I am not sure if this is Xubuntu specific, however, if recovering an
installation in the event of a drive failure, the UUID is reset, of
course. However, the the os_prober reads the UUID from another OS's
boot/grub.cfg file, rather than from the current root's
dev/disk/by-uuid. This means old UUID's are used on "other" OS
This seemed odd at first, but proven to be correct by removing the
secondary installation's boot/grub.cfg and running update-grub once
again. The UUID corrected itself.
I can open a bug with Grub if anyone can confirm this wasn't something
setup by the xubuntu dev team.
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