You're missing the most significant one, PID 1 itself: $ du -hs /usr/lib/systemd/systemd 1,5M /usr/lib/systemd/systemd And there's plenty more in /usr/

You're missing the most significant one, PID 1 itself: $ du -hs /usr/lib/systemd/systemd 1,5M /usr/lib/systemd/systemd And there's plenty more in /usr/lib/systemd (basically all the binaries that are not supposed to be in $PATH).