doc/apt.conf.5.xml

   1 <?xml version="1.0" encoding="utf-8" standalone="no"?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
   4
   5 <!ENTITY % aptent SYSTEM "apt.ent">
   6 %aptent;
   7
   8 <!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent">
   9 %aptverbatiment;
  10
  11 ]>
  12
  13 <refentry>
  14
  15  <refentryinfo>
  16    &apt-author.jgunthorpe;
  17    &apt-author.team;
  18    <author>
  19      &apt-name.dburrows;
  20      <contrib>Initial documentation of Debug::*.</contrib>
  21    </author>
  22    &apt-email;
  23    &apt-product;
  24    <!-- The last update date -->
  25    <date>2012-05-21T00:00:00Z</date>
  26  </refentryinfo>
  27
  28  <refmeta>
  29    <refentrytitle>apt.conf</refentrytitle>
  30    <manvolnum>5</manvolnum>
  31    <refmiscinfo class="manual">APT</refmiscinfo>
  32  </refmeta>
  33
  34  <!-- Man page title -->
  35  <refnamediv>
  36     <refname>apt.conf</refname>
  37     <refpurpose>Configuration file for APT</refpurpose>
  38  </refnamediv>
  39
  40  <refsect1><title>Description</title>
  41  <para><filename>apt.conf</filename> is the main configuration file for
  42    the APT suite of tools, but by far not the only place changes to options
  43    can be made. All tools therefore share the configuration files and also
  44    use a common command line parser to provide a uniform environment.</para>
  45    <orderedlist>
  46       <para>When an APT tool starts up it will read the configuration files
  47       in the following order:</para>
  48       <listitem><para>the file specified by the <envar>APT_CONFIG</envar>
  49          environment variable (if any)</para></listitem>
  50       <listitem><para>all files in <literal>Dir::Etc::Parts</literal> in
  51          alphanumeric ascending order which have either no or "<literal>conf</literal>"
  52          as filename extension and which only contain alphanumeric,
  53          hyphen (-), underscore (_) and period (.) characters.
  54          Otherwise APT will print a notice that it has ignored a file if the file
  55          doesn't match a pattern in the <literal>Dir::Ignore-Files-Silently</literal>
  56          configuration list - in this case it will be silently ignored.</para></listitem>
  57       <listitem><para>the main configuration file specified by
  58          <literal>Dir::Etc::main</literal></para></listitem>
  59       <listitem><para>the command line options are applied to override the
  60          configuration directives or to load even more configuration files.</para></listitem>
  61    </orderedlist>
  62    </refsect1>
  63    <refsect1><title>Syntax</title>
  64    <para>The configuration file is organized in a tree with options organized into
  65    functional groups. Option specification is given with a double colon
  66    notation, for instance <literal>APT::Get::Assume-Yes</literal> is an option within
  67    the APT tool group, for the Get tool. Options do not inherit from their
  68    parent groups.</para>
  69
  70    <para>Syntactically the configuration language is modeled after what the ISC tools
  71    such as bind and dhcp use. Lines starting with
  72    <literal>//</literal> are treated as comments (ignored), as well as all text
  73    between <literal>/*</literal> and <literal>*/</literal>, just like C/C++ comments.
  74    Each line is of the form
  75    <literal>APT::Get::Assume-Yes "true";</literal>. The trailing
  76    semicolon and the quotes are required. The value must be on one line, and
  77    there is no kind of string concatenation. It must not include inside quotes.
  78    The behavior of the backslash "\" and escaped characters inside a value is
  79    undefined and it should not be used. An option name may include
  80    alphanumerical characters and the "/-:._+" characters. A new scope can
  81    be opened with curly braces, like:</para>
  82
  83 <informalexample><programlisting>
  84 APT {
  85   Get {
  86     Assume-Yes "true";
  87     Fix-Broken "true";
  88   };
  89 };
  90 </programlisting></informalexample>
  91
  92    <para>with newlines placed to make it more readable. Lists can be created by
  93    opening a scope and including a single string enclosed in quotes followed by a
  94    semicolon. Multiple entries can be included, each separated by a semicolon.</para>
  95
  96 <informalexample><programlisting>
  97 DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
  98 </programlisting></informalexample>
  99
 100    <para>In general the sample configuration file in
 101    <filename>&docdir;examples/apt.conf</filename> &configureindex;
 102    is a good guide for how it should look.</para>
 103
 104    <para>The names of the configuration items are not case-sensitive. So in the previous example
 105    you could use <literal>dpkg::pre-install-pkgs</literal>.</para>
 106
 107    <para>Names for the configuration items are optional if a list is defined as it can be see in
 108    the <literal>DPkg::Pre-Install-Pkgs</literal> example above. If you don't specify a name a
 109    new entry will simply add a new option to the list. If you specify a name you can override
 110    the option as every other option by reassigning a new value to the option.</para>
 111
 112    <para>Two specials are allowed, <literal>#include</literal> (which is deprecated
 113    and not supported by alternative implementations) and <literal>#clear</literal>:
 114    <literal>#include</literal> will include the given file, unless the filename
 115    ends in a slash, then the whole directory is included.
 116    <literal>#clear</literal> is used to erase a part of the configuration tree. The
 117    specified element and all its descendants are erased.
 118    (Note that these lines also need to end with a semicolon.)</para>
 119
 120    <para>The #clear command is the only way to delete a list or a complete scope.
 121    Reopening a scope or the ::-style described below will <emphasis>not</emphasis>
 122    override previously written entries. Only options can be overridden by addressing a new
 123    value to it - lists and scopes can't be overridden, only cleared.</para>
 124
 125    <para>All of the APT tools take a -o option which allows an arbitrary configuration
 126    directive to be specified on the command line. The syntax is a full option
 127    name (<literal>APT::Get::Assume-Yes</literal> for instance) followed by an equals
 128    sign then the new value of the option. To append a new element to a list, add a
 129    trailing :: to the name of the list. (As you might suspect: The scope syntax can't
 130    be used on the command line.)</para>
 131
 132    <para>Note that you can use :: only for appending one item per line to a list and
 133    that you should not use it in combination with the scope syntax.
