[ELDK] udev/coldplug with eldk 5.2

Wolfgang Denk wd at denx.de
Thu May 24 15:02:39 CEST 2012

Dear Kolja,

In message <D42F060B3778074EA85B5FC2CC9E015C448BC0BE at MEN-EX2.intra.men.de> you wrote:
> I have this issue that is also mentioned in the FAQ[1]: Missing
> Device Files for Cold Plugged Devices.
> However, no /etc/dev.tar is present on my system. I am trying this on
> a Freescale P1022 -based board loaded with a Usb drive, a SATA disk
> and a µSD memory card. I am using ELDK 5.2 with the lsb-sdk and the
> sato-sdk root file systems. I can create the device files using mknod
> just fine, hotplugging works for USB (not SATA or µSD), none of them
> automatically show up after startup. Any idea what's wrong?

udev has always been a somewhat controversial area for embedded use.
You should probably ask yourself if you realy need it, or if for
example devtmpfs is not a much for efficient approach.

as for the udev cache thing, please have a look at /etc/init.d/udev
and search for DEVCACHE to understand how this is handled now.  The
feature is not activated by default; to do so one would create a file 
/etc/default/udev-cache which would/should look like this:

	# Default for /etc/init.d/udev

	# Comment this out to disable device cache

Then you have to _manually_ create the $DEVCACHE file; there are rules
in /etc/init.d/udev to unpack such a file, but none to create it.

> Moreover, is there a reason why fsck.ext[234] is not included in any
> of the larger root file systems? Should I be using a different
> approach for creating disc-based root file systems?

Most embedded systems use flash technology based storage these days,
and ext is not really a good choice there.  If you need such a
configuration, you can always add the needed features to your board

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
At the source of every error which is blamed on the computer you will
find at least two human errors, including the error of blaming it  on
the computer.

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