Puppet users - Jun 2007 - ''reconfigurable'' option for package providers

The deb-oriented package providers (and others perhaps, it''s only
debian
I''m looking at right now) allow one to set a seedfile with the
appropriate debconf responses when installing a package. However, there
doesn''t seem to be a tidy way inherent to puppet to handle
reconfiguring
the package if the seedfile changes.

It  can be done quite easily with something like the following:

exec{ "/usr/bin/debconf-set-selections $seedfile":
    subscribe => File[$seedfile],
    refreshonly => true,
}

exec{ "/usr/sbin/dpkg-reconfigure $package":
    subscribe => File[$seedfile],
    refreshonly => true,
}

What would be involved in adding a reconfigure parameter to the package
provider to streamline this? It''s trivial to wrap the above code in a
defined type, but it seems like it should be part of the package
provider  to me.  I''ve had a quick look already, and most of it seems
straightforward except I''m not sure how to arrange for the package
provider to be notified of a change in the seedfile.

> What would be involved in adding a reconfigure parameter to the package
> provider to streamline this? It''s trivial to wrap the above code
in a
> defined type, but it seems like it should be part of the package
> provider  to me.  I''ve had a quick look already, and most of it
seems
> straightforward except I''m not sure how to arrange for the package
> provider to be notified of a change in the seedfile.
>   
To answer my own question:

remotefile { "/var/lib/puppet/localeconf.seed":
    mode => 660,
    source => ''/apps/debconf/localeconf.seed'',
}

package { [localeconf]:
    ensure => installed,
    require => File[''/var/lib/puppet/localeconf.seed''],
    responsefile => ''/var/lib/puppet/localeconf.seed'',
    subscribe => File[''/var/lib/puppet/localeconf.seed''],
}


Will arrange for the package provider to be sent an event on change.
Adding a refresh method to type/package.rb will arrange for the provider
to handle getting a refresh:
# type/package/rb
def refresh
    self.info "Refreshing package"
    provider.reconfigure
end

And adding a ''reconfigure'' method to the specific provider
will handle that:

#provider/package/apt.rb
dpkgreconfigure => "/usr/sbin/dpkgreconfigure

...

def reconfigure
    self.run_preseed
    self.run_reconfigure
end

def run_reconfigure
    self.info ("Reconfigure %s " % @model[:name])
    dpkgreconfigure "-pcritical", @model[:name]
end


I haven''t submitted this as a diff because it obviously needs a lot of
error checking put in place on it.  Having gone down this path, I''ve
discovered that one of the packages I wanted this functionality for
doesn''t need it.

(Perhaps offtopic ? Relevant to any debian/ubuntu admins who might want
to use this sort of functionality.)

When debconf manages a config file (such as /etc/default/mdadm), there
are big warnings around to not edit the file, but to use
dpkg-reconfigure instead. That''s fine, you''d think - you
should be able
to reseed debconf via debconf-set-selections, and run dpkg-reconfigure,
and it will pick up the new selections. However, it appears that many
debian and ubuntu packagers acknowledge that people don''t listen to the
debconf warnings, and during the debconf stage will overwrite any
debconf answers with data stored in the config file they manage.

The upshot is if I try to use debconf-set-selections to reseed say,
mdadm, when I run dpkg-reconfigure on mdadm it will reread
/etc/default/mdadm and then use those values as the defaults, trumping
my reseed. I can get around this by using puppet to manage
/etc/default/mdadm of course, but I was trying to avoid using puppet to
manage debconf-managed files.
I suspect all files in /etc/default are all managed like this within
debconf, as I''ve seen the behaviour elsewhere as well.

Why should we care about it?  I''m mostly interested in this for future
proofing myself against the eventuality puppet is removed from service.
Any step that I would have done via dpkg-reconfigure, I would like to be
able to do via puppet.

The good news is that the reconfigure methods I outlined above will work
on other packages.  EG, if you want to change your locale settings on
all your boxes, you can just change the preseed file and it will trigger
an update. You can manage locales manually, but they''re nowhere as easy
to manage as say, timezones.

