add hidden config to set packages as Essential/Important

[apt.git] / doc / apt-cache.8.xml

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<refentry>

 <refentryinfo>
   &apt-author.jgunthorpe;
   &apt-author.team;
   &apt-email;
   &apt-product;
   <!-- The last update date -->
   <date>2016-09-20T00:00:00Z</date>
 </refentryinfo>
 
 <refmeta>
   <refentrytitle>apt-cache</refentrytitle>
   <manvolnum>8</manvolnum>
   <refmiscinfo class="manual">APT</refmiscinfo>
 </refmeta>
 
 <!-- Man page title -->
 <refnamediv>
    <refname>apt-cache</refname>
    <refpurpose>query the APT cache</refpurpose>
 </refnamediv>

 &synopsis-command-apt-cache;

 <refsect1><title>Description</title>
    <para>
       <command>apt-cache</command> performs a variety of operations on APT's
       package cache. <command>apt-cache</command> does not manipulate the
       state of the system but does provide operations to search and generate
       interesting output from the package metadata. The metadata is acquired
       and updated via the 'update' command of e.g. <command>apt-get</command>,
       so that it can be outdated if the last update is too long ago, but in
       exchange <command>apt-cache</command> works independently of the
       availability of the configured sources (e.g. offline).
    </para>

   <para>Unless the <option>-h</option>, or <option>--help</option> option is given, one of the
   commands below must be present.</para>

   <variablelist>
     <varlistentry><term><option>gencaches</option></term>
     <listitem><para><literal>gencaches</literal> creates APT's package cache. This is done
     implicitly by all commands needing this cache if it is missing or outdated.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>showpkg</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>showpkg</literal> displays information about the packages listed on the 
     command line. Remaining arguments are package names. The available 
     versions and reverse dependencies of each package listed are listed, as 
     well as forward dependencies for each version. Forward (normal) 
     dependencies are those packages upon which the package in question 
     depends; reverse dependencies are those packages that depend upon the 
     package in question. Thus, forward dependencies must be satisfied for a 
     package, but reverse dependencies need not be.
     For instance, <command>apt-cache showpkg libreadline2</command> would produce 
     output similar to the following:</para>
     
<informalexample><programlisting>
Package: libreadline2
Versions: 2.1-12(/var/state/apt/lists/foo_Packages),
Reverse Depends: 
  libreadlineg2,libreadline2
  libreadline2-altdev,libreadline2
Dependencies:
2.1-12 - libc5 (2 5.4.0-0) ncurses3.0 (0 (null))
Provides:
2.1-12 - 
Reverse Provides: 
</programlisting></informalexample>
			    
     <para>Thus it may be seen that libreadline2, version 2.1-12, depends on
     libc5 and ncurses3.0 which must be installed for libreadline2 to work. 
     In turn, libreadlineg2 and libreadline2-altdev depend on libreadline2. If
     libreadline2 is installed, libc5 and ncurses3.0 (and ldso) must also be
     installed; libreadlineg2 and libreadline2-altdev do not have to be
     installed. For the specific meaning of the remainder of the output it
     is best to consult the apt source code.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>stats</option></term><listitem><para><literal>stats</literal> displays some statistics about the cache.
     No further arguments are expected. Statistics reported are:
     <itemizedlist>
       <listitem><para><literal>Total package names</literal> is the number of package names found 
       in the cache.</para>
       </listitem>
       
       <listitem><para><literal>Normal packages</literal> is the number of regular, ordinary package 
       names; these are packages that bear a one-to-one correspondence between 
       their names and the names used by other packages for them in 
       dependencies. The majority of packages fall into this category.</para>
       </listitem>

       <listitem><para><literal>Pure virtual packages</literal> is the number of packages that exist 
       only as a virtual package name; that is, packages only "provide" the 
       virtual package name, and no package actually uses the name. For 
       instance, "mail-transport-agent" in the Debian system is a 
       pure virtual package; several packages provide "mail-transport-agent", 
       but there is no package named "mail-transport-agent".</para>
       </listitem>
   
