[yocto] mountall.sh, udev and read-only rootfs

[Petr Kubizňák]

Hi Yocto guys!

I experience problems with Yocto 1.7 Dizzy. I build an image with read-only
rootfs (EXTRA_IMAGE_FEATURES += "read-only-rootfs") and start kernel with
arguments "mem=256M root=/dev/mmcblk0p2 ro rootwait console=ttymxc1,115200
2". Please note the "ro" specifier. The specifier is needed on the release
configuration - rootfs at UBIFS on MTD. This is the simplest way how to
reproduce on a debug configuration with SD card.

Now the issue. When the system is booting, I receive udev errors, and udev
fails to start:
udevd[53]: bind failed: No such file or directory

udevd[53]: error binding udev control socket


Other parts of the system also do not work correctly, for example the
network is not set up. One finding is mainly interesting - devices listed
in /etc/fstab do not get mounted (so files fail to write to /var/run/, as
it remains read-only). It seems like if the /etc/init.d/mountall.sh script
(linked in /etc/rcS.d/S03mountall.sh) is not executed. I changed the order
of mountall and udev scripts by renaming the links as follows:
mv /etc/rcS.d/S03mountall.sh /etc/rcS.d/S04mountall.sh
mv /etc/rcS.d/S04udev /etc/rcS.d/S03udev

That resulted in successful mount of devices listed in /etc/fstab, and as a
consequence the network (and other services) was set up properly. Nothing
changed with the udev messages, though. It still fails to start.

Can anyone assist on this topic, please?

Petr

--
http://www.elnico.cz
http://www.sqm4.com
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