Re: Exim and hostname --fqdn, was Re: mutt attachment error
On Thu 12 May 2016 at 10:08:49 -0500, David Wright wrote:
> On Thu 12 May 2016 at 11:33:10 (+0100), Brian wrote:
> > On Wed 11 May 2016 at 14:51:31 -0500, David Wright wrote:
> > >
> > > BTW when will dpkg-reconfigure exim4-config either stop saying
> > > "hostname --fqdn did not return a fully qualified name, dc_minimaldns will not
> > > work. Please fix your /etc/hosts setup." or suggest a reasonable fix?
> > > Or IOW, why has bug #504427 never even received acknowledgment?
> >
> > It will stop, I suppose, when the user has a correct 127.0.1.1 line in
> > /etc/hosts.
>
> That just begs the question as to what is correct. Refer to:
> https://www.debian.org/doc/manuals/debian-reference/ch05.en.html#_the_hostname_resolution
The -devel thread referred to in #719621 is worth reading. There was no
consensus in it to support the suggestion that 127.0.0.1 is better than
127.0.1.1. The history of resolving local host/domainname goes back many
years and what we have now does just work. For now, the "correct way" is
the present way.
> and check mine over:
Nothing I say is meant to imply I have a deep knowledge of networking on
Debian. :)
[Configuration files snipped]
My nsswitch and hosts.conf are identical to yours and resolv.conf only
differs on this machine in the IP used. The difference is in /etc/hosts.
Mine is
127.0.0.1 localhost
127.0.1.1 desktop.lan desktop
The hosts manual says:
For each host a single line should be present with the following
information:
IP_address canonical_hostname [aliases...]
My canonical hostname is "desktop.lan" and it has the alias "desktop",
the hostname of the machine. 'hostname --fqdn' gives
desktop.lan
because the files method of nsswitch.conf matches the hostname with the
canonical hostname. Exim is happy with this because the fqdn has at
least one dot in it.
You have
127.0.0.1 localhost
127.0.1.1 alum
so the canonical hostname is alum. I'd expect 'hostname --fqdn' to have
no dots in it, so it is not a fully qualified name. Exim will not like
this if you want dc_minimaldns as "Yes".
You can view my "desktop.lan" as being made up (it needn't be) but it
satisfies Exim, as would anything.anything for the canonical hostname.
For Exim and minimaldns the question is
Does the hostname resolve to a fqdn (something with a dot in it)?
127.0.1.1 alum.anything_you_want alum
would do this.
Having said this it as well to realise Exim will HELO to a remote host
with "alum.anything_you_want". Some misguided hosts will deny contact
because there is no reverse lookup which satisfies them. ISP smarthosts
are generally very forgiving (they have to be!) so this is generally not
a problem with sending mail through them.
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