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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 09:59:37 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 09:59:37 +0000
commit76e2632459410dec81337edb6a9fee33c9a660f3 (patch)
treea73345df208eede4a4daad340515c9328f34625c /doc/apt.conf.5.xml
parentInitial commit. (diff)
downloadapt-76e2632459410dec81337edb6a9fee33c9a660f3.tar.xz
apt-76e2632459410dec81337edb6a9fee33c9a660f3.zip
Adding upstream version 2.7.12.upstream/2.7.12
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<?xml version="1.0" encoding="utf-8" standalone="no"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY % aptent SYSTEM "apt.ent"> %aptent;
+<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment;
+<!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor;
+]>
+
+<refentry>
+
+ <refentryinfo>
+ &apt-author.jgunthorpe;
+ &apt-author.team;
+ <author>
+ &apt-name.dburrows;
+ <contrib>Initial documentation of Debug::*.</contrib>
+ <email>dburrows@debian.org</email>
+ </author>
+ &apt-email;
+ &apt-product;
+ <!-- The last update date -->
+ <date>2024-02-20T00:00:00Z</date>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>apt.conf</refentrytitle>
+ <manvolnum>5</manvolnum>
+ <refmiscinfo class="manual">APT</refmiscinfo>
+ </refmeta>
+
+ <!-- Man page title -->
+ <refnamediv>
+ <refname>apt.conf</refname>
+ <refpurpose>Configuration file for APT</refpurpose>
+ </refnamediv>
+
+ <refsect1><title>Description</title>
+ <para><filename>/etc/apt/apt.conf</filename> is the main configuration
+ file shared by all the tools in the APT suite of tools, though it is by
+ no means the only place options can be set. The suite also shares a common
+ command line parser to provide a uniform environment.</para>
+
+ <orderedlist>
+ <para>When an APT tool starts up it will read the configuration files
+ in the following order:</para>
+ <listitem><para>the file specified by the <envar>APT_CONFIG</envar>
+ environment variable (if any)</para></listitem>
+ <listitem><para>all files in <literal>Dir::Etc::Parts</literal> in
+ alphanumeric ascending order which have either no or "<literal>conf</literal>"
+ as filename extension and which only contain alphanumeric,
+ hyphen (-), underscore (_) and period (.) characters.
+ Otherwise APT will print a notice that it has ignored a file, unless that
+ file matches a pattern in the <literal>Dir::Ignore-Files-Silently</literal>
+ configuration list - in which case it will be silently ignored.</para></listitem>
+ <listitem><para>the main configuration file specified by
+ <literal>Dir::Etc::main</literal></para></listitem>
+ <listitem><para>all options set in the binary specific configuration
+ subtree are moved into the root of the tree.</para></listitem>
+ <listitem><para>the command line options are applied to override the
+ configuration directives or to load even more configuration files.</para></listitem>
+ </orderedlist>
+ </refsect1>
+ <refsect1><title>Syntax</title>
+ <para>The configuration file is organized in a tree with options organized into
+ functional groups. Option specification is given with a double colon
+ notation; for instance <literal>APT::Get::Assume-Yes</literal> is an option within
+ the APT tool group, for the Get tool. Options do not inherit from their
+ parent groups.</para>
+
+ <para>Syntactically the configuration language is modeled after what the ISC tools
+ such as bind and dhcp use. Lines starting with
+ <literal>//</literal> are treated as comments (ignored), as well as all text
+ between <literal>/*</literal> and <literal>*/</literal>, just like C/C++ comments.
+ Lines starting with <literal>#</literal> are also treated as comments.
+ Each line is of the form
+ <literal>APT::Get::Assume-Yes "true";</literal>.
+ The quotation marks and trailing semicolon are required.
+ The value must be on one line, and there is no kind of string concatenation.
+ Values must not include backslashes or extra quotation marks.
+ Option names are made up of alphanumeric characters and the characters "/-:._+".
+ A new scope can be opened with curly braces, like this:</para>
+
+<informalexample><programlisting>
+APT {
+ Get {
+ Assume-Yes "true";
+ Fix-Broken "true";
+ };
+};
+</programlisting></informalexample>
+
+ <para>with newlines placed to make it more readable. Lists can be created by
+ opening a scope and including a single string enclosed in quotes followed by a
+ semicolon. Multiple entries can be included, separated by a semicolon.</para>
+
+<informalexample><programlisting>
+DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
+</programlisting></informalexample>
+
+ <para>In general the sample configuration file &configureindex;
+ is a good guide for how it should look.</para>
+
+ <para>Case is not significant in names of configuration items, so in the
+ previous example you could use <literal>dpkg::pre-install-pkgs</literal>.</para>
+
+ <para>Names for the configuration items are optional if a list is defined as can be seen in
+ the <literal>DPkg::Pre-Install-Pkgs</literal> example above. If you don't specify a name a
+ new entry will simply add a new option to the list. If you specify a name you can override
+ the option in the same way as any other option by reassigning a new value to the option.</para>
+
+ <para>Two special commands are defined: <literal>#include</literal> (which is
+ deprecated and not supported by alternative implementations) and
+ <literal>#clear</literal>. <literal>#include</literal> will include the
+ given file, unless the filename ends in a slash, in which case the whole
+ directory is included.
+ <literal>#clear</literal> is used to erase a part of the configuration tree. The
+ specified element and all its descendants are erased.
+ (Note that these lines also need to end with a semicolon.)</para>
+
+ <para>
+ The <literal>#clear</literal> command is the only way to delete a list or
+ a complete scope. Reopening a scope (or using the syntax described below
+ with an appended <literal>::</literal>) will <emphasis>not</emphasis>
+ override previously written entries. Options can only be overridden by
+ addressing a new value to them - lists and scopes can't be overridden,
+ only cleared.
+ </para>
+
+ <para>All of the APT tools take an -o option which allows an arbitrary configuration
+ directive to be specified on the command line. The syntax is a full option
+ name (<literal>APT::Get::Assume-Yes</literal> for instance) followed by an equals
+ sign then the new value of the option. To append a new element to a list, add a
+ trailing <literal>::</literal> to the name of the list.
