Waste land is an script to estimate and clean up the wasted space in
unused thumbnails in your home directory (in Free Desktops).
Thumbnails are small images (less than 50KiB) that help applications to show a fast preview of files (pictures, videos, text documents, etc.). For details, see Thumbnail Managing Standard.
Thumbnails are associated with files. When those files are moved, the association can be lost, leaving the thumbnails orphan. Although the space required by each thumbnail is very small, it can grow more than you think.
The thumbnails are stored in directories normal, large and fail. For
instance, if you have thounsands of pictures stored in different directories
in Pictures/Downdloads, then you could have thousands of thumbnails either
in normal, large or both. If you decide to move them to
Pictures/Reviewed, likely you will have twice the thumbnails than before.
The thumbnails are created on demand, so it will not happen overnight. But
it will happen at some point.
When you connect a camera or phone, likely, you will get thumbnails generated as you browse them. So, the next time you connect those devices the thumbnails would be there and you can browse them faster... only if you still have the same pictures in your camera (unlikely) and if you connect the camera to the same usb port.
I wrote this script in 2006, for my own purpose. However, one weekend, when
helping to do a backup (mirror) of a whole home directory, I noticed
that rsync was stuck in ~/.thumbnails/normal. I instructed rsync to
skip ~/.thumbnails and it was fast again (relatively). It seems rsync
pays a toll in very populated directories. When I ran waste land, there
were more than 45,000 orphan thumbnails using more than 750MB of space.
Your mileage may vary.
I had not share the script before because I consider it a quick hack.
It does not solve the problem, just a symptom. However, it would be worse
to delete the .thumbnails directory from time to time.