[juneau-lug] Re: capturing kernel messages

  • From: "Stephen E. Bodnar" <sbodnar@xxxxxxx>
  • To: juneau-lug@xxxxxxxxxxxxx
  • Date: Wed, 07 Jun 2006 21:58:55 -0800

You can set different levels to dmesg to get it more or less verbose.

 From the dmesg manpage:

dmesg [ -c ] [ -n level ] [ -s bufsize ]

-nlevel

Set the level at which logging of messages is done
to  the  console.   For  example,  -n  1 prevents
all messages, expect panic messages, from appearing
on the console.  All levels of messages are still
written to /proc/kmsg, so syslogd(8) can still be
used to control exactly where kernel messages appear.
When  the  -n option  is  used,  dmesg will not print
or clear the kernel ring buffer.

When both options are used, only the last option on
the  command line will have an effect.

Cheers,
  Stephen


>I track Debian testing, and so things break from time to time in small ways.
>
>I particularly notice that while booting, there are error messages that don't
>make it into dmesg.  This happened a lot after a major udev upgrade, and I
>had to change the syntax on some files.  Some of the errors were shown, but
>others I noticed while watching the machine boot and noting them on paper (if
>they didn't scroll by too quickly).
>
>It is almost as if the dmesg is just capturing standard output, and not
>standard error.  Modules and drivers that send their errors to standard out
>get logged, the ones that go to standard error don't.  (I'm not really a
>kernel guy, I'm just guessing this is what is happening.)
>
>Anyone know of a way to log ALL of the kernel messages displayed on screen
>during boot?
>
>James
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