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<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"" [
<!ENTITY % aptent SYSTEM "apt.ent">
<contrib>Initial documentation of Debug::*.</contrib>
<!-- The last update date -->
<date>16 January 2010</date>
<refmiscinfo class="manual">APT</refmiscinfo>
<!-- Man page title -->
<refpurpose>Configuration file for APT</refpurpose>
<para><filename>apt.conf</filename> is the main configuration file for
the APT suite of tools, but by far not the only place changes to options
can be made. All tools therefore share the configuration files and also
use a common command line parser to provide a uniform environment.</para>
<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 no or "<literal>conf</literal>"
as filename extension and which only contain alphanumeric,
hyphen (-), underscore (_) and period (.) characters -
otherwise they will be silently ignored.</para></listitem>
<listitem><para>the main configuration file specified by
<listitem><para>the command line options are applied to override the
configuration directives or to load even more configuration files.</para></listitem>
<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 trailing
semicolon and the quotes are required. The value must be on one line, and
there is no kind of string concatenation. It must not include inside quotes.
The behavior of the backslash "\" and escaped characters inside a value is
undefined and it should not be used. An option name may include
alphanumerical characters and the "/-:._+" characters. A new scope can
be opened with curly braces, like:</para>
Get {
Assume-Yes "true";
Fix-Broken "true";
<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, each separated by a semicolon.</para>
DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
<para>In general the sample configuration file in
<filename>&docdir;examples/apt.conf</filename> &configureindex;
is a good guide for how it should look.</para>
<para>The names of the configuration items are not case-sensitive. 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 it can be see 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 as every other option by reassigning a new value to the option.</para>
<para>Two specials are allowed, <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, then 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 #clear command is the only way to delete a list or a complete scope.
Reopening a scope or the ::-style described below will <emphasis>not</emphasis>
override previously written entries. Only options can be overridden by addressing a new
value to it - lists and scopes can't be overridden, only cleared.</para>
<para>All of the APT tools take a -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. Lists can be appended too by adding
a trailing :: to the list name. (As you might suspect: The scope syntax can't be used
on the command line.)</para>
<para>Note that you can use :: only for appending one item per line to a list and
that you should not use it in combination with the scope syntax.
(The scope syntax implicit insert ::) Using both syntaxes together will trigger a bug
which some users unfortunately relay on: An option with the unusual name "<literal>::</literal>"
which acts like every other option with a name. These introduces many problems
including that a user who writes multiple lines in this <emphasis>wrong</emphasis> syntax in
the hope to append to a list will gain the opposite as only the last assignment for this option
"<literal>::</literal>" will be used. Upcoming APT versions will raise errors and
will stop working if they encounter this misuse, so please correct such statements now
as long as APT doesn't complain explicit about them.</para>
<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>
<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>
<listitem><para>Default release to install packages from if more than one
version available. Contains release name, codename or release version. Examples: 'stable', 'testing',
'unstable', '&stable-codename;', '&testing-codename;', '4.0', '5.0*'. See also &apt-preferences;.</para></listitem>
<listitem><para>Ignore Held packages; This global option causes the problem resolver to
ignore held packages in its decision making.</para></listitem>
<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>
<listitem><para>Defaults to on which will cause APT to install essential and important packages
as fast as possible in the install/upgrade operation. This is done to limit the effect of a failing
&dpkg; call: If this option is disabled APT does treat an important package in the same way as
an extra package: Between the unpacking of the important package A and his configuration can then
be many other unpack or configuration calls, e.g. for package B which has no relation to A, but
causes the dpkg call to fail (e.g. because maintainer script of package B generates an error) which results
in a system state in which package A is unpacked but unconfigured - each package depending on A is now no
longer guaranteed to work as their dependency on A is not longer satisfied. The immediate configuration marker
is also applied to all dependencies which can generate a problem if the dependencies e.g. form a circle
as a dependency with the immediate flag is comparable with a Pre-Dependency. So in theory it is possible
that APT encounters a situation in which it is unable to perform immediate configuration, errors out and
refers to this option so the user can deactivate the immediate configuration temporarily to be able to perform
an install/upgrade again. Note the use of the word "theory" here as this problem was only encountered by now
in real world a few times 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 mentioned scenario above is not the only problem immediate configuration can help to prevent in the first place.