 134    (The scope syntax implicit insert ::) Using both syntaxes together will trigger a bug
 135    which some users unfortunately depend on: An option with the unusual name "<literal>::</literal>"
 136    which acts like every other option with a name. These introduces many problems
 137    including that a user who writes multiple lines in this <emphasis>wrong</emphasis> syntax in
 138    the hope to append to a list will gain the opposite as only the last assignment for this option
 139    "<literal>::</literal>" will be used. Upcoming APT versions will raise errors and
 140    will stop working if they encounter this misuse, so please correct such statements now
 141    as long as APT doesn't complain explicit about them.</para>
 142  </refsect1>
 143
 144  <refsect1><title>The APT Group</title>
 145    <para>This group of options controls general APT behavior as well as holding the
 146    options for all of the tools.</para>
 147
 148    <variablelist>
 149      <varlistentry><term><option>Architecture</option></term>
 150      <listitem><para>System Architecture; sets the architecture to use when fetching files and
 151      parsing package lists. The internal default is the architecture apt was
 152      compiled for.</para></listitem>
 153      </varlistentry>
 154
 155      <varlistentry><term><option>Architectures</option></term>
 156      <listitem><para>All Architectures the system supports. Processors implementing the
 157      <literal>amd64</literal> (also called <literal>x86-64</literal>) instruction set are
 158      e.g. also able to execute binaries compiled for the <literal>i386</literal>
 159      (<literal>x86</literal>) instruction set; This list is use when fetching files and
 160      parsing package lists. The internal default is always the native architecture (<literal>APT::Architecture</literal>)
 161      and all foreign architectures it can retrieve by calling <command>dpkg --print-foreign-architectures</command>.
 162      </para></listitem>
 163      </varlistentry>
 164
 165      <varlistentry><term><option>Default-Release</option></term>
 166      <listitem><para>Default release to install packages from if more than one
 167      version available. Contains release name, codename or release version. Examples: 'stable', 'testing',
 168      'unstable', '&stable-codename;', '&testing-codename;', '4.0', '5.0*'. See also &apt-preferences;.</para></listitem>
 169      </varlistentry>
 170
 171      <varlistentry><term><option>Ignore-Hold</option></term>
 172      <listitem><para>Ignore Held packages; This global option causes the problem resolver to
 173      ignore held packages in its decision making.</para></listitem>
 174      </varlistentry>
 175
 176      <varlistentry><term><option>Clean-Installed</option></term>
 177      <listitem><para>Defaults to on. When turned on the autoclean feature will remove any packages
 178      which can no longer be downloaded from the cache. If turned off then
 179      packages that are locally installed are also excluded from cleaning - but
 180      note that APT provides no direct means to reinstall them.</para></listitem>
 181      </varlistentry>
 182
 183      <varlistentry><term><option>Immediate-Configure</option></term>
 184      <listitem><para>Defaults to on which will cause APT to install essential and important packages
 185      as fast as possible in the install/upgrade operation. This is done to limit the effect of a failing
 186      &dpkg; call: If this option is disabled APT does treat an important package in the same way as
 187      an extra package: Between the unpacking of the important package A and his configuration can then
 188      be many other unpack or configuration calls, e.g. for package B which has no relation to A, but
 189      causes the dpkg call to fail (e.g. because maintainer script of package B generates an error) which results
 190      in a system state in which package A is unpacked but unconfigured - each package depending on A is now no
 191      longer guaranteed to work as their dependency on A is not longer satisfied. The immediate configuration marker
 192      is also applied to all dependencies which can generate a problem if the dependencies e.g. form a circle
 193      as a dependency with the immediate flag is comparable with a Pre-Dependency. So in theory it is possible
 194      that APT encounters a situation in which it is unable to perform immediate configuration, errors out and
 195      refers to this option so the user can deactivate the immediate configuration temporarily to be able to perform
 196      an install/upgrade again. Note the use of the word "theory" here as this problem was only encountered by now
 197      in real world a few times in non-stable distribution versions and was caused by wrong dependencies of the package
 198      in question or by a system in an already broken state, so you should not blindly disable this option as
 199      the mentioned scenario above is not the only problem immediate configuration can help to prevent in the first place.
 200      Before a big operation like <literal>dist-upgrade</literal> is run with this option disabled it should be tried to
 201      explicitly <literal>install</literal> the package APT is unable to configure immediately, but please make sure to
 202      report your problem also to your distribution and to the APT team with the buglink below so they can work on
 203      improving or correcting the upgrade process.</para></listitem>
 204      </varlistentry>
 205
 206      <varlistentry><term><option>Force-LoopBreak</option></term>
 207      <listitem><para>Never Enable this option unless you -really- know what you are doing. It
 208      permits APT to temporarily remove an essential package to break a
 209      Conflicts/Conflicts or Conflicts/Pre-Depend loop between two essential
 210      packages. SUCH A LOOP SHOULD NEVER EXIST AND IS A GRAVE BUG. This option
 211      will work if the essential packages are not tar, gzip, libc, dpkg, bash or
 212      anything that those packages depend on.</para></listitem>
 213      </varlistentry>
 214
 215      <varlistentry><term><option>Cache-Start</option></term><term><option>Cache-Grow</option></term><term><option>Cache-Limit</option></term>
 216      <listitem><para>APT uses since version 0.7.26 a resizable memory mapped cache file to store the 'available'
 217      information. <literal>Cache-Start</literal> acts as a hint to which size the Cache will grow
 218      and is therefore the amount of memory APT will request at startup. The default value is
 219      20971520 bytes (~20 MB). Note that this amount of space needs to be available for APT
 220      otherwise it will likely fail ungracefully, so for memory restricted devices this value should
 221      be lowered while on systems with a lot of configured sources it should be increased.
 222      <literal>Cache-Grow</literal> defines in bytes with the default of 1048576 (~1 MB) how much
 223      the Cache size will be increased in the event the space defined by <literal>Cache-Start</literal>
 224      is not enough. These value will be applied again and again until either the cache is big
 225      enough to store all information or the size of the cache reaches the <literal>Cache-Limit</literal>.
 226      The default of <literal>Cache-Limit</literal> is 0 which stands for no limit.
 227      If <literal>Cache-Grow</literal> is set to 0 the automatic grow of the cache is disabled.
 228      </para></listitem>
 229      </varlistentry>
 230
 231      <varlistentry><term><option>Build-Essential</option></term>
 232      <listitem><para>Defines which package(s) are considered essential build dependencies.</para></listitem>
 233      </varlistentry>
 234
 235      <varlistentry><term><option>Get</option></term>
 236      <listitem><para>The Get subsection controls the &apt-get; tool, please see its
 237      documentation for more information about the options here.</para></listitem>
 238      </varlistentry>
 239
 240      <varlistentry><term><option>Cache</option></term>
 241      <listitem><para>The Cache subsection controls the &apt-cache; tool, please see its
 242      documentation for more information about the options here.</para></listitem>
 243      </varlistentry>
 244
 245      <varlistentry><term><option>CDROM</option></term>
 246      <listitem><para>The CDROM subsection controls the &apt-cdrom; tool, please see its
 247      documentation for more information about the options here.</para></listitem>
 248      </varlistentry>
 249    </variablelist>
 250  </refsect1>
 251
 252  <refsect1><title>The Acquire Group</title>
 253    <para>The <literal>Acquire</literal> group of options controls the download of packages
 254    and the URI handlers.
