doc/apt.conf.5.xml

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   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 ]>
   9
  10 <refentry>
  11
  12  <refentryinfo>
  13    &apt-author.jgunthorpe;
  14    &apt-author.team;
  15    <author>
  16      <firstname>Daniel</firstname>
  17      <surname>Burrows</surname>
  18      <contrib>Initial documentation of Debug::*.</contrib>
  19      <email>dburrows@debian.org</email>
  20    </author>
  21    &apt-email;
  22    &apt-product;
  23    <!-- The last update date -->
  24    <date>10 December 2008</date>
  25  </refentryinfo>
  26
  27  <refmeta>
  28    <refentrytitle>apt.conf</refentrytitle>
  29    <manvolnum>5</manvolnum>
  30  </refmeta>
  31
  32  <!-- Man page title -->
  33  <refnamediv>
  34     <refname>apt.conf</refname>
  35     <refpurpose>Configuration file for APT</refpurpose>
  36  </refnamediv>
  37
  38  <refsect1><title>Description</title>
  39    <para><filename>apt.conf</filename> is the main configuration file for the APT suite of
  40    tools, all tools make use of the configuration file and a common command line
  41    parser to provide a uniform environment. When an APT tool starts up it will
  42    read the configuration specified by the <envar>APT_CONFIG</envar> environment
  43    variable (if any) and then read the files in <literal>Dir::Etc::Parts</literal>
  44    then read the main configuration file specified by
  45    <literal>Dir::Etc::main</literal> then finally apply the
  46    command line options to override the configuration directives, possibly
  47    loading even more config files.</para>
  48
  49    <para>The configuration file is organized in a tree with options organized into
  50    functional groups. option specification is given with a double colon
  51    notation, for instance <literal>APT::Get::Assume-Yes</literal> is an option within
  52    the APT tool group, for the Get tool. options do not inherit from their
  53    parent groups.</para>
  54
  55    <para>Syntactically the configuration language is modeled after what the ISC tools
  56    such as bind and dhcp use. Lines starting with
  57    <literal>//</literal> are treated as comments (ignored), as well as all text
  58    between <literal>/*</literal> and <literal>*/</literal>, just like C/C++ comments.
  59    Each line is of the form
  60    <literal>APT::Get::Assume-Yes "true";</literal> The trailing
  61    semicolon is required and the quotes are optional. A new scope can be
  62    opened with curly braces, like:</para>
  63
  64 <informalexample><programlisting>
  65 APT {
  66   Get {
  67     Assume-Yes "true";
  68     Fix-Broken "true";
  69   };
  70 };
  71 </programlisting></informalexample>
  72
  73    <para>with newlines placed to make it more readable. Lists can be created by
  74    opening a scope and including a single string enclosed in quotes followed by a
  75    semicolon. Multiple entries can be included, each separated by a semicolon.</para>
  76
  77 <informalexample><programlisting>
  78 DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
  79 </programlisting></informalexample>
  80
  81    <para>In general the sample configuration file in
  82    <filename>&docdir;examples/apt.conf</filename> &configureindex;
  83    is a good guide for how it should look.</para>
  84
  85    <para>The names of the configuration items are not case-sensitive. So in the previous example
  86    you could use <literal>dpkg::pre-install-pkgs</literal>.</para>
  87
  88    <para>Two specials are allowed, <literal>#include</literal> and <literal>#clear</literal>
  89    <literal>#include</literal> will include the given file, unless the filename
  90    ends in a slash, then the whole directory is included.
