Comment # 6 on bug 1093853 from Jiri Srain

(In reply to Freek de Kruijf from comment #4)
> (In reply to Neil Rickert from comment #3)
> > Just a comment from another user.
> > 
> > In addition to changing "/etc/fstab", you should look at "/etc/default/grub"
> > which might list file system(s) on the command line (such as the "resume="
> > parameter).  And you probably also need to rebuild the "initrd" for the
> > copied system.
> 
> To make it absolutely clear, this /etc/fstab is on the copied 42.3 system,
> while I work on the Tumbleweed system. So this "/etc/default/grub" is on the
> root partition of Tumbleweed. I did not need to rebuild initrd on the copied
> system, because that system did boot just fine after changing the UUID in
> the linux line of the grub menu.

Well, if you work on TW, it does not modify the GRUB configuration on the
copied 42.3, which then explains the behavior.

Neither YaST nor grub2_mkconfig or os-prober can know that your bootloader
configuration on the copied 42.3 is not adapted to it.

You really should remove (or adapt) all configuration, that is not adapted,
after the copy - be it /etc/default/grub as well as the generated menu.