Date: Tue, 22 Nov 2022 11:25:02 -0800 (PST) From: "Rodney W. Grimes" <freebsd-rwg@gndrsh.dnsmgr.net> To: Mike Karels <mike@karels.net> Cc: Dan Mack <mack@macktronics.com>, Warner Losh <imp@bsdimp.com>, freebsd-current@FreeBSD.org Subject: Re: dmesg content lifetime Message-ID: <202211221925.2AMJP2jT054228@gndrsh.dnsmgr.net> In-Reply-To: <21FB93B6-708F-4E69-B482-C7601C15394A@karels.net>
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> 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 <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? > >>> > >> > >> It already is a fixed memory size. Do you see it all disappear at once, or > >> over time? > >> > >> Warner > >> > > > -- Rod Grimes rgrimes@freebsd.org
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