Woah, I'm sure this has been thought of but I just want to query this and introduce a word of caution.
If you start the image installer process (using the OK button from a cold start) option 3 lets you format the 'User Partition'.
An (already installed) traditional ROM then has the job of re-populating this to a usable state - this is the traditional way of resetting one of these units to a virgin state.
Does anyone know what happens if you select this having repartitioned the NAND ? and what happens if this option can't find the User partition ?
It could possibly brick at worst case.
I don't really think it would brick the device. It would possibly screw up while trying to perform the thing, but I highly doubt it would trash a reserved service/utility part of the flash.
BTW: While we are at it I'm assuming that the Service Menus are in ROM and not FLASH but is this Japanese utility menu the same or does this class as a flash based bootloader ? If so then it would need patching to avoid the possibility of this issue.
As far as I understand it, both service menus and the Japanese utility are in flash. You can erase them, you can patch them, you can do whatever you want with them. But there is always a possibility to bootstrap the device, as the very basic first-stage bootloader resides in ROM and has a built-in possibility to restore the flash. There is an instruction for doing that, the link on it was posted on this board quite a while ago, but I think it's possible to find it. Or maybe someone could post it here if he has it saved.
You could argue that if you have gone to the effort of partitioning the flash like this then you are in an 'informed position' and wouldn't try this option. There again what happens if something 'breaks' that would be possible to fix in a service depot and you send it to some poor hapless dude whose first procedure is to wipe the user partition.
Hmm.. you may get back a brick and be charged for wasting time.
Well, in the worst case scenario, a real brick can drop from the rooftops and brick you on a way to service ;) My point is that thinking about that is a bit over the top. And well, I guess someone with the experience of the lowest-level bootstraping could just try that out :)
Wouldn't a safer option be to just make the initial root partition as small as possible, carry only the kernel, some minimal scripts and busybox that on an erase would set up the user partition as the real root. On a normal boot the root would pivot the root mount onto the user partition and remount itself in perhaps /boot ?.
This seems safer and keeps the partitioning scheme cool with the loader menus etc. It also means that you are still free to install almost everything including base stuff from IPK if your distro allows it.
Well, in my opinion, while I think it would be a small tiny bit safer, it would not pay off a single megabyte of the precise flash space wasted. Just relax, there are much more pressing issues on the agenda to mediate about :)