Re: apt_preferences(5) revision -- comments, please
On 7 Oct 2002, Thomas Hood wrote:
> In order to decide which version of a package to select, APT assigns a
> priority to each available version and selects the version with the
> highest priority. If two version have the same priority then the
> later one is selected. There are two exceptions to this, however.
> First, a version of a package that is earlier than the version that
> is installed is never selected if its priority is 1000 or less.
> Second, a version of a package is not installed if its priority is
> less than 0. [IS THIS CORRECT?]
s/not installed/not available/
All the priority mechanism does is select which version APT/Dselect see as
being 'new'. It's possible to make the version (and potentially package)
completely vanish with negative priorities.
> Package: *
> Pin: release v=2.1*
> Pin-Priority: 998
> </programlisting></informalexample>
> The first word of the default pin specification may be <literal/release/
> or <literal/origin/ (i.e., source). If more than one entry of this kind
> appears in the preferences file, only the first one that applies will be
> used. This kind of entry can be overridden by an entry that pins a
> particular package. [IS THIS TRUE? CLARIFICATION NEEDED HERE.]
Hum. You can have as many 'Package: *' entires as you want. The key is
that they match entire Package Files, the first one to match a given
package file gives it that priority.
> <para>
> If the Pin-Priority field is omitted then the value defaults to 989.
> <para>
> Some archives such as the <literal/experimental/ archive are marked
> <literal/Not Automatic/ and fall to the bottom of the selection pile.
> [DOES THIS MEAN THAT THEY EFFECTIVELY HAVE PRIORITIES OF LESS THAN
> 100, OR EFFECTIVE PRIORITIES OF LESS THAN 0?]
They are given a priority of 1.
> Users of third-party packages such as Helix GNOME can use the pinning
> mechanism to force the usage of these packages by setting the priority
> of the preferred origin sufficiently high.
Helix should probably be changed to the Xiamian or whatever.
Is that all of them?
Jason
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