OK, I deserved running into trouble trying this strange approach to multi-boot without knowing much of the basics. Still, having gotten that far, could anyone who knows what goes on behind the scenes pls. explain what I missed?

What I did was:

• Set up the boot menu on the 770 (works)
• Take a 2GB card, put it in my desktop PCs card reader to partition and format it.
• Use first ext2-partition for Debian (this works! I can boot into it)
• Use 2nd ext2-partition for OS2007HE (never boots, returns to boot menu)
• Use 3rd partition as FAT-data-partition (doesnt show up in file manager, doesnt mount automatically)

The fact that debian boots OK should mean that at least I got the basics of "How to dual boot" right, shouldn't it?

Now for the problems:

FAT-Partition (#3):
On a 2GB card, what could be the reason for a FAT-Partition not showing up in the file manager? I tried making it bootable, I tried type 6 (FAT16) or type C (WIN95 OSR2 FAT32), it simply says there's no memory card.
dmesg comes up with
which is funny because it should in fact be mmcblk0p3 (I also changed fstab to reflect that).
Does a data partition have to be #1 for the file manager to accept it? I think I can remember partition schemes where this was not the case... ?

OS2007HE (#2):
I tried to be extra-smart here. All the documents I found describe how to copy the running OS from internal flash to MMC. I run OS2006 and I didnt want to flash the HE, copy it, then re-flash OS2006 again.
What I did was: I extracted rootfs.jffs2 out of the 2007HE's fiasco image, mounted it on my PC and copied the files over to MMC. This seems to be OK; when I mount the partition and list the files, what I get seems to be a ITOS-style layout, including the correct owners, rights and stuff. Still, when I select this one from the boot menu, it won't boot.

Facts:
My original partinioning scheme was (device names taken from my desktop PC):
As I said, I changed the values in /dev/sdc3 quite a bit, changed the bootable flag, changed the FAT variant - had no effect at all.

I then went to do
later changing mkdosfs to mkdosfs -F 32 because I read it somewhere - nada.

The relevant parts of my bootmenu.conf are
so 2 and 3 are really pretty much the same, still 3 doesn't work at all.

From reading the forums (and I guess I must have read each and every related thread here) I get the impression the few who know are sick and tired of multi.boot related questions. Still... maybe... Where alse should I ask?

Well, I can tell you right now why it doesn't show your FAT; it needs to be the first partition. (As you can see, it looks at mmcblk0p1.)

For the other, I'm not sure; your ideas seem sound, and I'd have expected it to work. Read http://www.nmacleod.com/nokia/bin/nupgrade.sh and see how it differs from what you did; I see it creates a CLONE-COPY file; could that be needed? I haven't looked in any great depth.

I used a slightly hacked-up version of that to set up my quad-boot, and everything went well.

I would have hoped for a different explanation; it seems such an unnecessary restriction. Plus, I don't want to re-partition and do all the copying again
But reading what you say, I guess I'll have no other choice. Maybe though I'll wait until someone can point me to why my OS2007HE-partition fails. - I wouldn't want it to be "because it must not be partition 2" or something.

Meanwhile, thanks for helping here; I'm especially happy about the "your ideas seem sound, and I'd have expected it to work."-part

Well, you can always hack the scripts to make it work with some other partition. But that's a pain, and you'd have to watch that some update doesn't undo it...

Still, I think /usr/sbin/osso-mmc-mount or some such is a shell script that deals with that, so that's where I'd start looking, if you do want to take that route.

One more thing:

All the files within the fiasco image - is it really enough to extract and use rootfs.jffs2 only? First I thought so, but now it seems somewhat naive. Re-checking the contents, I found rootfs.jffs2 lacks not only the /mnt/initfs/-directory present on the 770, but also a whole bunch of nodes within /dev/ (and probably much more, I just have to figure out...). No wonder this doesn't boot.

I guess what I need is a way to put together all the contents of the fiasco image in the correct way on my desktop PC - this means learning a lot about how the maemo boot process works, I'm afraid

Did you get this to work?

I'm doing this on my host:

more notes here:
https://wiki.maemo.org/Booting_from_...card#MultiBoot