Serial console trouble: loader and login works, but no kernel messages

Carl Chave carl at
Sun Aug 23 21:47:20 UTC 2009

Did you try booting with the keyboard disconnected from the FreeBSD
machine?  Perhaps the vidconsole is favored when a keyboard is

On a linux box I had, I would get serial output from Grub, lose it
during kernel load and then get a login once the OS was up, much like
what you describe.  I had to add a kernel argument to my Grub config
so the kernel would output to the serial port.

Did you look here:

I think 7.2 might be what you are missing but I can't check it myself.

On Sun, Aug 23, 2009 at 3:13 PM, Thomas Backman<serenity at> wrote:
> On Aug 23, 2009, at 20:25, Tim Judd wrote:
>> On 8/23/09, Thomas Backman <serenity at> wrote:
>>> First off: Not subscribed to this list, please make sure to Cc me if
>>> you don't reply directly. :)
>>> Anyway, I finally got my null modem cable, and plugged in in between a
>>> machine running 8.0-BETA2 and one running WinXP using Hyperterminal.
>>> My settings:
>>> /boot/loader.conf:
>>> boot_multicons="YES"
>>> boot_serial="YES"
>>> comconsole_speed="115200"
>>> console="comconsole,vidconsole"
>>> /etc/ttys:
>>> # Serial terminals
>>> # The 'dialup' keyword identifies dialin lines to login, fingerd etc.
>>> ttyu0   "/usr/libexec/getty std.115200" vt100   on secure
>>> /boot.config (which is read properly):
>>> -Dh -S115200
>>> Anything wrong in the above?
>>> Hyperterminal is set to 115200 bps, 8 bits, no parity, 1 stop bit, and
>>> no flow control (if that's the correct translation to English).
>>> On the serial console, I go from the screen with the FreeBSD logo,
>>> with single-user options etc. (which works fine), and then nothing,
>>> until a login tty pops up (which also works fine). The main, if not
>>> only, reason I want a serial console is to be able to use it for
>>> single user mode, DDB, and so on.
>>> All kernel messages, and all rc messages are seen only on the graphics
>>> card; the serial console receives nothing but the "/boot.config: -
>>> Dh ...", the logo screen, and then the login screen, during startup
>>> and *nothing* at all during shutdown. Also, I'm able to login and use
>>> the system both via the serial console and via the graphics card/
>>> keyboard... Is this supposed to be? I'm not complaining, I just got
>>> the impression it was one or the other.
>>> Any advice on how to get the kernel/rc messages etc. to the serial
>>> console (only or as well)?
>>> Regards,
>>> Thomas
>> Do you use the VGA/vidconsole at all?
>> A serial-only device (think soekris, ALIX/WRAP boards) that has no VGA
>> will have different requirements than a serial-only device will.
>> Your loader.conf statements are different than mine in the definition
>> that you have more than I do to enable serial.
>> My loader.conf just has one statement:
>>  console="comconsole"  - to feed ALL bootloaders, kernel probing, rc
>> startup on the serial device.  /etc/ttys defines the login lines.
>> Though trial and error, I found when you use a dual-setup:
>> "comconsole,vidconsole", the first one (comconsole) will get rc
>> output, and vidconsole won't.
>> Of course, you're on 8.0 and I don't run BETAs.  So the 8.0 BETA might
>> still be having com port oddities, plus I noticed your ttys line is
>> ttyu0, not ttyd0.  Did 8.0 change the serial line device?
>> To enable a serial-only device in my setups:
>> /boot/loader.conf:
>>  console="comconsole"
>> /boot.config:
>>  -D
>> /etc/ttys:
>> # enable serial line, cons25 or vt100, depending if I'm originating
>> from a bsd or windows box.
>> Enabling dual-setups should be just the loader.conf change to dual
>> console.
>> HTH
> (Sorry for the lack of inline replies.)
> I do have a graphics card, and ideally I'd like to be able to use both, but
> serial has higher priority (with serial access, I can use minicom on another
> *nix box and essentially ssh into DDB, and stuff like that - right now I
> have to borrow a monitor, and write info down manually if needed, turning my
> head back and forth).
> I've tried lots of combinations of console=, including simply
> 'console="comconsole"' and/or combinations of that and -D, -h- -Dh and -P in
> /boot.config.
> The extra lines in loader.conf are from the handbook, which says they're
> needed to use comconsole_speed. It seems they do the same thing as -D and
> -h, though.
> Oh, and re: /etc/ttys: Yup, it's ttyuX when using uart(4) which seems to be
> the default now. Actually, since my last buildworld half an hour ago I'm on
> 9.0-CURRENT. ;)
> Also, I made sure to set flags to 0x10 for the serial port as per the
> handbook (although I did it using loader.conf, not the kernel config);
> before the change, dmesg didn't mention any flags, but it now does. Didn't
> help squat, though.
> "Though trial and error, I found when you use a dual-setup:
> "comconsole,vidconsole", the first one (comconsole) will get rc
> output, and vidconsole won't."
> This doesn't mirror my experience; comconsole and comconsole,vidconsole
> appears to be just the same for me. I've never gotten anything except the
> boot loader and a login prompt over to the serial line - at least not at
> speed/settings that the client is set up to receive.
> I'm gonna try 9600 bps soon just to be sure it isn't that, but seeing how
> many others have mentioned using "-S115200" I doubt it'll help.
> Thanks/regards,
> Thomas
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