EXT4-fs (nbd0): VFS: Can't find ext4 filesystem

[g <sendmailtogoran@gmail.com>]

Hi all,

I'm starting a diskless client via PXE-boot. All fine until the disk-image shall
be mounted.
Booting fails while initrd is loaded. 

First message is good

:: running hook [nbd]
nbd_host = 172.16.0.2
nbd_name = blade
nbd_port =
loading module...
connecting...
Negotiation: ..size = 2048MB
bs=1024, sz=2147483648 bytes

Second message is good too

:: performing fsck on '/dev/nbd0'
blade: clean, 37314/131072 files, 304256/524288 blocks

Last message is bad

:: mounting '/dev/nbd0' on real root
[    1.359849] EXT4-fs (nbd0): VFS: Can't find ext4 filesystem
mount: /new_root: wrong fs type, bad option, bad superblock on /dev/nbd0,
missing codepage or helper program, or other error.
You are now being dropped into an emergency shell.

Inside the emergency shell I do

nbd-client -d /dev/nbd0
disconnect, sock, done

nbd-client -N blade 172.16.0.2 /dev/nbd0
Negotiation: ..size = 2048MB
bs=1024, sz=2147483648 bytes

mkdir /mnt
mount /dev/nbd0 /mnt
ls /mnt
bin         home        mnt         run         tmp
boot        lib         opt         sbin        usr
dev         lib64       proc        srv         var
etc         lost+found  root        sys

I can mount the nbd but initrd not. Why is that?

Regards
Goran