I nuked &#x2F;usr on one of my servers for cleaning purposes some 5-6 years ago when I was still quite fresh to Unix. After reboot, I was unable to log in even as root. That was the day I learned not to change the shell of root to anything outside of &#x2F;bin (I had set it to &#x2F;usr&#x2F;bin&#x2F;bash).<p>I was able to recover the machine with a LiveCD but still, it was annoying.