No kernel messages displayed during boot

Jeremy Chadwick koitsu at
Mon Nov 19 06:47:53 PST 2007

On Mon, Nov 19, 2007 at 09:24:01AM +0100, Dmitry Karasik wrote:
>  Jeremy> On Sun, Nov 18, 2007 at 08:01:59PM +0100, Dmitry Karasik wrote:
>  >> I've re-run 'make installworld' and 'make installkernel' (as I had
>  >> leftovers from recent buildworld), - didn't help. I've tried to power
>  >> down the machine (suspecied video card trouble), I've resetted BIOS,
>  >> I've even disabled com port in BIOS (because the behavior looks like
>  >> booting on serial console) -- nothing, absolutely nothing changes it.
>  Jeremy> conscontrol(8) might help here ("conscontrol list").  Also worth
>  Jeremy> looking at is sysctl kern.console.
> Hello Jeremy,
> Thanks, at least this is a hint. That shows on my system:
> $ conscontrol list
> Configured: 
> Available: 
> Muting: off

Hmm, it looks as if the system doesn't have any indication of what the
local console is.  I would expect to see a "consolectl" listed under
the "Configured:" section.  See below for some of the output from our

> and sysctl kern.console is / (not that I know what that means).

I believe the sysctl is a comma-delimited list of what consoles are
configured and available/unused.  The "/" splits what's a configured
console and what's available/unused.  I bet conscontrol(8) just parses
the sysctl output, but I'd have to look at the code.

> $ conscontrol add /dev/console
> conscontrol: could not add console as a console: Device not configured
> $ conscontrol add /dev/consolectl 
> conscontrol: could not add consolectl as a console: Device not configured
> Is that the expected behavior? What else I might try?

I'm betting that's not expected behaviour.  :-)  It seems to indicate
the system has no knowledge of what the system console is.

Here's some data for comparison:

Our RELENG_6 systems which use serial console, and have a /boot.config
of -S115200 -Dh on them show the following:

eos# conscontrol list
Configured: ttyd0,consolectl
 Available: ttyd0,consolectl
    Muting: off
eos# sysctl kern.console
kern.console: ttyd0,consolectl,/ttyd0,consolectl,

And a RELENG_7 box with serial console (same /boot.config as above):

northstar# conscontrol list
Configured: ttyd0,consolectl,gdb
 Available: consolectl,gdb,ttyd0
    Muting: off
northstar# sysctl kern.console
kern.console: ttyd0,consolectl,gdb,/consolectl,gdb,ttyd0,

A RELENG_7 box with no serial console (no /boot.config):

icarus# conscontrol list
Configured: consolectl
 Available: consolectl,gdb,ttyd0
    Muting: off
icarus# sysctl kern.console
kern.console: consolectl,/consolectl,gdb,ttyd0,

| Jeremy Chadwick                                    jdc at |
| Parodius Networking                  |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |

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