How to find the biggest directories in my hard drive?

I logged into my server this morning and received a disk is full error. How do I fix this or find wherever all of this data is hiding?

Well, the first thing you want to do is try to login as root (recovery mode).

EDIT: If you are in recovery mode, you'll need to remount as RW. To do this, mount -o remount,rw /.

Run cd /. This allows you to enter the root and begin to trace the problem.

When you are in /, run du -sh *. This'll give you a list of all of the files in your hard drive. Let's say you see

2.6T var

You know that the problem is in /var. You then cd /var and run the du -sh * command again. Scroll and look for something like

2.6T zpanel

You then know the problem is in the ZPanel folder. (I am using ZPanel for this example, as I just recovered from this exact problem). By now you know the drill. You cd zpanel/ and du -sh *. Look for something like

2.6T backups

Same old, same old. cd backups/, du -sh *. But this time, you get

(size) zpanel_date_etc

The backups folder contains no more subdirectories, so you expunge the unnecessary files. In my case, I used rm -rf zpanel_* and went from 100% capacity to 25% capacity.

Then, you fix wherever the problem is. (For me, it's in ZPanel's backup settings, so I should change those).

This works with any situation, all you need to do is trace the problem.

N.B. I know you could have probably used a sort to do this, but if you have no temp space, you can't sort. This is the best option.