FreeBSD hang without panic

[James]

> On the machine itself no messages are shown and the machine responds to
> repeated ENTER key presses with the login prompt.  Once you enter "root"
> [ENTER] then no further responses (except line feeds as you press ENTER).
> 
> What kind of hang is this? Could it be a DoS attack? Or is it some
> internal process hanging?  I have a debug kernel but as the only solution
> is a power-off reset, I never get any dump.
> 
> Any suggestions please where I might start to look, or services to
> experiment disabling?
> 


My very first instinct was hardware failure. It has all the right
pieces: intermittent, came out of nowhere, weird problems as a result.

But. In the interests of science: I know you said  existing shells stop
working, but does that include the secure shell? ssh into the box when
it's frying itself and see what happens.

Presumably you've checked the /var/log stuff already?

James