From nobody Tue Nov 22 15:47:10 2022
X-Original-To: freebsd-current@mlmmj.nyi.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
	by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4NGpYL57Zjz4hwPL
	for <freebsd-current@mlmmj.nyi.freebsd.org>; Tue, 22 Nov 2022 15:47:34 +0000 (UTC)
	(envelope-from mack@macktronics.com)
Received: from mail.macktronics.com (coco.macktronics.com [209.181.253.65])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(Client did not present a certificate)
	by mx1.freebsd.org (Postfix) with ESMTPS id 4NGpYL4kH7z4Ql2
	for <freebsd-current@freebsd.org>; Tue, 22 Nov 2022 15:47:34 +0000 (UTC)
	(envelope-from mack@macktronics.com)
Authentication-Results: mx1.freebsd.org;
	none
Received: from olive.macktronics.com (unknown [209.181.253.67])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mail.macktronics.com (Postfix) with ESMTPS id E47021D0;
	Tue, 22 Nov 2022 09:47:10 -0600 (CST)
Date: Tue, 22 Nov 2022 09:47:10 -0600 (CST)
From: Dan Mack <mack@macktronics.com>
To: Alexander Kabaev <kabaev@gmail.com>
cc: freebsd-current@freebsd.org
Subject: Re: dmesg content lifetime
In-Reply-To: <20221122104445.4ed88f6f@kan>
Message-ID: <c4272589-572a-26a1-7e1e-6ffbe66fc615@macktronics.com>
References: <9d519f-ce87-72d-dc6-789817468974@macktronics.com> <20221122104445.4ed88f6f@kan>
List-Id: Discussions about the use of FreeBSD-current <freebsd-current.freebsd.org>
List-Archive: https://lists.freebsd.org/archives/freebsd-current
List-Help: <mailto:freebsd-current+help@freebsd.org>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Subscribe: <mailto:freebsd-current+subscribe@freebsd.org>
List-Unsubscribe: <mailto:freebsd-current+unsubscribe@freebsd.org>
Sender: owner-freebsd-current@freebsd.org
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
X-Rspamd-Queue-Id: 4NGpYL4kH7z4Ql2
X-Spamd-Bar: ----
X-Spamd-Result: default: False [-4.00 / 15.00];
	REPLY(-4.00)[];
	ASN(0.00)[asn:209, ipnet:209.181.252.0/23, country:US]
X-Rspamd-Pre-Result: action=no action;
	module=replies;
	Message is reply to one we originated
X-ThisMailContainsUnwantedMimeParts: N

On Tue, 22 Nov 2022, Alexander Kabaev wrote:

> On Tue, 22 Nov 2022 09:12:28 -0600 (CST)
> Dan Mack <mack@macktronics.com> wrote:
>
>> It seems like dmesg content ages out over time.   Is there a way to
>> leave the contents based on a fixed memory size instead?
>>
>> Dan
>>
> I think this is how it works: the kernel message bugger is of fixed
> size and kernel and syslog sequences (dmesg -a) share it. The other
> syslog users eventually puts enough content in there to displace all of
> kernel messages. If the kernel stays quiet, 'dmesg' then returns
> nothing, as by default it filters syslog entries that do not KERN
> facility out, see sbin/dmesg/dmesg.c.
>
> -- 
> Alexander Kabaev
>

Thank you Alexander, I did not know this.  I'll USL (use-the-source-luke) 
:-)

Dan