Just this morning I ran out of space on a small external drive that I use for system backups and stashing the odd ISO image.
And the first thing I grabbed after the error message was ncdu.
ncdu is one of the best tools available that doesn’t fit neatly into any one category. It’s not quite a file manager, even though it does have some fundamental file management functions.
And it’s not a tree navigator, even if it does display its information in a basic array of nested directory links.
What it does instead is run through the tree, find file sizes and show what’s taking up space. And at times, that can be the most amazing thing.
ncdu’s help screens appear with the ? key, which makes it very easy to learn. Sorting, reverse sorting, display options and error messages are all listed there.
The conventional du and df tools are fine and dandy, and I wouldn’t suggest replacing them at all.
I can say though that ncdu replaced them for me, years ago. And I still use it, even today. 😐