+ (As you might suspect, the scope syntax can't be used on the command line.)</para>
+
+ <para>
+ Note that appending items to a list using <literal>::</literal> only works
+ for one item per line, and that you should not use it in combination with
+ the scope syntax (which adds <literal>::</literal> implicitly). Using both
+ syntaxes together will trigger a bug which some users unfortunately depend
+ on: an option with the unusual name "<literal>::</literal>" which acts
+ like every other option with a name. This introduces many problems; for
+ one thing, users who write multiple lines in this
+ <emphasis>wrong</emphasis> syntax in the hope of appending to a list will
+ achieve the opposite, as only the last assignment for this option
+ "<literal>::</literal>" will be used. Future versions of APT will raise
+ errors and stop working if they encounter this misuse, so please correct
+ such statements now while APT doesn't explicitly complain about them.
+ </para>
+ </refsect1>
+
+ <refsect1><title>The APT Group</title>
+ <para>This group of options controls general APT behavior as well as holding the
+ options for all of the tools.</para>
+
+ <variablelist>
+ <varlistentry><term><option>Architecture</option></term>
+ <listitem><para>System Architecture; sets the architecture to use when fetching files and
+ parsing package lists. The internal default is the architecture apt was
+ compiled for.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Architectures</option></term>
+ <listitem><para>
+ All Architectures the system supports. For instance, CPUs implementing
+ the <literal>amd64</literal> (also called <literal>x86-64</literal>)
+ instruction set are also able to execute binaries compiled for the
+ <literal>i386</literal> (<literal>x86</literal>) instruction set. This
+ list is used when fetching files and parsing package lists. The
+ initial default is always the system's native architecture
+ (<literal>APT::Architecture</literal>), and foreign architectures are
+ added to the default list when they are registered via
+ <command>dpkg --add-architecture</command>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Compressor</option></term>
+ <listitem><para>
+ This scope defines which compression formats are supported, how compression
+ and decompression can be performed if support for this format isn't built
+ into apt directly and a cost-value indicating how costly it is to compress
+ something in this format. As an example the following configuration stanza
+ would allow apt to download and uncompress as well as create and store
+ files with the low-cost <literal>.reversed</literal> file extension which
+ it will pass to the command <command>rev</command> without additional
+ commandline parameters for compression and uncompression:</para>
+<informalexample><programlisting>
+APT::Compressor::rev {
+ Name "rev";
+ Extension ".reversed";
+ Binary "rev";
+ CompressArg {};
+ UncompressArg {};
+ Cost "10";
+};
+</programlisting></informalexample>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Build-Profiles</option></term>
+ <listitem><para>
+ List of all build profiles enabled for build-dependency resolution,
+ without the "<literal>profile.</literal>" namespace prefix.
+ By default this list is empty. The <envar>DEB_BUILD_PROFILES</envar>
+ as used by &dpkg-buildpackage; overrides the list notation.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Default-Release</option></term>
+ <listitem><para>Default release to install packages from if more than one
+ version is available. Contains release name, codename or release version. Examples: 'stable', 'testing',
+ 'unstable', '&debian-stable-codename;', '&debian-testing-codename;', '4.0', '5.0*'. See also &apt-preferences;.</para></listitem>
+ </varlistentry>
+ <varlistentry><term><option>Snapshot</option></term>
+ <listitem><para>Snapshot to use for all repositories configured with <literal>Snapshot: yes</literal>. See also &sources-list;, the <option>--snapshot</option> option that sets this value, and <option>Acquire::Snapshots::URI</option> below.</para></listitem>
+ </varlistentry>
+
+
+ <varlistentry><term><option>Ignore-Hold</option></term>
+ <listitem><para>Ignore held packages; this global option causes the problem resolver to
+ ignore held packages in its decision making.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Clean-Installed</option></term>
+ <listitem><para>Defaults to on. When turned on the autoclean feature will remove any packages
+ which can no longer be downloaded from the cache. If turned off then
+ packages that are locally installed are also excluded from cleaning - but
+ note that APT provides no direct means to reinstall them.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Immediate-Configure</option></term>
+ <listitem><para>
+ Defaults to on, which will cause APT to install essential and important
+ packages as soon as possible in an install/upgrade operation, in order
+ to limit the effect of a failing &dpkg; call. If this option is
+ disabled, APT treats an important package in the same way as an extra
+ package: between the unpacking of the package A and its configuration
+ there can be many other unpack or configuration calls for other
+ unrelated packages B, C etc. If these cause the &dpkg; call to fail
+ (e.g. because package B's maintainer scripts generate an error), this
+ results in a system state in which package A is unpacked but
+ unconfigured - so any package depending on A is now no longer
+ guaranteed to work, as its dependency on A is no longer satisfied.
+ </para><para>
+ The immediate configuration marker is also applied in the potentially
+ problematic case of circular dependencies, since a dependency with the
+ immediate flag is equivalent to a Pre-Dependency. In theory this allows
+ APT to recognise a situation in which it is unable to perform immediate
+ configuration, abort, and suggest to the user that the option should be
+ temporarily deactivated in order to allow the operation to proceed.
+ Note the use of the word "theory" here; in the real world this problem
+ has rarely been encountered, in non-stable distribution versions, and
+ was caused by wrong dependencies of the package in question or by a
+ system in an already broken state; so you should not blindly disable
+ this option, as the scenario mentioned above is not the only problem it
+ can help to prevent in the first place.
+ </para><para>
+ Before a big operation like <literal>dist-upgrade</literal> is run
+ with this option disabled you should try to explicitly
+ <literal>install</literal> the package APT is unable to configure
+ immediately; but please make sure you also report your problem to your
+ distribution and to the APT team with the bug link below, so they can
+ work on improving or correcting the upgrade process.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Force-LoopBreak</option></term>
+ <listitem><para>
+ Never enable this option unless you <emphasis>really</emphasis> know
+ what you are doing. It permits APT to temporarily remove an essential
+ package to break a Conflicts/Conflicts or Conflicts/Pre-Depends loop
+ between two essential packages. <emphasis>Such a loop should never exist
+ and is a grave bug</emphasis>. This option will work if the essential
+ packages are not <command>tar</command>, <command>gzip</command>,
+ <command>libc</command>, <command>dpkg</command>, <command>dash</command>
+ or anything that those packages depend on.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Cache-Start</option></term><term><option>Cache-Grow</option></term><term><option>Cache-Limit</option></term>
+ <listitem><para>APT uses since version 0.7.26 a resizable memory mapped cache file to store the available
+ information. <literal>Cache-Start</literal> acts as a hint of the size the cache will grow to,
+ and is therefore the amount of memory APT will request at startup. The default value is
+ 20971520 bytes (~20 MB). Note that this amount of space needs to be available for APT;
+ otherwise it will likely fail ungracefully, so for memory restricted devices this value should
+ be lowered while on systems with a lot of configured sources it should be increased.
