I don't have a 3rd partition and neither will anyone with a stock LS, right?
Wrong. Everyboy has the third partition, /dev/hda3. It is mounted on /mnt. And you are looking at the wrong configuration variable. ubpart is used to load and flash a ROM build from a RAM build.
In the standard configuration, U-Boot attempts to load the file boot/vmlinux.UBoot from the first hard disk partition, /dev/hda1. The partition and file name are stored in the environment variables "hdpart" and "hdfile" respectively. Note that the name of the file can be a symbolic link. Some of the precompiled binaries have changed the file name to "uImage" but if you compiled U-Boot yourself, this is not the case.
wrong? why? i have no idea about it, i am new user.