Creating a wireless ad-hoc network on linux is a fairly simple task. The only problem might be with the wifi device drivers as some may not support this feature. Make sure the normal wifi connection ( connection to an access point) works. If you have two Machines A and B this is what you would do.
On both machines:
iwconfig wlan0 mode Ad-hoc iwconfig wlan0 essid MyWifi
You can also set other options such as encrypting with the iwconfig command. Check
In my case, the mode change command gives a resource busy error if wlan0 interface is up. That is, if you can see wlan0 when you do ifconfig, then your wifi interface is up. Here is what I get:
Error for wireless request "Set Mode" (8B06) : SET failed on device wlan0 ; Device or resource busy.
The only way I found around this problem is to do the iwconfig commands before I configure the wifi interface with ifconfig.
On Machine A:
ifconfig wlan0 192.168.1.1 netmask 255.255.255.0
On Machine B:
ifconfig wlan0 192.168.1.2 netmask 255.255.255.0
You can choose different IP addresses but make sure you have the right subnet mask.
You should be set. You can now ping.