Re: kern.boottime drift after boot?

[Simon Burge <simonb%NetBSD.org@localhost>]

RVP wrote:

> On Wed, 11 Oct 2023, Simon Burge wrote:
>
> > RVP wrote:
> >
> >> I think what David's looking for is something akin to Linux's
> >>
> >> /proc/sys/kernel/random/boot_id
> >>
> >> something which only changes on every boot but is otherwise stable.
> >
> > I'm curious how well this boot_id works on Linux for things like a
> > embedded system (eg router) that boots from a ram disk and doesn't have
> > an RTC.  Essentially a similar problem to our long-running entropy
> > discussion.
>
> On embedded systems without an RTC, you _could_ get the same UUID in rare
> cases. But I think this would be a bug, because on Linux, any kind of jitter-
> source (interrupt timing, for instance) would perturb the generated UUID.

Hopefully!  Even though this jitter might not be high entropy, it should
(in theory) be enough to give a differnet UUID each boot.  Assuming of
course that the boot_id is generated after interrupts are enabled and
some jitter has been processed :).

Cheers,
Simon.