 255
 256    <variablelist>
 257      <varlistentry><term><option>Check-Valid-Until</option></term>
 258          <listitem><para>Security related option defaulting to true as an
 259          expiring validation for a Release file prevents longtime replay attacks
 260          and can e.g. also help users to identify no longer updated mirrors -
 261          but the feature depends on the correctness of the time on the user system.
 262          Archive maintainers are encouraged to create Release files with the
 263          <literal>Valid-Until</literal> header, but if they don't or a stricter value
 264          is volitional the following <literal>Max-ValidTime</literal> option can be used.
 265          </para></listitem>
 266      </varlistentry>
 267
 268      <varlistentry><term><option>Max-ValidTime</option></term>
 269          <listitem><para>Seconds the Release file should be considered valid after
 270          it was created (indicated by the <literal>Date</literal> header).
 271          If the Release file itself includes a <literal>Valid-Until</literal> header
 272          the earlier date of the two is used as the expiration date.
 273          The default value is <literal>0</literal> which stands for "for ever valid".
 274          Archive specific settings can be made by appending the label of the archive
 275          to the option name.
 276          </para></listitem>
 277      </varlistentry>
 278
 279      <varlistentry><term><option>Min-ValidTime</option></term>
 280          <listitem><para>Minimum of seconds the Release file should be considered
 281          valid after it was created (indicated by the <literal>Date</literal> header).
 282          Use this if you need to use a seldomly updated (local) mirror of a more
 283          regular updated archive with a <literal>Valid-Until</literal> header
 284          instead of completely disabling the expiration date checking.
 285          Archive specific settings can and should be used by appending the label of
 286          the archive to the option name.
 287          </para></listitem>
 288      </varlistentry>
 289
 290      <varlistentry><term><option>PDiffs</option></term>
 291          <listitem><para>Try to download deltas called <literal>PDiffs</literal> for
 292          Packages or Sources files instead of downloading whole ones. True
 293          by default.</para>
 294          <para>Two sub-options to limit the use of PDiffs are also available:
 295          With <literal>FileLimit</literal> can be specified how many PDiff files
 296          are downloaded at most to update a file. <literal>SizeLimit</literal>
 297          on the other hand is the maximum percentage of the size of all patches
 298          compared to the size of the targeted file. If one of these limits is
 299          exceeded the complete file is downloaded instead of the patches.
 300          </para></listitem>
 301      </varlistentry>
 302
 303      <varlistentry><term><option>Queue-Mode</option></term>
 304      <listitem><para>Queuing mode; <literal>Queue-Mode</literal> can be one of <literal>host</literal> or
 305      <literal>access</literal> which determines how  APT parallelizes outgoing
 306      connections. <literal>host</literal> means that one connection per target host
 307      will be opened, <literal>access</literal> means that one connection per URI type
 308      will be opened.</para></listitem>
 309      </varlistentry>
 310
 311      <varlistentry><term><option>Retries</option></term>
 312      <listitem><para>Number of retries to perform. If this is non-zero APT will retry failed
 313      files the given number of times.</para></listitem>
 314      </varlistentry>
 315
 316      <varlistentry><term><option>Source-Symlinks</option></term>
 317      <listitem><para>Use symlinks for source archives. If set to true then source archives will
 318      be symlinked when possible instead of copying. True is the default.</para></listitem>
 319      </varlistentry>
 320
 321      <varlistentry><term><option>http</option></term>
 322      <listitem><para>HTTP URIs; http::Proxy is the default http proxy to use. It is in the
 323      standard form of <literal>http://[[user][:pass]@]host[:port]/</literal>. Per
 324      host proxies can also be specified by using the form
 325      <literal>http::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal>
 326          meaning to use no proxies. If no one of the above settings is specified,
 327          <envar>http_proxy</envar> environment variable
 328          will be used.</para>
 329
 330      <para>Three settings are provided for cache control with HTTP/1.1 compliant
 331      proxy caches. <literal>No-Cache</literal> tells the proxy to not use its cached
 332      response under any circumstances, <literal>Max-Age</literal> is sent only for
 333      index files and tells the cache to refresh its object if it is older than
 334      the given number of seconds. Debian updates its index files daily so the
 335      default is 1 day. <literal>No-Store</literal> specifies that the cache should never
 336      store this request, it is only set for archive files. This may be useful
 337      to prevent polluting a proxy cache with very large .deb files. Note:
 338      Squid 2.0.2 does not support any of these options.</para>
 339
 340      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 341      this applies to all things including connection timeout and data timeout.</para>
 342
 343      <para>The setting <literal>Acquire::http::Pipeline-Depth</literal> can be used to
 344      enabled HTTP pipeling (RFC 2616 section 8.1.2.2) which can be beneficial e.g. on
 345      high-latency connections. It specifies how many requests are send in a pipeline.
 346      Previous APT versions had a default of 10 for this setting, but the default value
 347      is now 0 (= disabled) to avoid problems with the ever-growing amount of webservers
 348      and proxies which choose to not conform to the HTTP/1.1 specification.</para>
 349
 350      <para><literal>Acquire::http::AllowRedirect</literal> controls if APT will follow
 351      redirects, which is enabled by default.</para>
 352
 353      <para>The used bandwidth can be limited with <literal>Acquire::http::Dl-Limit</literal>
 354      which accepts integer values in kilobyte. The default value is 0 which deactivates
 355      the limit and tries uses as much as possible of the bandwidth (Note that this option implicit
 356      deactivates the download from multiple servers at the same time.)</para>
 357
 358      <para><literal>Acquire::http::User-Agent</literal> can be used to set a different
 359      User-Agent for the http download method as some proxies allow access for clients
 360      only if the client uses a known identifier.</para>
 361      </listitem>
 362      </varlistentry>
 363
 364      <varlistentry><term><option>https</option></term>
 365          <listitem><para>HTTPS URIs. Cache-control, Timeout, AllowRedirect, Dl-Limit and
 366          proxy options are the same as for <literal>http</literal> method and will also
 367          default to the options from the <literal>http</literal> method if they are not
 368          explicitly set for https. <literal>Pipeline-Depth</literal> option is not
 369          supported yet.</para>
 370
 371          <para><literal>CaInfo</literal> suboption specifies place of file that
 372          holds info about trusted certificates.
 373          <literal>&lt;host&gt;::CaInfo</literal> is corresponding per-host option.
