[tor-relays] Question on warnings

[Green Dream]

Hi. Thanks for running a relay. These notice messages are from the
monitoring tool Arm, and should not affect the Tor process.

If you don't care about Arm and Tor seems to be working okay otherwise, you
could safely ignore these messages. In case you want to look into them
further, I'll share some thoughts below. It looks like you're running on a
Unix or Linux system, I'll assume Debian or Ubuntu for the moment.

> 20:42:57 [ARM_NOTICE] Unable to prepopulate bandwidth information
> (unable to read the state file)


This is normal in my experience. Arm is trying to read your node's
bandwidth history to populate the graphs with data collected before you
started Arm. I don't know why it fails, but you could squelch it by adding
the following config line to ~/.arm/armrc:

  features.graph.bw.prepopulate false


> 20:42:56 [ARM_WARN] Unable to read tor's log file:
> /var/log/tor/log [1duplicate hidden]


It looks like Arm doesn't have permission to read /var/log/tor/log. I
normally start Arm with something like this, so it has the same permissions
as the Tor daemon:

  sudo -u debian-tor arm


> 20:42:56 [ARM_NOTICE] Tor is preventing system utilities like netstat
>  and lsof from working. This means that arm can't provide you with
> connection information. You can change this by adding
> 'DisableDebuggerAttachment 0' to your torrc and restarting tor. For
> more information see... https://trac.torproject.org/3313


You need to add the following to /etc/tor/torrc if you want to utilize all
the features of Arm:

  DisableDebuggerAttachment 0

It's disabled by default for security (with a value of '1'), so think
carefully before doing this. It "reduces security by enabling debugger
attachment to the Tor process. This can be used by an adversary to extract
keys." (Quoting from https://trac.torproject.org/projects/tor/ticket/13880).
If you do enable the deubgger attachment for Arm, make sure your control
port is locked down (not reachable from the Internet or from other hosts
you don't control, etc.)
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