I've seen this too:
ubuntu@ubuntu-virtual-machine:~$ ls /run/network ifstate ifup.eth0
ubuntu@ubuntu-virtual-machine:~$ cat /etc/network/interfaces auto lo iface lo inet loopback
I've seen this too:
ubuntu@ ubuntu- virtual- machine: ~$ ls /run/network
ifstate ifup.eth0
ubuntu@ ubuntu- virtual- machine: ~$ cat /etc/network/ interfaces
auto lo
iface lo inet loopback