Daniel

On Jun 9, 2007, at 3:44 PM, Daniel Lawson wrote:
> To answer my own question:
>
> remotefile { "/var/lib/puppet/localeconf.seed":
>     mode => 660,
>     source => ''/apps/debconf/localeconf.seed'',
> }
>
> package { [localeconf]:
>     ensure => installed,
>     require =>
File[''/var/lib/puppet/localeconf.seed''],
>     responsefile => ''/var/lib/puppet/localeconf.seed'',
>     subscribe =>
File[''/var/lib/puppet/localeconf.seed''],
> }
>
>
> Will arrange for the package provider to be sent an event on change.
> Adding a refresh method to type/package.rb will arrange for the  
> provider
> to handle getting a refresh:
> # type/package/rb
> def refresh
>     self.info "Refreshing package"
>     provider.reconfigure
> end
>
> And adding a ''reconfigure'' method to the specific
provider will
> handle that:
>
> #provider/package/apt.rb
> dpkgreconfigure => "/usr/sbin/dpkgreconfigure
This would be very easy to add generically -- I''d set it up so that  
all resource types would look for a ''refresh'' method on their
providers, and if present, it would be called.  So, you''d define a  
''refresh'' method on the apt provider (or, more likely, the
dpkg
provider), and everything else would happen automatically when the  
package received events from the file.

Note that Puppet automatically sets up a ''require''
relationship
between a package and its response file, but not a ''subscribe''
relationship (note also that having both is redundant -- the  
''require'' is ignored).
> ...
>
> def reconfigure
>     self.run_preseed
>     self.run_reconfigure
> end
>
> def run_reconfigure
>     self.info ("Reconfigure %s " % @model[:name])
>     dpkgreconfigure "-pcritical", @model[:name]
> end
>
>
> I haven''t submitted this as a diff because it obviously needs a
lot of
> error checking put in place on it.  Having gone down this path,
I''ve
> discovered that one of the packages I wanted this functionality for
> doesn''t need it.
Go ahead and submit it as an enhancement request.

  --
  Don''t throw away the old bucket until you know whether the new one  
holds
  water.  -- Swedish Proverb
  ---------------------------------------------------------------------
  Luke Kanies | http://reductivelabs.com | http://madstop.com

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On Saturday 09 June 2007, Daniel Lawson wrote:
> When debconf manages a config file (such as /etc/default/mdadm), there
> are big warnings around to not edit the file, but to use
> dpkg-reconfigure instead. That''s fine, you''d think - you
should be able
> to reseed debconf via debconf-set-selections, and run dpkg-reconfigure,
> and it will pick up the new selections. However, it appears that many
> debian and ubuntu packagers acknowledge that people don''t listen
to the
> debconf warnings, and during the debconf stage will overwrite any
> debconf answers with data stored in the config file they manage.
>
> The upshot is if I try to use debconf-set-selections to reseed say,
> mdadm, when I run dpkg-reconfigure on mdadm it will reread
> /etc/default/mdadm and then use those values as the defaults, trumping
> my reseed. I can get around this by using puppet to manage
> /etc/default/mdadm of course, but I was trying to avoid using puppet to
> manage debconf-managed files.
> I suspect all files in /etc/default are all managed like this within
> debconf, as I''ve seen the behaviour elsewhere as well.
>
> Why should we care about it?  I''m mostly interested in this for
future
> proofing myself against the eventuality puppet is removed from service.
> Any step that I would have done via dpkg-reconfigure, I would like to be
> able to do via puppet.
Reading values from configuration files as default values into debconf prior 
to reconfiguring is the proscribed Debian Default Behaviour. Every package 
should work like this, since as it is often repeated: "debconf is no 
registry".

The Right Way therefore is to handle only the most pressing (i.e. priority 
critical) questions via preseeding and then configure anything 
else "manually", since you always will need stuff like the 
configfile->servicerestart derpendency information in puppet _anyways_.
> The good news is that the reconfigure methods I outlined above will work
> on other packages.  EG, if you want to change your locale settings on
> all your boxes, you can just change the preseed file and it will trigger
> an update. You can manage locales manually, but they''re nowhere as
easy
> to manage as say, timezones.


Regards, David
- -- 
- - hallo... wie gehts heute?
- - *hust* gut *rotz* *keuch*
- - gott sei dank kommunizieren wir über ein septisches medium ;)
 -- Matthias Leeb, Uni f. angewandte Kunst, 2005-02-15
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