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 word 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 list of names.</para>
  92
  93    <para>All of the APT tools take a -o option which allows an arbitrary configuration
  94    directive to be specified on the command line. The syntax is a full option
  95    name (<literal>APT::Get::Assume-Yes</literal> for instance) followed by an equals
  96    sign then the new value of the option. Lists can be appended too by adding
  97    a trailing :: to the list name.</para>
  98  </refsect1>
  99
 100  <refsect1><title>The APT Group</title>
 101    <para>This group of options controls general APT behavior as well as holding the
 102    options for all of the tools.</para>
 103
 104    <variablelist>
 105      <varlistentry><term>Architecture</term>
 106      <listitem><para>System Architecture; sets the architecture to use when fetching files and
 107      parsing package lists. The internal default is the architecture apt was
 108      compiled for.</para></listitem>
 109      </varlistentry>
 110
 111      <varlistentry><term>Default-Release</term>
 112          <listitem><para>Default release to install packages from if more than one
 113          version available. Contains release name or release version. Examples: 'stable', 'testing', 'unstable', '4.0', '5.0*'. Release codenames ('etch', 'lenny' etc.) are not allowed now. See also &apt-preferences;.</para></listitem>
 114      </varlistentry>
 115
 116      <varlistentry><term>Ignore-Hold</term>
 117      <listitem><para>Ignore Held packages; This global option causes the problem resolver to
 118      ignore held packages in its decision making.</para></listitem>
 119      </varlistentry>
 120
 121      <varlistentry><term>Clean-Installed</term>
 122      <listitem><para>Defaults to on. When turned on the autoclean feature will remove any packages
 123      which can no longer be downloaded from the cache. If turned off then
 124      packages that are locally installed are also excluded from cleaning - but
 125      note that APT provides no direct means to reinstall them.</para></listitem>
 126      </varlistentry>
 127
 128      <varlistentry><term>Immediate-Configure</term>
 129      <listitem><para>Disable Immediate Configuration; This dangerous option disables some
 130      of APT's ordering code to cause it to make fewer dpkg calls. Doing
 131      so may be necessary on some extremely slow single user systems but
 132      is very dangerous and may cause package install scripts to fail or worse.
 133      Use at your own risk.</para></listitem>
 134      </varlistentry>
 135
 136      <varlistentry><term>Force-LoopBreak</term>
 137      <listitem><para>Never Enable this option unless you -really- know what you are doing. It
 138      permits APT to temporarily remove an essential package to break a
 139      Conflicts/Conflicts or Conflicts/Pre-Depend loop between two essential
 140      packages. SUCH A LOOP SHOULD NEVER EXIST AND IS A GRAVE BUG. This option
 141      will work if the essential packages are not tar, gzip, libc, dpkg, bash or
 142      anything that those packages depend on.</para></listitem>
 143      </varlistentry>
 144
 145      <varlistentry><term>Cache-Limit</term>
 146      <listitem><para>APT uses a fixed size memory mapped cache file to store the 'available'
 147      information. This sets the size of that cache (in bytes).</para></listitem>
 148      </varlistentry>
 149
 150      <varlistentry><term>Build-Essential</term>
 151      <listitem><para>Defines which package(s) are considered essential build dependencies.</para></listitem>
 152      </varlistentry>
 153
 154      <varlistentry><term>Get</term>
 155      <listitem><para>The Get subsection controls the &apt-get; tool, please see its
 156      documentation for more information about the options here.</para></listitem>
 157      </varlistentry>
 158
 159      <varlistentry><term>Cache</term>
 160      <listitem><para>The Cache subsection controls the &apt-cache; tool, please see its
 161      documentation for more information about the options here.</para></listitem>
 162      </varlistentry>
 163
 164      <varlistentry><term>CDROM</term>
 165      <listitem><para>The CDROM subsection controls the &apt-cdrom; tool, please see its
 166      documentation for more information about the options here.</para></listitem>
 167      </varlistentry>
 168    </variablelist>
 169  </refsect1>
 170
 171  <refsect1><title>The Acquire Group</title>
 172    <para>The <literal>Acquire</literal> group of options controls the download of packages
 173    and the URI handlers.