+ <literal>Cache-Grow</literal> defines in bytes with the default of 1048576 (~1 MB) how much
+ the cache size will be increased in the event the space defined by <literal>Cache-Start</literal>
+ is not enough. This value will be applied again and again until either the cache is big
+ enough to store all information or the size of the cache reaches the <literal>Cache-Limit</literal>.
+ The default of <literal>Cache-Limit</literal> is 0 which stands for no limit.
+ If <literal>Cache-Grow</literal> is set to 0 the automatic growth of the cache is disabled.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Build-Essential</option></term>
+ <listitem><para>Defines which packages are considered essential build dependencies.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Get</option></term>
+ <listitem><para>The Get subsection controls the &apt-get; tool; please see its
+ documentation for more information about the options here.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Cache</option></term>
+ <listitem><para>The Cache subsection controls the &apt-cache; tool; please see its
+ documentation for more information about the options here.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>CDROM</option></term>
+ <listitem><para>The CDROM subsection controls the &apt-cdrom; tool; please see its
+ documentation for more information about the options here.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ <option>NeverAutoRemove</option>
+ </term>
+ <listitem>
+ <para>
+ Never autoremove packages that match the regular expression(s).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ <option>Protect-Kernels</option>
+ </term>
+ <listitem>
+ <para>
+ This option tells apt autoremove that kernels are protected and
+ defaults to true. In case kernels are not protected they are
+ treated as any other package.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ <option>VersionedKernelPackages</option>
+ </term>
+ <listitem>
+ <para>
+ Define the regular expression(s) for versioned kernel packages.
+ Based on these expressions a rule set is injected into apt
+ similar to APT::NeverAutoRemove regular expressions.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ <option>NeverAutoRemove::KernelCount</option>
+ </term>
+ <listitem>
+ <para>
+ Keep a custom amount of kernels when autoremoving and defaults
+ to 2, meaning two kernels are kept. Apt will always keep the
+ running kernel and the latest one. If the latest kernel is the
+ same as the running kernel, the second latest kernel is kept.
+ Because of this, any value lower than 2 will be ignored. If you
+ want only the latest kernel, you should set
+ APT::Protect-Kernels to false.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <refsect1><title>The Acquire Group</title>
+ <para>The <literal>Acquire</literal> group of options controls the
+ download of packages as well as the various "acquire methods" responsible
+ for the download itself (see also &sources-list;).</para>
+
+ <variablelist>
+ <varlistentry><term><option>Check-Date</option></term>
+ <listitem><para>
+ Security related option defaulting to true, enabling time-related
+ checks. Disabling it means that the machine's time cannot be
+ trusted, and APT will hence disable all time-related checks,
+ such as <option>Check-Valid-Until</option> and verifying that
+ the Date field of a release file is not in the future.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Max-FutureTime</option></term>
+ <listitem><para>Maximum time (in seconds) before its creation (as indicated
+ by the <literal>Date</literal> header) that the <filename>Release</filename>
+ file should be considered valid.
+
+ The default value is <literal>10</literal>.
+ Archive specific settings can be made by appending the label of the archive
+ to the option name. Preferably, the same can be achieved for specific
+ &sources-list; entries by using the <option>Date-Max-Future</option> option there.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry><term><option>Check-Valid-Until</option></term>
+ <listitem><para>
+ Security related option defaulting to true, as giving a Release file's
+ validation an expiration date prevents replay attacks over a long
+ timescale, and can also for example help users to identify mirrors
+ that are no longer updated - but the feature depends on the
+ correctness of the clock on the user system. Archive maintainers are
+ encouraged to create Release files with the
+ <literal>Valid-Until</literal> header, but if they don't or a
+ stricter value is desired the <literal>Max-ValidTime</literal>
+ option below can be used.
+ The <option>Check-Valid-Until</option> option of &sources-list; entries should be
+ preferred to disable the check selectively instead of using this global override.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Max-ValidTime</option></term>
+ <listitem><para>Maximum time (in seconds) after its creation (as indicated
+ by the <literal>Date</literal> header) that the <filename>Release</filename>
+ file should be considered valid.
+ If the Release file itself includes a <literal>Valid-Until</literal> header
+ the earlier date of the two is used as the expiration date.
+ The default value is <literal>0</literal> which stands for "valid forever".
+ Archive specific settings can be made by appending the label of the archive
+ to the option name. Preferably, the same can be achieved for specific
+ &sources-list; entries by using the <option>Valid-Until-Max</option> option there.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Min-ValidTime</option></term>
+ <listitem><para>Minimum time (in seconds) after its creation (as indicated
+ by the <literal>Date</literal> header) that the <filename>Release</filename>
+ file should be considered valid.
+ Use this if you need to use a seldom updated (local) mirror of a more
+ frequently updated archive with a <literal>Valid-Until</literal> header
+ instead of completely disabling the expiration date checking.
