Comment 23 for bug 45842

I experienced the same problem, not mounting nfs shares at boot time on hardy (diskless client).
I solved the problem adding "auto eth0" to /etc/network/interfaces. Actually eth0 is already configured by the kernel when booting from the net, but the interface is not brought up "officially" when the keyword auto is missing in /etc/network/interfaces, according to /etc/udev/rules.d/85-ifupdown.rules.