Qnap [ Fdupes ] [ 2.2.1 ] a program for identifying duplicate files residing within specified directories.

Usage: fdupes [options] DIRECTORY...

 -r --recurse         for every directory given follow subdirectories
                      encountered within
 -R --recurse:        for each directory given after this option follow
                      subdirectories encountered within (note the ':' at
                      the end of the option, manpage for more details)
 -s --symlinks        follow symlinks
 -H --hardlinks       normally, when two or more files point to the same
                      disk area they are treated as non-duplicates; this
                      option will change this behavior
 -n --noempty         exclude zero-length files from consideration
 -A --nohidden        exclude hidden files from consideration
 -f --omitfirst       omit the first file in each set of matches
 -1 --sameline        list each set of matches on a single line
 -S --size            show size of duplicate files
 -m --summarize       summarize dupe information
 -q --quiet           hide progress indicator
 -d --delete          prompt user for files to preserve and delete all
                      others; important: under particular circumstances,
                      data may be lost when using this option together
                      with -s or --symlinks, or when specifying a
                      particular directory more than once; refer to the
                      fdupes documentation for additional information
 -N --noprompt        together with --delete, preserve the first file in
                      each set of duplicates and delete the rest without
                      prompting the user
 -I --immediate       delete duplicates as they are encountered, without
                      grouping into sets; implies --noprompt
 -p --permissions     don't consider files with different owner/group or
                      permission bits as duplicates
 -o --order=BY        select sort order for output and deleting; by file
                      modification time (BY='time'; default), status
                      change time (BY='ctime'), or filename (BY='name')
 -i --reverse         reverse order while sorting
 -v --version         display fdupes version
 -h --help            display this help message

Unless -1 or --sameline is specified, duplicate files are listed
together in groups, each file displayed on a separate line. The
groups are then separated from each other by blank lines.

When -1 or --sameline is specified, spaces and backslash characters (\)
appearing in a filename are preceded by a backslash character. For
instance, "with spaces" becomes "with\ spaces".

When using -d or --delete, care should be taken to insure against
accidental data loss. While no information will be immediately
lost, using this option together with -s or --symlink can lead
to confusing information being presented to the user when prompted
for files to preserve. Specifically, a user could accidentally
preserve a symlink while deleting the file it points to. A similar
problem arises when specifying a particular directory more than
once. All files within that directory will be listed as their own
duplicates, leading to data loss should a user preserve a file
without its "duplicate" (the file itself!).