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[[Category:Packaging Policies]]
{{introduction|This page explains how to manage coexisting different versions of a same software in ROSA Linux.}}

== Policy ==
=== When ===

If any of the following statements are true, you have to introduce a parallel version instead of replacing current one:

* this is an unstable version, and the stable one is already present in {{Версия|cooker}}
* this version is not compatible with the old one, and you are not able to create migration scripts which automatically reconfigure the new version with the old settings


=== How ===
==== Naming ====
So as to allow different versions to coexist, the new one must use a different name. This should be the name of the package, with the major version appended directly. Exceptions:

* If the package name ends with a number, an underscore must be intercaled between the name and the major version.
* If another parallel version already exist, major and minor version must be used.

There should always be a default version, without suffix, so as to have {{cmd|urpmi foo}} install {{pkg|foo}}.


==== Requires ====
you must add the following requirements to the spec file:
<pre>
Requires(post):     update-alternatives
Requires(postun):   update-alternatives
</pre>


==== Installation ====
For {{macro|%postun}} you need to test for the existence of the alternative in order to allow dropping the alternatively cleanly in the future:
<pre>
# This is *correct*:
%postun
if [ ! -e %{_bindir}/emacs-nox ]; then
  update-alternatives --remove emacs %{_bindir}/emacs-nox
fi

# This is *wrong*:
%postun
if [ $1 -eq 0 ]; then
  update-alternatives --remove emacs %{_bindir}/emacs-nox
fi
</pre>

Different scenarios:

* no parallel installation: the new version must be tagged as conflicting with the existing one
* parallel installation without alternative
* parallel installation with alternative


=== Examples ===
==== Gimp  ====
{{pkg|gimp}} and {{pkg|gimp2_2}} are in the distro, {{pkg|gimp2_2}} is the default.

<strong>This is WRONG</strong>, the default version of a package should be the simpler one, so that a {{cmd|urpmi gimp}} always install the default choosen version of a package.

The correct naming would be to have {{pkg|gimp}} (version 2.2) and {{pkg|gimp1.3}}.

==== MySQL ====
MySQL version 4.0 is in the distro, and you want to include the new development version MySQL-4.1.

The new package should be named {{pkg|MySQL41}}.

==== Postgresql ====
Postgresql 7.4.6 is in the distro, you want to keep it but you want to include, as default, the new postgresql 8.0.

You must rename the old {{pkg|postgresql}} to {{pkg|postgresql7}} (or {{pkg|postgresql74}}) and use the name '{{pkg|postgresql}}' for the new package.

<hr>

{{message|This Policy is based on the [http://wiki.mandriva.com/en/Development/Tasks/Packaging/Policies/Alternatives Mandriva Alternatives Policy].}}