  91    <literal>#clear</literal> is used to erase a part of the configuration tree. The
  92    specified element and all its descendents are erased.</para>
  93
  94    <para>All of the APT tools take a -o option which allows an arbitrary configuration
  95    directive to be specified on the command line. The syntax is a full option
  96    name (<literal>APT::Get::Assume-Yes</literal> for instance) followed by an equals
  97    sign then the new value of the option. Lists can be appended too by adding
  98    a trailing :: to the list name.</para>
  99  </refsect1>
 100
 101  <refsect1><title>The APT Group</title>
 102    <para>This group of options controls general APT behavior as well as holding the
 103    options for all of the tools.</para>
 104
 105    <variablelist>
 106      <varlistentry><term>Architecture</term>
 107      <listitem><para>System Architecture; sets the architecture to use when fetching files and
 108      parsing package lists. The internal default is the architecture apt was
 109      compiled for.</para></listitem>
 110      </varlistentry>
 111
 112      <varlistentry><term>Default-Release</term>
 113          <listitem><para>Default release to install packages from if more than one
 114          version available. Contains release name, codename or release version. Examples: 'stable', 'testing', 'unstable', 'lenny', 'squeeze', '4.0', '5.0*'. See also &apt-preferences;.</para></listitem>
 115      </varlistentry>
 116
 117      <varlistentry><term>Ignore-Hold</term>
 118      <listitem><para>Ignore Held packages; This global option causes the problem resolver to
 119      ignore held packages in its decision making.</para></listitem>
 120      </varlistentry>
 121
 122      <varlistentry><term>Clean-Installed</term>
 123      <listitem><para>Defaults to on. When turned on the autoclean feature will remove any packages
 124      which can no longer be downloaded from the cache. If turned off then
 125      packages that are locally installed are also excluded from cleaning - but
 126      note that APT provides no direct means to reinstall them.</para></listitem>
 127      </varlistentry>
 128
 129      <varlistentry><term>Immediate-Configure</term>
 130      <listitem><para>Disable Immediate Configuration; This dangerous option disables some
 131      of APT's ordering code to cause it to make fewer dpkg calls. Doing
 132      so may be necessary on some extremely slow single user systems but
 133      is very dangerous and may cause package install scripts to fail or worse.
 134      Use at your own risk.</para></listitem>
 135      </varlistentry>
 136
 137      <varlistentry><term>Force-LoopBreak</term>
 138      <listitem><para>Never Enable this option unless you -really- know what you are doing. It
 139      permits APT to temporarily remove an essential package to break a
 140      Conflicts/Conflicts or Conflicts/Pre-Depend loop between two essential
 141      packages. SUCH A LOOP SHOULD NEVER EXIST AND IS A GRAVE BUG. This option
 142      will work if the essential packages are not tar, gzip, libc, dpkg, bash or
 143      anything that those packages depend on.</para></listitem>
 144      </varlistentry>
 145
 146      <varlistentry><term>Cache-Limit</term>
 147      <listitem><para>APT uses a fixed size memory mapped cache file to store the 'available'
 148      information. This sets the size of that cache (in bytes).</para></listitem>
 149      </varlistentry>
 150
 151      <varlistentry><term>Build-Essential</term>
 152      <listitem><para>Defines which package(s) are considered essential build dependencies.</para></listitem>
 153      </varlistentry>
 154
 155      <varlistentry><term>Get</term>
 156      <listitem><para>The Get subsection controls the &apt-get; tool, please see its
 157      documentation for more information about the options here.</para></listitem>
 158      </varlistentry>
 159
 160      <varlistentry><term>Cache</term>
 161      <listitem><para>The Cache subsection controls the &apt-cache; tool, please see its
 162      documentation for more information about the options here.</para></listitem>
 163      </varlistentry>
 164
 165      <varlistentry><term>CDROM</term>
 166      <listitem><para>The CDROM subsection controls the &apt-cdrom; tool, please see its
 167      documentation for more information about the options here.</para></listitem>
 168      </varlistentry>
 169    </variablelist>
 170  </refsect1>
 171
 172  <refsect1><title>The Acquire Group</title>
 173    <para>The <literal>Acquire</literal> group of options controls the download of packages
 174    and the URI handlers.
