Install duff by entering the following commands in the terminal:
sudo apt update sudo apt install duff
Description:
Duplicate file finder
Duff is a command-line utility for identifying duplicates in a given set of files. It attempts to be usably fast and uses the SHA family of message digests as a part of the comparisons.
Homepage: http://duff.sourceforge.net/
Version: 0.5.2-1.1build1
Section: universe/utils