Date: Wed, 21 Mar 2001 10:24:53 +0100 (CET) From: Noel Koethe <noel@koethe.net> To: Thomas Moestl <tmoestl@gmx.net> Cc: freebsd-stable@freebsd.org Subject: Re: dmesg output Message-ID: <Pine.LNX.4.21.0103211020470.13790-100000@data.wipol.uni-bonn.de> In-Reply-To: <20010320181117.A2347@crow.dom2ip.de>
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On Tue, 20 Mar 2001, Thomas Moestl wrote: Hello Thomas, > > Why it is here normal on one machine and cutted on the other? > > And why does it work before ( I'm sure in December it doesn't work like > > now )? > > OK, I'll go into details a little more. Not too long ago, a patch was > MFCed that allows logging console output. To allow this, this ouput is > written into the kernel message buffer, where it can be picked up by > syslog using the /dev/klog interface. Normal kernel output is written > to the message buffer as is, while console output is prefixed with a > string in the form "<category>", where category is a number (118 in > this case, LOG_CONSOLE|LOG_INFO). dmesg will ignore messages that > start with such a string indicating that the message didn't come from > the kernel unless it is invoked with the -a option. If syslogd is > configured to echo some messages to the console, those messages will > be appended to the kernel message buffer, and if this happens too > often, this will overwrite all the kernel messages. A common situation > is that a lot of kernel messages are generated that fill up the message > buffer, syslog snarfs those a little later, writes them to the console > and thus overwrites the original kernel messages in turn. dmesg > will show nothing in this case, or, more often, a line that came from > the console, but of which the first character(s) were overwritten by a > new message (they don't start with a "<number>" magic string then, and > dmesg will print them). > So, dmesg will work as expected on machines that didn't generate > enough messages yet, or on systems from before the MFC. Thanks for this long explanation. Maybe the daily "security check output" will be correct: host.domain.de kernel log messages: > ia tun0 Again. Thanks for your answers. -- Noch einen schoenen Tag Noel To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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