For EasyDebian, see it's wiki:
http://wiki.maemo.org/Easy_Debian

...looking for "onfirstchroot" and similar scripts. Those are things, that get automatically executed, when you mount your debian partition/image file, or chroot into it, executed either from inside chroot, or from Maemo.

Alternatively, you may want to try latest Squeeze images of EasyDebian - they should have /home/user separated, already (via exact same method as I described - proper on*chroot script).

As for Ubuntu, I have no idea - probably, it depends if you also use easy-chroot for access it (if yes, same method with scripts in per-defined directory, should work).

You should also be aware, that Easy Debian have own thread:
http://talk.maemo.org/showthread.php?t=34550&page=290

...but you may want to start reading it non-chronological order, starting from last page, due to it's rather epic size.

Good luck and have fun!

/Estel