I'm trying to get john to try all passwords of length 6 that are just alpha. When I try

john -i:alpha -stdout

it's obviously not doing that. Maybe it's filtering it somehow? I also tried using the lanman generation, but I guess I don't understand it because it says it wants plaintext. Can anyone help? Thx

The order john gives out its words is indeed
quite weird, yet it seems to work (at least it
does for n=3). Use this command line with
Minlen=6 and Maxlen=6 and you should get
your 1.8 GB file.

You might want to read a tutorial about JTR, this is a good one:

http://blacksun.box.sk/john.txt