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 ]>
   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. The <envar>http_proxy</envar> environment variable
 206      will override all settings.</para>
 207
 208      <para>Three settings are provided for cache control with HTTP/1.1 compliant
 209      proxy caches. <literal>No-Cache</literal> tells the proxy to not use its cached
 210      response under any circumstances, <literal>Max-Age</literal> is sent only for
 211      index files and tells the cache to refresh its object if it is older than
 212      the given number of seconds. Debian updates its index files daily so the
 213      default is 1 day. <literal>No-Store</literal> specifies that the cache should never
 214      store this request, it is only set for archive files. This may be useful
 215      to prevent polluting a proxy cache with very large .deb files. Note:
 216      Squid 2.0.2 does not support any of these options.</para>
 217
 218      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 219      this applies to all things including connection timeout and data timeout.</para>
 220
 221      <para>One setting is provided to control the pipeline depth in cases where the
 222      remote server is not RFC conforming or buggy (such as Squid 2.0.2)
 223      <literal>Acquire::http::Pipeline-Depth</literal> can be a value from 0 to 5
 224      indicating how many outstanding requests APT should send. A value of
 225      zero MUST be specified if the remote host does not properly linger
 226      on TCP connections - otherwise data corruption will occur. Hosts which
 227      require this are in violation of RFC 2068.</para></listitem>
 228      </varlistentry>
 229
 230      <varlistentry><term>https</term>
 231          <listitem><para>HTTPS URIs. Cache-control and proxy options are the same as for
 232          <literal>http</literal> method.
 233          <literal>Pipeline-Depth</literal> option is not supported yet.</para>
 234
 235          <para><literal>CaInfo</literal> suboption specifies place of file that
 236          holds info about trusted certificates.
 237          <literal>&lt;host&gt;::CaInfo</literal> is corresponding per-host option.
 238          <literal>Verify-Peer</literal> boolean suboption determines whether verify
 239          server's host certificate against trusted certificates or not.
 240          <literal>&lt;host&gt;::Verify-Peer</literal> is corresponding per-host option.
 241          <literal>Verify-Host</literal> boolean suboption determines whether verify
 242          server's hostname or not.
 243          <literal>&lt;host&gt;::Verify-Host</literal> is corresponding per-host option.
 244          <literal>SslCert</literal> determines what certificate to use for client
 245          authentication. <literal>&lt;host&gt;::SslCert</literal> is corresponding per-host option.
 246          <literal>SslKey</literal> determines what private key to use for client
 247          authentication. <literal>&lt;host&gt;::SslKey</literal> is corresponding per-host option.
 248          <literal>SslForceVersion</literal> overrides default SSL version to use.
 249          Can contain 'TLSv1' or 'SSLv3' string.
 250          <literal>&lt;host&gt;::SslForceVersion</literal> is corresponding per-host option.
 251          </para></listitem></varlistentry>
 252
 253      <varlistentry><term>ftp</term>
 254      <listitem><para>FTP URIs; ftp::Proxy is the default proxy server to use. It is in the
 255      standard form of <literal>ftp://[[user][:pass]@]host[:port]/</literal> and is
 256      overridden by the <envar>ftp_proxy</envar> environment variable. To use a ftp
 257      proxy you will have to set the <literal>ftp::ProxyLogin</literal> script in the
 258      configuration file. This entry specifies the commands to send to tell
 259      the proxy server what to connect to. Please see
 260      &configureindex; for an example of
 261      how to do this. The substitution variables available are
 262      <literal>$(PROXY_USER)</literal> <literal>$(PROXY_PASS)</literal> <literal>$(SITE_USER)</literal>
 263      <literal>$(SITE_PASS)</literal> <literal>$(SITE)</literal> and <literal>$(SITE_PORT)</literal>
 264      Each is taken from it's respective URI component.</para>
 265
 266      <para>The option <literal>timeout</literal> sets the timeout timer used by the method,
 267      this applies to all things including connection timeout and data timeout.</para>
 268
 269      <para>Several settings are provided to control passive mode. Generally it is
 270      safe to leave passive mode on, it works in nearly every environment.