 374          <literal>Verify-Peer</literal> boolean suboption determines whether verify
 375          server's host certificate against trusted certificates or not.
 376          <literal>&lt;host&gt;::Verify-Peer</literal> is corresponding per-host option.
 377          <literal>Verify-Host</literal> boolean suboption determines whether verify
 378          server's hostname or not.
 379          <literal>&lt;host&gt;::Verify-Host</literal> is corresponding per-host option.
 380          <literal>SslCert</literal> determines what certificate to use for client
 381          authentication. <literal>&lt;host&gt;::SslCert</literal> is corresponding per-host option.
 382          <literal>SslKey</literal> determines what private key to use for client
 383          authentication. <literal>&lt;host&gt;::SslKey</literal> is corresponding per-host option.
 384          <literal>SslForceVersion</literal> overrides default SSL version to use.
 385          Can contain 'TLSv1' or 'SSLv3' string.
 386          <literal>&lt;host&gt;::SslForceVersion</literal> is corresponding per-host option.
 387          </para></listitem></varlistentry>
 388
 389      <varlistentry><term><option>ftp</option></term>
 390      <listitem><para>FTP URIs; ftp::Proxy is the default ftp proxy to use. It is in the
 391      standard form of <literal>ftp://[[user][:pass]@]host[:port]/</literal>. Per
 392      host proxies can also be specified by using the form
 393      <literal>ftp::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal>
 394          meaning to use no proxies. If no one of the above settings is specified,
 395          <envar>ftp_proxy</envar> environment variable
 396          will be used. To use a ftp
 397      proxy you will have to set the <literal>ftp::ProxyLogin</literal> script in the
 398      configuration file. This entry specifies the commands to send to tell
 399      the proxy server what to connect to. Please see
 400      &configureindex; for an example of
 401      how to do this. The substitution variables available are
 402      <literal>$(PROXY_USER)</literal> <literal>$(PROXY_PASS)</literal> <literal>$(SITE_USER)</literal>
 403      <literal>$(SITE_PASS)</literal> <literal>$(SITE)</literal> and <literal>$(SITE_PORT)</literal>
 404      Each is taken from it's respective URI component.</para>
 405
 406      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 407      this applies to all things including connection timeout and data timeout.</para>
 408
 409      <para>Several settings are provided to control passive mode. Generally it is
 410      safe to leave passive mode on, it works in nearly every environment.
 411      However some situations require that passive mode be disabled and port
 412      mode ftp used instead. This can be done globally, for connections that
 413      go through a proxy or for a specific host (See the sample config file
 414      for examples).</para>
 415
 416      <para>It is possible to proxy FTP over HTTP by setting the <envar>ftp_proxy</envar>
 417      environment variable to a http url - see the discussion of the http method
 418      above for syntax. You cannot set this in the configuration file and it is
 419      not recommended to use FTP over HTTP due to its low efficiency.</para>
 420
 421      <para>The setting <literal>ForceExtended</literal> controls the use of RFC2428
 422      <literal>EPSV</literal> and <literal>EPRT</literal> commands. The default is false, which means
 423      these commands are only used if the control connection is IPv6. Setting this
 424      to true forces their use even on IPv4 connections. Note that most FTP servers
 425      do not support RFC2428.</para></listitem>
 426      </varlistentry>
 427
 428      <varlistentry><term><option>cdrom</option></term>
 429      <listitem><para>CDROM URIs; the only setting for CDROM URIs is the mount point,
 430      <literal>cdrom::Mount</literal> which must be the mount point for the CDROM drive
 431      as specified in <filename>/etc/fstab</filename>. It is possible to provide
 432      alternate mount and unmount commands if your mount point cannot be listed
 433      in the fstab (such as an SMB mount and old mount packages). The syntax
 434      is to put <literallayout>/cdrom/::Mount "foo";</literallayout> within
 435      the cdrom block. It is important to have the trailing slash. Unmount
 436      commands can be specified using UMount.</para></listitem>
 437      </varlistentry>
 438
 439      <varlistentry><term><option>gpgv</option></term>
 440      <listitem><para>GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv.
 441      <literal>gpgv::Options</literal> Additional options passed to gpgv.
 442      </para></listitem>
 443      </varlistentry>
 444
 445      <varlistentry><term><option>CompressionTypes</option></term>
 446      <listitem><para>List of compression types which are understood by the acquire methods.
 447      Files like <filename>Packages</filename> can be available in various compression formats.
 448      Per default the acquire methods can decompress <command>bzip2</command>, <command>lzma</command>
 449      and <command>gzip</command> compressed files, with this setting more formats can be added
 450      on the fly or the used method can be changed. The syntax for this is:
 451      <synopsis>Acquire::CompressionTypes::<replaceable>FileExtension</replaceable> "<replaceable>Methodname</replaceable>";</synopsis>
 452      </para><para>Also the <literal>Order</literal> subgroup can be used to define in which order
 453      the acquire system will try to download the compressed files. The acquire system will try the first
 454      and proceed with the next compression type in this list on error, so to prefer one over the other type
 455      simple add the preferred type at first - not already added default types will be added at run time
 456      to the end of the list, so e.g. <synopsis>Acquire::CompressionTypes::Order:: "gz";</synopsis> can
 457      be used to prefer <command>gzip</command> compressed files over <command>bzip2</command> and <command>lzma</command>.
 458      If <command>lzma</command> should be preferred over <command>gzip</command> and <command>bzip2</command> the
 459      configure setting should look like this <synopsis>Acquire::CompressionTypes::Order { "lzma"; "gz"; };</synopsis>
 460      It is not needed to add <literal>bz2</literal> explicit to the list as it will be added automatic.</para>
 461      <para>Note that at run time the <literal>Dir::Bin::<replaceable>Methodname</replaceable></literal> will
 462      be checked: If this setting exists the method will only be used if this file exists, e.g. for
 463      the bzip2 method (the inbuilt) setting is: <literallayout>Dir::Bin::bzip2 "/bin/bzip2";</literallayout>
 464      Note also that list entries specified on the command line will be added at the end of the list
 465      specified in the configuration files, but before the default entries. To prefer a type in this case
 466      over the ones specified in the configuration files you can set the option direct - not in list style.
 467      This will not override the defined list, it will only prefix the list with this type.</para>
 468      <para>The special type <literal>uncompressed</literal> can be used to give uncompressed files a
 469      preference, but note that most archives don't provide uncompressed files so this is mostly only
 470      useable for local mirrors.</para></listitem>
 471      </varlistentry>
 472
 473      <varlistentry><term><option>GzipIndexes</option></term>
 474          <listitem><para>
 475          When downloading <literal>gzip</literal> compressed indexes (Packages, Sources, or
 476          Translations), keep them gzip compressed locally instead of unpacking
 477          them. This saves quite a lot of disk space at the expense of more CPU
 478          requirements when building the local package caches. False by default.
