Debian On Cf With Uboot What Should I Put On Sd ? Pdax ?

[ajnk]

Yesterday I managed to bork/recover my Debian install on the internal CF (replaced the microdrive) of my C3100.  Once the debian distro was broken the Z was useless until I could get it home/disassemble/restore to CF (I still had the microdrive with the debian on from ~1month ago).

Now the setup is a 2.6.24-yonggun kernel with uboot.  I believe I can install another distro on SD and boot it - I have seen various postings about using altboot/kexec/sharp bootloader.  As I understand it this would do 2 things :-

1) It would boot the SD distro if I forgot to hold down '2' when I reboot - rather than panicking.
2) If I mess up the debian install again I could probably fix it using the distro on the SD (chroot anyone ?)

Can install another distro on the SD - preferably pdax as i used to use it on a c860 (although i am having trouble working out what the latest usable version is) and boot it with uboot.

I don't understand much about the uboot boot process, so would like to add a distro to my current working setup rather than fiddle around with other boot methods and risk losing Debian.

I can't believe someone isn't doing this already :-)

Please no suggestions of what *might* be possible, contributions about confirmed working setups would be much appreciated.

[Capn_Fish]

Unless I am mistaken, the distro on SD and the distro on CF need to run the same kernel (unless you sue kexec). If you use Debian with the Angstrom kernel and dual-boot that way, it would likely work. Otherwise, probably not (unless I have faulty logic/bad information).

[ajnk]

Ahhh, that sound like the part of the jigsaw i was missing.  I am guessing the rest of the jigsaw is something like uboot has a kernel/modules sitting somewhere in nand, and it execs the target kernel at boot time, the target kernel boot= and root= parameters probably take care of which distro you end up with.

*off topic* When i boot the pdaxrom recovery kernel (reboot holding down OK). It mounts the cf card, but there is not /dev/hda1 file (there is a /dev/hda) and if I try to access it (cd /mnt/cf) it just hangs ?

[ZDevil]

Unless I am mistaken, the distro on SD and the distro on CF need to run the same kernel (unless you sue kexec). If you use Debian with the Angstrom kernel and dual-boot that way, it would likely work. Otherwise, probably not (unless I have faulty logic/bad information).

Not exactly. I am using the yonggun kernels, and each of them have specified where to boot from. So for the rootfs on CF/microdrive, we need hda1~4; for the rootfs on SD we need mmcblk0p1~2.
kexec-ing is the same game.

[ZDevil]

I also wanna know how to install pdaXrom/pdaXii on SD.
Now I am also doing multiplebooting:
Main system = Debian EABI Lenny/Sid on internal disk (the main working system)
Subsystem 1 = Debian EABI Sid on SD (sandbox & testing rootfs)
Subsystem 2 = Cacko 1.23 on NAND (for fun; with the hack to remove its restrictions on the internal disk)

[ajnk]

So what does holding down '2' at boot time tell the kernel ? /dev/hda2 ? CF ?

Are you saying that the yonggun kernels are hardcoded to boot off *either* CF or SD but not both or even they are locked down to boot from a particular partition ? .  

In which case the original question changes to 'can i put multiple distros (or multiple version of the same distro) on different partitions of the CF ?)  That way at least i could have a mini 'get out of jail' distro - as long as I don't bork the kernel.

Thanks for you helpful/knowledgable contribtions thus far.

[ZDevil]

So what does holding down '2' at boot time tell the kernel ? /dev/hda2 ? CF ?
Are you saying that the yonggun kernels are hardcoded to boot off *either* CF or SD but not both or even they are locked down to boot from a particular partition ? .  
In which case the original question changes to 'can i put multiple distros (or multiple version of the same distro) on different partitions of the CF ?)  That way at least i could have a mini 'get out of jail' distro - as long as I don't bork the kernel.

Actually I am talking about the yonggun kernels for Sharp bootloader ( http://yonggun.tistory.com/68 ). The method described in the other pinned thread is using these.
iirc for uboot the keys are hardcoded this way:
[1] = SD
[2] = internal disk
[3] = CF
(none) = Flash
[OK] = installation mode

[ajnk]

Had another thought on this .... boot to the pdaxrom emergency kernel (as i have uboot, i can hold down okay to reach this.  Install kexec in this environment and then exec the pdaxrom kernel on sd ?  I hope to give it a go this weekend if anyone has already tried - let me know ;-)