 271      However some situations require that passive mode be disabled and port
 272      mode ftp used instead. This can be done globally, for connections that
 273      go through a proxy or for a specific host (See the sample config file
 274      for examples).</para>
 275
 276      <para>It is possible to proxy FTP over HTTP by setting the <envar>ftp_proxy</envar>
 277      environment variable to a http url - see the discussion of the http method
 278      above for syntax. You cannot set this in the configuration file and it is
 279      not recommended to use FTP over HTTP due to its low efficiency.</para>
 280
 281      <para>The setting <literal>ForceExtended</literal> controls the use of RFC2428
 282      <literal>EPSV</literal> and <literal>EPRT</literal> commands. The default is false, which means
 283      these commands are only used if the control connection is IPv6. Setting this
 284      to true forces their use even on IPv4 connections. Note that most FTP servers
 285      do not support RFC2428.</para></listitem>
 286      </varlistentry>
 287
 288      <varlistentry><term>cdrom</term>
 289      <listitem><para>CDROM URIs; the only setting for CDROM URIs is the mount point,
 290      <literal>cdrom::Mount</literal> which must be the mount point for the CDROM drive
 291      as specified in <filename>/etc/fstab</filename>. It is possible to provide
 292      alternate mount and unmount commands if your mount point cannot be listed
 293      in the fstab (such as an SMB mount and old mount packages). The syntax
 294      is to put <literallayout>"/cdrom/"::Mount "foo";</literallayout> within
 295      the cdrom block. It is important to have the trailing slash. Unmount
 296      commands can be specified using UMount.</para></listitem>
 297      </varlistentry>
 298
 299      <varlistentry><term>gpgv</term>
 300      <listitem><para>GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv.
 301      <literal>gpgv::Options</literal> Additional options passed to gpgv.
 302      </para></listitem>
 303      </varlistentry>
 304
 305    </variablelist>
 306   </para>
 307  </refsect1>
 308
 309  <refsect1><title>Directories</title>
 310
 311    <para>The <literal>Dir::State</literal> section has directories that pertain to local
 312    state information. <literal>lists</literal> is the directory to place downloaded
 313    package lists in and <literal>status</literal> is the name of the dpkg status file.
 314    <literal>preferences</literal> is the name of the APT preferences file.
 315    <literal>Dir::State</literal> contains the default directory to prefix on all sub
 316    items if they do not start with <filename>/</filename> or <filename>./</filename>.</para>
 317
 318    <para><literal>Dir::Cache</literal> contains locations pertaining to local cache
 319    information, such as the two package caches <literal>srcpkgcache</literal> and
 320    <literal>pkgcache</literal> as well as the location to place downloaded archives,
 321    <literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
 322    by setting their names to be blank. This will slow down startup but
 323    save disk space. It is probably preferred to turn off the pkgcache rather
 324    than the srcpkgcache. Like <literal>Dir::State</literal> the default
 325    directory is contained in <literal>Dir::Cache</literal></para>
 326
 327    <para><literal>Dir::Etc</literal> contains the location of configuration files,
 328    <literal>sourcelist</literal> gives the location of the sourcelist and
 329    <literal>main</literal> is the default configuration file (setting has no effect,
 330    unless it is done from the config file specified by
 331    <envar>APT_CONFIG</envar>).</para>
 332
 333    <para>The <literal>Dir::Parts</literal> setting reads in all the config fragments in
 334    lexical order from the directory specified. After this is done then the
 335    main config file is loaded.</para>
 336
 337    <para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal>
 338    specifies the location of the method handlers and <literal>gzip</literal>,
 339    <literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal>
 340    <literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
 341    of the respective programs.</para>
 342
 343    <para>
 344      The configuration item <literal>RootDir</literal> has a special
 345      meaning.  If set, all paths in <literal>Dir::</literal> will be
 346      relative to <literal>RootDir</literal>, <emphasis>even paths that
 347      are specified absolutely</emphasis>.  So, for instance, if
 348      <literal>RootDir</literal> is set to
 349      <filename>/tmp/staging</filename> and
 350      <literal>Dir::State::status</literal> is set to
 351      <filename>/var/lib/dpkg/status</filename>, then the status file
 352      will be looked up in
 353      <filename>/tmp/staging/var/lib/dpkg/status</filename>.
 354    </para>
 355  </refsect1>
 356
 357  <refsect1><title>APT in DSelect</title>
 358    <para>
 359    When APT is used as a &dselect; method several configuration directives
 360    control the default behaviour. These are in the <literal>DSelect</literal> section.</para>
 361
 362    <variablelist>
 363      <varlistentry><term>Clean</term>
 364      <listitem><para>Cache Clean mode; this value may be one of always, prompt, auto,
 365      pre-auto and never.  always and prompt will remove all packages from
 366      the cache after upgrading, prompt (the default) does so conditionally.
