Re: dmesg content lifetime

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

> 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
>>