udev [ -f /dev/.udev.tdb ] test

Kevin P. Fleming kpfleming at linuxfromscratch.org
Thu Sep 23 21:30:09 PDT 2004

Nathan Coulson wrote:

> [ -f /dev/.udev.tdb ]  && exit 0
> It means, if /dev is writeable before udev, and something causes a
> hotplug event [on a system with /sbin/hotplug].

This is true.

> Mostly the people working on the bootcd's have noticed this.  (BTW,
> there's a sed on the kernel page to prevent hotpug from running until
> userspace is ready for it)

That is correct, but many people (myself included) forget to reapply it 
after putting in kernel upgrades.

> If people want it to stay, I am going to have it output a warning
> message saying devices have already been initialized.

For my systems, I have moved to a different initialization technique 
that doesn't have any trouble with this... It's just safer at this point 
(IMO) to throw away any /dev directory contents that got created prior 
to the initscripts running and recreate them, rather than try to get it 
right and just leave /dev alone.

Personally, I think Alexander's method of storing up early-userspace 
hotplug events until the system is ready to process them is a good idea; 
I can't see any system that builds /dev in an initrd/initramfs and then 
moves it into the "real" root filesystem being very manageable, because 
it means any changes that the admin makes in 
/etc/udev/{rules,permissions}.d have to be mirrored into that 
initrd/initramfs, which is a pain in the butt to do.

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