 174
 175    <variablelist>
 176      <varlistentry><term>PDiffs</term>
 177          <listitem><para>Try do download deltas called <literal>PDiffs</literal> for
 178          Packages or Sources files instead of downloading whole ones. True
 179          by default.</para></listitem>
 180      </varlistentry>
 181
 182      <varlistentry><term>Queue-Mode</term>
 183      <listitem><para>Queuing mode; <literal>Queue-Mode</literal> can be one of <literal>host</literal> or
 184      <literal>access</literal> which determines how  APT parallelizes outgoing
 185      connections. <literal>host</literal> means that one connection per target host
 186      will be opened, <literal>access</literal> means that one connection per URI type
 187      will be opened.</para></listitem>
 188      </varlistentry>
 189
 190      <varlistentry><term>Retries</term>
 191      <listitem><para>Number of retries to perform. If this is non-zero APT will retry failed
 192      files the given number of times.</para></listitem>
 193      </varlistentry>
 194
 195      <varlistentry><term>Source-Symlinks</term>
 196      <listitem><para>Use symlinks for source archives. If set to true then source archives will
 197      be symlinked when possible instead of copying. True is the default.</para></listitem>
 198      </varlistentry>
 199
 200      <varlistentry><term>http</term>
 201      <listitem><para>HTTP URIs; http::Proxy is the default http proxy to use. It is in the
 202      standard form of <literal>http://[[user][:pass]@]host[:port]/</literal>. Per
 203      host proxies can also be specified by using the form
 204      <literal>http::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal>
 205          meaning to use no proxies. If no one of the above settings is specified,
 206          <envar>http_proxy</envar> environment variable
 207          will be used.</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 ftp proxy to use. It is in the
 256      standard form of <literal>ftp://[[user][:pass]@]host[:port]/</literal>. Per
 257      host proxies can also be specified by using the form
 258      <literal>ftp::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal>
 259          meaning to use no proxies. If no one of the above settings is specified,
 260          <envar>ftp_proxy</envar> environment variable
 261          will be used. To use a ftp
 262      proxy you will have to set the <literal>ftp::ProxyLogin</literal> script in the
 263      configuration file. This entry specifies the commands to send to tell
 264      the proxy server what to connect to. Please see
 265      &configureindex; for an example of
 266      how to do this. The substitution variables available are
 267      <literal>$(PROXY_USER)</literal> <literal>$(PROXY_PASS)</literal> <literal>$(SITE_USER)</literal>
 268      <literal>$(SITE_PASS)</literal> <literal>$(SITE)</literal> and <literal>$(SITE_PORT)</literal>
 269      Each is taken from it's respective URI component.</para>
 270
 271      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 272      this applies to all things including connection timeout and data timeout.</para>
 273
 274      <para>Several settings are provided to control passive mode. Generally it is
 275      safe to leave passive mode on, it works in nearly every environment.
 276      However some situations require that passive mode be disabled and port
 277      mode ftp used instead. This can be done globally, for connections that
 278      go through a proxy or for a specific host (See the sample config file
 279      for examples).</para>
 280
 281      <para>It is possible to proxy FTP over HTTP by setting the <envar>ftp_proxy</envar>
 282      environment variable to a http url - see the discussion of the http method
 283      above for syntax. You cannot set this in the configuration file and it is
 284      not recommended to use FTP over HTTP due to its low efficiency.</para>
 285
 286      <para>The setting <literal>ForceExtended</literal> controls the use of RFC2428
 287      <literal>EPSV</literal> and <literal>EPRT</literal> commands. The default is false, which means
 288      these commands are only used if the control connection is IPv6. Setting this
 289      to true forces their use even on IPv4 connections. Note that most FTP servers
 290      do not support RFC2428.</para></listitem>
 291      </varlistentry>
 292
 293      <varlistentry><term>cdrom</term>
 294      <listitem><para>CDROM URIs; the only setting for CDROM URIs is the mount point,
 295      <literal>cdrom::Mount</literal> which must be the mount point for the CDROM drive
 296      as specified in <filename>/etc/fstab</filename>. It is possible to provide
 297      alternate mount and unmount commands if your mount point cannot be listed
 298      in the fstab (such as an SMB mount and old mount packages). The syntax
 299      is to put <literallayout>"/cdrom/"::Mount "foo";</literallayout> within
 300      the cdrom block. It is important to have the trailing slash. Unmount
 301      commands can be specified using UMount.</para></listitem>
 302      </varlistentry>
 303
 304      <varlistentry><term>gpgv</term>
 305      <listitem><para>GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv.
