yum-software-management/en_US yum-software-management.xml,1.2,1.3

Stuart Ellis (elliss) fedora-docs-commits at redhat.com
Sun Mar 19 21:39:15 UTC 2006


Author: elliss

Update of /cvs/docs/yum-software-management/en_US
In directory cvs-int.fedora.redhat.com:/tmp/cvs-serv23713/en_US

Modified Files:
	yum-software-management.xml 
Log Message:
- Added section on customizing yum, and plugins.
- Added section on caching.




Index: yum-software-management.xml
===================================================================
RCS file: /cvs/docs/yum-software-management/en_US/yum-software-management.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- yum-software-management.xml	13 Mar 2006 00:23:33 -0000	1.2
+++ yum-software-management.xml	19 Mar 2006 21:39:08 -0000	1.3
@@ -44,10 +44,10 @@
         This document is a reference for using <command>yum</command>.
         You may wish to read some or all of the sections, depending upon
         your needs and level of experience. If you are a new user, read
-        the <xref
-      linkend="sn-software-management-concepts"/>
-        before using <command>yum</command> for the first time.
-        Experienced Linux users should start with
+        <xref
+      linkend="sn-software-management-concepts"/> before
+        using <command>yum</command> for the first time. Experienced
+        Linux users should start with
         <xref linkend="sn-managing-packages"/>.
       </para>
 
@@ -225,7 +225,7 @@
       </indexterm>
       <para>
         A <firstterm>repository</firstterm> is a prepared directory or
-        web site that contains software packages and index files.
+        Web site that contains software packages and index files.
         Software management utilities such as <command>yum</command>
         automatically locate and obtain the correct RPM packages from
         these repositories. This method frees you from having to
@@ -557,18 +557,18 @@
       manually install and remove packages from your system. If you
       install software with the <command>rpm</command> utility, you must
       manually check and install any dependencies. For this reason,
-      <command>yum</command> is the recommended method for installing
-      software.
+      <application>pirut</application> and <command>yum</command> are
+      the recommended methods for installing software.
     </para>
 
     <caution>
       <title>Current Package Versions</title>
 
       <para>
-        The <application>Add/Remove Software</application> and
-        <command>yum</command> utilities ensure that you have the most
-        recent version of software packages. Other methods do not
-        guarantee that the packages are current.
+        The <application>pirut</application> and <command>yum</command>
+        utilities ensure that you have the most recent version of
+        software packages. Other methods do not guarantee that the
+        packages are current.
       </para>
     </caution>
   </section>
@@ -722,15 +722,19 @@
       and verified, <command>yum</command> applies them to your system.
     </para>
 
-    <para>
-      Every completed transaction records the affected packages in the
-      log file
-      <indexterm>
-        <primary>log file</primary>
-      </indexterm>
-      <filename>/var/log/yum.log</filename>. You may only read this file
-      with <systemitem class="username">root</systemitem> access.
-    </para>
+    <note>
+      <title>Transaction Log</title>
+
+      <para>
+        Every completed transaction records the affected packages in the
+        log file
+        <indexterm>
+          <primary>log file</primary>
+        </indexterm>
+        <filename>/var/log/yum.log</filename>. You may only read this
+        file with <systemitem class="username">root</systemitem> access.
+      </para>
+    </note>
 
     <section id="sn-yum-installing-withrepositories">
       <title>Installing New Software with <command>yum</command></title>
@@ -817,6 +821,20 @@
         </para>
       </important>
 
+      <note>
+        <title>Kernel Packages</title>
+
+        <para>
+          Kernel packages remain on the system after they have been
+          superseded by newer versions. This enables you to boot your
+          system with an older kernel if an error occurs with the
+          current kernel. To minimize maintenance,
+          <command>yum</command> automatically removes obsolete kernel
+          packages from your system, retaining only the current kernel
+          and the previous version.
+        </para>
+      </note>
+
       <para>
         To update all of the packages in the package group
         <filename>MySQL Database</filename>, enter the command:
@@ -964,14 +982,14 @@
         <option>search</option> or <option>provides</option> options.
         Alternatively, use wild cards or regular expressions with any
         <command>yum</command> search option to broaden the search
-        critieria.
+        criteria.
       </para>
 
       <para>
         The <option>search</option> option checks the names,
         descriptions, summaries and listed package maintainers of all of
         the available packages to find those that match. For example, to
-        search for all packages that relate to PalmPilots, type:
+        search for all packages that relate to Palm Pilots, type:
       </para>
 <screen>
 <userinput>su -c 'yum search <replaceable>PalmPilot</replaceable>'</userinput>
@@ -1011,11 +1029,11 @@
       </para>
 