 367      auto removes only those packages which are no longer downloadable
 368      (replaced with a new version for instance).  pre-auto performs this
 369      action before downloading new packages.</para></listitem>
 370      </varlistentry>
 371
 372      <varlistentry><term>options</term>
 373      <listitem><para>The contents of this variable is passed to &apt-get; as command line
 374      options when it is run for the install phase.</para></listitem>
 375      </varlistentry>
 376
 377      <varlistentry><term>Updateoptions</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 update phase.</para></listitem>
 380      </varlistentry>
 381
 382      <varlistentry><term>PromptAfterUpdate</term>
 383      <listitem><para>If true the [U]pdate operation in &dselect; will always prompt to continue.
 384      The default is to prompt only on error.</para></listitem>
 385      </varlistentry>
 386    </variablelist>
 387  </refsect1>
 388
 389  <refsect1><title>How APT calls dpkg</title>
 390    <para>Several configuration directives control how APT invokes &dpkg;. These are
 391    in the <literal>DPkg</literal> section.</para>
 392
 393    <variablelist>
 394      <varlistentry><term>options</term>
 395      <listitem><para>This is a list of options to pass to dpkg. The options must be specified
 396      using the list notation and each list item is passed as a single argument
 397      to &dpkg;.</para></listitem>
 398      </varlistentry>
 399
 400      <varlistentry><term>Pre-Invoke</term><term>Post-Invoke</term>
 401      <listitem><para>This is a list of shell commands to run before/after invoking &dpkg;.
 402      Like <literal>options</literal> this must be specified in list notation. The
 403      commands are invoked in order using <filename>/bin/sh</filename>, should any
 404      fail APT will abort.</para></listitem>
 405      </varlistentry>
 406
 407      <varlistentry><term>Pre-Install-Pkgs</term>
 408      <listitem><para>This is a list of shell commands to run before invoking dpkg. Like
 409      <literal>options</literal> this must be specified in list notation. The commands
 410      are invoked in order using <filename>/bin/sh</filename>, should any fail APT
 411      will abort. APT will pass to the commands on standard input the
 412      filenames of all .deb files it is going to install, one per line.</para>
 413
 414      <para>Version 2 of this protocol dumps more information, including the
 415      protocol version, the APT configuration space and the packages, files
 416      and versions being changed. Version 2 is enabled by setting
 417      <literal>DPkg::Tools::options::cmd::Version</literal> to 2. <literal>cmd</literal> is a
 418      command given to <literal>Pre-Install-Pkgs</literal>.</para></listitem>
 419      </varlistentry>
 420
 421      <varlistentry><term>Run-Directory</term>
 422      <listitem><para>APT chdirs to this directory before invoking dpkg, the default is
 423      <filename>/</filename>.</para></listitem>
 424      </varlistentry>
 425
 426      <varlistentry><term>Build-options</term>
 427      <listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages,
 428      the default is to disable signing and produce all binaries.</para></listitem>
 429      </varlistentry>
 430    </variablelist>
 431  </refsect1>
 432
 433  <refsect1>
 434    <title>Periodic and Archives options</title>
 435    <para><literal>APT::Periodic</literal> and <literal>APT::Archives</literal>
 436    groups of options configure behavior of apt periodic updates, which is
 437    done by <literal>/etc/cron.daily/apt</literal> script. See header of
 438    this script for the brief documentation of these options.
 439    </para>
 440  </refsect1>
 441
 442  <refsect1>
 443    <title>Debug options</title>
 444    <para>
 445      Enabling options in the <literal>Debug::</literal> section will
 446      cause debugging information to be sent to the standard error
 447      stream of the program utilizing the <literal>apt</literal>
 448      libraries, or enable special program modes that are primarily
 449      useful for debugging the behavior of <literal>apt</literal>.
 450      Most of these options are not interesting to a normal user, but a
 451      few may be:
 452
 453      <itemizedlist>
 454        <listitem>
 455          <para>
 456            <literal>Debug::pkgProblemResolver</literal> enables output
 457            about the decisions made by
 458            <literal>dist-upgrade, upgrade, install, remove, purge</literal>.
 459          </para>
 460        </listitem>
 461
 462        <listitem>
 463          <para>
 464            <literal>Debug::NoLocking</literal> disables all file
 465            locking.  This can be used to run some operations (for
 466            instance, <literal>apt-get -s install</literal>) as a
 467            non-root user.
 468          </para>
 469        </listitem>
 470
 471        <listitem>
 472          <para>
 473            <literal>Debug::pkgDPkgPM</literal> prints out the actual
 474            command line each time that <literal>apt</literal> invokes
 475            &dpkg;.
