NM config after PXE/NFS live CD install

[Sven Ulland]

Hi, all. How can I avoid ending up with an unconfigured NetworkManager
after installing Ubuntu via a PXE/NFS-booted live CD image?

I provide verbatim K/X/Ubuntu live CDs loopback mounted and directly
bootable over PXE+NFS so that users can boot into the live environment
and choose to install from there. The only modification is the
pxelinux config to enable netboot. This works really well, except that
the network ends up being unconfigured after the installation
completes. Here's why:

Casper's scripts/casper-bottom/23networking sees NETBOOT on the
cmdline, and populates /etc/network/interfaces with "iface eth0 inet
manual" to avoid breaking the NFS root mount.

In the live env, NetworkManager avoids touching the network config
since it sees the interface being configured in
/etc/network/interfaces and /etc/NetworkManager/NetworkManager.conf
has managed=false in the ifupdown section.

So far so good.

Now, during the installation, ubiquity/scripts/plugininstall.py
configure_network() copies the live env's /etc/network/interfaces to
the target, which will prevent NetworkManager from handling the
interface on the next boot.

What's an appropriate way to avoid this so that NetworkManager ends up
in a working state after booting into the new installation?

My first thought was to check for a cmdline parameter to avoid
carrying over the live env's network config, but it is probably a bit
too specialized.

sven