I did a pcakge upgrade one of my juju deployed vms and rebooted. The vm came up without any network interfaces. I had power off the vm and mount it's root volume on another vm to diagnose and patch around the problem. One of the updated packages creates a /etc/network/interfaces.py which overwrites the /etc/network/interfaces file. This new processes fails to generate the correct network interfaces and no longer includes the /etc/network/interfaces.d/.cfg files. I tried to update the /etc/network/interfaces.templ to at least include the interfaces.d/*.cfg files, but it appears to overwrite the interfaces.templ on every bootup.
My final solution was to do the ifconfig commands in the /etc/rc.local file so I could get the vm up and functioning again.
Does anyone know what package this new process comes from? And how I can get it configured to actually work? I have lots of other cloud vms that need security updates done to them, but I can't afford to have each of them disappear from the network when I do.