&apt-email;
&apt-product;
<!-- The last update date -->
- <date>18 September 2009</date>
+ <date>16 January 2010</date>
</refentryinfo>
<refmeta>
</refnamediv>
<refsect1><title>Description</title>
- <para><filename>apt.conf</filename> is the main configuration file for the APT suite of
- tools, all tools make use of the configuration file and a common command line
- parser to provide a uniform environment. When an APT tool starts up it will
- read the configuration specified by the <envar>APT_CONFIG</envar> environment
- variable (if any) and then read the files in <literal>Dir::Etc::Parts</literal>
- then read the main configuration file specified by
- <literal>Dir::Etc::main</literal> then finally apply the
- command line options to override the configuration directives, possibly
- loading even more config files.</para>
-
+ <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>
+ <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 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
+ <literal>Dir::Etc::main</literal></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
+ 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
+ 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
<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
+ <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
</varlistentry>
<varlistentry><term>Default-Release</term>
- <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', 'lenny', 'squeeze', '4.0', '5.0*'. See also &apt-preferences;.</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>
</varlistentry>
-
+
<varlistentry><term>Ignore-Hold</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>Immediate-Configure</term>
- <listitem><para>Disable Immediate Configuration; This dangerous option disables some
- of APT's ordering code to cause it to make fewer dpkg calls. Doing
- so may be necessary on some extremely slow single user systems but
- is very dangerous and may cause package install scripts to fail or worse.
- Use at your own risk.</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>
</varlistentry>
<varlistentry><term>Force-LoopBreak</term>
anything that those packages depend on.</para></listitem>
</varlistentry>
- <varlistentry><term>Cache-Limit</term>
- <listitem><para>APT uses a fixed size memory mapped cache file to store the 'available'
- information. This sets the size of that cache (in bytes).</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.
+ </para></listitem>
</varlistentry>
<varlistentry><term>Build-Essential</term>
and the URI handlers.
<variablelist>
+ <varlistentry><term>Check-Valid-Until</term>
+ <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.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>Max-ValidTime</term>
+ <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.
+ </para></listitem>
+ </varlistentry>
+
<varlistentry><term>PDiffs</term>
<listitem><para>Try to download deltas called <literal>PDiffs</literal> for
Packages or Sources files instead of downloading whole ones. True
- by default.</para></listitem>
+ 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.
+ </para></listitem>
</varlistentry>
<varlistentry><term>Queue-Mode</term>
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)
+ 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
<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></listitem>
+ 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>
</varlistentry>
<varlistentry><term>https</term>
- <listitem><para>HTTPS URIs. Cache-control and proxy options are the same as for
- <literal>http</literal> method.
- <literal>Pipeline-Depth</literal> option is not supported yet.</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.
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>
</varlistentry>
+
+ <varlistentry><term>GzipIndexes</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>Languages</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 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>
+ </varlistentry>
+
</variablelist>
</para>
</refsect1>
will be looked up in
<filename>/tmp/staging/var/lib/dpkg/status</filename>.
</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>
<variablelist>
<varlistentry><term>DPkg::NoTriggers</term>
- <listitem><para>Add the no triggers flag to all dpkg calls (expect the ConfigurePending call).
+ <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 then this flag is present unless it is explicit called to do so in an extra call.
+ 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>
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
- relay 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 implicit activate also the next option per
+ 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!
</para></listitem>
</varlistentry>
<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 this sceneries you could
+ 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>
</varlistentry>
<varlistentry><term>DPkg::TriggersPending</term>
</listitem>
</varlistentry>
-->
+
</variablelist>
</refsect1>
projects / apt.git / blobdiff