How does dmesg(8) information survive a reboot ?

Lowell Gilbert freebsd-questions-local at
Thu Jul 20 12:33:49 UTC 2006

"Ricardo Branco" <goabranco at> writes:

> I've just tried this Frenzy Live-CD at a few
> hours ago. It's based on FreeBSD 6.1-STABLE. Then I rebooted into my
> FreeBSD 6.1-RELEASE box and suddenly dmesg(8) now outputs the content
> from the previous 2 sessions with the live-CD and my current session
> with the one I have installed. This is great. I have seen those
> "Rebooting..." lines but I've always thought they were written to
> /var/log/dmesg* right before the actual reboot with dmesg(8) somehow
> retrieving them at the next boot. What is the black magic here?

It's just a memory buffer.  I very much doubt you would see the
carry-over between boots if you were doing a cold shutdown rather 
than a warm reboot...

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