Before a big operation like <literal>dist-upgrade</literal> is run with this option disabled it should be tried to
explicitly <literal>install</literal> the package APT is unable to configure immediately, but please make sure to
report your problem also 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>
<listitem><para>Never Enable this option unless you -really- know what you are doing. It
permits APT to temporarily remove an essential package to break a
Conflicts/Conflicts or Conflicts/Pre-Depend loop between two essential
will work if the essential packages are not tar, gzip, libc, dpkg, bash or
anything that those packages depend on.</para></listitem>
<varlistentry><term>Cache-Start, Cache-Grow and Cache-Limit</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 to which size the Cache will grow
and is therefore the amount of memory APT will request at startup. The default value is
20971520 bytes (~20 MB). Note that these amount of space need to be available for APT
otherwise it will likely fail ungracefully, so for memory restricted devices these value should
be lowered while on systems with a lot of configured sources this might be increased.
<literal>Cache-Grow</literal> defines in byte 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. These 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 grow of the cache is disabled.
<listitem><para>Defines which package(s) are considered essential build dependencies.</para></listitem>
<listitem><para>The Get subsection controls the &apt-get; tool, please see its
documentation for more information about the options here.</para></listitem>
<listitem><para>The Cache subsection controls the &apt-cache; tool, please see its
documentation for more information about the options here.</para></listitem>
<listitem><para>The CDROM subsection controls the &apt-cdrom; tool, please see its
documentation for more information about the options here.</para></listitem>
<refsect1><title>The Acquire Group</title>
<para>The <literal>Acquire</literal> group of options controls the download of packages
and the URI handlers.
<listitem><para>Security related option defaulting to true as an
expiring validation for a Release file prevents longtime replay attacks
and can e.g. also help users to identify no longer updated mirrors -
but the feature depends on the correctness of the time 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 volitional the following <literal>Max-ValidTime</literal> option can be used.
<listitem><para>Seconds the Release file should be considered valid after
it was created. The default is "for ever" (0) if the Release file of the
archive doesn't include a <literal>Valid-Until</literal> header.
If it does then this date is the default. The date from the Release file or
the date specified by the creation time of the Release file
(<literal>Date</literal> header) plus the seconds specified with this
options are used to check if the validation of a file has expired by using
the earlier date of the two. Archive specific settings can be made by
appending the label of the archive to the option name.
<listitem><para>Try to download deltas called <literal>PDiffs</literal> for
Packages or Sources files instead of downloading whole ones. True
by default.</para>
<para>Two sub-options to limit the use of PDiffs are also available:
With <literal>FileLimit</literal> can be specified how many PDiff files
are downloaded at most to patch a file. <literal>SizeLimit</literal>
on the other hand is the maximum precentage 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.
<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>
<listitem><para>Number of retries to perform. If this is non-zero APT will retry failed
files the given number of times.</para></listitem>
<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>
<listitem><para>HTTP URIs; http::Proxy is the default http proxy to use. It is in the
standard form of <literal>http://[[user][:pass]@]host[:port]/</literal>. Per
host proxies can also be specified by using the form
<literal>http::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>http_proxy</envar> environment variable
will be used.</para>
<para>Three settings are provided for cache control with HTTP/1.1 compliant
proxy caches. <literal>No-Cache</literal> tells the proxy to not use its cached
response under any circumstances, <literal>Max-Age</literal> is sent only for
index files and tells the cache to refresh its object if it is older than
the given number of seconds. Debian updates its index files daily so the
default is 1 day. <literal>No-Store</literal> specifies that the cache should never
store this request, it is only set for archive files. This may be useful
to prevent polluting a proxy cache with very large .deb files. Note:
Squid 2.0.2 does not support any of these options.</para>
<para>The option <literal>timeout</literal> sets the timeout timer used by the method,
this applies to all things including connection timeout and data timeout.</para>
<para>One setting is provided to control the pipeline depth in cases where the
remote server is not RFC conforming or buggy (such as Squid 2.0.2).
