how did I do it?

first of all, what is the purpose? I want to use my ethernet connection on my computer, to tether it to my iPhone  over my wireless card.

DISCLAIMER:

I know what I do while I do it. If you do not and just copy & paste the commands, don’t complain if you break your system. I take no responsibility upon your work.
Lines starting with a # are commands to type in your terminal

what do we need?

an internet connection, a computer with an ethernet and wireless card running Ubuntu or Crunchbang (as my eee 901 does) and an iphone.

set up (source):

get firestarter,

# sudo apt-get install firestarter

stop the network-manager and create a copy of your file

# sudo cp /etc/network/interfaces /etc/network/interfaces.org

edit your network interfaces

# sudo gedit /etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

auto wireless0
iface wireless0 inet static
wireless-key 1234567890
wireless-channel 6
wireless-mode ad-hoc
wireless-essid ‘iPhoneNet’
address 192.168.0.2
gateway 127.0.0.1
netmask 255.255.255.0

change eth0 with your ethernet interface and wireless0 with your wireless interface, without forgetting a stronger WEP-KEY instead of 1234567890.

restart your network devices

# sudo /etc/init.d/networking restart

After that, we’ll fire up Firestarter:

# gksudo firestarter

A wizard should appear. Follow through these steps:

1. Press Next.
2. Choose eth0 (or your Ethernet device’s name) as the Internet device. If your IP configuration is assigned by DHCP, check/uncheck the corresponding box according to your situation.
3. Choose wireless0 (or your wireless device’s name) as the device which will share Internet. Check the box that says to share Internet.

4. Do NOT activate the option to enable DHCP in the Local Network.

5. Press Save.

Now configure your iPhone:

iphone wifi settings

as you can see in the image above, I used static IP settings, as router I set the address of the wireless interface wich I set before

.. (from above)
wireless-essid ‘iPhoneNet’
address 192.168.0.2
gateway 127.0.0.1
netmask 255.255.255.0
..

and for the DNS I opted for the local DNS server.

There you go. If everything worked fine you should have your WiFi internet on the iPhone over your PC WiFi Card.