Mailinglist Archive: opensuse (4343 mails)

[Thibaut Cousin <cousin@xxxxxxxx>]

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Le Vendredi 8 Novembre 2002 07:24, Richard Bos a écrit :
> >   Apt relies only on the information provided in the RPM packages,
> > whereas YaST (1 or 2) has a "meta-database" to sort things out. So Apt
> > can run into situations where it does the wrong thing.
> > For example, what happened to
> > you: Apt removed too many things in order to remove CUPS, then was not
> > aware of the damage and reinstalled only what you explicitely told him to
> > (+ dependencies).
>
> APT did exactly what Kevin/Tom asked remove cups and leave the system in a
> consistent state, so a meta database would not helped here.  An example of
> a meta db for apt is the /etc/apt/rpmpriorities file.  Are there btw other
> situaties in which a metabase would be needed?

  The meta-database can contain some more information like "CUPS provides a 
certain functionality". In this case, if you have several incompatible 
packages providing that functionality, like CUPS and LPRng, other packages 
can just depend on that functionality instead of explicitely depending on 
CUPS. Apt does not see that, so it does not *insist* on replacing CUPS with 
another package providing the same functionality.

> Can you reveal which information can't be stored in an rpm that can be
> stored in deb package?

  Well, I've been a Debian user for years and I've yet to find as good a 
package management. First, the Deb format supports virtual packages, that can 
be used to give generic names to certain functionalities (see above) or to 
"regroup" packages. So Apt would never have allowed the removal of CUPS 
without installing something else.
  Second, but nothing to do with the present discussion, the Deb format has 
several priority levels for packages, "extra", "optional", "normal", "base" 
and "required".
  It also has fine-tuned dependency: a package can "provide" another one, or 
"replace" it, or "conflict" with it, "suggest" another, "recommend" another 
or "require" another.
  The package management system is able update packages while they are still 
running, to select "alternatives" between several packages, etc.
  Building a Deb package or rebuilding it is very, very easy and much more 
liable. No dirty hack in the spec file, etc. 
  And the list can go on. All Deb package are official so you cannot run into 
"Oh, this RPM is for Redhat, I can't install it on my SuSE".
  Too bad Debian is so barbaric in other aspects.

  I'm aware some of those are becoming available in RPM format, but it is very 
recent. And they just come from the Deb format (the "conflict" and "provide" 
fields, the /etc/alternatives directory, etc). For example, only YaST2 is 
able to diagnose dependency problems, not RPM alone. No such distinction on 
Debian. Oh, and the apt-get tool comes from Debian, where it has worked for 
years with the infamous dselect. ;-)

- -- 
Thibaut Cousin
E-mail : cousin@xxxxxxxx
Web : http://clrwww.in2p3.fr
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