 479          </para></listitem>
 480      </varlistentry>
 481
 482      <varlistentry><term><option>Languages</option></term>
 483      <listitem><para>The Languages subsection controls which <filename>Translation</filename> files are downloaded
 484      and in which order APT tries to display the Description-Translations. APT will try to display the first
 485      available Description in the Language which is listed at first. Languages can be defined with their
 486      short or long Languagecodes. Note that not all archives provide <filename>Translation</filename>
 487      files for every Language - especially the long Languagecodes are rare, so please
 488      inform you which ones are available before you set here impossible values.</para>
 489      <para>The default list includes "environment" and "en". "<literal>environment</literal>" has a special meaning here:
 490      It will be replaced at runtime with the languagecodes extracted from the <literal>LC_MESSAGES</literal> environment variable.
 491      It will also ensure that these codes are not included twice in the list. If <literal>LC_MESSAGES</literal>
 492      is set to "C" only the <filename>Translation-en</filename> file (if available) will be used.
 493      To force apt to use no Translation file use the setting <literal>Acquire::Languages=none</literal>. "<literal>none</literal>"
 494      is another special meaning code which will stop the search for a fitting <filename>Translation</filename> file.
 495      This can be used by the system administrator to let APT know that it should download also this files without
 496      actually use them if the environment doesn't specify this languages. So the following example configuration will
 497      result in the order "en, de" in an english and in "de, en" in a german localization. Note that "fr" is downloaded,
 498      but not used if APT is not used in a french localization, in such an environment the order would be "fr, de, en".
 499      <programlisting>Acquire::Languages { "environment"; "de"; "en"; "none"; "fr"; };</programlisting></para>
 500      <para>Note: To prevent problems resulting from APT being executed in different environments
 501      (e.g. by different users or by other programs) all Translation files which are found in
 502      <filename>/var/lib/apt/lists/</filename> will be added to the end of the list
 503      (after an implicit "<literal>none</literal>").</para>
 504      </listitem>
 505      </varlistentry>
 506
 507    </variablelist>
 508   </para>
 509  </refsect1>
 510
 511  <refsect1><title>Directories</title>
 512
 513    <para>The <literal>Dir::State</literal> section has directories that pertain to local
 514    state information. <literal>lists</literal> is the directory to place downloaded
 515    package lists in and <literal>status</literal> is the name of the dpkg status file.
 516    <literal>preferences</literal> is the name of the APT <filename>preferences</filename> file.
 517    <literal>Dir::State</literal> contains the default directory to prefix on all sub
 518    items if they do not start with <filename>/</filename> or <filename>./</filename>.</para>
 519
 520    <para><literal>Dir::Cache</literal> contains locations pertaining to local cache
 521    information, such as the two package caches <literal>srcpkgcache</literal> and
 522    <literal>pkgcache</literal> as well as the location to place downloaded archives,
 523    <literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
 524    by setting their names to be blank. This will slow down startup but
 525    save disk space. It is probably preferred to turn off the pkgcache rather
 526    than the srcpkgcache. Like <literal>Dir::State</literal> the default
 527    directory is contained in <literal>Dir::Cache</literal></para>
 528
 529    <para><literal>Dir::Etc</literal> contains the location of configuration files,
 530    <literal>sourcelist</literal> gives the location of the sourcelist and
 531    <literal>main</literal> is the default configuration file (setting has no effect,
 532    unless it is done from the config file specified by
 533    <envar>APT_CONFIG</envar>).</para>
 534
 535    <para>The <literal>Dir::Parts</literal> setting reads in all the config fragments in
 536    lexical order from the directory specified. After this is done then the
 537    main config file is loaded.</para>
 538
 539    <para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal>
 540    specifies the location of the method handlers and <literal>gzip</literal>,
 541    <literal>bzip2</literal>, <literal>lzma</literal>,
 542    <literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal>
 543    <literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
 544    of the respective programs.</para>
 545
 546    <para>
 547      The configuration item <literal>RootDir</literal> has a special
 548      meaning.  If set, all paths in <literal>Dir::</literal> will be
 549      relative to <literal>RootDir</literal>, <emphasis>even paths that
 550      are specified absolutely</emphasis>.  So, for instance, if
 551      <literal>RootDir</literal> is set to
 552      <filename>/tmp/staging</filename> and
 553      <literal>Dir::State::status</literal> is set to
 554      <filename>/var/lib/dpkg/status</filename>, then the status file
 555      will be looked up in
 556      <filename>/tmp/staging/var/lib/dpkg/status</filename>.
 557    </para>
 558
 559    <para>
 560       The <literal>Ignore-Files-Silently</literal> list can be used to specify
 561       which files APT should silently ignore while parsing the files in the
 562       fragment directories. Per default a file which end with <literal>.disabled</literal>,
 563       <literal>~</literal>, <literal>.bak</literal> or <literal>.dpkg-[a-z]+</literal>
 564       is silently ignored. As seen in the last default value these patterns can use regular
 565       expression syntax.
 566    </para>
 567  </refsect1>
 568
 569  <refsect1><title>APT in DSelect</title>
 570    <para>
 571    When APT is used as a &dselect; method several configuration directives
 572    control the default behaviour. These are in the <literal>DSelect</literal> section.</para>
 573
 574    <variablelist>
 575      <varlistentry><term><option>Clean</option></term>
 576      <listitem><para>Cache Clean mode; this value may be one of always, prompt, auto,
 577      pre-auto and never.  always and prompt will remove all packages from
 578      the cache after upgrading, prompt (the default) does so conditionally.
 579      auto removes only those packages which are no longer downloadable
 580      (replaced with a new version for instance).  pre-auto performs this
 581      action before downloading new packages.</para></listitem>
 582      </varlistentry>
 583
 584      <varlistentry><term><option>options</option></term>
 585      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 586      options when it is run for the install phase.</para></listitem>
 587      </varlistentry>
 588
 589      <varlistentry><term><option>Updateoptions</option></term>
 590      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 591      options when it is run for the update phase.</para></listitem>
 592      </varlistentry>
 593
 594      <varlistentry><term><option>PromptAfterUpdate</option></term>
 595      <listitem><para>If true the [U]pdate operation in &dselect; will always prompt to continue.
