I would like to connect to my PI through wireless USB dongle, how can I setup an AP or an Ad-Hoc under Arch Linux?
I know this question asks for instructions on Arch Linux, but since I have been struggling for several days with the exact same issue on Raspbian Wheezy I thought it might be helpful if I shared my solution anyway.
Basically, I ended up creating a solution where my Raspberry Pi (RPi) tries to connect to one of its known wireless networks, and if that do not succeed (WiFi is not in range or the DHCP is not leasing), the RPi creates an encrypted DHCP-enabled ad-hoc network instead. In that way, I can always access the RPi through SSH no matter where the RPi is located.
wpa_supplicant for managing the wireless WPA2 connections, and
iwconfig for creating the encrypted ad-hoc network (with
dhcpd for managing IP leases on the ad-hoc network).
I have compiled a complete tutorial on this subject which can be found here: http://lcdev.dk/2012/11/18/raspberry-pi-tutorial-connect-to-wifi-or-create-an-encrypted-dhcp-enabled-ad-hoc-network-as-fallback/
Hope it helps someone.
The easiest way (in my opinion) is to use the create_ap script as linked in: https://wiki.archlinux.org/index.php/Software_Access_Point
For setting up a Pi as a wifi access point try my site at www.pi-point.co.uk, which as long as your wifi adaptor supports AP mode should hopefully get you sorted.
I know this isn't for ARCH but hopefully it will give you all the clues you need.