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Re: What about default-syslog [Re: new release goal default-mta?]

On Tue, May 05, 2009 at 09:07:34PM +0900, Osamu Aoki wrote:

> On Tue, May 05, 2009 at 11:52:29AM +0100, Roger Leigh wrote:
> > On Tue, May 05, 2009 at 10:36:51AM +0200, Michael Biebl wrote:
> > > martin f krafft wrote:
> > > > [moving debian-release@l.d.o to Bcc, continuing discussion in bug log]
> ...
> > I think it is a problem extending to all virtual packages, and I would
> > like to see a more general solution which is applicable to all.  It
> > might be worth revisiting past discussion, for example this thread:
> > 
> > http://lists.debian.org/debian-devel/2006/08/msg01281.html
> > 
> > (I've CCd -devel and -policy because it's a general issue which should
> > ideally be in policy)
> > 
> > The above discussion proposed a solution like default-mta.  At the time,
> > I also wrote a sample "virtual-default" package which generated these
> > -defaults packages for all virtual packages in the archive.  At the time
> > I held off actually implementing this because Anthony Towns said he was
> > implementing a better method in dpkg itself.  However, I've not seen any
> > more about this other than that single time, and if mta-defaults is being
> > created it looks like we are still looking for a solution.
> A word like "default" tends to create tension.  Extending existing idea
> like "sensible-utils" package for "sensible-*" command wrapper seems to
> be good idea. 

I'm not sure I understand what you mean here.  The sensible-* command
wrappers are wrappers for individual commands.  The above discussion
isn't about default commands, but packages.  For each virtual package,
we (as a distribution) need to choose a default package to provide a
concrete implementation.  It /is/ a default, and I'm not sure I
understand the need to name it differently.  It is always possible for
the system administrator to install any other package also providing
the virtual package, but a default /must/ exist.

> > It would be great if we can have a general method for specifying
> > distribution-wide virtual package defaults, of which
> > mail-transport-agent-default is just one.
> As I read this and looking at our archive, we have:
> Package sensible-mda (Priority: extra)
>     * Packaged by: Richard Nelson <cowboy@debian.org>
>     * Sendmail source package
>     * On and after lenny (stable) (mail): Mail Delivery Agent wrapper
>       used by dspam and sendmail
>       procmail | maildrop | deliver
> Package sensible-utils (Priority: required)
>     * Packaged by: Clint Adams <schizo@debian.org>
>     * Sensible-utils  source package
>     * On and after squeeze (testing) (utils): Utilities for sensible alternative selection
>       these scripts used to be part of debianutils
>       this provides sensible-{browser,editor,pager}
> If a command is expected to be always on the system, integrate it into
> sensible-utils seems good idea ... especially for mta and syslog if
> Clint agrees.
> (If a command is an optional one on the system, create package like
> sensible-mda.)

While it's typically the case that an MTA and system logger are installer,
it isn't /required/.  It also doesn't cover the more general case for
all virtual packages.  Where a package provides a network service, for
example, the common feature between the packages is that they listen
on the same port and talk the same protocol.  A sensible-* command is
not useful in this scenario--the init script, executable binaries etc.
might have nothing in common.

A virtual package provides an implementation of something.  That might be
a command, network service, or any other facility so long as the packages
providing it agree on what the "something" is.  This can only be solved
at the level of package dependencies (or a configurable virtual defaults
mapping in dpkg, but this doesn't exist).


  .''`.  Roger Leigh
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