 175
 176    <variablelist>
 177      <varlistentry><term>PDiffs</term>
 178          <listitem><para>Try to download deltas called <literal>PDiffs</literal> for
 179          Packages or Sources files instead of downloading whole ones. True
 180          by default.</para></listitem>
 181      </varlistentry>
 182
 183      <varlistentry><term>Queue-Mode</term>
 184      <listitem><para>Queuing mode; <literal>Queue-Mode</literal> can be one of <literal>host</literal> or
 185      <literal>access</literal> which determines how  APT parallelizes outgoing
 186      connections. <literal>host</literal> means that one connection per target host
 187      will be opened, <literal>access</literal> means that one connection per URI type
 188      will be opened.</para></listitem>
 189      </varlistentry>
 190
 191      <varlistentry><term>Retries</term>
 192      <listitem><para>Number of retries to perform. If this is non-zero APT will retry failed
 193      files the given number of times.</para></listitem>
 194      </varlistentry>
 195
 196      <varlistentry><term>Source-Symlinks</term>
 197      <listitem><para>Use symlinks for source archives. If set to true then source archives will
 198      be symlinked when possible instead of copying. True is the default.</para></listitem>
 199      </varlistentry>
 200
 201      <varlistentry><term>http</term>
 202      <listitem><para>HTTP URIs; http::Proxy is the default http proxy to use. It is in the
 203      standard form of <literal>http://[[user][:pass]@]host[:port]/</literal>. Per
 204      host proxies can also be specified by using the form
 205      <literal>http::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal>
 206      meaning to use no proxies. The <envar>http_proxy</envar> environment variable
 207      will override all settings.</para>
 208
 209      <para>Three settings are provided for cache control with HTTP/1.1 compliant
 210      proxy caches. <literal>No-Cache</literal> tells the proxy to not use its cached
 211      response under any circumstances, <literal>Max-Age</literal> is sent only for
 212      index files and tells the cache to refresh its object if it is older than
 213      the given number of seconds. Debian updates its index files daily so the
 214      default is 1 day. <literal>No-Store</literal> specifies that the cache should never
 215      store this request, it is only set for archive files. This may be useful
 216      to prevent polluting a proxy cache with very large .deb files. Note:
 217      Squid 2.0.2 does not support any of these options.</para>
 218
 219      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 220      this applies to all things including connection timeout and data timeout.</para>
 221
 222      <para>One setting is provided to control the pipeline depth in cases where the
 223      remote server is not RFC conforming or buggy (such as Squid 2.0.2)
 224      <literal>Acquire::http::Pipeline-Depth</literal> can be a value from 0 to 5
 225      indicating how many outstanding requests APT should send. A value of
 226      zero MUST be specified if the remote host does not properly linger
 227      on TCP connections - otherwise data corruption will occur. Hosts which
 228      require this are in violation of RFC 2068.</para></listitem>
 229      </varlistentry>
 230
 231      <varlistentry><term>https</term>
 232          <listitem><para>HTTPS URIs. Cache-control and proxy options are the same as for
 233          <literal>http</literal> method.
 234          <literal>Pipeline-Depth</literal> option is not supported yet.</para>
 235
 236          <para><literal>CaInfo</literal> suboption specifies place of file that
 237          holds info about trusted certificates.
 238          <literal>&lt;host&gt;::CaInfo</literal> is corresponding per-host option.
 239          <literal>Verify-Peer</literal> boolean suboption determines whether verify
 240          server's host certificate against trusted certificates or not.
 241          <literal>&lt;host&gt;::Verify-Peer</literal> is corresponding per-host option.
 242          <literal>Verify-Host</literal> boolean suboption determines whether verify
 243          server's hostname or not.
 244          <literal>&lt;host&gt;::Verify-Host</literal> is corresponding per-host option.
 245          <literal>SslCert</literal> determines what certificate to use for client
 246          authentication. <literal>&lt;host&gt;::SslCert</literal> is corresponding per-host option.
 247          <literal>SslKey</literal> determines what private key to use for client
 248          authentication. <literal>&lt;host&gt;::SslKey</literal> is corresponding per-host option.
 249          <literal>SslForceVersion</literal> overrides default SSL version to use.
 250          Can contain 'TLSv1' or 'SSLv3' string.
 251          <literal>&lt;host&gt;::SslForceVersion</literal> is corresponding per-host option.
 252          </para></listitem></varlistentry>
 253
 254      <varlistentry><term>ftp</term>
 255      <listitem><para>FTP URIs; ftp::Proxy is the default proxy server to use. It is in the
 256      standard form of <literal>ftp://[[user][:pass]@]host[:port]/</literal> and is
 257      overridden by the <envar>ftp_proxy</envar> environment variable. To use a ftp
 258      proxy you will have to set the <literal>ftp::ProxyLogin</literal> script in the
 259      configuration file. This entry specifies the commands to send to tell
 260      the proxy server what to connect to. Please see
 261      &configureindex; for an example of
 262      how to do this. The substitution variables available are
 263      <literal>$(PROXY_USER)</literal> <literal>$(PROXY_PASS)</literal> <literal>$(SITE_USER)</literal>
 264      <literal>$(SITE_PASS)</literal> <literal>$(SITE)</literal> and <literal>$(SITE_PORT)</literal>
 265      Each is taken from it's respective URI component.</para>
 266
 267      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 268      this applies to all things including connection timeout and data timeout.</para>
 269
 270      <para>Several settings are provided to control passive mode. Generally it is
 271      safe to leave passive mode on, it works in nearly every environment.
