Setting up an ad-hoc wireless network between 2 Ubuntu machines

You can create an ad-hoc wireless network between 2 linux hosts as shown below. Let us assume that we have two machine A and B both running ubuntu. We will assign 192.168.1.1 to A and 192.168.1.2 to B. I am also assuming that the drivers for the wireless card ( wlan0 here) are loaded already.
Run the following commands:
On machine A.

 ifconfig wlan0 down

iwconfig  wlan0 channel 4

iwconfig  wlan0 mode ad-hoc

iwconfig  wlan0 essid 'fermilevel'

iwconfig  wlan0 key 1234567890

ifconfig  wlan0 192.168.1.1

On machine B

 ifconfig wlan0 down

iwconfig  wlan0 channel 4

iwconfig  wlan0 mode ad-hoc

iwconfig  wlan0 essid 'fermilevel'

iwconfig  wlan0 key 1234567890

ifconfig  wlan0 192.168.1.2

Please note that essid and key must be same on both machines. You can change the given values.