Dmesg truncated

[Ian Dowse]

In message <18716.153.2.247.31.1102941083.squirrel at www.mddsg.com>, David Ericks
on writes:
>I've been having this problem for quite a whlie but it's never bothered me
>too much until I had some free time on my hand to look into it.  Is there
>any kernel parameter that could be truncating my dmesg buffer.  Dmesg only
>seems to have 1 line ever buffered which kinda sucks.  I do have a custom
>kernel built as thin as possible so im thinking that one of the options I
>may have left out thinking I didn't need it or something along those
>lines.

The message buffer is used to store kernel log messages including
console output as well as "normal" kernel messages; run `dmesg -a'
to get the full message buffer contents.  Typically these other log
messages fill up the buffer so the kernel messages get overwritten.

The logging of console output can be useful at boot time, but is
often less important later since it is often just syslog messages
that are already logged elsewhere. You can arrange for only boot-time
console output to be recorded in the message buffer by adding the
following line to the end of /etc/rc.local, creating that file if
necessary (you could also use /etc/sysctl.conf, but rc.local is
better because it happens a bit later):

	sysctl kern.log_console_output=0

Finally, you can increase the message buffer size by recompiling
your kernel with a custom MSGBUF_SIZE setting.

Ian