       <para>
-        Use the standard wildcard characters to run any search option
+        Use the standard wild-card characters to run any search option
         with a partial word or name: <option>?</option> to represent any
         one character, and <option>*</option> to mean zero or more
         characters. Always add the escape character (<option>\</option>)
-        before wildcards.
+        before wild-cards.
       </para>
 
       <para>
@@ -1041,7 +1059,7 @@
         Searches with <command>yum</command> show all of the packages
         that match your criteria. Packages must meet the terms of the
         search exactly to be considered matches, unless you use
-        wildcards or a regular expression.
+        wild-cards or a regular expression.
       </para>
 
       <para>
@@ -1109,8 +1127,8 @@
           script <filename>/etc/rc.d/init.d/yum</filename>. This control
           script activates the script
           <filename>/etc/cron.daily/yum.cron</filename>, which causes
-          the <command>cron</command> service to perform the system
-          update automatically at 4am each day.
+          the <command>cron</command> service to automatically begin a
+          system update at 4am each day.
         </para>
       </note>
     </section>
@@ -1386,125 +1404,155 @@
     </caution>
   </section>
 
-  <section id="sn-yum-maintenance">
-    <title>Maintaining <command>yum</command></title>
-
+  <section id="sn-yum-customizing">
+    <title>Customizing <command>yum</command></title>
+<!-- SE: The dictionary says "plug-in", but yum documentation uses "plugin". For consistency, I'm using "plugin" in this document. -->
     <para>
-      The <command>yum</command> system does not require any routine
-      maintenance. To ensure that <command>yum</command> operations are
-      carried out at optimal speed, disable or remove repository
-      definitions which you no longer require. You may also clear the
-      files from the <command>yum</command> caches in order to recover
-      disk space.
+      To change the behavior of <command>yum</command>, you may either
+      edit the configuration files, or install
+      <firstterm>plugins</firstterm>. Plugins enable developers to add
+      new features to <command>yum</command>.
     </para>
 
-    <section id="sn-removing-sources">
-      <title>Disabling or Removing Package Sources</title>
+    <section id="sn-yum-configfile">
+      <title>Editing the <command>yum</command> Configuration</title>
       <indexterm>
-        <primary>repositories</primary>
-        <secondary>disabling in yum</secondary>
-      </indexterm>
-      <indexterm>
-        <primary>repositories</primary>
-        <secondary>removing from yum</secondary>
+        <primary>configuration files</primary>
       </indexterm>
       <para>
-        Set <command>enable=0</command> in a definition file to prevent
-        <command>yum</command> from using that repository. The
-        <command>yum</command> utility ignores any definition file with
-        this setting.
+        The file <filename>/etc/yum.conf</filename> provides the main
+        configuration for <command>yum</command>. Settings in a
+        repository definition file override the main configuration for
+        those operations that use the defined repository.
       </para>
 
       <para>
-        To completely remove access to a repository:
+        To edit <filename>/etc/yum.conf</filename>, run a text editor
+        with <systemitem class="username">root</systemitem> privileges.
+        This command opens <filename>/etc/yum.conf</filename> with
+        <application>gedit</application>, the default text editor for
+        &FED; desktop systems:
+      </para>
+<screen>
+<userinput>su -c 'gedit /etc/yum.conf'</userinput>
+</screen>
+      <para>
+        Enter the password for the
+        <systemitem class="username">root</systemitem> account when
+        prompted.
       </para>
-      <procedure>
-        <step>
-          <para>
-            Delete the relevant file from
-            <filename>/etc/yum.repos.d/</filename>.
-          </para>
-        </step>
-        <step>
-          <para>
-            Delete the cache directory from
-            <filename>/var/cache/yum/</filename>.
-          </para>
-        </step>
-      </procedure>
-<!-- What with the "web of trust," removing GPG keys is not really -->
-<!-- something we should encourage. Having an extra GPG key in the RPM -->
-<!-- database is not a vulnerability, nor does it hamper the system in -->
-<!-- any way.  These are probably a couple of reasons Seth didn't build -->
-<!-- this function into yum as part of "clean all," for example.  Since -->
-<!-- we just had several admonitions against people running the rpm -->
-<!-- command on its own anyway, I would just omit this part -->
-<!-- completely. [PWF] -->
-<!--
 