 272      However some situations require that passive mode be disabled and port
 273      mode ftp used instead. This can be done globally, for connections that
 274      go through a proxy or for a specific host (See the sample config file
 275      for examples).</para>
 276
 277      <para>It is possible to proxy FTP over HTTP by setting the <envar>ftp_proxy</envar>
 278      environment variable to a http url - see the discussion of the http method
 279      above for syntax. You cannot set this in the configuration file and it is
 280      not recommended to use FTP over HTTP due to its low efficiency.</para>
 281
 282      <para>The setting <literal>ForceExtended</literal> controls the use of RFC2428
 283      <literal>EPSV</literal> and <literal>EPRT</literal> commands. The default is false, which means
 284      these commands are only used if the control connection is IPv6. Setting this
 285      to true forces their use even on IPv4 connections. Note that most FTP servers
 286      do not support RFC2428.</para></listitem>
 287      </varlistentry>
 288
 289      <varlistentry><term>cdrom</term>
 290      <listitem><para>CDROM URIs; the only setting for CDROM URIs is the mount point,
 291      <literal>cdrom::Mount</literal> which must be the mount point for the CDROM drive
 292      as specified in <filename>/etc/fstab</filename>. It is possible to provide
 293      alternate mount and unmount commands if your mount point cannot be listed
 294      in the fstab (such as an SMB mount and old mount packages). The syntax
 295      is to put <literallayout>"/cdrom/"::Mount "foo";</literallayout> within
 296      the cdrom block. It is important to have the trailing slash. Unmount
 297      commands can be specified using UMount.</para></listitem>
 298      </varlistentry>
 299
 300      <varlistentry><term>gpgv</term>
 301      <listitem><para>GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv.
 302      <literal>gpgv::Options</literal> Additional options passed to gpgv.
 303      </para></listitem>
 304      </varlistentry>
 305
 306      <varlistentry><term>CompressionTypes</term>
 307      <listitem><para>List of compression types which are understood by the acquire methods.
 308      Files like <filename>Packages</filename> can be available in various compression formats.
 309      This list defines in which order the acquire methods will try to download these files.
 310      Per default <command>bzip2</command> compressed files will be prefered over
 311      <command>lzma</command>, <command>gzip</command> and uncompressed files. The syntax for
 312      the configuration fileentry (this option can't be set at runtime with the -o option) is
 313      <synopsis>Acquire::CompressionTypes::<replaceable>FileExtension</replaceable> "<replaceable>Methodname</replaceable>";</synopsis>
 314      e.g. <synopsis>Acquire::CompressionTypes::bz2 "bzip2";</synopsis>
 315      Note that at runtime the <literal>Dir::Bin::<replaceable>Methodname</replaceable></literal> will
 316      be checked: If this setting exists the method will only be used if this file exists, e.g. for
 317      the bzip2 method above (the inbuilt) setting is <literallayout>Dir::Bin::bzip2 "/bin/bzip2";</literallayout>
 318      </para></listitem>
 319      </varlistentry>
 320    </variablelist>
 321   </para>
 322  </refsect1>
 323
 324  <refsect1><title>Directories</title>
 325
 326    <para>The <literal>Dir::State</literal> section has directories that pertain to local
 327    state information. <literal>lists</literal> is the directory to place downloaded
 328    package lists in and <literal>status</literal> is the name of the dpkg status file.
 329    <literal>preferences</literal> is the name of the APT preferences file.
 330    <literal>Dir::State</literal> contains the default directory to prefix on all sub
 331    items if they do not start with <filename>/</filename> or <filename>./</filename>.</para>
 332
 333    <para><literal>Dir::Cache</literal> contains locations pertaining to local cache
 334    information, such as the two package caches <literal>srcpkgcache</literal> and
 335    <literal>pkgcache</literal> as well as the location to place downloaded archives,
 336    <literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
 337    by setting their names to be blank. This will slow down startup but
 338    save disk space. It is probably preferred to turn off the pkgcache rather
 339    than the srcpkgcache. Like <literal>Dir::State</literal> the default
 340    directory is contained in <literal>Dir::Cache</literal></para>
 341
 342    <para><literal>Dir::Etc</literal> contains the location of configuration files,
 343    <literal>sourcelist</literal> gives the location of the sourcelist and
 344    <literal>main</literal> is the default configuration file (setting has no effect,
 345    unless it is done from the config file specified by
 346    <envar>APT_CONFIG</envar>).</para>
 347
 348    <para>The <literal>Dir::Parts</literal> setting reads in all the config fragments in
 349    lexical order from the directory specified. After this is done then the
 350    main config file is loaded.</para>
 351
 352    <para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal>
 353    specifies the location of the method handlers and <literal>gzip</literal>,
 354    <literal>bzip2</literal>, <literal>lzma</literal>,
 355    <literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal>
 356    <literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
 357    of the respective programs.</para>
 358
 359    <para>
 360      The configuration item <literal>RootDir</literal> has a special
 361      meaning.  If set, all paths in <literal>Dir::</literal> will be
 362      relative to <literal>RootDir</literal>, <emphasis>even paths that
 363      are specified absolutely</emphasis>.  So, for instance, if
 364      <literal>RootDir</literal> is set to
 365      <filename>/tmp/staging</filename> and
 366      <literal>Dir::State::status</literal> is set to
 367      <filename>/var/lib/dpkg/status</filename>, then the status file
 368      will be looked up in
 369      <filename>/tmp/staging/var/lib/dpkg/status</filename>.