 306      <literal>gpgv::Options</literal> Additional options passed to gpgv.
 307      </para></listitem>
 308      </varlistentry>
 309
 310    </variablelist>
 311   </para>
 312  </refsect1>
 313
 314  <refsect1><title>Directories</title>
 315
 316    <para>The <literal>Dir::State</literal> section has directories that pertain to local
 317    state information. <literal>lists</literal> is the directory to place downloaded
 318    package lists in and <literal>status</literal> is the name of the dpkg status file.
 319    <literal>preferences</literal> is the name of the APT preferences file.
 320    <literal>Dir::State</literal> contains the default directory to prefix on all sub
 321    items if they do not start with <filename>/</filename> or <filename>./</filename>.</para>
 322
 323    <para><literal>Dir::Cache</literal> contains locations pertaining to local cache
 324    information, such as the two package caches <literal>srcpkgcache</literal> and
 325    <literal>pkgcache</literal> as well as the location to place downloaded archives,
 326    <literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
 327    by setting their names to be blank. This will slow down startup but
 328    save disk space. It is probably preferred to turn off the pkgcache rather
 329    than the srcpkgcache. Like <literal>Dir::State</literal> the default
 330    directory is contained in <literal>Dir::Cache</literal></para>
 331
 332    <para><literal>Dir::Etc</literal> contains the location of configuration files,
 333    <literal>sourcelist</literal> gives the location of the sourcelist and
 334    <literal>main</literal> is the default configuration file (setting has no effect,
 335    unless it is done from the config file specified by
 336    <envar>APT_CONFIG</envar>).</para>
 337
 338    <para>The <literal>Dir::Parts</literal> setting reads in all the config fragments in
 339    lexical order from the directory specified. After this is done then the
 340    main config file is loaded.</para>
 341
 342    <para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal>
 343    specifies the location of the method handlers and <literal>gzip</literal>,
 344    <literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal>
 345    <literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
 346    of the respective programs.</para>
 347
 348    <para>
 349      The configuration item <literal>RootDir</literal> has a special
 350      meaning.  If set, all paths in <literal>Dir::</literal> will be
 351      relative to <literal>RootDir</literal>, <emphasis>even paths that
 352      are specified absolutely</emphasis>.  So, for instance, if
 353      <literal>RootDir</literal> is set to
 354      <filename>/tmp/staging</filename> and
 355      <literal>Dir::State::status</literal> is set to
 356      <filename>/var/lib/dpkg/status</filename>, then the status file
 357      will be looked up in
 358      <filename>/tmp/staging/var/lib/dpkg/status</filename>.
 359    </para>
 360  </refsect1>
 361
 362  <refsect1><title>APT in DSelect</title>
 363    <para>
 364    When APT is used as a &dselect; method several configuration directives
 365    control the default behaviour. These are in the <literal>DSelect</literal> section.</para>
 366
 367    <variablelist>
 368      <varlistentry><term>Clean</term>
 369      <listitem><para>Cache Clean mode; this value may be one of always, prompt, auto,
 370      pre-auto and never.  always and prompt will remove all packages from
 371      the cache after upgrading, prompt (the default) does so conditionally.
 372      auto removes only those packages which are no longer downloadable
 373      (replaced with a new version for instance).  pre-auto performs this
 374      action before downloading new packages.</para></listitem>
 375      </varlistentry>
 376
 377      <varlistentry><term>options</term>
 378      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 379      options when it is run for the install phase.</para></listitem>
 380      </varlistentry>
 381
 382      <varlistentry><term>Updateoptions</term>
 383      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 384      options when it is run for the update phase.</para></listitem>
 385      </varlistentry>
 386
 387      <varlistentry><term>PromptAfterUpdate</term>
 388      <listitem><para>If true the [U]pdate operation in &dselect; will always prompt to continue.
 389      The default is to prompt only on error.</para></listitem>
 390      </varlistentry>
 391    </variablelist>
 392  </refsect1>
 393
 394  <refsect1><title>How APT calls dpkg</title>
 395    <para>Several configuration directives control how APT invokes &dpkg;. These are
 396    in the <literal>DPkg</literal> section.</para>
 397
 398    <variablelist>
 399      <varlistentry><term>options</term>
 400      <listitem><para>This is a list of options to pass to dpkg. The options must be specified
 401      using the list notation and each list item is passed as a single argument
 402      to &dpkg;.</para></listitem>
 403      </varlistentry>
 404
 405      <varlistentry><term>Pre-Invoke</term><term>Post-Invoke</term>
 406      <listitem><para>This is a list of shell commands to run before/after invoking &dpkg;.