       <listitem><para><literal>Single virtual packages</literal> is the number of packages with only 
       one package providing a particular virtual package. For example, in the
       Debian system, "X11-text-viewer" is a virtual package, but 
       only one package, xless, provides "X11-text-viewer".</para>
       </listitem>

       <listitem><para><literal>Mixed virtual packages</literal> is the number of packages that either 
       provide a particular virtual package or have the virtual package name 
       as the package name. For instance, in the Debian system, 
       "debconf" is both an actual package, and provided by the debconf-tiny
       package.</para>
       </listitem>
   
       <listitem><para><literal>Missing</literal> is the number of package names that were referenced in
       a dependency but were not provided by any package. Missing packages may 
       be an evidence if a full distribution is not accessed, or if a package
       (real or virtual) has been dropped from the distribution. Usually they
       are referenced from Conflicts or Breaks statements.</para>
       </listitem>

       <listitem><para><literal>Total distinct</literal> versions is the number of package versions 
       found in the cache. If more than one distribution is being accessed
       (for instance, "stable" and "unstable"), this value
       can be considerably larger than the number of total package names.</para>
       </listitem>

       <listitem><para><literal>Total dependencies</literal> is the number of dependency relationships 
       claimed by all of the packages in the cache.</para>
       </listitem>
     </itemizedlist>
     </para></listitem>
     </varlistentry>
     
     <varlistentry><term><option>showsrc</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>showsrc</literal> displays all the
     source package records that match the given package names. All
     versions are shown, as well as all records that declare the name
     to be a binary package. Use <option>--only-source</option> to
     display only source package names.
     </para></listitem>
     </varlistentry>
     
     <varlistentry><term><option>dump</option></term>
     <listitem><para><literal>dump</literal> shows a short listing of every package in the cache. It is 
     primarily for debugging.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>dumpavail</option></term>
     <listitem><para><literal>dumpavail</literal> prints out an available list to stdout. This is 
     suitable for use with &dpkg; and is used by the &dselect; method.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>unmet</option></term>
     <listitem><para><literal>unmet</literal> displays a summary of all unmet dependencies in the 
     package cache.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>show</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>show</literal> performs a function similar to 
     <command>dpkg --print-avail</command>; it displays the package records for the 
     named packages.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>search</option> <option><replaceable>&synopsis-regex;</replaceable>…</option></term>
     <listitem><para><literal>search</literal> performs a full text search on all available package
     lists for the POSIX regex pattern given, see &regex;.
     It searches the package names and the
     descriptions for an occurrence of the regular expression and prints out
     the package name and the short description, including virtual package
     names.
     If <option>--full</option> is given
     then output identical to <literal>show</literal> is produced for each matched
     package, and if <option>--names-only</option> is given then the long description
     is not searched, only the package name and provided packages are.</para>
     <para>
     Separate arguments can be used to specify multiple search patterns that 
     are and'ed together.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>depends</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>depends</literal> shows a listing of each dependency a package has 
     and all the possible other packages that can fulfill that dependency.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>rdepends</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>rdepends</literal> shows a listing of each reverse dependency a
      package has.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>pkgnames</option> <optional><replaceable>&synopsis-prefix;</replaceable></optional></term>
     <listitem><para>This command prints the name of each package APT knows. The optional
     argument is a prefix match to filter the name list. The output is suitable
     for use in a shell tab complete function and the output is generated 
     extremely quickly. This command is best used with the 
     <option>--generate</option> option.</para>
     <para>Note that a package which APT knows of is not necessarily available to download,
     installable or installed, e.g. virtual packages are also listed in the generated list.
     </para></listitem>
     </varlistentry>
     
