origin can be used to match a hostname (Closes: #352667)

[apt.git] / doc / apt_preferences.5.xml

diff --git a/doc/apt_preferences.5.xml b/doc/apt_preferences.5.xml
index 159d61f2b2402561836f2eefb3e7d623daaac6bf..c927f327a4a1d0fc080d4f2bda80a712ba88d4db 100644 (file)
--- a/doc/apt_preferences.5.xml
+++ b/doc/apt_preferences.5.xml
@@ -14,7 +14,7 @@
    &apt-email;
    &apt-product;
    <!-- The last update date -->
-   <date>04 May 2009</date>
+   <date>16 February 2010</date>
  </refentryinfo>
 
  <refmeta>
@@ -53,6 +53,24 @@ earliest in the &sources-list; file.
 The APT preferences file does not affect the choice of instance, only
 the choice of version.</para>
 
+<para>Preferences are a strong power in the hands of a system administrator
+but they can become also their biggest nightmare if used without care!
+APT will not questioning the preferences so wrong settings will therefore
+lead to uninstallable packages or wrong decisions while upgrading packages.
+Even more problems will arise if multiply distribution releases are mixed
+without a good understanding of the following paragraphs.
+Packages included in a specific release aren't tested in and
+therefore doesn't always work as expected in older or newer releases or
+together with other packages from different releases.
+You have been warned.</para>
+
+<para>Note that the files in the <filename>/etc/apt/preferences.d</filename>
+directory are parsed in alphanumeric ascending order and need to obey the
+following naming convention: The files have no or "<literal>pref</literal>"
+as filename extension and which only contain alphanumeric,  hyphen (-),
+underscore (_) and period (.) characters - otherwise they will be silently
+ignored.</para>
+
 <refsect2><title>APT's Default Priority Assignments</title>
 
 <para>If there is no preferences file or if there is no entry in the file
@@ -177,8 +195,15 @@ Pin: origin ""
 Pin-Priority: 999
 </programlisting>
 
-<simpara>A note of caution: the keyword used here is "<literal>origin</literal>".
-This should not be confused with the Origin of a distribution as
+<simpara>A note of caution: the keyword used here is "<literal>origin</literal>"
+which can be used to match a hostname. The following record will assign a high priority
+to all versions available from the server identified by the hostname "ftp.de.debian.org"</simpara>
+<programlisting>
+Package: *
+Pin: origin "ftp.de.debian.org"
+Pin-Priority: 999
+</programlisting>
+<simpara>This should <emphasis>not</emphasis> be confused with the Origin of a distribution as
 specified in a <filename>Release</filename> file.  What follows the "Origin:" tag
 in a <filename>Release</filename> file is not an Internet address
 but an author or vendor name, such as "Debian" or "Ximian".</simpara>
@@ -576,7 +601,7 @@ Pin-Priority: 900
 
 Explanation: Debian unstable is always codenamed with sid
 Package: *
-Pin: release a=sid
+Pin: release n=sid
 Pin-Priority: 800
 
 Package: *