[OE-core] [PATCH] udev - only use devtmpfs for udev

[Alex Olson]

udev - only use devtmpfs for udev

Fix for bug: https://bugzilla.yoctoproject.org/show_bug.cgi?id=4632
Since udev 172, the 'mknod' logic was removed from udev. Yocto Dylan
is now using udev 182. This means /dev is now required to be a
devtmpfs filesystem (maintained by the kernel).    If the root
filesystem is a ramdisk,  the kernel's auto-mount of /dev doesn't
activate since there is no rootfs to actually mount...  The bug causes
an unusable system as /dev doesn't contain even basic nodes required
to even get a login prompt.

The Yocto  udev/init script mounts tmpfs if it does not detect tmpfs
or devtmpfs mounted at /dev.  This appears to be  outdated logic that
is no longer correct. I believe the Yocto udev init script should be
checking and mounting only 'devtmpfs' on dev.


Signed-off-by: Alex Olson <alex.olson+yocto at gmail.com>
--- a/meta/recipes-core/udev/udev/init  2013-05-18 14:38:09.000000000 -0500
+++ b/meta/recipes-core/udev/udev/init  2013-06-25 14:21:15.859918023 -0500
@@ -44,8 +44,8 @@
         halt
     fi
     # mount the tmpfs on /dev, if not already done
-    LANG=C awk '$2 == "/dev" && ($3 == "tmpfs" || $3 == "devtmpfs") {
exit 1 }' /proc/mounts && {
-            mount -n -o mode=0755 -t tmpfs none "/dev"
+    LANG=C awk '$2 == "/dev" && ($3 == "devtmpfs") { exit 1 }'
/proc/mounts && {
+            mount -n -o mode=0755 -t devtmpfs none "/dev"
     }
     [ -e /dev/pts ] || mkdir -m 0755 /dev/pts
     [ -e /dev/shm ] || mkdir -m 1777 /dev/shm