netcfg does not configure network with dash or bash as /bin/sh

[Vinson Lee]

I have a modified Ubuntu netboot image that uses dash instead of BusyBox sh as /bin/sh in the initrd.

Starting with Ubuntu 16.04 Xenial, netcfg fails to automatically configure the network interface during netboot in my configuration. Instead I will be presented with a menu pop-up where I have to manually select the network interface before the netboot can continue.

Since having dash as /bin/sh in the netboot initrd worked previously in Ubuntu 15.10, I was able to bisect this issue to this upstream dash commit between 0.5.7 and 0.5.8 (http://git.kernel.org/cgit/utils/dash/dash.git/commit/?id=46d3c1a614f11f0d40a7e73376359618ff07abcd). However, since netcfg doesn't work with bash either, this could be a netcfg bug that just happens to work with BusyBox sh.

I can reproduce this issue with the latest Ubuntu 16.10 Yakkety netboot installer as well.