 370    </para>
 371  </refsect1>
 372
 373  <refsect1><title>APT in DSelect</title>
 374    <para>
 375    When APT is used as a &dselect; method several configuration directives
 376    control the default behaviour. These are in the <literal>DSelect</literal> section.</para>
 377
 378    <variablelist>
 379      <varlistentry><term>Clean</term>
 380      <listitem><para>Cache Clean mode; this value may be one of always, prompt, auto,
 381      pre-auto and never.  always and prompt will remove all packages from
 382      the cache after upgrading, prompt (the default) does so conditionally.
 383      auto removes only those packages which are no longer downloadable
 384      (replaced with a new version for instance).  pre-auto performs this
 385      action before downloading new packages.</para></listitem>
 386      </varlistentry>
 387
 388      <varlistentry><term>options</term>
 389      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 390      options when it is run for the install phase.</para></listitem>
 391      </varlistentry>
 392
 393      <varlistentry><term>Updateoptions</term>
 394      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 395      options when it is run for the update phase.</para></listitem>
 396      </varlistentry>
 397
 398      <varlistentry><term>PromptAfterUpdate</term>
 399      <listitem><para>If true the [U]pdate operation in &dselect; will always prompt to continue.
 400      The default is to prompt only on error.</para></listitem>
 401      </varlistentry>
 402    </variablelist>
 403  </refsect1>
 404
 405  <refsect1><title>How APT calls dpkg</title>
 406    <para>Several configuration directives control how APT invokes &dpkg;. These are
 407    in the <literal>DPkg</literal> section.</para>
 408
 409    <variablelist>
 410      <varlistentry><term>options</term>
 411      <listitem><para>This is a list of options to pass to dpkg. The options must be specified
 412      using the list notation and each list item is passed as a single argument
 413      to &dpkg;.</para></listitem>
 414      </varlistentry>
 415
 416      <varlistentry><term>Pre-Invoke</term><term>Post-Invoke</term>
 417      <listitem><para>This is a list of shell commands to run before/after invoking &dpkg;.
 418      Like <literal>options</literal> this must be specified in list notation. The
 419      commands are invoked in order using <filename>/bin/sh</filename>, should any
 420      fail APT will abort.</para></listitem>
 421      </varlistentry>
 422
 423      <varlistentry><term>Pre-Install-Pkgs</term>
 424      <listitem><para>This is a list of shell commands to run before invoking dpkg. Like
 425      <literal>options</literal> this must be specified in list notation. The commands
 426      are invoked in order using <filename>/bin/sh</filename>, should any fail APT
 427      will abort. APT will pass to the commands on standard input the
 428      filenames of all .deb files it is going to install, one per line.</para>
 429
 430      <para>Version 2 of this protocol dumps more information, including the
 431      protocol version, the APT configuration space and the packages, files
 432      and versions being changed. Version 2 is enabled by setting
 433      <literal>DPkg::Tools::options::cmd::Version</literal> to 2. <literal>cmd</literal> is a
 434      command given to <literal>Pre-Install-Pkgs</literal>.</para></listitem>
 435      </varlistentry>
 436
 437      <varlistentry><term>Run-Directory</term>
 438      <listitem><para>APT chdirs to this directory before invoking dpkg, the default is
 439      <filename>/</filename>.</para></listitem>
 440      </varlistentry>
 441
 442      <varlistentry><term>Build-options</term>
 443      <listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages,
 444      the default is to disable signing and produce all binaries.</para></listitem>
 445      </varlistentry>
 446    </variablelist>
 447  </refsect1>
 448
 449  <refsect1>
 450    <title>Periodic and Archives options</title>
 451    <para><literal>APT::Periodic</literal> and <literal>APT::Archives</literal>
 452    groups of options configure behavior of apt periodic updates, which is
 453    done by <literal>/etc/cron.daily/apt</literal> script. See header of
 454    this script for the brief documentation of these options.
