I'm working on my first preseed file, and to avoid having to re-burn a DVD every time I make a change, I'm hosting it on a webserver and loading it with preseed/url=...

To load the preseed, I'm booting a virtual machine from an edubuntu 12.04 LTS DVD, selecting the Install Edubuntu option, pressing F6, and replacing the file=... with auto url=...

According to the logs on my webserver, the preseed file is getting downloaded by the installer, but then... as far as I can tell, it isn't being used. For example, I get prompted to select a language even though d-i debian-installer/locale string en_US is right there at the top of the preseed. I also tried this "100% automated" preseed with the same results.

So, apparently something is going wrong between the installer retrieving my preseed and the contents thereof actually getting used, and I'm at a loss for how to troubleshoot this further.

If I do a Ctrl+Alt+F2 while the installer starts, I can see a bunch of stuff happening, including several "Authentication Failed" messages that may or may not mean anything, but if that output gets saved in any way that lets me do a meaningful examination of it I haven't found it.

I'm sure I can't be the first person to have this problem, but I didn't find much when I searched for "preseed troubleshooting" here or on the Ubuntu forums, so perhaps this would be a good thread to start. Any advice would be greatly appreciated!