[maemo-users] dual boot with 2007 from device and 2008 from MMC - possible?

From: Frantisek Dufka dufkaf at seznam.cz
Date: Wed Nov 28 10:30:55 EET 2007
Piotr Zagorowski wrote:
> Now, I'd like to test/adjust/play with new OS2008 beta.
> My question is: can I use dual boot, one from n800 device with OS2008 
> and one from MMC card with existing (I mean currently used, highly 
> customised etc) OS2007?

It somewhat works. You can boot both 2007 and 2008 systems but there are 
some (serious) issues. There is only one linux kernel but OS2008 system 
uses 2.6.21 and OS2007 uses 2.6.18.

It seems that OS2007 boots fine with newer 2.6.21 kernel but wi-fi 
doesn't work (no crash but you don't see any networks) and arrow keys do 
not work (other keys do). Otherwise it seems to work so you can get to 
your data and use device offline.

All this means that you can test OS2008 but when going back to 2007 you 
need to flash older kernel to have it completely working (and flash 
newer one back when you want to use OS2008 again). You can keep kernels 
in the opposite system and flash them from device right before booting 
the other system but this is of course not ideal. I did not try booting 
2008 with older 2.6.18 yet but I expect problems.

Luckily 2.6.21 already has kexec for ARM merged so in theory and with 
some tweaks (kexec for generic ARM does not mean it works on OMAP2) it 
may be possible to boot older kernel from newer one without flashing via 
kexec mechanism.

Another solution is to tweak OS2007 a bit and make it working with newer 
kernel. Arrow keys may be simple but I am not sure about differencies in 
wi-fi driver and connection manager userspace stuff. And there may be 
also other issues yet unreported. Advantage of this solution would be to 
run OS2007 with CPU at 400MHz.

> If so, will procedure from existing how-to work? I believe I will do 
> some test anyway, but first would like to ask has someone tried.

Yes, the procedure works but I am not sure about right tar for OS2008. 
But you can still boot OS2007 where you already have tar working and 
clone OS20008 from flash to another MMC partition (if you have more of 
them). Or you can just keep 2008 in flash for testing.


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