From nobody Tue Nov 22 19:25:02 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 4NGvNT2Yc4z4hNmF for ; Tue, 22 Nov 2022 19:25:13 +0000 (UTC) (envelope-from freebsd-rwg@gndrsh.dnsmgr.net) Received: from gndrsh.dnsmgr.net (br1.CN84in.dnsmgr.net [69.59.192.140]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4NGvNS4sV9z3wkP for ; Tue, 22 Nov 2022 19:25:12 +0000 (UTC) (envelope-from freebsd-rwg@gndrsh.dnsmgr.net) Authentication-Results: mx1.freebsd.org; none Received: from gndrsh.dnsmgr.net (localhost [127.0.0.1]) by gndrsh.dnsmgr.net (8.13.3/8.13.3) with ESMTP id 2AMJP2Nx054229; Tue, 22 Nov 2022 11:25:02 -0800 (PST) (envelope-from freebsd-rwg@gndrsh.dnsmgr.net) Received: (from freebsd-rwg@localhost) by gndrsh.dnsmgr.net (8.13.3/8.13.3/Submit) id 2AMJP2jT054228; Tue, 22 Nov 2022 11:25:02 -0800 (PST) (envelope-from freebsd-rwg) From: "Rodney W. Grimes" Message-Id: <202211221925.2AMJP2jT054228@gndrsh.dnsmgr.net> Subject: Re: dmesg content lifetime In-Reply-To: <21FB93B6-708F-4E69-B482-C7601C15394A@karels.net> To: Mike Karels Date: Tue, 22 Nov 2022 11:25:02 -0800 (PST) CC: Dan Mack , Warner Losh , freebsd-current@FreeBSD.org X-Mailer: ELM [version 2.4ME+ PL121h (25)] List-Id: Discussions about the use of FreeBSD-current List-Archive: https://lists.freebsd.org/archives/freebsd-current List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-current@freebsd.org MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 4NGvNS4sV9z3wkP X-Spamd-Bar: ---- X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:13868, ipnet:69.59.192.0/19, country:US] X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-ThisMailContainsUnwantedMimeParts: N > On 22 Nov 2022, at 9:34, Dan Mack wrote: > > > It disappears a piece at a time - the oldest entries disappear first. However, it vanishes even when there are only 2-3 lines in it so I didn't think capacity was in play as I expected. > > > > So for example I might see a rate-limit entry from someone spamming the system and then it will usually be gone in a couple days and the buffer is completely empty. Similarly if I do something like ifconfig em0 down; ifconfig em0 up ; it's logged but disappears after a day or so. > > > > I'm looking to see if this is just a cron job or something clearing it as it might be user-error on my part. Also this is an older system so I'll probably look at it again after I update. > > I noticed this too, but discovered with ?dmesg -a? that the buffer was full > of syslog messages, so dmesg without -a showed nothing. > > It seems unfortunate that syslog messages logged in the message buffer, at > least once syslogd is running. Apparently this happens because they are > output to /dev/console. > > Mike I very much dislike this behavior. I though that the kernel dmesg buffer was for kernel messages only and that I could always count on going there for any kernel messages about a problem that has occurred, expecting to see my boot time output if nothing had happened since boot. Now instead I am almost always greated with an empty buffer :-(. Rod > > > Thank you, > > > > Dan > > > > > > On Tue, 22 Nov 2022, Warner Losh wrote: > > > >> On Tue, Nov 22, 2022 at 8:13 AM Dan Mack 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? > >>> > >> > >> It already is a fixed memory size. Do you see it all disappear at once, or > >> over time? > >> > >> Warner > >> > > > -- Rod Grimes rgrimes@freebsd.org