Date: Thu, 19 Jan 1995 01:54:48 -0500 (EST) From: Wankle Rotary Engine <wpaul@skynet.ctr.columbia.edu> To: freebsd-hackers@FreeBSD.org Subject: More serial console stuff... Message-ID: <199501190654.BAA00363@skynet.ctr.columbia.edu>
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Okay, I think I'm almost ready to actually commit the serial console
stuff to the boot blocks and kernel. ("Hide the kids! He's going to
commit!") But I've got a couple small things I need to ask about before
taking the plunge:
First, there's one thing I always do to the boot blocks when I do an
installation, which is to change the way 'unit' is calculated. Normally
it says this:
part = unit = 0;
This always forces unit 0 to be the default, which screws up autobooting
on my system because my root disk is unit 1 (wd1). The change I always
make is:
part = 0;
unit = (drive & 0x7F);
This automagically sets the unit to 0 or 1 accordingly. I've seen this
bandied about on the newsgroups, but I've often wondered why it never
became official. My guess is that this causes other problems that I'm
not aware of (which are undoubtedly related to SCSI disks, which I don't
have.) I'm tempted to sneak this in while I'm in the neighborhood, but
first I want to find out if this hack was already rejected for a reason.
Second, there are incidental problems involved with booting with a serial
port as a console. For one thing, you have to remember to edit /etc/ttys
properly before you bring the system up multi-user for the first time, or
you won't get a login prompt. Newbies aren't likely to be able to
figure this out, so I want to idiot-proof it for them. What I want to do
is change the default /etc/ttys, but I'm not sure exactly how to go
about it. I can either add another getty entry for 'ttyd0' or put a getty
on 'console'. Each of these options has its own problems.
The latter idea means turning off the getty on 'ttyv0,' otherwise
there would be two gettys on the same terminal in the case where you
boot in VGA console mode. The former costs you another getty process
for a terminal device that might not be used at all (the newbie has
to figure out how to turn it off too -- serial port questions galore).
Putting a getty on 'console' is really the nice way to do it, but
there are a few small complications:
- the getty on /dev/ttyv0 has to go away. This means that if you boot
from the VGA console but force the kernel to use a serial console,
ttyv0 winds up missing in action. Fixing it is simple: you just need
to edit /etc/ttys to suit your system, but again: newbies ahoy.
- the default terminal type can't be 'cons25' and 'vt100' (or whatever)
at the same time. Leave it set to cons25, and booting from a VT-100
terminal doesn't work quite right. Make it vt100, and syscons gives
you grief. SunOS has the same problem and there really isn't a fix:
it's up to the user/admin to edit /etc/ttys (/etc/ttytab in SunOS)
to take care of this. All aboard the newbie express.
- ps and w get confused (w especially): I don't know how many of you
have noticed this, but if you actually edit /etc/ttys and replace
'ttyv0' with 'console' (which should be allowed), ps still says that
your tty is 'v0' (it should say 'co'). w gets into trouble too, with
the result being that it fails to show the commands being run by the
user on the console because it can't match 'co' (which it gets from
utmp) with any active terminal devices. I haven't even begun to
look into the cause of this. Lobotomizing the kernel seems
unavoidable. ("You're on a bus hacking at 50 miles an hour and
you're trying to juggle a dozen different system configuration
details at once. If you mess one of them up, the newbies start
pestering you with questions. What do you do? WHAT DO YOU DO?!" :)
Anyway, I'm rambling. Quick summary: why the hardcoded unit number
in the boot blocks, and does anyone have any suggestions about how
to deal with /etc/ttys?
-Bill
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~T~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Bill Paul (212) 854-6020 | System Manager
Work: wpaul@ctr.columbia.edu | Center for Telecommunications Research
Home: wpaul@skynet.ctr.columbia.edu | Columbia University, New York City
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Møøse Illuminati: ignore it and be confused, or join it and be confusing!
~~~~~~~~ FreeBSD 2.1.0-Development #0: Fri Jan 13 22:04:07 EST 1995 ~~~~~~~~~
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