I am wondering how to share my mac desktop's wifi to an ubuntu 12.04 box via ethernet. I know how to share the internet from the mac but don't know how to connect to it on the ubuntu box. I have made ipv4 connection but internet doesnt work on both.
I'm not a Mac user, but I would think from the perspective of the Linux box, it shouldn’t require any special handling. The Mac is doing all the routing. The only thing the Linux box has to do is behave normally; make its DHCP request over the ethernet cable between itself and the Mac. IOW, the Mac is doing all the heavy lifting and behaving like a WAN.
If it’s still not working, and your Mac machine is using a wireless router, then you don’t even need routing. Again, leaving the Linux machine as-is (w/ DHCP enabled), you just need to bridge the Mac and Linux network connections on the Mac.
Now no connection at all occurs. Ubuntu searches once the ethernet is plugged in but doesn't establish a connection. Do I need change some setting? I just installed new so nothing has been messed with.
So if you have Lion, the setup is identical. Notice he has the XBOX initially setup for w/ manual network settings because it was connected to a Mac prior to Lion. Apparently using internet sharing was more laborious prior to Lion (perhaps there wasn’t a DHCP server on the Mac back then, so the ethernet adapters on both the Mac and XBOX had to be set manually). Notice he changes the XBOX from manual settings to DHCP (automatic). And that’s just how your Linux machine’s ethernet adapter is setup by default, w/ DHCP (not unless you messed w/ it). As I said initially, it’s likely you don’t have to do anything on the Linux machine. It’s all a Mac configuration problem, complicated by the fact that internet sharing methods have changed from release to release.
So if you have Lion or later, follow the video. Leave the Linux network adapter to defaults (DHCP), just like the XBOX. Just configure the Mac as he shows. It should work.