Use tmpfs if devtmpfs is not available

This makes the ramdisk always mount some kind of /dev,
and then try to move it to the new root.
This unbreaks handling of nodes created pre-udev likefor example lvm does.

defaults/initrd.scripts

@@ -308,13 +308,15 @@ run_shell() {
 
 runmdev() {
 	# Use devtmpfs if enabled in kernel,
-	# else busybox udev replacement
+	# else tmpfs. Always run mdev just in case
+	devfs=tmpfs
 	if grep -qs devtmpfs /proc/filesystems ; then
-		# Options copied from /etc/init.d/udev-mount, should probably be kept in sync
+		devfs=devtmpfs
-		mount -t devtmpfs -o "exec,nosuid,mode=0755,size=10M" udev /dev
-	else
-		mdev -s
 	fi
+
+	# Options copied from /etc/init.d/udev-mount, should probably be kept in sync
+	mount -t $devfs -o "exec,nosuid,mode=0755,size=10M" udev /dev
+	mdev -s
 }
 
 test_success() {

defaults/linuxrc

@@ -727,11 +727,11 @@ echo -ne "${BOLD}.${NORMAL}"
 
 # If devtmpfs is mounted, try move it to the new root
 # If that fails, try to unmount all possible mounts of devtmpfs as stuff breaks otherwise
-if grep -qs devtmpfs /proc/mounts
+if grep -qs "/dev " /proc/mounts
 then
 	if ! mount --move /dev "${CHROOT}"/dev
 	then
-		umount -t devtmpfs || echo '*: Failed to move and unmount the devtmpfs /dev!'
+		umount /dev || echo '*: Failed to move and unmount the ramdisk /dev!'
 	fi
 fi