I use an application called connectify to turn my laptop to a wifi router and provide other devices with internet using my DSL connection. But after I switched to Ubuntu 11.10 I can't use this any more. Is there any Linux software or trick available to do this?
yes, Ubuntu and many of it's flavors have feature called "ad-hoc network" and "wifi tethering"
To make wifie hotspot, you need to have some connection (cable connection, or another wifi connection (that woudl require a second wifi adapter).
Remember, you can't use the same adapter as WiFi receiver and wifi spot.
Go to network settings ->
Edit Connections ->
Create a new connection and select
Mode you can specify a password and enjoy.
there is bug currently in Ubuntu so there is work around for making ad hoc wifi access point, queting bellow:
"connecting with shared with other computers connection in NetworkManager. Other computer gets IP but NetworkManager disconnects the shared connection after half a second. This same setup worked perfectly fine in 11.04. Is there any fix, workaround or alternative way to share a connection with another computer over an Ethernet cable. (I can downgrade to 11.04 but I'd rather not ).
EDIT: found a workaround The workaround for now is to set IPv6 options to Ignore and then sudo killall dnsmasq. Reconnect and it should work."
I done it on my laptop with Ubuntu 12.04 and mine working fine now.