     <varlistentry><term><option>dotty</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>dotty</literal> takes a list of packages on the command line and 
     generates output suitable for use by dotty from the 
     <ulink url="http://www.research.att.com/sw/tools/graphviz/">GraphViz</ulink>
     package. The result will be a set of nodes and edges representing the 
     relationships between the packages. By default the given packages will 
     trace out all dependent packages; this can produce a very large graph. 
     To limit the output to only the packages listed on the command line,
     set the <literal>APT::Cache::GivenOnly</literal> option.</para>

     <para>The resulting nodes will have several shapes; normal packages are boxes,
     pure virtual packages are triangles, mixed virtual packages are diamonds,
     missing packages are hexagons. Orange boxes mean recursion was stopped 
     (leaf packages), blue lines are pre-depends, green lines are conflicts.</para>

     <para>Caution, dotty cannot graph larger sets of packages.</para></listitem>
     </varlistentry>
     
     <varlistentry><term><option>xvcg</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
	 <listitem><para>The same as <literal>dotty</literal>, only for xvcg from the
	 <ulink url="http://rw4.cs.uni-sb.de/users/sander/html/gsvcg1.html">VCG tool</ulink>.
	 </para></listitem></varlistentry>

	 <varlistentry><term><option>policy</option> <optional><replaceable>&synopsis-pkg;</replaceable>…</optional></term>
     <listitem><para><literal>policy</literal> is meant to help debug issues relating to the 
     preferences file. With no arguments it will print out the 
     priorities of each source. Otherwise it prints out detailed information
     about the priority selection of the named package.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>madison</option> <option><replaceable>&synopsis-pkg;</replaceable>…</option></term>
     <listitem><para><literal>apt-cache</literal>'s <literal>madison</literal> command attempts to mimic
     the output format and a subset of the functionality of the Debian
     archive management tool, <literal>madison</literal>.  It displays
     available versions of a package in a tabular format.  Unlike the
     original <literal>madison</literal>, it can only display information for
     the architecture for which APT has retrieved package lists
     (<literal>APT::Architecture</literal>).</para></listitem>
     </varlistentry>
   </variablelist>
 </refsect1>
 
 <refsect1><title>options</title>
   &apt-cmdblurb;
   
   <variablelist>
     <varlistentry><term><option>-p</option></term><term><option>--pkg-cache</option></term>
     <listitem><para>Select the file to store the package cache. The package cache is the 
     primary cache used by all operations.
     Configuration Item: <literal>Dir::Cache::pkgcache</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>-s</option></term><term><option>--src-cache</option></term>
     <listitem><para>Select the file to store the source cache. The source is used only by
     <literal>gencaches</literal> and it stores a parsed version of the package 
     information from remote sources. When building the package cache the 
     source cache is used to avoid reparsing all of the package files.
     Configuration Item: <literal>Dir::Cache::srcpkgcache</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>-q</option></term><term><option>--quiet</option></term>
     <listitem><para>Quiet; produces output suitable for logging, omitting progress indicators.
     More q's will produce more quietness up to a maximum of 2. You can also use
     <option>-q=#</option> to set the quietness level, overriding the configuration file.
     Configuration Item: <literal>quiet</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>-i</option></term><term><option>--important</option></term>
     <listitem><para>Print only important dependencies; for use with <literal>unmet</literal>
     and <literal>depends</literal>. Causes only Depends and
     Pre-Depends relations to be printed.
     Configuration Item: <literal>APT::Cache::Important</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>--no-pre-depends</option></term>
		   <term><option>--no-depends</option></term>
		   <term><option>--no-recommends</option></term>
		   <term><option>--no-suggests</option></term>
		   <term><option>--no-conflicts</option></term>
		   <term><option>--no-breaks</option></term>
		   <term><option>--no-replaces</option></term>
		   <term><option>--no-enhances</option></term>
		   <listitem><para>Per default the <command>depends</command> and
     <command>rdepends</command> print all dependencies. This can be tweaked with
     these flags which will omit the specified dependency type.
     Configuration Item: <literal>APT::Cache::Show<replaceable>DependencyType</replaceable></literal>
     e.g. <literal>APT::Cache::ShowRecommends</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>--implicit</option></term>
	<listitem><para>Per default <command>depends</command> and <command>rdepends</command>
	      print only dependencies explicitly expressed in the metadata. With this flag
	      it will also show dependencies implicitly added based on the encountered data.
	      A <literal>Conflicts: foo</literal> e.g. expresses implicitly that this package
	      also conflicts with the package foo from any other architecture.
	      Configuration Item: <literal>APT::Cache::ShowImplicit</literal>.
	</para></listitem>
     </varlistentry>

