Documentation for sysctl MIBs

[Emilian Ursu]

Hi,

What you're looking for are the man pages that come with the operating system 
which can be consulted using the command # man
The MIB names are suggestive and will clue you in where to look for more
documentation.

For example hw.acpi.suspend_state has to do with hardware and more specifically 
with acpi, so the best place to find information about it would be:
# man acpi

net.inet.ip.intr_queue_maxlen has to do with networking and more specifically
with the ip protocol, so the best place to find information would be
# man ip
# man inet

Some options may not be documented in the man page because they are self explanatory or,
because you need to have some prior knowledge about them.
For example if you want to understand all MIBs in the net.inet.tcp namespace
then you will need to have a complete understanding of the tcp/ip protocol
for which you will find documentation online especially in the RFCs.

In order to find out how to enable powersaving on your wifi card the best place to
start is the man page for your wifi card and also # man ifconfig 
which handles networking.


Regards

On Sun, Jan 26, 2020 at 09:22:18PM -0800, Ihor Antonov wrote:
> 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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