+ Archive specific settings can and should be used by appending the label of
+ the archive to the option name. Preferably, the same can be achieved for specific
+ &sources-list; entries by using the <option>Valid-Until-Min</option> option there.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>AllowTLS</option></term>
+ <listitem><para>
+ Allow use of the internal TLS support in the http method. If set to false,
+ this completely disables support for TLS in apt's own methods (excluding
+ the curl-based https method). No TLS-related functions will be called
+ anymore.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>PDiffs</option></term>
+ <listitem><para>Try to download deltas called <literal>PDiffs</literal> for
+ indexes (like <filename>Packages</filename> files) instead of
+ downloading whole ones. True by default. Preferably, this can be set
+ for specific &sources-list; entries or index files by using the
+ <option>PDiffs</option> option there.</para>
+ <para>Two sub-options to limit the use of PDiffs are also available:
+ <literal>FileLimit</literal> can be used to specify a maximum number of
+ PDiff files should be downloaded to update a file. <literal>SizeLimit</literal>
+ on the other hand is the maximum percentage of the size of all patches
+ compared to the size of the targeted file. If one of these limits is
+ exceeded the complete file is downloaded instead of the patches.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>By-Hash</option></term>
+ <listitem><para>Try to download indexes via an URI constructed from a
+ hashsum of the expected file rather than downloaded via a well-known
+ stable filename. True by default, but automatically disabled if the
+ source indicates no support for it. Usage can be forced with the special
+ value "force". Preferably, this can be set for specific &sources-list; entries
+ or index files by using the <option>By-Hash</option> option there.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Queue-Mode</option></term>
+ <listitem><para>Queuing mode; <literal>Queue-Mode</literal> can be one of <literal>host</literal> or
+ <literal>access</literal> which determines how APT parallelizes outgoing
+ connections. <literal>host</literal> means that one connection per target host
+ will be opened, <literal>access</literal> means that one connection per URI type
+ will be opened.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Retries</option></term>
+ <listitem><para>Number of retries to perform. If this is non-zero APT will retry failed
+ files the given number of times.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Source-Symlinks</option></term>
+ <listitem><para>Use symlinks for source archives. If set to true then source archives will
+ be symlinked when possible instead of copying. True is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>http</option> <option>https</option></term>
+ <listitem><para>The options in these scopes configure APT's acquire transports for the protocols
+ HTTP and HTTPS and are documented in the &apt-transport-http; and &apt-transport-https;
+ manpages respectively.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>ftp</option></term>
+ <listitem><para>
+ <literal>ftp::Proxy</literal> sets the default proxy to use for FTP URIs.
+ It is in the standard form of <literal>ftp://[[user][:pass]@]host[:port]/</literal>.
+ Per host proxies can also be specified by using the form
+ <literal>ftp::Proxy::&lt;host&gt;</literal> with the special keyword <literal>DIRECT</literal>
+ meaning to use no proxies. If no one of the above settings is specified,
+ <envar>ftp_proxy</envar> environment variable
+ will be used. To use an FTP
+ proxy you will have to set the <literal>ftp::ProxyLogin</literal> script in the
+ configuration file. This entry specifies the commands to send to tell
+ the proxy server what to connect to. Please see
+ &configureindex; for an example of
+ how to do this. The substitution variables representing the corresponding
+ URI component are <literal>$(PROXY_USER)</literal>,
+ <literal>$(PROXY_PASS)</literal>, <literal>$(SITE_USER)</literal>,
+ <literal>$(SITE_PASS)</literal>, <literal>$(SITE)</literal> and
+ <literal>$(SITE_PORT)</literal>.</para>
+
+ <para>The option <literal>timeout</literal> sets the timeout timer used by the method;
+ this value applies to the connection as well as the data timeout.</para>
+
+ <para>Several settings are provided to control passive mode. Generally it is
+ safe to leave passive mode on; it works in nearly every environment.
+ However, some situations require that passive mode be disabled and port
+ mode FTP used instead. This can be done globally or for connections that
+ go through a proxy or for a specific host (see the sample config file
+ for examples).</para>
+
+ <para>It is possible to proxy FTP over HTTP by setting the <envar>ftp_proxy</envar>
+ environment variable to an HTTP URL - see the discussion of the http method
+ above for syntax. You cannot set this in the configuration file and it is
+ not recommended to use FTP over HTTP due to its low efficiency.</para>
+
+ <para>The setting <literal>ForceExtended</literal> controls the use of RFC2428
+ <literal>EPSV</literal> and <literal>EPRT</literal> commands. The default is false, which means
+ these commands are only used if the control connection is IPv6. Setting this
+ to true forces their use even on IPv4 connections. Note that most FTP servers
+ do not support RFC2428.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>cdrom</option></term>
+ <listitem><para>
+ For URIs using the <literal>cdrom</literal> method, the only configurable
+ option is the mount point, <literal>cdrom::Mount</literal>, which must be
+ the mount point for the CD-ROM (or DVD, or whatever) drive as specified in
+ <filename>/etc/fstab</filename>. It is possible to provide alternate mount
+ and unmount commands if your mount point cannot be listed in the fstab.
+ The syntax is to put <literallayout>/cdrom/::Mount "foo";</literallayout> within
+ the <literal>cdrom</literal> block. It is important to have the trailing slash.
+ Unmount commands can be specified using UMount.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>gpgv</option></term>
+ <listitem><para>
+ For GPGV URIs the only configurable option is <literal>gpgv::Options</literal>,
+ which passes additional parameters to gpgv.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>CompressionTypes</option></term>
+ <listitem><para>List of compression types which are understood by the acquire methods.
+ Files like <filename>Packages</filename> can be available in various compression formats.
+ By default the acquire methods can decompress and recompress many common formats like <command>xz</command> and
+ <command>gzip</command>; with this scope the supported formats can be queried, modified
+ as well as support for more formats added (see also <option>APT::Compressor</option>). The syntax for this is:
+ <synopsis>Acquire::CompressionTypes::<replaceable>FileExtension</replaceable> "<replaceable>Methodname</replaceable>";</synopsis>
+ </para><para>Also, the <literal>Order</literal> subgroup can be used to define in which order
+ the acquire system will try to download the compressed files. The acquire system will try the first
+ and proceed with the next compression type in this list on error, so to prefer one over the other type
+ simply add the preferred type first - types not already added will be implicitly appended
+ to the end of the list, so e.g. <synopsis>Acquire::CompressionTypes::Order:: "gz";</synopsis> can
+ be used to prefer <command>gzip</command> compressed files over all other compression formats.