<literal>Acquire::http::Pipeline-Depth</literal> can be a value from 0 to 5
indicating how many outstanding requests APT should send. A value of
zero MUST be specified if the remote host does not properly linger
on TCP connections - otherwise data corruption will occur. Hosts which
require this are in violation of RFC 2068.</para>
<para>The used bandwidth can be limited with <literal>Acquire::http::Dl-Limit</literal>
which accepts integer values in kilobyte. The default value is 0 which deactivates
the limit and tries uses as much as possible of the bandwidth (Note that this option implicit
deactivates the download from multiple servers at the same time.)</para>
<para><literal>Acquire::http::User-Agent</literal> can be used to set a different
User-Agent for the http download method as some proxies allow access for clients
only if the client uses a known identifier.</para>
<listitem><para>HTTPS URIs. Cache-control, Timeout, AllowRedirect, Dl-Limit and
proxy options are the same as for <literal>http</literal> method and will also
default to the options from the <literal>http</literal> method if they are not
explicitly set for https. <literal>Pipeline-Depth</literal> option is not
supported yet.</para>
<para><literal>CaInfo</literal> suboption specifies place of file that
holds info about trusted certificates.
<literal>&lt;host&gt;::CaInfo</literal> is corresponding per-host option.
<literal>Verify-Peer</literal> boolean suboption determines whether verify
server's host certificate against trusted certificates or not.
<literal>&lt;host&gt;::Verify-Peer</literal> is corresponding per-host option.
<literal>Verify-Host</literal> boolean suboption determines whether verify
server's hostname or not.
<literal>&lt;host&gt;::Verify-Host</literal> is corresponding per-host option.
<literal>SslCert</literal> determines what certificate to use for client
authentication. <literal>&lt;host&gt;::SslCert</literal> is corresponding per-host option.
<literal>SslKey</literal> determines what private key to use for client
authentication. <literal>&lt;host&gt;::SslKey</literal> is corresponding per-host option.
<literal>SslForceVersion</literal> overrides default SSL version to use.
Can contain 'TLSv1' or 'SSLv3' string.
<literal>&lt;host&gt;::SslForceVersion</literal> is corresponding per-host option.
<listitem><para>FTP URIs; ftp::Proxy is the default ftp proxy to use. 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 a 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 available 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>
Each is taken from it's respective URI component.</para>
<para>The option <literal>timeout</literal> sets the timeout timer used by the method,
this applies to all things including connection timeout and 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, 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 a 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>
<listitem><para>CDROM URIs; the only setting for CDROM URIs is the mount point,
<literal>cdrom::Mount</literal> which must be the mount point for the CDROM 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 (such as an SMB mount and old mount packages). The syntax
is to put <literallayout>/cdrom/::Mount "foo";</literallayout> within
the cdrom block. It is important to have the trailing slash. Unmount
commands can be specified using UMount.</para></listitem>
<listitem><para>GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv.
<literal>gpgv::Options</literal> Additional options passed to gpgv.
<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.
Per default the acquire methods can decompress <command>bzip2</command>, <command>lzma</command>
and <command>gzip</command> compressed files, with this setting more formats can be added
on the fly or the used method can be changed. 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
simple add the preferred type at first - not already added default types will be added at run time
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 <command>bzip2</command> and <command>lzma</command>.
If <command>lzma</command> should be preferred over <command>gzip</command> and <command>bzip2</command> the
configure setting should look like this <synopsis>Acquire::CompressionTypes::Order { "lzma"; "gz"; };</synopsis>
It is not needed to add <literal>bz2</literal> explicit to the list as it will be added automatic.</para>
<para>Note that at run time the <literal>Dir::Bin::<replaceable>Methodname</replaceable></literal> will
be checked: If this setting exists the method will only be used if this file exists, e.g. for
the bzip2 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 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>While it is possible to add an empty compression type to the order list, but APT in its current
version doesn't understand it correctly and will display many warnings about not downloaded files -
these warnings are most of the time false negatives. Future versions will maybe include a way to
really prefer uncompressed files to support the usage of local mirrors.</para></listitem>
<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 at first. Languages can be defined with their
short or long Languagecodes. Note that not all archives provide <filename>Translation</filename>
files for every Language - especially the long Languagecodes are rare, so please
inform you which ones are available before you set here impossible values.</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 languagecodes 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 fitting <filename>Translation</filename> file.
