[[!comment format=mdwn
 username="joey"
 subject="""comment 2"""
 date="2017-12-20T21:36:36Z"
 content="""
AFAICS, DiskImage.imageFinalized creates any mount points that were not
rsynced over from the chroot. But, I guess that partitionsPopulated is
expecting the mount point to exist in order to rsync its content over,
and if nothing created /boot/efi that would explain the rsync error.
I've added a check to prevent that problem.

As for the unmount problem, it's a problem with the order
it traverses the mount points for unmounting. That is using
"unmountBelow" with the directory where the disk image partitions
are loop mounted. If that unmounts `boot` first, it will implicitly
unmount `boot/efi` (due to --lazy) and then will fail when it
tries to explicitly unmount it. Added sorting that should fix that.

Let me know how that goes, I've not tested it with your config.
"""]]
