[Tor-BSD] Kernel crashes FreeBSD 11

[Christian Sturm]

On 05/15/2017 13:52, Paul wrote:
> I am running Exits on Tor 0.2.9.10 on FreeBSD 11.0-RELEASE-p9 with rather small RAM.
> It works well apart from the fact that it crashes from time to time leaving one of the following messages in the log:

Is that really a crash of the kernel? What do you see? I'd expect just
Tor to crash or is that what you meant?

I suppose you are running something like a relay or a bridge.

You could/should increase maxfiles, but what else you could do is reduce
the advertised bandwidth. You can do so with the MaxAdvertisedBandwidth
option.

This will reduce the advertised, but not the actually used bandwidth (so
you are not helping less, but more, since your relay will stay up),
which means that you hopefully don't have so many file
descriptors/connections open after changing this.

Indeed running with a low amount of memory isn't good, but right now it
sounds like you only run out of virtual limits, which FreeBSD is very
conservative on by default. Even though you don't have much memory you
should be save to increase it, if you didn't increase it already.

You can compare the output of sysctl kern.maxfiles (which is the limit)
with sysctl kern.openfiles (which is the actual value), to see how close
you are to that limit. You could use that for resetting, as you
mentioned, but I'd suggest to change OS and/or Tor settings instead.

Two more tips if you are running low on memory and are running a relay.

If your relay also acts as a directory mirror, stop doing so. This will
reduce the amount of resources and the network isn't short of them for
now. It also means that your traffic will instead go towards actual Tor
connections, which might be a nice side effect, and generally
recommended for systems with lower resources.

Something that would greatly reduce all kinds of resources is running as
a bridge.

I hope that helped.

Chris

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