 596      The default is to prompt only on error.</para></listitem>
 597      </varlistentry>
 598    </variablelist>
 599  </refsect1>
 600
 601  <refsect1><title>How APT calls dpkg</title>
 602    <para>Several configuration directives control how APT invokes &dpkg;. These are
 603    in the <literal>DPkg</literal> section.</para>
 604
 605    <variablelist>
 606      <varlistentry><term><option>options</option></term>
 607      <listitem><para>This is a list of options to pass to dpkg. The options must be specified
 608      using the list notation and each list item is passed as a single argument
 609      to &dpkg;.</para></listitem>
 610      </varlistentry>
 611
 612      <varlistentry><term><option>Pre-Invoke</option></term><term><option>Post-Invoke</option></term>
 613      <listitem><para>This is a list of shell commands to run before/after invoking &dpkg;.
 614      Like <literal>options</literal> this must be specified in list notation. The
 615      commands are invoked in order using <filename>/bin/sh</filename>, should any
 616      fail APT will abort.</para></listitem>
 617      </varlistentry>
 618
 619      <varlistentry><term><option>Pre-Install-Pkgs</option></term>
 620      <listitem><para>This is a list of shell commands to run before invoking dpkg. Like
 621      <literal>options</literal> this must be specified in list notation. The commands
 622      are invoked in order using <filename>/bin/sh</filename>, should any fail APT
 623      will abort. APT will pass to the commands on standard input the
 624      filenames of all .deb files it is going to install, one per line.</para>
 625
 626      <para>Version 2 of this protocol dumps more information, including the
 627      protocol version, the APT configuration space and the packages, files
 628      and versions being changed. Version 2 is enabled by setting
 629      <literal>DPkg::Tools::options::cmd::Version</literal> to 2. <literal>cmd</literal> is a
 630      command given to <literal>Pre-Install-Pkgs</literal>.</para></listitem>
 631      </varlistentry>
 632
 633      <varlistentry><term><option>Run-Directory</option></term>
 634      <listitem><para>APT chdirs to this directory before invoking dpkg, the default is
 635      <filename>/</filename>.</para></listitem>
 636      </varlistentry>
 637
 638      <varlistentry><term><option>Build-options</option></term>
 639      <listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages,
 640      the default is to disable signing and produce all binaries.</para></listitem>
 641      </varlistentry>
 642    </variablelist>
 643
 644    <refsect2><title>dpkg trigger usage (and related options)</title>
 645      <para>APT can call dpkg in a way so it can make aggressive use of triggers over
 646      multiple calls of dpkg. Without further options dpkg will use triggers only in between his
 647      own run. Activating these options can therefore decrease the time needed to perform the
 648      install / upgrade. Note that it is intended to activate these options per default in the
 649      future, but as it changes the way APT calling dpkg drastically it needs a lot more testing.
 650      <emphasis>These options are therefore currently experimental and should not be used in
 651      productive environments.</emphasis> Also it breaks the progress reporting so all frontends will
 652      currently stay around half (or more) of the time in the 100% state while it actually configures
 653      all packages.</para>
 654      <para>Note that it is not guaranteed that APT will support these options or that these options will
 655      not cause (big) trouble in the future. If you have understand the current risks and problems with
 656      these options, but are brave enough to help testing them create a new configuration file and test a
 657      combination of options. Please report any bugs, problems and improvements you encounter and make sure
 658      to note which options you have used in your reports. Asking dpkg for help could also be useful for
 659      debugging proposes, see e.g. <command>dpkg --audit</command>. A defensive option combination would be
 660 <literallayout>DPkg::NoTriggers "true";
 661 PackageManager::Configure "smart";
 662 DPkg::ConfigurePending "true";
 663 DPkg::TriggersPending "true";</literallayout></para>
 664
 665      <variablelist>
 666        <varlistentry><term><option>DPkg::NoTriggers</option></term>
 667        <listitem><para>Add the no triggers flag to all dpkg calls (except the ConfigurePending call).
 668        See &dpkg; if you are interested in what this actually means. In short: dpkg will not run the
 669        triggers when this flag is present unless it is explicitly called to do so in an extra call.
 670        Note that this option exists (undocumented) also in older apt versions with a slightly different
 671        meaning: Previously these option only append --no-triggers to the configure calls to dpkg -
 672        now apt will add these flag also to the unpack and remove calls.</para></listitem>
 673        </varlistentry>
 674        <varlistentry><term><option>PackageManager::Configure</option></term>
 675        <listitem><para>Valid values are "<literal>all</literal>", "<literal>smart</literal>" and "<literal>no</literal>".
 676        "<literal>all</literal>" is the default value and causes APT to configure all packages explicit.
 677        The "<literal>smart</literal>" way is it to configure only packages which need to be configured before
 678        another package can be unpacked (Pre-Depends) and let the rest configure by dpkg with a call generated
 679        by the next option. "<literal>no</literal>" on the other hand will not configure anything and totally
 680        rely on dpkg for configuration (which will at the moment fail if a Pre-Depends is encountered).
 681        Setting this option to another than the all value will implicitly activate also the next option per
 682        default as otherwise the system could end in an unconfigured status which could be unbootable!
 683        </para></listitem>
 684        </varlistentry>
 685        <varlistentry><term><option>DPkg::ConfigurePending</option></term>
 686        <listitem><para>If this option is set apt will call <command>dpkg --configure --pending</command>
 687        to let dpkg handle all required configurations and triggers. This option is activated automatic
 688        per default if the previous option is not set to <literal>all</literal>, but deactivating could be useful
 689        if you want to run APT multiple times in a row - e.g. in an installer. In these sceneries you could
 690        deactivate this option in all but the last run.</para></listitem>
 691        </varlistentry>
 692        <varlistentry><term><option>DPkg::TriggersPending</option></term>
 693        <listitem><para>Useful for <literal>smart</literal> configuration as a package which has pending
 694        triggers is not considered as <literal>installed</literal> and dpkg treats them as <literal>unpacked</literal>
 695        currently which is a dealbreaker for Pre-Dependencies (see debbugs #526774). Note that this will
 696        process all triggers, not only the triggers needed to configure this package.</para></listitem>
 697        </varlistentry>
 698        <varlistentry><term><option>PackageManager::UnpackAll</option></term>
 699        <listitem><para>As the configuration can be deferred to be done at the end by dpkg it can be
 700        tried to order the unpack series only by critical needs, e.g. by Pre-Depends. Default is true
 701        and therefore the "old" method of ordering in various steps by everything. While both method
 702        were present in earlier APT versions the <literal>OrderCritical</literal> method was unused, so
 703        this method is very experimental and needs further improvements before becoming really useful.