 407      Like <literal>options</literal> this must be specified in list notation. The
 408      commands are invoked in order using <filename>/bin/sh</filename>, should any
 409      fail APT will abort.</para></listitem>
 410      </varlistentry>
 411
 412      <varlistentry><term>Pre-Install-Pkgs</term>
 413      <listitem><para>This is a list of shell commands to run before invoking dpkg. Like
 414      <literal>options</literal> this must be specified in list notation. The commands
 415      are invoked in order using <filename>/bin/sh</filename>, should any fail APT
 416      will abort. APT will pass to the commands on standard input the
 417      filenames of all .deb files it is going to install, one per line.</para>
 418
 419      <para>Version 2 of this protocol dumps more information, including the
 420      protocol version, the APT configuration space and the packages, files
 421      and versions being changed. Version 2 is enabled by setting
 422      <literal>DPkg::Tools::options::cmd::Version</literal> to 2. <literal>cmd</literal> is a
 423      command given to <literal>Pre-Install-Pkgs</literal>.</para></listitem>
 424      </varlistentry>
 425
 426      <varlistentry><term>Run-Directory</term>
 427      <listitem><para>APT chdirs to this directory before invoking dpkg, the default is
 428      <filename>/</filename>.</para></listitem>
 429      </varlistentry>
 430
 431      <varlistentry><term>Build-options</term>
 432      <listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages,
 433      the default is to disable signing and produce all binaries.</para></listitem>
 434      </varlistentry>
 435    </variablelist>
 436  </refsect1>
 437
 438  <refsect1>
 439    <title>Periodic and Archives options</title>
 440    <para><literal>APT::Periodic</literal> and <literal>APT::Archives</literal>
 441    groups of options configure behavior of apt periodic updates, which is
 442    done by <literal>/etc/cron.daily/apt</literal> script. See header of
 443    this script for the brief documentation of these options.
 444    </para>
 445  </refsect1>
 446
 447  <refsect1>
 448    <title>Debug options</title>
 449    <para>
 450      Enabling options in the <literal>Debug::</literal> section will
 451      cause debugging information to be sent to the standard error
 452      stream of the program utilizing the <literal>apt</literal>
 453      libraries, or enable special program modes that are primarily
 454      useful for debugging the behavior of <literal>apt</literal>.
 455      Most of these options are not interesting to a normal user, but a
 456      few may be:
 457
 458      <itemizedlist>
 459        <listitem>
 460          <para>
 461            <literal>Debug::pkgProblemResolver</literal> enables output
 462            about the decisions made by
 463            <literal>dist-upgrade, upgrade, install, remove, purge</literal>.
 464          </para>
 465        </listitem>
 466
 467        <listitem>
 468          <para>
 469            <literal>Debug::NoLocking</literal> disables all file
 470            locking.  This can be used to run some operations (for
 471            instance, <literal>apt-get -s install</literal>) as a
 472            non-root user.
 473          </para>
 474        </listitem>
 475
 476        <listitem>
 477          <para>
 478            <literal>Debug::pkgDPkgPM</literal> prints out the actual
 479            command line each time that <literal>apt</literal> invokes
 480            &dpkg;.
 481          </para>
 482        </listitem>
 483
 484        <listitem>
 485          <para>
 486            <literal>Debug::IdentCdrom</literal> disables the inclusion
 487            of statfs data in CDROM IDs.  <!-- TODO: provide a
 488            motivating example, except I haven't a clue why you'd want
 489            to do this. -->
 490          </para>
 491        </listitem>
 492      </itemizedlist>
 493    </para>
 494
 495    <para>
 496      A full list of debugging options to apt follows.
 497    </para>
 498
 499    <variablelist>
 500      <varlistentry>
 501        <term><literal>Debug::Acquire::cdrom</literal></term>
 502
 503        <listitem>
 504          <para>
 505            Print information related to accessing
 506            <literal>cdrom://</literal> sources.