+ If <command>xz</command> should be preferred over <command>gzip</command> and <command>bzip2</command> the
+ configure setting should look like this: <synopsis>Acquire::CompressionTypes::Order { "xz"; "gz"; };</synopsis>
+ It is not needed to add <literal>bz2</literal> to the list explicitly as it will be added automatically.</para>
+ <para>Note that the
+ <literal>Dir::Bin::<replaceable>Methodname</replaceable></literal>
+ will be checked at run time. If this option has been set and support for
+ this format isn't directly built into apt, the method will only be used if
+ this file exists; e.g. for the <literal>bzip2</literal> method (the
+ inbuilt) setting is: <literallayout>Dir::Bin::bzip2 "/bin/bzip2";</literallayout>
+ Note also that list entries specified on the command line will be added at the end of the list
+ specified in the configuration files, but before the default entries. To prefer a type in this case
+ over the ones specified in the configuration files you can set the option direct - not in list style.
+ This will not override the defined list; it will only prefix the list with this type.</para>
+ <para>The special type <literal>uncompressed</literal> can be used to give uncompressed files a
+ preference, but note that most archives don't provide uncompressed files so this is mostly only
+ usable for local mirrors.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>GzipIndexes</option></term>
+ <listitem><para>
+ When downloading <literal>gzip</literal> compressed indexes (Packages, Sources, or
+ Translations), keep them gzip compressed locally instead of unpacking
+ them. This saves quite a lot of disk space at the expense of more CPU
+ requirements when building the local package caches. False by default.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Languages</option></term>
+ <listitem><para>The Languages subsection controls which <filename>Translation</filename> files are downloaded
+ and in which order APT tries to display the description-translations. APT will try to display the first
+ available description in the language which is listed first. Languages can be defined with their
+ short or long language codes. Note that not all archives provide <filename>Translation</filename>
+ files for every language - the long language codes are especially rare.</para>
+ <para>The default list includes "environment" and "en". "<literal>environment</literal>" has a special meaning here:
+ it will be replaced at runtime with the language codes extracted from the <literal>LC_MESSAGES</literal> environment variable.
+ It will also ensure that these codes are not included twice in the list. If <literal>LC_MESSAGES</literal>
+ is set to "C" only the <filename>Translation-en</filename> file (if available) will be used.
+ To force APT to use no Translation file use the setting <literal>Acquire::Languages=none</literal>. "<literal>none</literal>"
+ is another special meaning code which will stop the search for a suitable <filename>Translation</filename> file.
+ This tells APT to download these translations too, without actually
+ using them unless the environment specifies the languages. So the
+ following example configuration will result in the order "en, de" in an
+ English locale or "de, en" in a German one. Note that "fr" is
+ downloaded, but not used unless APT is used in a French locale (where
+ the order would be "fr, de, en").
+ <programlisting>Acquire::Languages { "environment"; "de"; "en"; "none"; "fr"; };</programlisting></para>
+ <para>Note: To prevent problems resulting from APT being executed in different environments
+ (e.g. by different users or by other programs) all Translation files which are found in
+ <filename>/var/lib/apt/lists/</filename> will be added to the end of the list
+ (after an implicit "<literal>none</literal>").</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>ForceIPv4</option></term>
+ <listitem><para>
+ When downloading, force to use only the IPv4 protocol.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>ForceIPv6</option></term>
+ <listitem><para>
+ When downloading, force to use only the IPv6 protocol.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>MaxReleaseFileSize</option></term>
+ <listitem><para>
+ The maximum file size of Release/Release.gpg/InRelease files.
+ The default is 10MB.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>EnableSrvRecords</option></term>
+ <listitem><para>
+ This option controls if apt will use the DNS SRV server record
+ as specified in RFC 2782 to select an alternative server to
+ connect to.
+ The default is "true".
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>AllowInsecureRepositories</option></term>
+ <listitem><para>
+ Allow update operations to load data files from
+ repositories without sufficient security information.
+ The default value is "<literal>false</literal>".
+ Concept, implications as well as alternatives are detailed in &apt-secure;.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>AllowWeakRepositories</option></term>
+ <listitem><para>
+ Allow update operations to load data files from
+ repositories which provide security information, but these
+ are deemed no longer cryptographically strong enough.
+ The default value is "<literal>false</literal>".
+ Concept, implications as well as alternatives are detailed in &apt-secure;.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>AllowDowngradeToInsecureRepositories</option></term>
+ <listitem><para>
+ Allow that a repository that was previously gpg signed to become
+ unsigned during an update operation. When there is no valid signature
+ for a previously trusted repository apt will refuse the update. This
+ option can be used to override this protection. You almost certainly
+ never want to enable this. The default is <literal>false</literal>.
+ Concept, implications as well as alternatives are detailed in &apt-secure;.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Changelogs::URI</option> scope</term>
+ <listitem><para>
+ Acquiring changelogs can only be done if an URI is known from where to get them.
+ Preferable the Release file indicates this in a 'Changelogs' field. If this isn't
+ available the Label/Origin field of the Release file is used to check if a
+ <literal>Acquire::Changelogs::URI::Label::<replaceable>LABEL</replaceable></literal> or
+ <literal>Acquire::Changelogs::URI::Origin::<replaceable>ORIGIN</replaceable></literal> option
+ exists and if so this value is taken. The value in the Release file can be overridden
+ with <literal>Acquire::Changelogs::URI::Override::Label::<replaceable>LABEL</replaceable></literal>
+ or <literal>Acquire::Changelogs::URI::Override::Origin::<replaceable>ORIGIN</replaceable></literal>.
+
+ The value should be a normal URI to a text file, except that package specific data is
+ replaced with the placeholder <literal>@CHANGEPATH@</literal>. The
+ value for it is: 1. if the package is from a component (e.g. <literal>main</literal>)
+ this is the first part otherwise it is omitted, 2. the first letter of source package name,
+ except if the source package name starts with '<literal>lib</literal>' in which case it will
+ be the first four letters. 3. The complete source package name. 4. the complete name again and
+ 5. the source version.
+ The first (if present), second, third and fourth part are separated by a slash ('<literal>/</literal>')
+ and between the fourth and fifth part is an underscore ('<literal>_</literal>').
+
+ The special value '<literal>no</literal>' is available for this option indicating that
+ this source can't be used to acquire changelog files from. Another source will be tried
+ if available in this case.
+ </para></listitem>
+</varlistentry>
+
+ <varlistentry><term><option>Snapshots::URI</option> scope</term>
+ <listitem><para>
+ Like changelogs, snapshots can only be acquired if an URI is known from where to get them.
