I copied a Linux installation from one partition to another partition on a different drive. I did this from a live usb and omitted dev, /proc and /sys. I ran update-grub from the original install, it found the copy installment and created an entry. The entry looks fine. I edited the new /etc/fstab as a last step by commenting out old stuff and writing new stuff using the new UUIDs.
The original install is Debian installed onto LVM on LUKS. It is a non encrypted boot partition and a LUKS partition which holds a swap partition and a root partition via LVM. The new partition is just one single unencrypted partition.
However, when I try to boot the new GRUB entry, it always loads the old version from the old partition, even when the UUIDs in the grub.cfg are definitely the right ones. I am always asked to unlock the old partition while booting from the new one, and when I do that and let it boot through, only the old partition is mounted, not the new one.