did i get it right? i can keep my cacko installation and my hd partition and install
debian on sd, kexecuting cacko kernel from debian?
I think so. Simply put, there is no special installation apart from setting up each system separately and then flashing a kexec-capable kernel. Just reboot and kexec from there. If at some point you don't like this setup anymore, say you want to go back and stick with Sharp/Cacko rom only, then simply reflash the Sharp/Cacko kernel and that's it (no more kexec).
another question: is there a 2.4 kernel which supports kexec so that i can use
cacko/sharp as my main distribution and kexec debian and so on for testing?
afaik kexec is supported in kernel 2.6 but not 2.4.
In reality it doesn't make a big difference if you simply do dualbooting (such as Debian/Cacko), as long as either of them can use kexec.
The "catch" here, if i am forced to say, is you must boot into the kexec-ready rootfs in the very first boot after setting everything up. And a simple reboot will boot into this rootfs first. But rebooting is not absolutely necessary (and not a very cool thing to do) if things are running well.
Then each time you want to load the other system it's a (warm) reboot. So it's like:
-- (first boot) --> Debian -- (reboot with kexec) --> Cacko -- (normal reboot again) -- > Debian -- (reboot with kexec again) --> Cacko -- ...... ad infinitum
(Hope this doesn't sound too confusing )
(The great thing about the Zaurus is we seldom shut it down totally because it is instant-on/off. )
Of course triple/multiple booting is a different story. A full "juggling" mode is to make each system accessible from one another:
e.g. a "perfect" triple booting = a<-->b; b<-->c; c<-->a
Altboot and uboot are great solutions to this. But at this stage only Angstrom has altboot. uboot is not widely supported (esp. in upstream). There are also some kind of pivot booting (like the OpenBSD/Cacko dualbooting hack), but it doesn't apply to many systems.
