Re: [exim] Fixing IPV6 network is unreachable error messages

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Author: Phil Pennock
Date:  
To: Thomas Leavitt
CC: exim-users
Subject: Re: [exim] Fixing IPV6 network is unreachable error messages
On 2013-03-29 at 12:23 -0700, Thomas Leavitt wrote:
> When I add either this: disable_ipv6, or dns_ipv4_lookup, I get "not found".
> usr/sbin/update-exim4.conf: 33: /etc/exim4/update-exim4.conf.conf:
> disable_ipv6: not found


Where are you adding those? "disable_ipv6" and "dns_ipv4_lookup" are
main section configuration options, the first is a boolean and the
second is a domain-list, so you might set it to "*" to match all
domains, but I recommend "disable_ipv6" as the better approach of the
two.

> I've dug through Google thoroughly, and don't see any reference to this,
> nor do I see any instructions in the Exim4 documentation or on the wiki.


Go to <http://www.exim.org/> and look near the top to find a search box
which says "Search Docs" inside it. Type IPv6 into that, and the first
result is:

http://www.exim.org/exim-html-current/doc/html/spec_html/ch-starting_the_daemon_and_the_use_of_network_interfaces.html

You'll quickly get to "Disabling IPv6" within that. If there's anything
more we can do to aid discoverability, I'm interested in hearing
suggestions.

> I'm not an expert at Exim4 by any means... I'm guessing that there's some
> stanzas in a template somewhere that are missing that refer to this? Do
> they need to be added to the exim4.conf.template file?
>
> ... as I wrote this, I did one final Google search and located a forum
> thread from 2005 that says simply delete any IPv6 addresses from the
> "dc_local_interfaces" line... and discussed this whole not very obvious
> issue in detail.


If you need to use "dc_*" options, then you're using the configuration
layer added by Debian; nothing dc_* is part of Exim as supplied by the
Exim Maintainers. None of our documentation covers a system which we
don't provide; we do try to provide some pointers towards accurate
resources, and can probably do better here. Seriously: suggestions
welcome.

You should probably take a look at /usr/share/doc/exim4/README.Debian.gz
on your system, to understand what's happening. The configuration file
supplied by Exim is available on Debian/Ubuntu as:

/usr/share/doc/exim4/examples/example.conf.gz

and looking at that may help in developing a more accurate mental model
of what our documentation is talking about. Everything before the first
"begin" line ("begin acl" in this case) is the "main" section, where the
disable_ipv6 option belongs.

If you run "exim --version" (or "exim -bV") then the last line will tell
you the path to the configuration file as used by Exim itself. That
might be "/var/lib/exim4/config.autogenerated" for instance. Looking at
that file will tell you whether the configuration changes made by you
propagated to the configuration file used by Exim, when you told your
system to regenerate the configuration file.

Regards,
-Phil