-      <important>
-        <title>Remove Unneeded Public Keys</title>
+      <para>
+        The main configuration file provides the settings that apply to
+        all <command>yum</command> operations. These include caching
+        options, and proxy server settings. The directory
+        <filename>/etc/yum.repos.d/</filename> holds definition files
+        for each repository that <command>yum</command> uses. Plugins
+        use the configuration files in the directory
+        <filename>/etc/yum/pluginconf.d/</filename>.
+      </para>
+
+      <para>
+        The following sections in this document provide further
+        information on configuring <command>yum</command>:
+      </para>
 
+      <para>
+        <itemizedlist>
+          <listitem>
+            <para>
+              <xref linkend="sn-using-repositories"/>
+            </para>
+          </listitem>
+          <listitem>
+            <para>
+              <xref linkend="sn-yum-managing-plugins"/>
+            </para>
+          </listitem>
+          <listitem>
+            <para>
+              <xref linkend="sn-yum-enabling-caching"/>
+            </para>
+          </listitem>
+          <listitem>
+            <para>
+              <xref linkend="sn-yum-proxy-server"/>
+            </para>
+          </listitem>
+        </itemizedlist>
+      </para>
+      <tip>
+        <title>Further Documentation</title>
         <para>
-          If you will not be using any further packages from a provider,
-	  remove their public key from the <command>rpm</command>
-	  keyring using the procedure described in
-          <xref linkend="sn-removing-publickeys" />.
+          Refer to the <command>man</command> page for
+          <filename>yum.conf</filename> for a complete list of the
+          configuration options supported by <command>yum</command>.
         </para>
-      </important>
+      </tip>
     </section>
 
-    <section id="sn-removing-publickeys">
-      <title>Removing Public Keys</title>
+    <section id="sn-yum-managing-plugins">
+      <title>Working with <command>yum</command> Plugins</title>
       <indexterm>
-        <primary>public keys, removing</primary>
+        <primary>plugins</primary>
+        <secondary>installing</secondary>
       </indexterm>
       <para>
-        To remove a public key from the keyring you first must determine
-        the full name of the key, as it registered in
-        <command>rpm</command>. Run this command to view the details of
-        the public keys on the <command>rpm</command> keyring:
+        Each <command>yum</command> plugin is a single file, written in
+        the Python programming language. You may download plugins from
+        the <command>yum</command> project Web site, or from third-party
+        providers. The <command>yum</command> project maintains a list
+        of plugins on the page
+        <ulink url="http://wiki.linux.duke.edu/YumPlugins"/>.
       </para>
-<screen>
-<userinput>rpm -qi gpg-pubkey-*</userinput>
-</screen>
+      <tip>
+        <title>Plugin File Extension</title>
+        <para>
+          The names of <command>yum</command> plugin files end with
+          <filename>.py</filename>, the standard file extension for
+          Python files.
+        </para>
+      </tip>
       <para>
-        Locate the heading for the relevant public key. The public key
-        headings follow this format:
+        To install a plugin, copy it to the directory
+        <filename>/usr/lib/yum-plugins/</filename>. Create a
+        configuration file for the plugin in the directory
+        <filename>/etc/yum/pluginconf.d/</filename>. Save the
+        configuration file with the same name as the plugin, but with
+        the extension <filename>.conf</filename>.
       </para>
 
-      <example id="publickey-header-format">
-        <title>Format of <command>rpm</command> Public Key Headers</title>
+      <note>
+        <title><systemitem class="username">root</systemitem> Privileges Required</title>
+
+        <para>
+          You must have <systemitem class="username">root</systemitem>
+          access to add files to the directories
+          <filename>/usr/lib/yum-plugins/</filename> and
+          <filename>/etc/yum/pluginconf.d/</filename>.
+        </para>
+      </note>
+
+      <para>
+        For example, to copy the plugin
+        <filename>exampleplugin.py</filename>, enter the command:
+      </para>
 <screen>
-<computeroutput>Name        : gpg-pubkey                   Relocations: (not relocatable)
-Version     : 4f2a6fd2                          Vendor: (none)
-Release     : 3f9d9d3b                      Build Date: Wed 15 Jun 2005 09:55:33 PM BST
-Install Date: Wed 15 Jun 2005 09:55:33 PM BST      Build Host: localhost
-Group       : Public Keys                   Source RPM: (none)
-Size        : 0                                License: pubkey
-Signature   : (none)
-Summary     : gpg(Fedora Project &lt;fedora at redhat.com&gt;)
-Description :</computeroutput>
+<userinput>su -c 'cp example-lugin.py /usr/lib/yum-plugins/'</userinput>
 </screen>
-      </example>
-
       <para>
-        Add the <option>Version</option> and <option>Release</option>
-        attributes to <option>gpg-pubkey-</option> to make the complete
-        name of the key, in the form
-        <option>gpg-pubkey-Version_number-Release_number</option>. The
-        <command>rpm</command> identification for the &FP; public key
-        shown above is: <option>gpg-pubkey-4f2a6fd2-3f9d9d3b</option>.
+        Enter the password for the
+        <systemitem class="username">root</systemitem> account when
+        prompted.
       </para>
 