 704        </para></listitem>
 705        </varlistentry>
 706        <varlistentry><term><option>OrderList::Score::Immediate</option></term>
 707        <listitem><para>Essential packages (and there dependencies) should be configured immediately
 708        after unpacking. It will be a good idea to do this quite early in the upgrade process as these
 709        these configure calls require currently also <literal>DPkg::TriggersPending</literal> which
 710        will run quite a few triggers (which maybe not needed). Essentials get per default a high score
 711        but the immediate flag is relatively low (a package which has a Pre-Depends is higher rated).
 712        These option and the others in the same group can be used to change the scoring. The following
 713        example shows the settings with there default values.
 714        <literallayout>OrderList::Score {
 715         Delete 500;
 716         Essential 200;
 717         Immediate 10;
 718         PreDepends 50;
 719 };</literallayout>
 720        </para></listitem>
 721        </varlistentry>
 722      </variablelist>
 723    </refsect2>
 724  </refsect1>
 725
 726  <refsect1>
 727    <title>Periodic and Archives options</title>
 728    <para><literal>APT::Periodic</literal> and <literal>APT::Archives</literal>
 729    groups of options configure behavior of apt periodic updates, which is
 730    done by <literal>/etc/cron.daily/apt</literal> script. See header of
 731    this script for the brief documentation of these options.
 732    </para>
 733  </refsect1>
 734
 735  <refsect1>
 736    <title>Debug options</title>
 737    <para>
 738      Enabling options in the <literal>Debug::</literal> section will
 739      cause debugging information to be sent to the standard error
 740      stream of the program utilizing the <literal>apt</literal>
 741      libraries, or enable special program modes that are primarily
 742      useful for debugging the behavior of <literal>apt</literal>.
 743      Most of these options are not interesting to a normal user, but a
 744      few may be:
 745
 746      <itemizedlist>
 747        <listitem>
 748          <para>
 749            <literal>Debug::pkgProblemResolver</literal> enables output
 750            about the decisions made by
 751            <literal>dist-upgrade, upgrade, install, remove, purge</literal>.
 752          </para>
 753        </listitem>
 754
 755        <listitem>
 756          <para>
 757            <literal>Debug::NoLocking</literal> disables all file
 758            locking.  This can be used to run some operations (for
 759            instance, <literal>apt-get -s install</literal>) as a
 760            non-root user.
 761          </para>
 762        </listitem>
 763
 764        <listitem>
 765          <para>
 766            <literal>Debug::pkgDPkgPM</literal> prints out the actual
 767            command line each time that <literal>apt</literal> invokes
 768            &dpkg;.
 769          </para>
 770        </listitem>
 771
 772        <listitem>
 773          <para>
 774            <literal>Debug::IdentCdrom</literal> disables the inclusion
 775            of statfs data in CDROM IDs.  <!-- TODO: provide a
 776            motivating example, except I haven't a clue why you'd want
 777            to do this. -->
 778          </para>
 779        </listitem>
 780      </itemizedlist>
 781    </para>
 782
 783    <para>
 784      A full list of debugging options to apt follows.
 785    </para>
 786
 787    <variablelist>
 788      <varlistentry>
 789        <term><option>Debug::Acquire::cdrom</option></term>
 790
 791        <listitem>
 792          <para>
 793            Print information related to accessing
 794            <literal>cdrom://</literal> sources.
 795          </para>
 796        </listitem>
 797      </varlistentry>
 798
 799      <varlistentry>
 800        <term><option>Debug::Acquire::ftp</option></term>
 801
 802        <listitem>
 803          <para>
 804            Print information related to downloading packages using
 805            FTP.
 806          </para>
 807        </listitem>
 808      </varlistentry>
 809
 810      <varlistentry>
 811        <term><option>Debug::Acquire::http</option></term>
 812
 813        <listitem>
 814          <para>
 815            Print information related to downloading packages using
 816            HTTP.
 817          </para>
 818        </listitem>
 819      </varlistentry>
 820
 821      <varlistentry>
 822        <term><option>Debug::Acquire::https</option></term>
 823
 824        <listitem>
 825          <para>
 826            Print information related to downloading packages using
 827            HTTPS.
 828          </para>
 829        </listitem>
 830      </varlistentry>
 831
 832      <varlistentry>
 833        <term><option>Debug::Acquire::gpgv</option></term>
 834
 835        <listitem>
 836          <para>
 837            Print information related to verifying cryptographic
 838            signatures using <literal>gpg</literal>.
 839          </para>
 840        </listitem>
 841      </varlistentry>
 842
 843      <varlistentry>
 844        <term><option>Debug::aptcdrom</option></term>
 845
 846        <listitem>
 847          <para>
 848            Output information about the process of accessing
 849            collections of packages stored on CD-ROMs.
 850          </para>
 851        </listitem>
 852      </varlistentry>
 853
 854      <varlistentry>
 855        <term><option>Debug::BuildDeps</option></term>
 856        <listitem>
 857          <para>
 858            Describes the process of resolving build-dependencies in
 859            &apt-get;.
 860          </para>
 861        </listitem>
 862      </varlistentry>
 863
 864      <varlistentry>
 865        <term><option>Debug::Hashes</option></term>
 866        <listitem>
 867          <para>
 868            Output each cryptographic hash that is generated by the
 869            <literal>apt</literal> libraries.
 870          </para>
 871        </listitem>
 872      </varlistentry>
 873
 874      <varlistentry>
 875        <term><option>Debug::IdentCDROM</option></term>
 876        <listitem>
 877          <para>
 878            Do not include information from <literal>statfs</literal>,
 879            namely the number of used and free blocks on the CD-ROM
 880            filesystem, when generating an ID for a CD-ROM.
 881          </para>
 882        </listitem>
 883      </varlistentry>
 884
 885      <varlistentry>
 886        <term><option>Debug::NoLocking</option></term>
 887        <listitem>
 888          <para>
 889            Disable all file locking.  For instance, this will allow
 890            two instances of <quote><literal>apt-get
 891            update</literal></quote> to run at the same time.
 892          </para>
 893        </listitem>
 894      </varlistentry>
 895
 896      <varlistentry>
 897        <term><option>Debug::pkgAcquire</option></term>
 898
 899        <listitem>
 900          <para>
 901            Log when items are added to or removed from the global
 902            download queue.
 903          </para>
 904        </listitem>
 905      </varlistentry>
 906
 907      <varlistentry>
 908        <term><option>Debug::pkgAcquire::Auth</option></term>
 909        <listitem>
 910          <para>
 911            Output status messages and errors related to verifying
 912            checksums and cryptographic signatures of downloaded files.
 913          </para>
 914        </listitem>
 915      </varlistentry>
 916
 917      <varlistentry>
 918        <term><option>Debug::pkgAcquire::Diffs</option></term>
 919        <listitem>
 920          <para>
 921            Output information about downloading and applying package
 922            index list diffs, and errors relating to package index list
 923            diffs.
