How to find largest files or directories on Linux system

sudo cd /
sudo find . -type f -print0 | xargs -0 du | sort -nr | head -20 | cut -f2 | xargs -I{} du -sh {}
or
sudo find . -type d -print0 | xargs -0 du | sort -nr | head -20 | cut -f2 | xargs -I{} du -sh {}