       <para>
-        Once you know the identification name of the key, use the
-        command <command>rpm <option>-e</option></command> to remove it.
-        To remove the &FP; public key shown above the exact command
-        would be:
+        You may then create a configuration file for the plugin with a
+        text editor. This example uses <application>gedit</application>,
+        the default text editor for &FED; desktop systems:
       </para>
 <screen>
-<userinput>su -c 'rpm -e <replaceable>gpg-pubkey-4f2a6fd2-3f9d9d3b</replaceable>'</userinput>
+<userinput>su -c 'gedit /etc/yum/pluginconf.d/exampleplugin.conf'</userinput>
 </screen>
       <para>
         Enter the password for the
@@ -1512,42 +1560,163 @@
         prompted.
       </para>
 
--->
-    </section>
-
-    <section id="sn-yum-clearance">
-      <title>Clearing the <command>yum</command> Caches</title>
-      <indexterm>
-        <primary>yum</primary>
-        <secondary>cleaning caches</secondary>
-      </indexterm>
       <para>
-        If you configure it to do so, <command>yum</command> retains the
-        packages and package data files that it downloads, so that they
-        may be reused in future operations without being downloaded
-        again. To purge the package data files, use this command:
+        Each plugin configuration file includes the
+        <command>enabled</command> setting. Some plugins also require
+        additional settings. To determine the correct settings, either
+        refer to the documentation supplied with the plugin, or read the
+        plugin file itself with any text editor.
       </para>
-<screen>
-<userinput>su -c 'yum clean headers'</userinput>
+
+      <example>
+        <title>Example Plugin Configuration File</title>
+<screen>
+<computeroutput>[main]
+enabled=1
+anotheroption=0</computeroutput>
 </screen>
+      </example>
+
+      <note>
+        <title>Plugin Installed by Default</title>
+
+        <para>
+          <indexterm>
+            <primary>plugins</primary>
+            <secondary>installonlyn</secondary>
+          </indexterm>
+          &FC; includes the <filename>installonlyn</filename> plugin.
+          This plugin modifies <command>yum</command> to remove excess
+          kernel packages, so that no more than a set number of kernels
+          exist on the system. By default,
+          <filename>installonlyn</filename> retains the two most current
+          kernels, and automatically removes older kernel packages.
+        </para>
+      </note>
+
       <para>
-        Run this command to remove all of the packages held in the
-        caches:
+        <indexterm>
+          <primary>plugins</primary>
+          <secondary>removing</secondary>
+        </indexterm>
+        To remove a plugin, delete both the original file and the
+        automatically generated bytecode file from
+        <filename>/usr/lib/yum-plugins/</filename>. The bytecode file
+        uses the same name as the plugin, but has the extension
+        <filename>.pyc</filename>. Remove the relevant configuration
+        file in <filename>/etc/yum/pluginconf.d/</filename>.
+      </para>
+
+      <para>
+        This command removes the plugin
+        <filename>exampleplugin</filename>:
       </para>
 <screen>
-<userinput>su -c 'yum clean packages'</userinput>
+<userinput>su -c 'rm -f /etc/yum/pluginconf.d/exampleplugin.conf; rm -f /usr/lib/yum-plugins/exampleplugin.p*'</userinput>
 </screen>
       <para>
-        When using these commands, at the prompt, enter the password for
-        the <systemitem class="username">root</systemitem> account.
+        Enter the password for the
+        <systemitem class="username">root</systemitem> account when
+        prompted.
       </para>
+    </section>
+  </section>
+
+  <section id="sn-yum-enabling-caching">
+    <title>Enabling the Caches</title>
+    <indexterm>
+      <primary>caching</primary>
+    </indexterm>
+    <indexterm>
+      <primary>packages</primary>
+      <secondary>caching</secondary>
+    </indexterm>
+    <para>
+      By default, current versions of <command>yum</command> delete the
+      data files and packages that they download, after these have been
+      successfully used for an operation. This minimizes the amount of
+      storage space that <command>yum</command> uses. To configure
+      <command>yum</command> to retain downloaded files rather than
+      discarding them, set the <command>keepcache</command> option in
+      <filename>/etc/yum.conf</filename> to <userinput>1</userinput>:
+    </para>
+<screen>
+<computeroutput>
+keepcache=1
+</computeroutput>
+</screen>
+    <para>
+      Enabling this option provides three advantages:
+    </para>
+
+    <para>
+      <itemizedlist>
+        <listitem>
+          <para>
+            Performance increases, as cached files may be reused, rather
+            than being downloaded for each operation that requires them
+          </para>
+        </listitem>
+        <listitem>
+          <para>
+            You may carry out <command>yum</command> operations without
+            a network connection, by using only the caches
+          </para>
+        </listitem>
+        <listitem>
+          <para>
+            You may copy packages from the caches and reuse them
+            elsewhere
+          </para>
+        </listitem>
+      </itemizedlist>
+    </para>
+
+    <para>
+      To carry out a <command>yum</command> command without a network
+      connection, add the <option>-C</option> option. This causes
+      <command>yum</command> to proceed without checking any network
+      repositories, and use only cached files. In this mode,
+      <command>yum</command> may only install packages that have been
+      downloaded and cached by a previous operation.
+    </para>
+
+    <para>
+      To search for the package <filename>tsclient</filename> without
+      using a network connection, enter the command:
+    </para>
+<screen>
+<userinput>su -c 'yum -C list <replaceable>tsclient</replaceable>'</userinput>
+</screen>
+    <para>
+      Enter the password for the
+      <systemitem class="username">root</systemitem> account when
+      prompted.
+    </para>
 