This can be used by the system administrator to let APT know that it should download also this files without
actually use them if the environment doesn't specify this languages. So the following example configuration will
result in the order "en, de" in an english and in "de, en" in a german localization. Note that "fr" is downloaded,
but not used if APT is not used in a french localization, in such an environment the order would be "fr, de, en".
<programlisting>Acquire::Languages { "environment"; "de"; "en"; "none"; "fr"; };</programlisting></para></listitem>
<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 preferences 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 their names to be blank. This will slow down startup but
save disk space. It is probably preferred 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
* merged with apt--fixes--0 Patches applied: * * fixed incorrect man-page example * * changelog udpate * * we only need to check once for xmlto * * fix a bug in a man-page, fix a problem with overly long lines in apt-cdrom * * merged with apt--main--0 * * fix a incorrect error message (it always added .gz regardless what was downloaded) * * merged with main * * added Hashsum support for file and cdrom * * added README.arch * * merged with main * * move the changelog to the right place * * Change pkgPolicy::Pin from private to protected * * added a default constructor for PrvIterator * * applied otavios patch to reread the statusFile on debSystem::Initialize * Reread status configuration, needed for clients using independent apt ...
17 years ago
<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>
The configuration item <literal>RootDir</literal> has a special
meaning. If set, all paths in <literal>Dir::</literal> 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
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.
<refsect1><title>APT in DSelect</title>
When APT is used as a &dselect; method several configuration directives
control the default behaviour. These are in the <literal>DSelect</literal> section.</para>
<listitem><para>Cache Clean mode; this value may be one of always, prompt, auto,
pre-auto and never. always and prompt will remove all packages from
the cache after upgrading, prompt (the default) does so conditionally.
auto removes only those packages which are no longer downloadable
(replaced with a new version for instance). pre-auto performs this
action before downloading new packages.</para></listitem>
<listitem><para>The contents of this variable is passed to &apt-get; as command line
options when it is run for the install phase.</para></listitem>
<listitem><para>The contents of this variable is passed to &apt-get; as command line
options when it is run for the update phase.</para></listitem>
<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>
<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>
<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>
<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>
<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 to the commands on standard input the
filenames of all .deb files it is going to install, one per line.</para>
<para>Version 2 of this protocol dumps more information, including the
protocol version, the APT configuration space and the packages, files
and versions being changed. Version 2 is enabled by setting
<literal>DPkg::Tools::options::cmd::Version</literal> to 2. <literal>cmd</literal> is a
command given to <literal>Pre-Install-Pkgs</literal>.</para></listitem>
<listitem><para>APT chdirs to this directory before invoking dpkg, the default is
<listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages,
the default is to disable signing and produce all binaries.</para></listitem>
<refsect2><title>dpkg trigger usage (and related options)</title>
<para>APT can call dpkg in a way so it can make aggressive use of triggers over
multiply calls of dpkg. Without further options dpkg will use triggers only in between his
own run. Activating these options can therefore decrease the time needed to perform the
install / upgrade. Note that it is intended to activate these options per default in the
future, but as it changes the way APT calling dpkg drastically it needs a lot more testing.
<emphasis>These options are therefore currently experimental and should not be used in
productive environments.</emphasis> Also it breaks the progress reporting so all frontends will
currently stay around half (or more) of the time in the 100% state while it actually configures
all packages.</para>
<para>Note that it is not guaranteed that APT will support these options or that these options will
not cause (big) trouble in the future. If you have understand the current risks and problems with
these options, but are brave enough to help testing them create a new configuration file and test a
combination of options. Please report any bugs, problems and improvements you encounter and make sure
to note which options you have used in your reports. Asking dpkg for help could also be useful for
debugging proposes, see e.g. <command>dpkg --audit</command>. A defensive option combination would be
<literallayout>DPkg::NoTriggers "true";
PackageManager::Configure "smart";
DPkg::ConfigurePending "true";
DPkg::TriggersPending "true";</literallayout></para>
<listitem><para>Add the no triggers flag to all dpkg calls (except the ConfigurePending call).