 507          </para>
 508        </listitem>
 509      </varlistentry>
 510
 511      <varlistentry>
 512        <term><literal>Debug::Acquire::ftp</literal></term>
 513
 514        <listitem>
 515          <para>
 516            Print information related to downloading packages using
 517            FTP.
 518          </para>
 519        </listitem>
 520      </varlistentry>
 521
 522      <varlistentry>
 523        <term><literal>Debug::Acquire::http</literal></term>
 524
 525        <listitem>
 526          <para>
 527            Print information related to downloading packages using
 528            HTTP.
 529          </para>
 530        </listitem>
 531      </varlistentry>
 532
 533      <varlistentry>
 534        <term><literal>Debug::Acquire::https</literal></term>
 535
 536        <listitem>
 537          <para>
 538            Print information related to downloading packages using
 539            HTTPS.
 540          </para>
 541        </listitem>
 542      </varlistentry>
 543
 544      <varlistentry>
 545        <term><literal>Debug::Acquire::gpgv</literal></term>
 546
 547        <listitem>
 548          <para>
 549            Print information related to verifying cryptographic
 550            signatures using <literal>gpg</literal>.
 551          </para>
 552        </listitem>
 553      </varlistentry>
 554
 555      <varlistentry>
 556        <term><literal>Debug::aptcdrom</literal></term>
 557
 558        <listitem>
 559          <para>
 560            Output information about the process of accessing
 561            collections of packages stored on CD-ROMs.
 562          </para>
 563        </listitem>
 564      </varlistentry>
 565
 566      <varlistentry>
 567        <term><literal>Debug::BuildDeps</literal></term>
 568        <listitem>
 569          <para>
 570            Describes the process of resolving build-dependencies in
 571            &apt-get;.
 572          </para>
 573        </listitem>
 574      </varlistentry>
 575
 576      <varlistentry>
 577        <term><literal>Debug::Hashes</literal></term>
 578        <listitem>
 579          <para>
 580            Output each cryptographic hash that is generated by the
 581            <literal>apt</literal> libraries.
 582          </para>
 583        </listitem>
 584      </varlistentry>
 585
 586      <varlistentry>
 587        <term><literal>Debug::IdentCDROM</literal></term>
 588        <listitem>
 589          <para>
 590            Do not include information from <literal>statfs</literal>,
 591            namely the number of used and free blocks on the CD-ROM
 592            filesystem, when generating an ID for a CD-ROM.
 593          </para>
 594        </listitem>
 595      </varlistentry>
 596
 597      <varlistentry>
 598        <term><literal>Debug::NoLocking</literal></term>
 599        <listitem>
 600          <para>
 601            Disable all file locking.  For instance, this will allow
 602            two instances of <quote><literal>apt-get
 603            update</literal></quote> to run at the same time.
 604          </para>
 605        </listitem>
 606      </varlistentry>
 607
 608      <varlistentry>
 609        <term><literal>Debug::pkgAcquire</literal></term>
 610
 611        <listitem>
 612          <para>
 613            Log when items are added to or removed from the global
 614            download queue.
 615          </para>
 616        </listitem>
 617      </varlistentry>
 618
 619      <varlistentry>
 620        <term><literal>Debug::pkgAcquire::Auth</literal></term>
 621        <listitem>
 622          <para>
 623            Output status messages and errors related to verifying
 624            checksums and cryptographic signatures of downloaded files.
 625          </para>
 626        </listitem>
 627      </varlistentry>
 628
 629      <varlistentry>
 630        <term><literal>Debug::pkgAcquire::Diffs</literal></term>
 631        <listitem>
 632          <para>
 633            Output information about downloading and applying package
 634            index list diffs, and errors relating to package index list
 635            diffs.
 636          </para>
 637        </listitem>
 638      </varlistentry>
 639
 640      <varlistentry>
 641        <term><literal>Debug::pkgAcquire::RRed</literal></term>
 642
 643        <listitem>
 644          <para>
 645            Output information related to patching apt package lists
 646            when downloading index diffs instead of full indices.
 647          </para>
 648        </listitem>
 649      </varlistentry>
 650
 651      <varlistentry>
 652        <term><literal>Debug::pkgAcquire::Worker</literal></term>
 653
 654        <listitem>
 655          <para>
 656            Log all interactions with the sub-processes that actually
 657            perform downloads.
