Date: Tue, 22 Nov 2022 15:03:50 -0600 (CST) From: Ted Hatfield <ted@io-tx.com> To: "Rodney W. Grimes" <freebsd-rwg@gndrsh.dnsmgr.net> Cc: Mike Karels <mike@karels.net>, Dan Mack <mack@macktronics.com>, Warner Losh <imp@bsdimp.com>, freebsd-current@FreeBSD.org Subject: Re: dmesg content lifetime Message-ID: <8e999d31-e37f-7cda-509e-cf1d83fc9fca@io-tx.com> In-Reply-To: <202211221925.2AMJP2jT054228@gndrsh.dnsmgr.net> References: <202211221925.2AMJP2jT054228@gndrsh.dnsmgr.net>
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On Tue, 22 Nov 2022, Rodney W. Grimes wrote: >> 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 > It's been this way for as long as I can remember. Decades probably. Ted >> >>> 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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