/sbin/sulogin depends on libfreebl3, which is installed in /usr; if /usr does not come up on boot, rc.sysinit tries to dump to repair shell and just reboots since sulogin cannot run. Only fix is init=/bin/sh or similar, at that point. (What's worse, there's no chance to even see the error since the system reboots so quickly once sulogin fails.) No other runtime dependency on /usr exists for sulogin. F11 sulogin does not have this dependency (unconfirmed).
/usr/lib{,64}/libfreebl3.so should be in /lib{,64} *** This bug has been marked as a duplicate of bug 552434 ***