Comment # 3 on bug 1209729 from Antonio Feijoo

(In reply to geheim geheim from comment #0)
> - dracut have to check if filesystem of the root partition into the kernel
> or if it exists as module
> - if it exists as module it must be included into initrd
> - if no driver is found then dracut must abort and complain that the system
> is not able to boot after this update

If you're creating a hostonly initrd (TW default), the first two steps are
currently being performed. Regarding the third, dracut assumes that the system
it is called from has all the necessary file system drivers loaded, so if jfs
is loaded in your system, it should work.

Please, could you attach the output of `dracut -f --debug test.img`

> 
> NOGO: run silent and leave system in non bootable state

That's a different story, because if a command (in this case dracut) is called
in a %posttrans script from another package (that's the case of zypper dup), it
cannot control the flow of the upgrade, that should be done by that package.