RE: MTA packaging (exim, postfix, sendmail, ssmtp)

["Pierre A. Humblet" <Pierre dot Humblet at ieee dot org>]

> -----Original Message-----
> From: Christian Franke
> Sent: Wednesday, October 08, 2014 12:32
> 
> Yaakov Selkowitz wrote:
> > On 2014-10-08 07:52, Corinna Vinschen wrote:
> >> On Oct  6 17:19, Yaakov Selkowitz wrote:
> >>> Because MTAs must be user-configured, and we certainly don't want to
> >>> lose the selection during package upgrades, the alternatives cannot
> >>> be handled in package postinst/prerm.  I think the only way to make
> >>> this work is for each MTA config script to handle these instead by
> >>> including the following snippets in the respective MTA config
> >>> scripts.
> >>>
> >>> Please review this carefully in case I missed anything.
> >>
> >> The ssmtp part looks ok to me.  Two questions:
> >>
> >> - Don't we have to add something to preremove as well?
> >
> > No, because we don't distinguish between removing and upgrading a
> > package in preremove.  Whenever a user wishes to switch MTAs, they
> > will need to run alternatives --set, preferably via the MTA config
> > scripts.
> 
> The cron package is also affected. Its postinstall script sets a symlink
> /usr/sbin/sendmail -> /usr/bin/cronlog if sendmail does not exist. This
would
> break alternatives setting in MTA configure script because alternatives
would
> never replace the existing symlink.
> 
> Possible workaround: Add rm -f /usr/sbin/sendmail ... to MTA configure
> scripts.

I was going to mention that and suggest to add another alternative in
cron-config 
/usr/sbin/alternatives --install /usr/sbin/sendmail mta /usr/bin/cronlog 0 

That way all cases are treated uniformly.
I don't dispute that it may be safer to rm the old (pre alternatives)
sendmail, mailq, etc links before installing with alternatives 
  
I am fine with the proposal for exim, except that I was not planning to add
rmail, rsmtp, and runq
Those are for compatibility with smail. 
I never included them in the cygwin distribution and nobody  has ever
complained.

Also exim itself can run perfectly fine if the mta alternatives is set to
another mta, except that mailq and sendmail won't call exim.
So in exim-config I was going to present the current mta alternative to the
user, explain the above, and ask if it should be changed.

Pierre