PXE NFS diskless machine - NFS root filesystem not mounted by systemd

Hi,

I'm trying to get a diskless set up to work (PXE). It is mostly working but upon booting the installed system it drops me into an emergency shell because it couldn't mount the root filesystem. I can manually continue and boot thereafter.

I use pxelinux to do the PXE stuff and this is how I installed openSUSE (using Factory-Snapshot20140909, since the official 13.1 release iso doesn't work)


I then installed the system by mounting only one partition on / in the partition manager: /volume1/srv/tftpboot/pxelinux.cfg/persistent

Then I tried booting the system with various options. The only option (so far) that gets me to an emergency shell from which I'm able to continue is:

This drops me into an emergency shell because it cannot mount the root filesystem. This I can manually achieve by typing:
Funny enough, after the ifup em1 the machine has IP address 192.168.0.8 (which is in the PXE range): I have two DNS servers in my network:
* one serving out addresses to non-pxe requests 192.168.0.100 - 254
* one serving out addresses to pxe requests 192.168.0.3-8

It seems to go wrong shortly after:
[ 15.711198] linux-pg59 systemd-udevd[300]: renamed network interface eth0 to em1

So either the em1 interface isn't set up properly, or the renaming action destroys the set-up. Weird.

Anyone a clue as to how this can be fixed?
* how can I make sure the network set-up is working properly? Is this a bug that makes booting with NFS root filesystem impossible?
* how can I ensure myself the above steps get executed automatically at the right moment?

Thanks for your input