+    <para>
+      By default, <command>yum</command> stores temporary files under
+      the directory <filename>/var/cache/yum/</filename>, with one
+      subdirectory for each configured repository. The
+      <filename>packages/</filename> directory within each repository
+      directory holds the cached packages. For example, the directory
+      <filename>/var/cache/yum/development/packages/</filename> holds
+      packages downloaded from the <filename>development</filename>
+      repository.
+    </para>
+    <tip>
+      <title>Clearing the <command>yum</command> Caches</title>
       <para>
-        Purging cached files causes those files to downloaded again the
-        next time that they are required. This increases the amount of
-        time required to complete the operation.
+        Cached files use disk space until removed. You may wish to
+        periodically clear the <command>yum</command> caches to recover
+        capacity. Refer to <xref linkend="sn-yum-clearance"/> for
+        information on clearing the caches.
       </para>
-    </section>
+    </tip>
+    <para>
+      If you remove a package from the cache, you do not affect the copy
+      of the software installed on your system.
+    </para>
   </section>
 
   <section id="sn-yum-proxy-server">
@@ -1681,10 +1850,174 @@
     </section>
   </section>
 
+  <section id="sn-yum-maintenance">
+    <title>Maintaining <command>yum</command></title>
+
+    <para>
+      The <command>yum</command> system does not require any routine
+      maintenance. To ensure that <command>yum</command> operations are
+      carried out at optimal speed, disable or remove repository
+      definitions which you no longer require. You may also clear the
+      files from the <command>yum</command> caches in order to recover
+      disk space.
+    </para>
+
+    <section id="sn-removing-sources">
+      <title>Disabling or Removing Package Sources</title>
+      <indexterm>
+        <primary>repositories</primary>
+        <secondary>disabling in yum</secondary>
+      </indexterm>
+      <indexterm>
+        <primary>repositories</primary>
+        <secondary>removing from yum</secondary>
+      </indexterm>
+      <para>
+        Set <command>enable=0</command> in a definition file to prevent
+        <command>yum</command> from using that repository. The
+        <command>yum</command> utility ignores any definition file with
+        this setting.
+      </para>
+
+      <para>
+        To completely remove access to a repository:
+      </para>
+      <procedure>
+        <step>
+          <para>
+            Delete the relevant file from
+            <filename>/etc/yum.repos.d/</filename>.
+          </para>
+        </step>
+        <step>
+          <para>
+            Delete the cache directory from
+            <filename>/var/cache/yum/</filename>.
+          </para>
+        </step>
+      </procedure>
+<!-- What with the "web of trust," removing GPG keys is not really -->
+<!-- something we should encourage. Having an extra GPG key in the RPM -->
+<!-- database is not a vulnerability, nor does it hamper the system in -->
+<!-- any way.  These are probably a couple of reasons Seth didn't build -->
+<!-- this function into yum as part of "clean all," for example.  Since -->
+<!-- we just had several admonitions against people running the rpm -->
+<!-- command on its own anyway, I would just omit this part -->
+<!-- completely. [PWF] -->
+<!--
+
+      <important>
+        <title>Remove Unneeded Public Keys</title>
+
+        <para>
+          If you will not be using any further packages from a provider,
+	  remove their public key from the <command>rpm</command>
+	  keyring using the procedure described in
+          <xref linkend="sn-removing-publickeys" />.
+        </para>
+      </important>
+    </section>
+
+    <section id="sn-removing-publickeys">