See &dpkg; if you are interested in what this actually means. In short: dpkg will not run the
triggers when this flag is present unless it is explicitly called to do so in an extra call.
Note that this option exists (undocumented) also in older apt versions with a slightly different
meaning: Previously these option only append --no-triggers to the configure calls to dpkg -
now apt will add these flag also to the unpack and remove calls.</para></listitem>
<listitem><para>Valid values are "<literal>all</literal>", "<literal>smart</literal>" and "<literal>no</literal>".
"<literal>all</literal>" is the default value and causes APT to configure all packages explicit.
The "<literal>smart</literal>" way is it to configure only packages which need to be configured before
another package can be unpacked (Pre-Depends) and let the rest configure by dpkg with a call generated
by the next option. "<literal>no</literal>" on the other hand will not configure anything and totally
rely on dpkg for configuration (which will at the moment fail if a Pre-Depends is encountered).
Setting this option to another than the all value will implicitly activate also the next option per
default as otherwise the system could end in an unconfigured status which could be unbootable!
<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 automatic
per default if the previous option is not set to <literal>all</literal>, but deactivating could be useful
if you want to run APT multiple times in a row - e.g. in an installer. In these sceneries you could
deactivate this option in all but the last run.</para></listitem>
<listitem><para>Useful for <literal>smart</literal> configuration as a package which has pending
triggers is not considered as <literal>installed</literal> and dpkg treats them as <literal>unpacked</literal>
currently which is a dealbreaker for Pre-Dependencies (see debbugs #526774). Note that this will
process all triggers, not only the triggers needed to configure this package.</para></listitem>
<listitem><para>As the configuration can be deferred to be done at the end by dpkg it can be
tried to order the unpack series only by critical needs, e.g. by Pre-Depends. Default is true
and therefore the "old" method of ordering in various steps by everything. While both method
were present in earlier APT versions the <literal>OrderCritical</literal> method was unused, so
this method is very experimental and needs further improvements before becoming really useful.
<listitem><para>Essential packages (and there dependencies) should be configured immediately
after unpacking. It will be a good idea to do this quite early in the upgrade process as these
these configure calls require currently also <literal>DPkg::TriggersPending</literal> which
will run quite a few triggers (which maybe not needed). Essentials get per default a high score
but the immediate flag is relatively low (a package which has a Pre-Depends is higher rated).
These option and the others in the same group can be used to change the scoring. The following
example shows the settings with there default values.
<literallayout>OrderList::Score {
Delete 500;
Essential 200;
Immediate 10;
PreDepends 50;
<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 <literal>/etc/cron.daily/apt</literal> script. See header of
this script for the brief documentation of these options.
<title>Debug options</title>
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:
<literal>Debug::pkgProblemResolver</literal> enables output
about the decisions made by
<literal>dist-upgrade, upgrade, install, remove, purge</literal>.
<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.
<literal>Debug::pkgDPkgPM</literal> prints out the actual
command line each time that <literal>apt</literal> invokes
<literal>Debug::IdentCdrom</literal> disables the inclusion
of statfs data in CDROM IDs. <!-- TODO: provide a
motivating example, except I haven't a clue why you'd want
to do this. -->
A full list of debugging options to apt follows.
Print information related to accessing
<literal>cdrom://</literal> sources.
Print information related to downloading packages using
Print information related to downloading packages using
Print information related to downloading packages using
Print information related to verifying cryptographic
signatures using <literal>gpg</literal>.
Output information about the process of accessing
collections of packages stored on CD-ROMs.
Describes the process of resolving build-dependencies in
Output each cryptographic hash that is generated by the
<literal>apt</literal> libraries.
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.
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.
Log when items are added to or removed from the global
download queue.
Output status messages and errors related to verifying
checksums and cryptographic signatures of downloaded files.
Output information about downloading and applying package
index list diffs, and errors relating to package index list
Output information related to patching apt package lists
when downloading index diffs instead of full indices.
Log all interactions with the sub-processes that actually
perform downloads.
Log events related to the automatically-installed status of
packages and to the removal of unused packages.