 476          </para>
 477        </listitem>
 478
 479        <listitem>
 480          <para>
 481            <literal>Debug::IdentCdrom</literal> disables the inclusion
 482            of statfs data in CDROM IDs.  <!-- TODO: provide a
 483            motivating example, except I haven't a clue why you'd want
 484            to do this. -->
 485          </para>
 486        </listitem>
 487      </itemizedlist>
 488    </para>
 489
 490    <para>
 491      A full list of debugging options to apt follows.
 492    </para>
 493
 494    <variablelist>
 495      <varlistentry>
 496        <term><literal>Debug::Acquire::cdrom</literal></term>
 497
 498        <listitem>
 499          <para>
 500            Print information related to accessing
 501            <literal>cdrom://</literal> sources.
 502          </para>
 503        </listitem>
 504      </varlistentry>
 505
 506      <varlistentry>
 507        <term><literal>Debug::Acquire::ftp</literal></term>
 508
 509        <listitem>
 510          <para>
 511            Print information related to downloading packages using
 512            FTP.
 513          </para>
 514        </listitem>
 515      </varlistentry>
 516
 517      <varlistentry>
 518        <term><literal>Debug::Acquire::http</literal></term>
 519
 520        <listitem>
 521          <para>
 522            Print information related to downloading packages using
 523            HTTP.
 524          </para>
 525        </listitem>
 526      </varlistentry>
 527
 528      <varlistentry>
 529        <term><literal>Debug::Acquire::https</literal></term>
 530
 531        <listitem>
 532          <para>
 533            Print information related to downloading packages using
 534            HTTPS.
 535          </para>
 536        </listitem>
 537      </varlistentry>
 538
 539      <varlistentry>
 540        <term><literal>Debug::Acquire::gpgv</literal></term>
 541
 542        <listitem>
 543          <para>
 544            Print information related to verifying cryptographic
 545            signatures using <literal>gpg</literal>.
 546          </para>
 547        </listitem>
 548      </varlistentry>
 549
 550      <varlistentry>
 551        <term><literal>Debug::aptcdrom</literal></term>
 552
 553        <listitem>
 554          <para>
 555            Output information about the process of accessing
 556            collections of packages stored on CD-ROMs.
 557          </para>
 558        </listitem>
 559      </varlistentry>
 560
 561      <varlistentry>
 562        <term><literal>Debug::BuildDeps</literal></term>
 563        <listitem>
 564          <para>
 565            Describes the process of resolving build-dependencies in
 566            &apt-get;.
 567          </para>
 568        </listitem>
 569      </varlistentry>
 570
 571      <varlistentry>
 572        <term><literal>Debug::Hashes</literal></term>
 573        <listitem>
 574          <para>
 575            Output each cryptographic hash that is generated by the
 576            <literal>apt</literal> libraries.
 577          </para>
 578        </listitem>
 579      </varlistentry>
 580
 581      <varlistentry>
 582        <term><literal>Debug::IdentCDROM</literal></term>
 583        <listitem>
 584          <para>
 585            Do not include information from <literal>statfs</literal>,
 586            namely the number of used and free blocks on the CD-ROM
 587            filesystem, when generating an ID for a CD-ROM.
 588          </para>
 589        </listitem>
 590      </varlistentry>
 591
 592      <varlistentry>
 593        <term><literal>Debug::NoLocking</literal></term>
 594        <listitem>
 595          <para>
 596            Disable all file locking.  For instance, this will allow
 597            two instances of <quote><literal>apt-get
 598            update</literal></quote> to run at the same time.
 599          </para>
 600        </listitem>
 601      </varlistentry>
 602
 603      <varlistentry>
 604        <term><literal>Debug::pkgAcquire</literal></term>
 605
 606        <listitem>
 607          <para>
 608            Log when items are added to or removed from the global
 609            download queue.
 610          </para>
 611        </listitem>
 612      </varlistentry>
 613
 614      <varlistentry>
 615        <term><literal>Debug::pkgAcquire::Auth</literal></term>
 616        <listitem>
 617          <para>
 618            Output status messages and errors related to verifying
 619            checksums and cryptographic signatures of downloaded files.
 620          </para>
 621        </listitem>
 622      </varlistentry>
 623
 624      <varlistentry>
 625        <term><literal>Debug::pkgAcquire::Diffs</literal></term>
 626        <listitem>
 627          <para>
 628            Output information about downloading and applying package
 629            index list diffs, and errors relating to package index list
 630            diffs.
 631          </para>
 632        </listitem>
 633      </varlistentry>
 634
 635      <varlistentry>
 636        <term><literal>Debug::pkgAcquire::RRed</literal></term>
 637
 638        <listitem>
 639          <para>
 640            Output information related to patching apt package lists
 641            when downloading index diffs instead of full indices.
