@Mohsen47 ’s answer is correct, but a cleaner solution is to install ncdu:

Ubuntu:

sudo apt-get install ncdu

CentOS/Fedora:

sudo yum install ncdu

Once installed, you can simply run this:

ncdu /

@andya

Use this command to check which directory is eating your disk space

cd / && sudo du -h --max-depth=1 .

It might take a while to get executed.

Hope this helps.