[Buildroot] Using udev, non-static /dev, and ramfs (or tmpfs)

[Buildroot] Using udev, non-static /dev, and ramfs (or tmpfs)

[don]

I have a buildroot system that has been working fine (thanks) using
a static /dev in a ramfs rootfs.  Now I want to add a USB device and it 
seems like I should let udev etc. handle it.

However udev cannot make entries in a read-only /dev.

Is there a simple recipe for mounting /dev as writable?

There are several compilcations:

	Normally to mount with ramfs I'd use /dev/ram*.  
	How does that work with mounting /dev?

	What about all the existing static /dev/entries?

I see that /etc/init.d/S10udev tries to use "/sbin/udevstart", but
I don't have that.

Would I be better off to keep things static?

Thanks
Don Reid

[Buildroot] Using udev, non-static /dev, and ramfs (or tmpfs)

[Rob Landley]

On Saturday 21 October 2006 2:34 pm, don wrote:
> I have a buildroot system that has been working fine (thanks) using
> a static /dev in a ramfs rootfs.  Now I want to add a USB device and it 
> seems like I should let udev etc. handle it.

I'd recommend mdev from busybox, but then I wrote it. :)

> However udev cannot make entries in a read-only /dev.
>
> Is there a simple recipe for mounting /dev as writable?

mount -t tmpfs /dev /dev
 
> There are several compilcations:
> 
> 	Normally to mount with ramfs I'd use /dev/ram*. 

No, that's a ram disk not ramfs.  A ramfs (or tmpfs) doesn't have backing 
store.

Install a recent busybox (1.2.2 would be best, once I get that up. :)

To populate dev:

  mdev -s

To handle hotplug events:

  echo "/sbin/mdev" > /proc/sys/kernel/hotplug

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery

[Buildroot] Using udev, non-static /dev, and ramfs (or tmpfs)

[Nathanael D. Noblet]

On Sat, 2006-10-21 at 11:34 -0700, don wrote:

> I see that /etc/init.d/S10udev tries to use "/sbin/udevstart", but
> I don't have that.
> 
> Would I be better off to keep things static?

I've been using udev for a bit (I think I added the original patch for
it). Since then a few things have changed. I've cleaned it up a bit
lately and have some patches for udev to fix exactly what you just
described. I'm not completely done yet, however here is a patch that
should fix most of that. Its created in the udev directory itself so as
not to pick up all the other changes in limbo.


-- 
Nathanael D. Noblet <nathanael@gnat.ca>
Gnat Solutions, Inc
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