title: Change filenames to lowercase in Ubuntu in all subdirectories
body: <p>I know it's been asked but what I've found has not worked out so far.
  The closet I came is this : <code>rename -n 'y[A-Z]/[a-z]/' *</code>
  which works for the current directory. I'm not too good at Linux terminal so what
  should I add to this command to apply it to all of the files in all the sub-directories from which I am in, thanks!</p>