Massively duplicated files are oftentimes a problem with music and movie collections. Because hunting for dupes by hand is definitely not the way to go, you may want to look to command-line tools like fdupes for help.

fdupes is available via apt-get in Ubuntu, so install it first:

sudo apt-get install fdupes

This is the basic syntax for looking up duplicated files:

fdupes -r [target-directory]

How to delete all duplicates and generate a report at the same time:

fdupes -rdN [target-directory] > textfile.txt

A quick overview of what the options mean:

• -r recursive, traverse subdirectories
• -d delete, delete duplicates
• -N keep the first file, remove other (duplicate) files

Needless to say: use this with caution! Files will be deleted forever.

Find more information on fdupes here (UbuntuGeek).