[ On , June 6, 1998 at 09:29:58 (-0400), rvb@sicily.odyssey.cs.cmu.edu wrote: ]
> Subject: serial console
>
> I've been playing with the serial console for a few days --
> it's really neat.   But I have a few suggestions.  The problem
> was layed out in mail a few months back.  I would really like
> "main" to a initio(CONSDEV_AUTO) to look for any serial line
> and fall back to the pc keyboard by default if nothing is 
> listening on a serial line.

You mention laptops, which probably don't have an easy way to disconnect
the keyboard (unless perhaps it's an IBM ThinkPad), but for 99% of other
situations I think it makes more sense to probe for a keyboard, and if
none is found then assume that a specified serial port will be the
console.  It should not matter if there's a terminal attached at the
moment, or not, and any RS232 console worth its salt will have 6+8+20
wired back so that it appears as a local terminal and there'll be no way
to "sense" if there's anything "listening".

I don't know how it compares because I've only ever used it on serial
console machines, but I think the FreeBSD serial console support is
excellent (and it would seem it doesn't compare at all).  In FreeBSD's
boot(8), at least in their -stable version, there's support for a
"/boot.conf" file in which default runtime command-line options for the
boot program can be specified.  One combination of those options will
cause the boot program to probe for a keyboard, and if one is found then
both the serial port and the keyboard & display will get the boot
message and prompt, and if the user types on one or the other it'll
become the boot device, otherwise the specified default is chosen
(normally one would default to the serial port).  Of course if a
keyboard is not connected then you boot only on the serial console.

This makes the most sense for a server which may be connected to a
serial console server or even a serial switch, but which may also
optionally have a keyboard connected (possibly also through a switch)
for maintenance mode when you need to get to the stupid BIOS which won't
support a serial console.

-- 
							Greg A. Woods

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