Sometimes you may want to configure a wireless interface on a system with Ubuntu Server. The most common use case (for me, at least) is to run some tests with server, which require two network interfaces, on a laptop (it’s what I have available to play with) with an ethernet interface and a wireless interface. As long as Ubuntu sees the wireless interface, it’s quite easy to set things up so the wireless comes up at boot time.
You will probably need to set up the server to forward and masquerade the internal network (usually, the ethernet segment is the internal one, while the wireless counts as the “outside” interface). There are plenty of tutorials to do this over the internet, so I won’t extend this post by detailing that.
Of course, the wireless will grab a dynamic IP address, so use caution with that as the address may change (or, assign a static one from your router’s unused range). Anyway. Put this in /etc/network/interfaces:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
iface lo inet loopback
iface eth0 inet static
iface wlan0 inet dhcp
Then you can do ifup wlan0 to bring the interface up. It should also come up automagically at boot time.