Update: Thanks for the help! We got to the problem quickly. Forever's log files were what's taking up all the space. I deleted them and freed up many gigs. 

TL;DR -- Running Ubuntu, I need a way to find out which folders are using 99 percent of the space on my disk. 

I have a number of servers on AWS running Ubuntu, running Node apps under Forever. One of them has a single app, called wo.js. Dropbox is also running on the machine.

A few days ago my servermonitor app reported that wo.js wasn't running, so I went to check it out and the Forever list was empty. Which is weird because a crashed app should still be in the list, with a big word STOPPED next to its name. But there was no sign of wo.js.

The app keeps a cache of rendered pages in its folder, so I figured that folder had gotten too big, so I deleted it, 

rm -rf renderedPages

Then relaunched the app, and it was good. That appeared to have solved the problem.

But a couple of days later same thing happened.

I am very much a newbie when it comes to running a Ubuntu server. So far I haven't had to know very much. Just the basics. I asked how much disk space was available on the server.

df -h

It said the disk was 7.8GB and it was using all of it. Okay that's the problem. So I removed renderedPages again, and took another look. That only freed up about 10MB. The disk was still almost totally full.

So....

The problem was not that my app was using too much space, something else is. This is where I need help. I have no idea where to look to find the files that are using up all that space. I'd rather not have to reprovision the server, so any advice would be appreciated.