cd /tmp. Unzip some file with some system image - usr, etc, lib, the usual - that should be unpacked in /. Do what needs to be done. rm -fr /usr. WAIT, NO! ^C. "Backup, could you be so kind as to restore the ABC server /usr tree? I think I made a huge mistake. Thank you."

Good times. Learned a lot about why I need a VM with an image of a given system.