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<!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>2018-09-27T00:00:00Z</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.
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>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 buglink 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>
</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 APTs 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>
</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 end 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>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>