     <varlistentry><term><option>-f</option></term><term><option>--full</option></term>
     <listitem><para>Print full package records when searching. 
     Configuration Item: <literal>APT::Cache::ShowFull</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>-a</option></term><term><option>--all-versions</option></term>
     <listitem><para>Print full records for all available versions. This is the
     default; to turn it off, use <option>--no-all-versions</option>.
     If <option>--no-all-versions</option> is specified, only the candidate version
     will be displayed (the one which would be selected for installation).
     This option is only applicable to  the <literal>show</literal> command.
     Configuration Item: <literal>APT::Cache::AllVersions</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>-g</option></term><term><option>--generate</option></term>
     <listitem><para>Perform automatic package cache regeneration, rather than use the cache 
     as it is. This is the default; to turn it off, use <option>--no-generate</option>.
     Configuration Item: <literal>APT::Cache::Generate</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>--names-only</option></term><term><option>-n</option></term>
     <listitem><para>Only search on the package and provided package names, not the long descriptions.
     Configuration Item: <literal>APT::Cache::NamesOnly</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>--all-names</option></term>
     <listitem><para>Make <literal>pkgnames</literal> print all names, including virtual packages 
     and missing dependencies. 
     Configuration Item: <literal>APT::Cache::AllNames</literal>.</para></listitem>
     </varlistentry>

     <varlistentry><term><option>--recurse</option></term>
     <listitem><para>Make <literal>depends</literal> and <literal>rdepends</literal> recursive so
     that all packages mentioned are printed once.
     Configuration Item: <literal>APT::Cache::RecurseDepends</literal>.</para></listitem>
     </varlistentry>

      <varlistentry><term><option>--installed</option></term>
      <listitem><para>
      Limit the output of <literal>depends</literal> and <literal>rdepends</literal> to
      packages which are currently installed.
      Configuration Item: <literal>APT::Cache::Installed</literal>.</para></listitem>
      </varlistentry>

      <varlistentry><term><option>--with-source</option> <option>&synopsis-param-filename;</option></term>
      <listitem><para>
      Adds the given file as a source for metadata. Can be repeated to add multiple files.
      Supported are currently <literal>*.deb</literal>, <literal>*.dsc</literal>,
      <literal>*.changes</literal>, <literal>Sources</literal> and
      <literal>Packages</literal> files as well as source package directories.
      Files are matched based on their name only, not their content!</para>
      <para><literal>Sources</literal> and <literal>Packages</literal> can be compressed in any
      format apt supports as long as they have the correct extension. If you need to store
      multiple of these files in one directory you can prefix a name of your choice with the
      last character being an underscore ("<literal>_</literal>"). Example: my.example_Packages.xz</para>
      <para>Note that these sources are treated as trusted (see &apt-secure;).
      Configuration Item: <literal>APT::Sources::With</literal>.</para></listitem>
      </varlistentry>

     &apt-commonoptions;
     
   </variablelist>
 </refsect1>

 <refsect1><title>Files</title>
   <variablelist>
     &file-sourceslist;
     &file-statelists;
   </variablelist>
 </refsect1>

 <refsect1><title>See Also</title>
   <para>&apt-conf;, &sources-list;, &apt-get;
   </para>
 </refsect1>

 <refsect1><title>Diagnostics</title>
   <para><command>apt-cache</command> returns zero on normal operation, decimal 100 on error.
   </para>
 </refsect1>

 &manbugs;
 
</refentry>