Bug#481597: dpkg-reconfigure exim4-config does not recognize changed hostname

[Marc Haber]

On Wed, Jun 04, 2008 at 04:27:34PM +1000, Andrew Vaughan wrote:
> On Sunday 25 May 2008 18:42, Marc Haber wrote:
> > On Sat, May 24, 2008 at 04:44:27AM +1000, Andrew Vaughan wrote:
> > > On Saturday 24 May 2008 02:43, Marc Haber wrote:
> > > > On Sat, May 17, 2008 at 07:34:22PM +1000, Andrew Vaughan wrote:
> > > > > I changed the hostname on my home server.  I changed /etc/hostname
> > > > > and /etc/mailname, rebooted and ran dpkg-reconfigure exim4-config
> > > > > thinking that that should be enough to get exim configured for the
> > > > > new hostname.
> > > >
> > > > Did you also change your /etc/hosts?
> > >
> > > No, but the new hostname is listed as an alias (and has been for 2
> > > years).
> > >
> > > Experimenting shows that this does seem to the the problem.
> >
> > Yes, it is. Exim tries to determine its FQDN on startup to be able to
> > correctly process the @ macro. Without /etc/hosts, the FQDN cannot
> > be correctly obtained since /etc/hostname only sets the unqualified
> > host name.
> 
> I wasn't even aware that the local machine should be listed in /etc/hosts.

It should. A lot of daemons rely on the local host name being
resolveable before the network is brought up.

> I note that if I remove that line, dpkg-reconfigure exim-config will happily 
> complete, but that question 5 shows that exim-config doesn't know what the 
> local hostname is.  (Something complains "hostname: Unknown host", but 
> exim-config doesn't seem to actually care about the error.)

Oh, interesting. Thanks for spotting this, fixed in svn (it is
actually only an error message that is not sent to /dev/null before
properly handling that case).

> I guess that the FQDN at startup can legitimately be different from the FQDN 
> at debconf question 3, otherwise you wouldn't be asking question 3.  

The debconf questions do not have numbers (and it depends on your
answers to previous questions wether they are asked or not, so the
numbers are in fact meaningless). Which question wording do
you mean?

> In this case it simply occurred to me that a machine accepting mail for all 
> of its hostname aliases would possibly be a reasonable default config, and 
> is potentially desirable.  

Not, it is not desireable in the general case.

> If exim were to attempt to notify root of email problems, it should try to 
> avoid letting the notification also get stuck.

That is very very hard to do.

> > If you want to be notified about stuck messages, use eximstats on a
> > regular basis and/or install a log management/check package.
> >
> I don't want to be running such checks manually.  But unless I'm missing 
> something, I can't think of an easy way to automate such checks that would 
> work when exim fails to deliver mail from cron?

Neither can I, especially if it's necessary to have this as a general
mechanism. Debian doesn't have such a mechanism.

> Thanks for your help.  Feel free to close and/or downgrade this bug if you 
> won't/can't make exim/exim-config more robust against this type of 
> mis-configuration, and don't see any other issues from what I wrote above.

I'll take care of that during next bug triage.

Greetings
Marc

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