+ Preferable the Release file indicates this in a 'Snapshots' field. If this isn't
+ available the Label/Origin field of the Release file is used to check if a
+ <literal>Acquire::Snapshots::URI::Label::<replaceable>LABEL</replaceable></literal> or
+ <literal>Acquire::Snapshots::URI::Origin::<replaceable>ORIGIN</replaceable></literal> option
+ exists and if so this value is taken. The value in the Release file can be overridden
+ with <literal>Acquire::Snapshots::URI::Override::Label::<replaceable>LABEL</replaceable></literal>
+ or <literal>Acquire::Snapshots::URI::Override::Origin::<replaceable>ORIGIN</replaceable></literal>.
+
+ The value should be a normal URI to a directory, except that the snapshot ID replaced with the
+ placeholder <literal>@SNAPSHOTID</literal>.
+
+ The special value '<literal>no</literal>' is available for this option indicating that
+ this source cannot be used to acquire snapshots from. Another source will be tried
+ if available in this case.
+ </para></listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <refsect1><title>Binary specific configuration</title>
+ <para>Especially with the introduction of the <command>apt</command> binary
+ it can be useful to set certain options only for a specific binary as
+ even options which look like they would effect only a certain binary like
+ <option>APT::Get::Show-Versions</option> effect
+ <command>apt-get</command> as well as <command>apt</command>.
+ </para>
+ <para>Setting an option for a specific binary only can be achieved by
+ setting the option inside the
+ <option>Binary::<replaceable>specific-binary</replaceable></option>
+ scope. Setting the option <option>APT::Get::Show-Versions</option> for
+ the <command>apt</command> only can e.g. by done by setting
+ <option>Binary::apt::APT::Get::Show-Versions</option> instead.</para>
+ <para>Note that as seen in the DESCRIPTION section further above you can't
+ set binary-specific options on the commandline itself nor in
+ configuration files loaded via the commandline.</para>
+ </refsect1>
+
+ <refsect1><title>Directories</title>
+
+ <para>The <literal>Dir::State</literal> section has directories that pertain to local
+ state information. <literal>lists</literal> is the directory to place downloaded
+ package lists in and <literal>status</literal> is the name of the &dpkg; status file.
+ <literal>preferences</literal> is the name of the APT <filename>preferences</filename> file.
+ <literal>Dir::State</literal> contains the default directory to prefix on all
+ sub-items if they do not start with <filename>/</filename> or <filename>./</filename>.</para>
+
+ <para><literal>Dir::Cache</literal> contains locations pertaining to local cache
+ information, such as the two package caches <literal>srcpkgcache</literal> and
+ <literal>pkgcache</literal> as well as the location to place downloaded archives,
+ <literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
+ by setting <literal>pkgcache</literal> or <literal>srcpkgcache</literal> to
+ <literal>""</literal>. This will slow down startup but save disk space. It
+ is probably preferable to turn off the pkgcache rather than the srcpkgcache.
+ Like <literal>Dir::State</literal> the default directory is contained in
+ <literal>Dir::Cache</literal></para>
+
+ <para><literal>Dir::Etc</literal> contains the location of configuration files,
+ <literal>sourcelist</literal> gives the location of the sourcelist and
+ <literal>main</literal> is the default configuration file (setting has no effect,
+ unless it is done from the config file specified by
+ <envar>APT_CONFIG</envar>).</para>
+
+ <para>The <literal>Dir::Parts</literal> setting reads in all the config fragments in
+ lexical order from the directory specified. After this is done then the
+ main config file is loaded.</para>
+
+ <para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal>
+ specifies the location of the method handlers and <literal>gzip</literal>,
+ <literal>bzip2</literal>, <literal>lzma</literal>,
+ <literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal>
+ <literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
+ of the respective programs.</para>
+
+ <para>
+ The configuration item <literal>RootDir</literal> has a special
+ meaning. If set, all paths will be
+ relative to <literal>RootDir</literal>, <emphasis>even paths that
+ are specified absolutely</emphasis>. So, for instance, if
+ <literal>RootDir</literal> is set to
+ <filename>/tmp/staging</filename> and
+ <literal>Dir::State::status</literal> is set to
+ <filename>/var/lib/dpkg/status</filename>, then the status file
+ will be looked up in
+ <filename>/tmp/staging/var/lib/dpkg/status</filename>.
+ If you want to prefix only relative paths, set <literal>Dir</literal> instead.
+ </para>
+
+ <para>
+ The <literal>Ignore-Files-Silently</literal> list can be used to specify
+ which files APT should silently ignore while parsing the files in the
+ fragment directories. Per default a file which ends with <literal>.disabled</literal>,
+ <literal>~</literal>, <literal>.bak</literal> or <literal>.dpkg-[a-z]+</literal>
+ is silently ignored. As seen in the last default value these patterns can use regular
+ expression syntax.
+ </para>
+ </refsect1>
+
+ <refsect1><title>APT in DSelect</title>
+ <para>
+ When APT is used as a &dselect; method several configuration directives
+ control the default behavior. These are in the <literal>DSelect</literal> section.</para>
+
+ <variablelist>
+ <varlistentry><term><option>Clean</option></term>
+ <listitem><para>Cache Clean mode; this value may be one of
+ <literal>always</literal>, <literal>prompt</literal>,
+ <literal>auto</literal>, <literal>pre-auto</literal> and
+ <literal>never</literal>.
+ <literal>always</literal> and <literal>prompt</literal> will remove
+ all packages from the cache after upgrading, <literal>prompt</literal>
+ (the default) does so conditionally.
+ <literal>auto</literal> removes only those packages which are no longer
+ downloadable (replaced with a new version for instance).
+ <literal>pre-auto</literal> performs this action before downloading
+ new packages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>options</option></term>
+ <listitem><para>The contents of this variable are passed to &apt-get; as command line
+ options when it is run for the install phase.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Updateoptions</option></term>
+ <listitem><para>The contents of this variable are passed to &apt-get; as command line
+ options when it is run for the update phase.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>PromptAfterUpdate</option></term>
+ <listitem><para>If true the [U]pdate operation in &dselect; will always prompt to continue.
