This is a quick post just to note down the steps required to get a computer running wpa_supplicant to connect to the internet using an iPhone hotspot. Add the following to the file /etc/wpa_supplicant.conf:

network={
    ssid="<Name of your iPhone>"
    psk="<Your password>"
    priority=2
}

This is rather straightforward, as you've probably a line looking pretty much like that in your file, for you home WiFi. In the example above, I set the priority to 2; the idea is to set it to a value that will play nicely with the other networks defined in the file. You don't want to connect to your phone's hotspot when you're home, but you probably want to prefer your personal connection over everything in public places (at least I know I do… remember I live in France, where free, unlimited and secure public WiFi remains a wild dream). As explained in the man page of wpa_supplicant.conf, the default is 0, and higher values make a network more desirable. My home network has a priority of 5, public WiFis I don't want anything to do with get the default 0, and my phone is in between with a 2. Is that all there is to it? well, almost. There's a catch: by default, iOS gives your phone a name like "Sergey Brin's iPhone". This is all well (provided you like advertising your name to everyone, everywhere you go), but this causes a problem with wpa_supplicant. For some reason, you can't connect to an SSID containing an apostrophe. Since iOS won't let you change the SSID, you must change the name of your phone to something more reasonable. Now, for wpa_supplicant to reload its configuration and restart the network:

# wpa_cli reconfigure
# service netif restart

You should now be connected to your iPhone's hotspot!