 455    </para>
 456  </refsect1>
 457
 458  <refsect1>
 459    <title>Debug options</title>
 460    <para>
 461      Enabling options in the <literal>Debug::</literal> section will
 462      cause debugging information to be sent to the standard error
 463      stream of the program utilizing the <literal>apt</literal>
 464      libraries, or enable special program modes that are primarily
 465      useful for debugging the behavior of <literal>apt</literal>.
 466      Most of these options are not interesting to a normal user, but a
 467      few may be:
 468
 469      <itemizedlist>
 470        <listitem>
 471          <para>
 472            <literal>Debug::pkgProblemResolver</literal> enables output
 473            about the decisions made by
 474            <literal>dist-upgrade, upgrade, install, remove, purge</literal>.
 475          </para>
 476        </listitem>
 477
 478        <listitem>
 479          <para>
 480            <literal>Debug::NoLocking</literal> disables all file
 481            locking.  This can be used to run some operations (for
 482            instance, <literal>apt-get -s install</literal>) as a
 483            non-root user.
 484          </para>
 485        </listitem>
 486
 487        <listitem>
 488          <para>
 489            <literal>Debug::pkgDPkgPM</literal> prints out the actual
 490            command line each time that <literal>apt</literal> invokes
 491            &dpkg;.
 492          </para>
 493        </listitem>
 494
 495        <listitem>
 496          <para>
 497            <literal>Debug::IdentCdrom</literal> disables the inclusion
 498            of statfs data in CDROM IDs.  <!-- TODO: provide a
 499            motivating example, except I haven't a clue why you'd want
 500            to do this. -->
 501          </para>
 502        </listitem>
 503      </itemizedlist>
 504    </para>
 505
 506    <para>
 507      A full list of debugging options to apt follows.
 508    </para>
 509
 510    <variablelist>
 511      <varlistentry>
 512        <term><literal>Debug::Acquire::cdrom</literal></term>
 513
 514        <listitem>
 515          <para>
 516            Print information related to accessing
 517            <literal>cdrom://</literal> sources.
 518          </para>
 519        </listitem>
 520      </varlistentry>
 521
 522      <varlistentry>
 523        <term><literal>Debug::Acquire::ftp</literal></term>
 524
 525        <listitem>
 526          <para>
 527            Print information related to downloading packages using
 528            FTP.
 529          </para>
 530        </listitem>
 531      </varlistentry>
 532
 533      <varlistentry>
 534        <term><literal>Debug::Acquire::http</literal></term>
 535
 536        <listitem>
 537          <para>
 538            Print information related to downloading packages using
 539            HTTP.
 540          </para>
 541        </listitem>
 542      </varlistentry>
 543
 544      <varlistentry>
 545        <term><literal>Debug::Acquire::https</literal></term>
 546
 547        <listitem>
 548          <para>
 549            Print information related to downloading packages using
 550            HTTPS.
 551          </para>
 552        </listitem>
 553      </varlistentry>
 554
 555      <varlistentry>
 556        <term><literal>Debug::Acquire::gpgv</literal></term>
 557
 558        <listitem>
 559          <para>
 560            Print information related to verifying cryptographic
 561            signatures using <literal>gpg</literal>.
 562          </para>
 563        </listitem>
 564      </varlistentry>
 565
 566      <varlistentry>
 567        <term><literal>Debug::aptcdrom</literal></term>
 568
 569        <listitem>
 570          <para>
 571            Output information about the process of accessing
 572            collections of packages stored on CD-ROMs.
 573          </para>
 574        </listitem>
 575      </varlistentry>
 576
 577      <varlistentry>
 578        <term><literal>Debug::BuildDeps</literal></term>
 579        <listitem>
 580          <para>
 581            Describes the process of resolving build-dependencies in
 582            &apt-get;.
 583          </para>
 584        </listitem>
 585      </varlistentry>
 586
 587      <varlistentry>
 588        <term><literal>Debug::Hashes</literal></term>
 589        <listitem>
 590          <para>
 591            Output each cryptographic hash that is generated by the
 592            <literal>apt</literal> libraries.
