Here are some instructions for creating iPhone ringtones under Linux.
Start with an audio file. Just about anything will work; a recording, or a music file. In my example, I start with a WAV file my kids recorded on their cell phone.
First, I loaded the file up into audacity and cut it down to just the part that I want. Then, I exported it as a WAV file.
If that works for you, GREAT, it makes the process a bit easier. But, for some reason my computer couldn't play the wav files that audacity exported, so I exported it to OGG format, then converted it back to WAV. There's some loss related to that, but for a ringtone, it probably doesn't matter much.
Next, convert the file to WAV format. I used mplayer for this, here's the command line.
mplayer -ao pcm kids_song_cut.ogg -ao pcm:file="kids_song_cut.wav"
Now that I have my WAV, I'm going to convert it to a ringtone file (M4A format). For that, I use faac. Here's the command line.
faac kids_song_cut.wav -o kids_song_cut.m4a
iTunes will recognize it as a ringtone if the file extension is changed to M4R. So, rename the M4A file to M4R and you are ready to drag and drop it into iTunes.