 
> (hda, and hdb) and their partitions showed up as symlinks to 
> /dev/ide/host0/etc... The rest of them were not symlinks and were placed 
> directly in /dev (e.g. /dev/hde and /dev/hde3).
> 
> Despite these oddities, I was able to manually create /dev/null, 
> /dev/random, and /dev/tty[0-9] and everything on my machine worked.
> 
> So...given the limited information that seems to be available for udev, 
> I have a few questions:
> 1) should the missing devices be created by udev? Is this a [known] problem?

Yes they should, as long as they are exported in sysfs somewhere.

> 2) Why are some drives symlinked and others not?

I don't know.  What kind of udev.rules file did you use for this?  I
think the debian package is trying to emulate devfs names, which I don't
necessarily think is the best idea, as they are not LSB compliant.

> 3) Does it make sense that the debian package operates on /udev and I'm 
> testing it by creating a symlink to /dev? If not, how should things be done?

Right now it's good to play around in /udev.  When udev matures, then it
will be ok to move it to use /dev.  I don't think we are quite there
yet.

thanks for your report.

greg k-h


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