 593          </para>
 594        </listitem>
 595      </varlistentry>
 596
 597      <varlistentry>
 598        <term><literal>Debug::IdentCDROM</literal></term>
 599        <listitem>
 600          <para>
 601            Do not include information from <literal>statfs</literal>,
 602            namely the number of used and free blocks on the CD-ROM
 603            filesystem, when generating an ID for a CD-ROM.
 604          </para>
 605        </listitem>
 606      </varlistentry>
 607
 608      <varlistentry>
 609        <term><literal>Debug::NoLocking</literal></term>
 610        <listitem>
 611          <para>
 612            Disable all file locking.  For instance, this will allow
 613            two instances of <quote><literal>apt-get
 614            update</literal></quote> to run at the same time.
 615          </para>
 616        </listitem>
 617      </varlistentry>
 618
 619      <varlistentry>
 620        <term><literal>Debug::pkgAcquire</literal></term>
 621
 622        <listitem>
 623          <para>
 624            Log when items are added to or removed from the global
 625            download queue.
 626          </para>
 627        </listitem>
 628      </varlistentry>
 629
 630      <varlistentry>
 631        <term><literal>Debug::pkgAcquire::Auth</literal></term>
 632        <listitem>
 633          <para>
 634            Output status messages and errors related to verifying
 635            checksums and cryptographic signatures of downloaded files.
 636          </para>
 637        </listitem>
 638      </varlistentry>
 639
 640      <varlistentry>
 641        <term><literal>Debug::pkgAcquire::Diffs</literal></term>
 642        <listitem>
 643          <para>
 644            Output information about downloading and applying package
 645            index list diffs, and errors relating to package index list
 646            diffs.
 647          </para>
 648        </listitem>
 649      </varlistentry>
 650
 651      <varlistentry>
 652        <term><literal>Debug::pkgAcquire::RRed</literal></term>
 653
 654        <listitem>
 655          <para>
 656            Output information related to patching apt package lists
 657            when downloading index diffs instead of full indices.
 658          </para>
 659        </listitem>
 660      </varlistentry>
 661
 662      <varlistentry>
 663        <term><literal>Debug::pkgAcquire::Worker</literal></term>
 664
 665        <listitem>
 666          <para>
 667            Log all interactions with the sub-processes that actually
 668            perform downloads.
 669          </para>
 670        </listitem>
 671      </varlistentry>
 672
 673      <varlistentry>
 674        <term><literal>Debug::pkgAutoRemove</literal></term>
 675
 676        <listitem>
 677          <para>
 678            Log events related to the automatically-installed status of
 679            packages and to the removal of unused packages.
 680          </para>
 681        </listitem>
 682      </varlistentry>
 683
 684      <varlistentry>
 685        <term><literal>Debug::pkgDepCache::AutoInstall</literal></term>
 686        <listitem>
 687          <para>
 688            Generate debug messages describing which packages are being
 689            automatically installed to resolve dependencies.  This
 690            corresponds to the initial auto-install pass performed in,
 691            e.g., <literal>apt-get install</literal>, and not to the
 692            full <literal>apt</literal> dependency resolver; see
 693            <literal>Debug::pkgProblemResolver</literal> for that.
 694          </para>
 695        </listitem>
 696      </varlistentry>
 697
 698      <varlistentry>
 699        <term><literal>Debug::pkgDepCache::Marker</literal></term>
 700        <listitem>
 701         <para>
 702            Generate debug messages describing which package is marked
 703           as keep/install/remove while the ProblemResolver does his work.
 704           Each addition or deletion may trigger additional actions;
 705           they are shown indented two additional space under the original entry.
 706           The format for each line is <literal>MarkKeep</literal>,
 707           <literal>MarkDelete</literal> or <literal>MarkInstall</literal> followed by
 708           <literal>package-name &lt;a.b.c -&gt; d.e.f | x.y.z&gt; (section)</literal>
 709           where <literal>a.b.c</literal> is the current version of the package,
 710           <literal>d.e.f</literal> is the version considered for installation and
 711           <literal>x.y.z</literal> is a newer version, but not considered for installation
 712           (because of a low pin score). The later two can be omitted if there is none or if
 713           it is the same version as the installed.
 714           <literal>section</literal> is the name of the section the package appears in.