 658          </para>
 659        </listitem>
 660      </varlistentry>
 661
 662      <varlistentry>
 663        <term><literal>Debug::pkgAutoRemove</literal></term>
 664
 665        <listitem>
 666          <para>
 667            Log events related to the automatically-installed status of
 668            packages and to the removal of unused packages.
 669          </para>
 670        </listitem>
 671      </varlistentry>
 672
 673      <varlistentry>
 674        <term><literal>Debug::pkgDepCache::AutoInstall</literal></term>
 675        <listitem>
 676          <para>
 677            Generate debug messages describing which packages are being
 678            automatically installed to resolve dependencies.  This
 679            corresponds to the initial auto-install pass performed in,
 680            e.g., <literal>apt-get install</literal>, and not to the
 681            full <literal>apt</literal> dependency resolver; see
 682            <literal>Debug::pkgProblemResolver</literal> for that.
 683          </para>
 684        </listitem>
 685      </varlistentry>
 686
 687      <!-- Question: why doesn't this do anything?  The code says it should. -->
 688      <varlistentry>
 689        <term><literal>Debug::pkgInitConfig</literal></term>
 690        <listitem>
 691          <para>
 692            Dump the default configuration to standard output on
 693            startup.
 694          </para>
 695        </listitem>
 696      </varlistentry>
 697
 698      <varlistentry>
 699        <term><literal>Debug::pkgDPkgPM</literal></term>
 700        <listitem>
 701          <para>
 702            When invoking &dpkg;, output the precise command line with
 703            which it is being invoked, with arguments separated by a
 704            single space character.
 705          </para>
 706        </listitem>
 707      </varlistentry>
 708
 709      <varlistentry>
 710        <term><literal>Debug::pkgDPkgProgressReporting</literal></term>
 711        <listitem>
 712          <para>
 713            Output all the data received from &dpkg; on the status file
 714            descriptor and any errors encountered while parsing it.
 715          </para>
 716        </listitem>
 717      </varlistentry>
 718
 719      <varlistentry>
 720        <term><literal>Debug::pkgOrderList</literal></term>
 721
 722        <listitem>
 723          <para>
 724            Generate a trace of the algorithm that decides the order in
 725            which <literal>apt</literal> should pass packages to
 726            &dpkg;.
 727          </para>
 728        </listitem>
 729      </varlistentry>
 730
 731      <varlistentry>
 732        <term><literal>Debug::pkgPackageManager</literal></term>
 733
 734        <listitem>
 735          <para>
 736            Output status messages tracing the steps performed when
 737            invoking &dpkg;.
 738          </para>
 739        </listitem>
 740      </varlistentry>
 741
 742      <varlistentry>
 743        <term><literal>Debug::pkgPolicy</literal></term>
 744
 745        <listitem>
 746          <para>
 747            Output the priority of each package list on startup.
 748          </para>
 749        </listitem>
 750      </varlistentry>
 751
 752      <varlistentry>
 753        <term><literal>Debug::pkgProblemResolver</literal></term>
 754
 755        <listitem>
 756          <para>
 757            Trace the execution of the dependency resolver (this
 758            applies only to what happens when a complex dependency
 759            problem is encountered).
 760          </para>
 761        </listitem>
 762      </varlistentry>
 763
 764      <varlistentry>
 765        <term><literal>Debug::sourceList</literal></term>
 766
 767        <listitem>
 768          <para>
 769            Print information about the vendors read from
 770            <filename>/etc/apt/vendors.list</filename>.
 771          </para>
 772        </listitem>
 773      </varlistentry>
 774
 775      <varlistentry>
 776        <term><literal>Debug::Vendor</literal></term>
 777
 778        <listitem>
 779          <para>
 780            Print information about each vendor.
 781          </para>
 782        </listitem>
 783      </varlistentry>
 784    </variablelist>
 785  </refsect1>
 786
 787  <refsect1><title>Examples</title>
 788    <para>&configureindex; is a
 789    configuration file showing example values for all possible
 790    options.</para>
 791  </refsect1>
 792
 793  <refsect1><title>Files</title>
 794    <para><filename>/etc/apt/apt.conf</filename></para>
 795  </refsect1>
 796
 797  <refsect1><title>See Also</title>
 798    <para>&apt-cache;, &apt-config;<!-- ? reading apt.conf -->, &apt-preferences;.</para>
 799  </refsect1>
 800
 801  &manbugs;
 802
 803 </refentry>
 804