I'm trying to set up a static IP address for my LTSP server as to configure one of my two NICs (internal one : Server -> Light client) via the /etc/network/interfaces , but when I open the interfaces file all I can see is this :
auto lo
iface lo inet loopback
Is this normal?
This is normal. What you have is exactly the same as what's in /etc/network/interfaces on my Ubuntu 14.04 system (which is working fine and networking actively through two separate physical interfaces).
By default an Ubuntu desktop system uses NetworkManager to manage network connections automatically and dynamically. This does not require (and in fact typically requires there not be) entries detailing configuration of your physical interfaces in /etc/network/interfaces.
(NetworkManager, if changed from running in "unnmanaged mode" to "managed mode," will recognize and work with /etc/network/interfaces entries. But unmanaged mode is the default.)
Sources:
/usr/share/doc/network-manager/README.Debian, and related)
