[tor-relays] Correctly setting up arm

[Roger Dingledine]

On Mon, Sep 22, 2014 at 09:34:40PM +0100, Chris Whittleston wrote:
> Previously, I've run arm using 'sudo -u debian-tor arm'. As was mentioned
> here previously, this is not how you should run it - in fact there is a bit
> of documentation to suggest how it should be done.

Yep. See https://trac.torproject.org/projects/tor/ticket/10700
for the discussion.

> Unfortunately I'm having
> some issues getting arm working correctly as described here in step 14:
> 
> https://www.torproject.org/docs/tor-relay-debian.html.en#after
> 
> Having added my user (pi) to the debian-tor group, I try to run 'arm' and
> get the following:
> 
> Failed to read authentication cookie (permission denied):
> /var/run/tor/control.authcookie

What Tor version are you using? There was a bug in Tor 0.2.5.1-alpha
through 0.2.5.6-alpha that broke cookie auth for this situation:
https://trac.torproject.org/projects/tor/ticket/12864
It is fixed in 0.2.5.7-rc.

> I've tried reinstalling arm, relogged and checked that I'm in the right
> group still using 'groups' (which I am) - no joy.
> 
> CookieAuthentication wasn't initially enabled, turning it on makes no
> difference, I get the same error.

As Grace pointed out, torrc isn't the only config file that your
Tor deb uses.

> Am I missing something when it comes to setting up CookieAuthentication? I
> guess I must be...although it seems strange that I was getting that error
> even with CookieAuthentication disabled.

If the Tor version hint doesn't do it for you, I'm not sure what the
next step is. Hopefully it does. :)

--Roger