 715         </para>
 716        </listitem>
 717      </varlistentry>
 718
 719      <!-- Question: why doesn't this do anything?  The code says it should. -->
 720      <varlistentry>
 721        <term><literal>Debug::pkgInitConfig</literal></term>
 722        <listitem>
 723          <para>
 724            Dump the default configuration to standard error on
 725            startup.
 726          </para>
 727        </listitem>
 728      </varlistentry>
 729
 730      <varlistentry>
 731        <term><literal>Debug::pkgDPkgPM</literal></term>
 732        <listitem>
 733          <para>
 734            When invoking &dpkg;, output the precise command line with
 735            which it is being invoked, with arguments separated by a
 736            single space character.
 737          </para>
 738        </listitem>
 739      </varlistentry>
 740
 741      <varlistentry>
 742        <term><literal>Debug::pkgDPkgProgressReporting</literal></term>
 743        <listitem>
 744          <para>
 745            Output all the data received from &dpkg; on the status file
 746            descriptor and any errors encountered while parsing it.
 747          </para>
 748        </listitem>
 749      </varlistentry>
 750
 751      <varlistentry>
 752        <term><literal>Debug::pkgOrderList</literal></term>
 753
 754        <listitem>
 755          <para>
 756            Generate a trace of the algorithm that decides the order in
 757            which <literal>apt</literal> should pass packages to
 758            &dpkg;.
 759          </para>
 760        </listitem>
 761      </varlistentry>
 762
 763      <varlistentry>
 764        <term><literal>Debug::pkgPackageManager</literal></term>
 765
 766        <listitem>
 767          <para>
 768            Output status messages tracing the steps performed when
 769            invoking &dpkg;.
 770          </para>
 771        </listitem>
 772      </varlistentry>
 773
 774      <varlistentry>
 775        <term><literal>Debug::pkgPolicy</literal></term>
 776
 777        <listitem>
 778          <para>
 779            Output the priority of each package list on startup.
 780          </para>
 781        </listitem>
 782      </varlistentry>
 783
 784      <varlistentry>
 785        <term><literal>Debug::pkgProblemResolver</literal></term>
 786
 787        <listitem>
 788          <para>
 789            Trace the execution of the dependency resolver (this
 790            applies only to what happens when a complex dependency
 791            problem is encountered).
 792          </para>
 793        </listitem>
 794      </varlistentry>
 795
 796      <varlistentry>
 797        <term><literal>Debug::pkgProblemResolver::ShowScores</literal></term>
 798        <listitem>
 799         <para>
 800           Display a list of all installed packages with their calculated score
 801           used by the pkgProblemResolver. The description of the package
 802           is the same as described in <literal>Debug::pkgDepCache::Marker</literal>
 803         </para>
 804        </listitem>
 805      </varlistentry>
 806
 807      <varlistentry>
 808        <term><literal>Debug::sourceList</literal></term>
 809
 810        <listitem>
 811          <para>
 812            Print information about the vendors read from
 813            <filename>/etc/apt/vendors.list</filename>.
 814          </para>
 815        </listitem>
 816      </varlistentry>
 817
 818 <!-- 2009/07/11 Currently used nowhere. The corresponding code
 819 is commented.
 820      <varlistentry>
 821        <term><literal>Debug::Vendor</literal></term>
 822
 823        <listitem>
 824          <para>
 825            Print information about each vendor.
 826          </para>
 827        </listitem>
 828      </varlistentry>
 829 -->
 830    </variablelist>
 831  </refsect1>
 832
 833  <refsect1><title>Examples</title>
 834    <para>&configureindex; is a
 835    configuration file showing example values for all possible
 836    options.</para>
 837  </refsect1>
 838
 839  <refsect1><title>Files</title>
 840    <variablelist>
 841       <varlistentry><term><filename>/etc/apt/apt.conf</filename></term>
 842       <listitem><para>APT configuration file.
 843       Configuration Item: <literal>Dir::Etc::Main</literal>.</para></listitem>
 844       </varlistentry>
 845
 846       <varlistentry><term><filename>/etc/apt/apt.conf.d/</filename></term>
 847       <listitem><para>APT configuration file fragments.
 848       Configuration Item: <literal>Dir::Etc::Parts</literal>.</para></listitem>
 849       </varlistentry>
 850    </variablelist>
 851  </refsect1>
 852
 853  <refsect1><title>See Also</title>
 854    <para>&apt-cache;, &apt-config;<!-- ? reading apt.conf -->, &apt-preferences;.</para>
 855  </refsect1>
 856
 857  &manbugs;
 858
 859 </refentry>
 860