 924          </para>
 925        </listitem>
 926      </varlistentry>
 927
 928      <varlistentry>
 929        <term><option>Debug::pkgAcquire::RRed</option></term>
 930
 931        <listitem>
 932          <para>
 933            Output information related to patching apt package lists
 934            when downloading index diffs instead of full indices.
 935          </para>
 936        </listitem>
 937      </varlistentry>
 938
 939      <varlistentry>
 940        <term><option>Debug::pkgAcquire::Worker</option></term>
 941
 942        <listitem>
 943          <para>
 944            Log all interactions with the sub-processes that actually
 945            perform downloads.
 946          </para>
 947        </listitem>
 948      </varlistentry>
 949
 950      <varlistentry>
 951        <term><option>Debug::pkgAutoRemove</option></term>
 952
 953        <listitem>
 954          <para>
 955            Log events related to the automatically-installed status of
 956            packages and to the removal of unused packages.
 957          </para>
 958        </listitem>
 959      </varlistentry>
 960
 961      <varlistentry>
 962        <term><option>Debug::pkgDepCache::AutoInstall</option></term>
 963        <listitem>
 964          <para>
 965            Generate debug messages describing which packages are being
 966            automatically installed to resolve dependencies.  This
 967            corresponds to the initial auto-install pass performed in,
 968            e.g., <literal>apt-get install</literal>, and not to the
 969            full <literal>apt</literal> dependency resolver; see
 970            <literal>Debug::pkgProblemResolver</literal> for that.
 971          </para>
 972        </listitem>
 973      </varlistentry>
 974
 975      <varlistentry>
 976        <term><option>Debug::pkgDepCache::Marker</option></term>
 977        <listitem>
 978         <para>
 979            Generate debug messages describing which package is marked
 980           as keep/install/remove while the ProblemResolver does his work.
 981           Each addition or deletion may trigger additional actions;
 982           they are shown indented two additional space under the original entry.
 983           The format for each line is <literal>MarkKeep</literal>,
 984           <literal>MarkDelete</literal> or <literal>MarkInstall</literal> followed by
 985           <literal>package-name &lt;a.b.c -&gt; d.e.f | x.y.z&gt; (section)</literal>
 986           where <literal>a.b.c</literal> is the current version of the package,
 987           <literal>d.e.f</literal> is the version considered for installation and
 988           <literal>x.y.z</literal> is a newer version, but not considered for installation
 989           (because of a low pin score). The later two can be omitted if there is none or if
 990           it is the same version as the installed.
 991           <literal>section</literal> is the name of the section the package appears in.
 992         </para>
 993        </listitem>
 994      </varlistentry>
 995
 996      <!-- Question: why doesn't this do anything?  The code says it should. -->
 997      <varlistentry>
 998        <term><option>Debug::pkgInitConfig</option></term>
 999        <listitem>
1000          <para>
1001            Dump the default configuration to standard error on
1002            startup.
1003          </para>
1004        </listitem>
1005      </varlistentry>
1006
1007      <varlistentry>
1008        <term><option>Debug::pkgDPkgPM</option></term>
1009        <listitem>
1010          <para>
1011            When invoking &dpkg;, output the precise command line with
1012            which it is being invoked, with arguments separated by a
1013            single space character.
1014          </para>
1015        </listitem>
1016      </varlistentry>
1017
1018      <varlistentry>
1019        <term><option>Debug::pkgDPkgProgressReporting</option></term>
1020        <listitem>
1021          <para>
1022            Output all the data received from &dpkg; on the status file
1023            descriptor and any errors encountered while parsing it.
1024          </para>
1025        </listitem>
1026      </varlistentry>
1027
1028      <varlistentry>
1029        <term><option>Debug::pkgOrderList</option></term>
1030
1031        <listitem>
1032          <para>
1033            Generate a trace of the algorithm that decides the order in
1034            which <literal>apt</literal> should pass packages to
1035            &dpkg;.
1036          </para>
1037        </listitem>
1038      </varlistentry>
1039
1040      <varlistentry>
1041        <term><option>Debug::pkgPackageManager</option></term>
1042
1043        <listitem>
1044          <para>
1045            Output status messages tracing the steps performed when
1046            invoking &dpkg;.
1047          </para>
1048        </listitem>
1049      </varlistentry>
1050
1051      <varlistentry>
1052        <term><option>Debug::pkgPolicy</option></term>
1053
1054        <listitem>
1055          <para>
1056            Output the priority of each package list on startup.
1057          </para>
1058        </listitem>
1059      </varlistentry>
1060
1061      <varlistentry>
1062        <term><option>Debug::pkgProblemResolver</option></term>
1063
1064        <listitem>
1065          <para>
1066            Trace the execution of the dependency resolver (this
1067            applies only to what happens when a complex dependency
1068            problem is encountered).
1069          </para>
1070        </listitem>
1071      </varlistentry>
1072
1073      <varlistentry>
1074        <term><option>Debug::pkgProblemResolver::ShowScores</option></term>
1075        <listitem>
1076         <para>
1077           Display a list of all installed packages with their calculated score
1078           used by the pkgProblemResolver. The description of the package
1079           is the same as described in <literal>Debug::pkgDepCache::Marker</literal>
1080         </para>
1081        </listitem>
1082      </varlistentry>
1083
1084      <varlistentry>
1085        <term><option>Debug::sourceList</option></term>
1086
1087        <listitem>
1088          <para>
1089            Print information about the vendors read from
1090            <filename>/etc/apt/vendors.list</filename>.
1091          </para>
1092        </listitem>
1093      </varlistentry>
1094
1095 <!-- 2009/07/11 Currently used nowhere. The corresponding code
1096 is commented.
1097      <varlistentry>
1098        <term><literal>Debug::Vendor</literal></term>
1099
1100        <listitem>
1101          <para>
1102            Print information about each vendor.
1103          </para>
1104        </listitem>
1105      </varlistentry>
1106 -->
1107
1108    </variablelist>
1109  </refsect1>
1110
1111  <refsect1><title>Examples</title>
1112    <para>&configureindex; is a
1113    configuration file showing example values for all possible
1114    options.</para>
1115  </refsect1>
1116
1117  <refsect1><title>Files</title>
1118    <variablelist>
1119       &file-aptconf;
1120    </variablelist>
1121  </refsect1>
1122
1123  <refsect1><title>See Also</title>
1124    <para>&apt-cache;, &apt-config;<!-- ? reading apt.conf -->, &apt-preferences;.</para>
1125  </refsect1>
1126
1127  &manbugs;
1128
1129 </refentry>
1130