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

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