+ The default is to prompt only on error.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1><title>How APT calls &dpkg;</title>
+ <para>Several configuration directives control how APT invokes &dpkg;. These are
+ in the <literal>DPkg</literal> section.</para>
+
+ <variablelist>
+ <varlistentry><term><option>options</option></term>
+ <listitem><para>This is a list of options to pass to &dpkg;. The options must be specified
+ using the list notation and each list item is passed as a single argument
+ to &dpkg;.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Path</option></term>
+ <listitem><para>This is a string that defines the <envar>PATH</envar>
+ environment variable used when running dpkg. It may be set to any
+ valid value of that environment variable; or the empty string, in
+ which case the variable is not changed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Pre-Invoke</option></term><term><option>Post-Invoke</option></term>
+ <listitem><para>This is a list of shell commands to run before/after invoking &dpkg;.
+ Like <literal>options</literal> this must be specified in list notation. The
+ commands are invoked in order using <filename>/bin/sh</filename>; should any
+ fail APT will abort.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Pre-Install-Pkgs</option></term>
+ <listitem><para>This is a list of shell commands to run before invoking &dpkg;. Like
+ <literal>options</literal> this must be specified in list notation. The commands
+ are invoked in order using <filename>/bin/sh</filename>; should any fail APT
+ will abort. APT will pass the filenames of all .deb files it is going to
+ install to the commands, one per line on the requested file descriptor, defaulting
+ to standard input.</para>
+
+ <para>Version 2 of this protocol sends more information through the requested
+ file descriptor: a line with the text <literal>VERSION 2</literal>,
+ the APT configuration space, and a list of package actions with filename
+ and version information.</para>
+
+ <para>Each configuration directive line has the form
+ <literal>key=value</literal>. Special characters (equal signs, newlines,
+ nonprintable characters, quotation marks, and percent signs in
+ <literal>key</literal> and newlines, nonprintable characters, and percent
+ signs in <literal>value</literal>) are %-encoded. Lists are represented
+ by multiple <literal>key::=value</literal> lines with the same key. The
+ configuration section ends with a blank line.</para>
+
+ <para>Package action lines consist of five fields in Version 2: package
+ name (without architecture qualification even if foreign), old version,
+ direction of version change (&lt; for upgrades, &gt; for downgrades, = for
+ no change), new version, action. The version fields are "-" for no version
+ at all (for example when installing a package for the first time; no
+ version is treated as earlier than any real version, so that is an
+ upgrade, indicated as <literal>- &lt; 1.23.4</literal>). The action field
+ is "**CONFIGURE**" if the package is being configured, "**REMOVE**" if it
+ is being removed, or the filename of a .deb file if it is being
+ unpacked.</para>
+
+ <para>In Version 3 after each version field follows the architecture
+ of this version, which is "-" if there is no version, and a field showing
+ the MultiArch type "same", "foreign", "allowed" or "none". Note that "none"
+ is an incorrect typename which is just kept to remain compatible, it
+ should be read as "no" and users are encouraged to support both.</para>
+
+ <para>The version of the protocol to be used for the command
+ <literal><replaceable>cmd</replaceable></literal> can be chosen by setting
+ <literal>DPkg::Tools::options::<replaceable>cmd</replaceable>::Version</literal>
+ accordingly, the default being version 1. If APT isn't supporting the requested
+ version it will send the information in the highest version it has support for instead.
+ </para>
+
+ <para>The file descriptor to be used to send the information can be requested with
+ <literal>DPkg::Tools::options::<replaceable>cmd</replaceable>::InfoFD</literal>
+ which defaults to <literal>0</literal> for standard input and is available since
+ version 0.9.11. Support for the option can be detected by looking for the environment
+ variable <envar>APT_HOOK_INFO_FD</envar> which contains the number of the used
+ file descriptor as a confirmation.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Run-Directory</option></term>
+ <listitem><para>APT chdirs to this directory before invoking &dpkg;, the default is
+ <filename>/</filename>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>Build-options</option></term>
+ <listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages;
+ the default is to disable signing and produce all binaries.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><option>DPkg::ConfigurePending</option></term>
+ <listitem><para>If this option is set APT will call <command>dpkg --configure --pending</command>
+ to let &dpkg; handle all required configurations and triggers. This option is activated by default,
+ but deactivating it could be useful if you want to run APT multiple times in a row - e.g. in an installer.
+ In this scenario you could deactivate this option in all but the last run.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Periodic and Archives options</title>
+ <para><literal>APT::Periodic</literal> and <literal>APT::Archives</literal>
+ groups of options configure behavior of apt periodic updates, which is
+ done by the <literal>/usr/lib/apt/apt.systemd.daily</literal> script. See the top of
+ this script for the brief documentation of these options.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Debug options</title>
+ <para>
+ Enabling options in the <literal>Debug::</literal> section will
+ cause debugging information to be sent to the standard error
+ stream of the program utilizing the <literal>apt</literal>
+ libraries, or enable special program modes that are primarily
+ useful for debugging the behavior of <literal>apt</literal>.
+ Most of these options are not interesting to a normal user, but a
+ few may be:
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>Debug::pkgProblemResolver</literal> enables output
+ about the decisions made by
+ <literal>dist-upgrade, upgrade, install, remove, purge</literal>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <literal>Debug::NoLocking</literal> disables all file
+ locking. This can be used to run some operations (for
+ instance, <literal>apt-get -s install</literal>) as a
+ non-root user.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <literal>Debug::pkgDPkgPM</literal> prints out the actual
+ command line each time that <literal>apt</literal> invokes
+ &dpkg;.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ <literal>Debug::IdentCdrom</literal> disables the inclusion
+ of statfs data in CD-ROM IDs. <!-- TODO: provide a
+ motivating example, except I haven't a clue why you'd want
+ to do this. -->
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ A full list of debugging options to apt follows.
