[yocto] Related to mounting USB

[Wolfgang Denk]

Dear Navani Kamal Srivastava,

In message <9BACABF0C6B14A4D8C33B42A795119BE096D7BA7 at POCITMSEXMB03.LntUniverse.com> you wrote:
>
> I am facing problem in mounting USB. At the time of system bootup if
> USB stick is plugged, it shows messages like
...
> But I won't get any sda or sda1 in /dev to mount. If I am
> unplugging the USB stick and again plug it I would be able to look
> for it in /dev and mount it. Please look after this issue.

This is a known problem.  Some even call it a feature ;-)

Yocto tries to speedup the boot process by caching the /dev contents:
it creates an archive "/etc/dev.tar" on the first boot and, if this
archive exists during the next boot, it gets extracted and most of
the coldplug events are filtered. Only if the archive doesn't exist a
full scan is performed.

This seems to be a good solution for a root file system used inside a
typical embedded device (as scanning for cold plug events is known to
be slow) but this clearly doesn't work in your setup where the booted
configuration changes.

As a workaround you just need to remove the "/etc/dev.tar" file from
the root file system.

As a real fix you might want to disable this functionality for
your configuration.

Best regards,

Wolfgang Denk

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