+      <title>Removing Public Keys</title>
+      <indexterm>
+        <primary>public keys, removing</primary>
+      </indexterm>
+      <para>
+        To remove a public key from the keyring you first must determine
+        the full name of the key, as it registered in
+        <command>rpm</command>. Run this command to view the details of
+        the public keys on the <command>rpm</command> keyring:
+      </para>
+<screen>
+<userinput>rpm -qi gpg-pubkey-*</userinput>
+</screen>
+      <para>
+        Locate the heading for the relevant public key. The public key
+        headings follow this format:
+      </para>
+
+      <example id="publickey-header-format">
+        <title>Format of <command>rpm</command> Public Key Headers</title>
+<screen>
+<computeroutput>Name        : gpg-pubkey                   Relocations: (not relocatable)
+Version     : 4f2a6fd2                          Vendor: (none)
+Release     : 3f9d9d3b                      Build Date: Wed 15 Jun 2005 09:55:33 PM BST
+Install Date: Wed 15 Jun 2005 09:55:33 PM BST      Build Host: localhost
+Group       : Public Keys                   Source RPM: (none)
+Size        : 0                                License: pubkey
+Signature   : (none)
+Summary     : gpg(Fedora Project &lt;fedora at redhat.com&gt;)
+Description :</computeroutput>
+</screen>
+      </example>
+
+      <para>
+        Add the <option>Version</option> and <option>Release</option>
+        attributes to <option>gpg-pubkey-</option> to make the complete
+        name of the key, in the form
+        <option>gpg-pubkey-Version_number-Release_number</option>. The
+        <command>rpm</command> identification for the &FP; public key
+        shown above is: <option>gpg-pubkey-4f2a6fd2-3f9d9d3b</option>.
+      </para>
+
+      <para>
+        Once you know the identification name of the key, use the
+        command <command>rpm <option>-e</option></command> to remove it.
+        To remove the &FP; public key shown above the exact command
+        would be:
+      </para>
+<screen>
+<userinput>su -c 'rpm -e <replaceable>gpg-pubkey-4f2a6fd2-3f9d9d3b</replaceable>'</userinput>
+</screen>
+      <para>
+        Enter the password for the
+        <systemitem class="username">root</systemitem> account when
+        prompted.
+      </para>
+
+-->
+    </section>
+
+    <section id="sn-yum-clearance">
+      <title>Clearing the <command>yum</command> Caches</title>
+      <indexterm>
+        <primary>yum</primary>
+        <secondary>cleaning caches</secondary>
+      </indexterm>
+      <para>
+        If you configure it to do so, <command>yum</command> retains the
+        packages and package data files that it downloads, so that they
+        may be reused in future operations without being downloaded
+        again. To purge the package data files, use this command:
+      </para>
+<screen>
+<userinput>su -c 'yum clean headers'</userinput>
+</screen>
+      <para>
+        Run this command to remove all of the packages held in the
+        caches:
+      </para>
+<screen>
+<userinput>su -c 'yum clean packages'</userinput>
+</screen>
+      <para>
+        When using these commands, at the prompt, enter the password for
+        the <systemitem class="username">root</systemitem> account.
+      </para>
+
+      <para>
+        Purging cached files causes those files to downloaded again the
+        next time that they are required. This increases the amount of
+        time required to complete the operation.
+      </para>
+    </section>
+  </section>
+
 <!-- SE: This is at the end of the document, since it looks out of place in section 1 -->
 
-  <section id="sn-acknowledgements">
-    <title>Acknowledgements</title>
+  <section id="sn-acknowledgments">
+    <title>Acknowledgments</title>
 
     <para>
       Paul Frields edited this document. Timothy Murphy reviewed the




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