+ </para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>Debug::Acquire::cdrom</option></term>
+
+ <listitem>
+ <para>
+ Print information related to accessing
+ <literal>cdrom://</literal> sources.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::Acquire::ftp</option></term>
+
+ <listitem>
+ <para>
+ Print information related to downloading packages using
+ FTP.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::Acquire::http</option></term>
+
+ <listitem>
+ <para>
+ Print information related to downloading packages using
+ HTTP.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::Acquire::https</option></term>
+
+ <listitem>
+ <para>
+ Print information related to downloading packages using
+ HTTPS.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::Acquire::gpgv</option></term>
+
+ <listitem>
+ <para>
+ Print information related to verifying cryptographic
+ signatures using <literal>gpg</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::aptcdrom</option></term>
+
+ <listitem>
+ <para>
+ Output information about the process of accessing
+ collections of packages stored on CD-ROMs.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::BuildDeps</option></term>
+ <listitem>
+ <para>
+ Describes the process of resolving build-dependencies in
+ &apt-get;.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::Hashes</option></term>
+ <listitem>
+ <para>
+ Output each cryptographic hash that is generated by the
+ <literal>apt</literal> libraries.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::IdentCDROM</option></term>
+ <listitem>
+ <para>
+ Do not include information from <literal>statfs</literal>,
+ namely the number of used and free blocks on the CD-ROM
+ filesystem, when generating an ID for a CD-ROM.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::NoLocking</option></term>
+ <listitem>
+ <para>
+ Disable all file locking. For instance, this will allow
+ two instances of <quote><literal>apt-get
+ update</literal></quote> to run at the same time.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgAcquire</option></term>
+
+ <listitem>
+ <para>
+ Log when items are added to or removed from the global
+ download queue.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgAcquire::Auth</option></term>
+ <listitem>
+ <para>
+ Output status messages and errors related to verifying
+ checksums and cryptographic signatures of downloaded files.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgAcquire::Diffs</option></term>
+ <listitem>
+ <para>
+ Output information about downloading and applying package
+ index list diffs, and errors relating to package index list
+ diffs.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgAcquire::RRed</option></term>
+
+ <listitem>
+ <para>
+ Output information related to patching apt package lists
+ when downloading index diffs instead of full indices.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgAcquire::Worker</option></term>
+
+ <listitem>
+ <para>
+ Log all interactions with the sub-processes that actually
+ perform downloads.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgAutoRemove</option></term>
+
+ <listitem>
+ <para>
+ Log events related to the automatically-installed status of
+ packages and to the removal of unused packages.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgDepCache::AutoInstall</option></term>
+ <listitem>
+ <para>
+ Generate debug messages describing which packages are being
+ automatically installed to resolve dependencies. This
+ corresponds to the initial auto-install pass performed in,
+ e.g., <literal>apt-get install</literal>, and not to the
+ full <literal>apt</literal> dependency resolver; see
+ <literal>Debug::pkgProblemResolver</literal> for that.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgDepCache::Marker</option></term>
+ <listitem>
+ <para>
+ Generate debug messages describing which packages are marked
+ as keep/install/remove while the ProblemResolver does his work.
+ Each addition or deletion may trigger additional actions;
+ they are shown indented two additional spaces under the original entry.
+ The format for each line is <literal>MarkKeep</literal>,
+ <literal>MarkDelete</literal> or <literal>MarkInstall</literal> followed by
+ <literal>package-name &lt;a.b.c -&gt; d.e.f | x.y.z&gt; (section)</literal>
+ where <literal>a.b.c</literal> is the current version of the package,
+ <literal>d.e.f</literal> is the version considered for installation and
+ <literal>x.y.z</literal> is a newer version, but not considered for installation
+ (because of a low pin score). The later two can be omitted if there is none or if
+ it is the same as the installed version.
+ <literal>section</literal> is the name of the section the package appears in.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgDPkgPM</option></term>
+ <listitem>
+ <para>
+ When invoking &dpkg;, output the precise command line with
+ which it is being invoked, with arguments separated by a
+ single space character.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgDPkgProgressReporting</option></term>
+ <listitem>
+ <para>
+ Output all the data received from &dpkg; on the status file
+ descriptor and any errors encountered while parsing it.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgOrderList</option></term>
+
+ <listitem>
+ <para>
+ Generate a trace of the algorithm that decides the order in
+ which <literal>apt</literal> should pass packages to
+ &dpkg;.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgPackageManager</option></term>
+
+ <listitem>
+ <para>
+ Output status messages tracing the steps performed when
+ invoking &dpkg;.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgPolicy</option></term>
+
+ <listitem>
+ <para>
+ Output the priority of each package list on startup.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgProblemResolver</option></term>
+
+ <listitem>
+ <para>
+ Trace the execution of the dependency resolver (this
+ applies only to what happens when a complex dependency
+ problem is encountered).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::pkgProblemResolver::ShowScores</option></term>
+ <listitem>
+ <para>
+ Display a list of all installed packages with their calculated score
+ used by the pkgProblemResolver. The description of the package
+ is the same as described in <literal>Debug::pkgDepCache::Marker</literal>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::sourceList</option></term>
+
+ <listitem>
+ <para>
+ Print information about the vendors read from
+ <filename>/etc/apt/vendors.list</filename>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>Debug::RunScripts</option></term>
+ <listitem>
+ <para>
+ Display the external commands that are called by apt hooks.
+ This includes e.g. the config options
+ <literal>DPkg::{Pre,Post}-Invoke</literal> or
+ <literal>APT::Update::{Pre,Post}-Invoke</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+<!-- 2009/07/11 Currently used nowhere. The corresponding code
+is commented.
+ <varlistentry>
+ <term><literal>Debug::Vendor</literal></term>
+
+ <listitem>
+ <para>
+ Print information about each vendor.
+ </para>
+ </listitem>
+ </varlistentry>
+-->
+
+ </variablelist>
+ </refsect1>
+
+ <refsect1><title>Examples</title>
+ <para>&configureindex; is a
+ configuration file showing example values for all possible
+ options.</para>
+ </refsect1>
+
+ <refsect1><title>Files</title>
+ <variablelist>
+ &file-aptconf;
+ </variablelist>
+ </refsect1>
+
+ <refsect1><title>See Also</title>
+ <para>&apt-cache;, &apt-config;<!-- ? reading apt.conf -->, &apt-preferences;.</para>
+ </refsect1>
+
+ &manbugs;
+
+</refentry>
+