 642          </para>
 643        </listitem>
 644      </varlistentry>
 645
 646      <varlistentry>
 647        <term><literal>Debug::pkgAcquire::Worker</literal></term>
 648
 649        <listitem>
 650          <para>
 651            Log all interactions with the sub-processes that actually
 652            perform downloads.
 653          </para>
 654        </listitem>
 655      </varlistentry>
 656
 657      <varlistentry>
 658        <term><literal>Debug::pkgAutoRemove</literal></term>
 659
 660        <listitem>
 661          <para>
 662            Log events related to the automatically-installed status of
 663            packages and to the removal of unused packages.
 664          </para>
 665        </listitem>
 666      </varlistentry>
 667
 668      <varlistentry>
 669        <term><literal>Debug::pkgDepCache::AutoInstall</literal></term>
 670        <listitem>
 671          <para>
 672            Generate debug messages describing which packages are being
 673            automatically installed to resolve dependencies.  This
 674            corresponds to the initial auto-install pass performed in,
 675            e.g., <literal>apt-get install</literal>, and not to the
 676            full <literal>apt</literal> dependency resolver; see
 677            <literal>Debug::pkgProblemResolver</literal> for that.
 678          </para>
 679        </listitem>
 680      </varlistentry>
 681
 682      <!-- Question: why doesn't this do anything?  The code says it should. -->
 683      <varlistentry>
 684        <term><literal>Debug::pkgInitConfig</literal></term>
 685        <listitem>
 686          <para>
 687            Dump the default configuration to standard output on
 688            startup.
 689          </para>
 690        </listitem>
 691      </varlistentry>
 692
 693      <varlistentry>
 694        <term><literal>Debug::pkgDPkgPM</literal></term>
 695        <listitem>
 696          <para>
 697            When invoking &dpkg;, output the precise command line with
 698            which it is being invoked, with arguments separated by a
 699            single space character.
 700          </para>
 701        </listitem>
 702      </varlistentry>
 703
 704      <varlistentry>
 705        <term><literal>Debug::pkgDPkgProgressReporting</literal></term>
 706        <listitem>
 707          <para>
 708            Output all the data received from &dpkg; on the status file
 709            descriptor and any errors encountered while parsing it.
 710          </para>
 711        </listitem>
 712      </varlistentry>
 713
 714      <varlistentry>
 715        <term><literal>Debug::pkgOrderList</literal></term>
 716
 717        <listitem>
 718          <para>
 719            Generate a trace of the algorithm that decides the order in
 720            which <literal>apt</literal> should pass packages to
 721            &dpkg;.
 722          </para>
 723        </listitem>
 724      </varlistentry>
 725
 726      <varlistentry>
 727        <term><literal>Debug::pkgPackageManager</literal></term>
 728
 729        <listitem>
 730          <para>
 731            Output status messages tracing the steps performed when
 732            invoking &dpkg;.
 733          </para>
 734        </listitem>
 735      </varlistentry>
 736
 737      <varlistentry>
 738        <term><literal>Debug::pkgPolicy</literal></term>
 739
 740        <listitem>
 741          <para>
 742            Output the priority of each package list on startup.
 743          </para>
 744        </listitem>
 745      </varlistentry>
 746
 747      <varlistentry>
 748        <term><literal>Debug::pkgProblemResolver</literal></term>
 749
 750        <listitem>
 751          <para>
 752            Trace the execution of the dependency resolver (this
 753            applies only to what happens when a complex dependency
 754            problem is encountered).
 755          </para>
 756        </listitem>
 757      </varlistentry>
 758
 759      <varlistentry>
 760        <term><literal>Debug::sourceList</literal></term>
 761
 762        <listitem>
 763          <para>
 764            Print information about the vendors read from
 765            <filename>/etc/apt/vendors.list</filename>.
 766          </para>
 767        </listitem>
 768      </varlistentry>
 769
 770      <varlistentry>
 771        <term><literal>Debug::Vendor</literal></term>
 772
 773        <listitem>
 774          <para>
 775            Print information about each vendor.
 776          </para>
 777        </listitem>
 778      </varlistentry>
 779    </variablelist>
 780  </refsect1>
 781
 782  <refsect1><title>Examples</title>
 783    <para>&configureindex; is a
 784    configuration file showing example values for all possible
 785    options.</para>
 786  </refsect1>
 787
 788  <refsect1><title>Files</title>
 789    <para><filename>/etc/apt/apt.conf</filename></para>
 790  </refsect1>
 791
 792  <refsect1><title>See Also</title>
 793    <para>&apt-cache;, &apt-config;<!-- ? reading apt.conf -->, &apt-preferences;.</para>
 794  </refsect1>
 795
 796  &manbugs;
 797
 798 </refentry>
 799