In-Reply-To: <200603141216.23335.gene.heskett@verizon.net>
References: <200603140901.27746.cijoml@volny.cz> <20060314083812.GA27338@brainysmurf.cs.umu.se> <4416DBC2.8000103@cfl.rr.com> <200603141216.23335.gene.heskett@verizon.net>
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Cc: LKML Kernel <linux-kernel@vger.kernel.org>,
       Phillip Susi <psusi@cfl.rr.com>, CIJOML <cijoml@volny.cz>,
       Peter Hagervall <hager@cs.umu.se>
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From: Kyle Moffett <mrmacman_g4@mac.com>
Subject: Re: Dmesg is not showing whole boot list
Date: Tue, 14 Mar 2006 12:28:49 -0500
To: Gene Heskett <gene.heskett@verizononline.net>
Sender: linux-kernel-owner@vger.kernel.org
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On Mar 14, 2006, at 12:16:23, Gene Heskett wrote:
> On Tuesday 14 March 2006 10:05, Phillip Susi wrote:
>> Or look in your /var/log/kern.log file instead of asking dmesg.   
>> dmesg just dumps the kernel ring buffer which is of finite size.   
>> The entire contents should be logged to /var/log/kern.log.
>
> You've got to have /var checked and mounted to be able to do that  
> log write, if the buffer overflows before that, then the head end  
> of the dmesg dump to the /var/log/dmesg file is lost forever.
>
> There is a line that can be changed, in xconfig or by hand, to  
> control the memory allocated for this ring buffer.
>
> Finally found it in the xconfig display, left panel line=kernel  
> hacking, right panel its under kernel debugging and shows only if  
> thats checked, double click on the line that says : kernel log  
> buffer size and enter a one digit increment from whats there now,  
> maybe 2, I have mine set for 16.  Your default may be as low as 14,  
> why I have NDI because 16k sure as heck isn't enough if something  
> gets chatty.

To continue this point; on my desktop I have root/var/tmp/vicepa-on- 
LVM-on-RAID5, boot-on-RAID1, and swap-on-RAID1, so I would easily  
overflow the default SMP dmesg buffer size in messages well before  
syslogd/bootlogd got started.  I finally ended up having to increment  
the default by 3 in order to have the boot messages still available  
after booting.  It would be nice if we could quiet down some of the  
more excessively verbose kernel messages, there's a lot of mostly- 
irrelevant spew that chews up log buffer space.

Cheers,
Kyle Moffett
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