Some older instalations require /usr to be on / for access during boot but I don't think any current dist requires this.

I managed to install Slack 3.? on my 386-25 with a 20MB HD from 4.25" floppies.  It used to route my ppp connection and print serve.
-- 
Marc A. Ohmann
Digital Solutions, Inc
http://ds6.net
marc at ds6.net