Show the Disk Usage

  df -h

Show the current file system usage of each subdirectory of the root directory

  du -hs /*

Show file system usage of the current directory

  du -hs ./*

When the df and du commands return different results, lsof is your friend!

Sometimes, files get ‘unlinked’ from the filesystem. They could have been deleted but held open by a process. You can find them by typing

sudo lsof | grep deleted

or perhaps

sudo lsof | grep DEL

Sometimes you can find a process is holding onto a file so you can kill it, or try a reboot.