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Date:      Sun, 26 Jan 2020 21:22:18 -0800
From:      Ihor Antonov <ihor@antonovs.family>
To:        freebsd-questions@freebsd.org
Subject:   Documentation for sysctl MIBs
Message-ID:  <20200127052218.3icxzqtxnbm6raa3@sea-ll-10936>

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Hi everyone,

Various manuals and FreeBSD Handbook often instruct user to tweak kernel
parameters with sysctl to achieve something. Although the explanation of
what exactly given parameter is doing is often omitted.

As a curious person I don't like to follow manual blindly and I always
try to understand what am I doing. So I started looking for
documentation of sysctl MIB's, hoping that rumors that "FreeBSD is
famous for its good and extensive documentation" will turn out to be
true.

Unfortunately after days of searching and reading the best answer I
could find is sysctl -d 

There is no documented list of MIBs and sysctl -d often gives very brief
one-line explanations, which often create more question. Sometimes there
is no explanation at all:

# sysctl -d hw.acpi.suspend_state
hw.acpi.suspend_state:

I have Absolute FreeBSD book on my table, it also does not provide much
insight into how a user can get more information about sysctl MIBs.

So my question to the community: how do you understand what given MIB is
doing? Where to find more extensive documentation? Is there some kind of
framework that would allow a user to understand when and what needs to
be tweaked (e.g. how to enable powersaving on my wifi card? is this
bootloader tunable? kernel parameter? rc.conf? ...)



P.S. Here are example articles that explain how to get FreeBSD running
on laptops, but what is never explained is how did the author come up
with all these tweaks: 
https://genneko.github.io/playing-with-bsd/hardware/freebsd-on-thinkpad-t480/
https://www.c0ffee.net/blog/freebsd-on-a-laptop/



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