man > APT.CONF

APT.CONF(5)                                      APT                                     APT.CONF(5)

NAME
       apt.conf - Configuration file for APT

DESCRIPTION
       /etc/apt/apt.conf 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.

       When an APT tool starts up it will read the configuration files in the following order:

        1. the file specified by the APT_CONFIG environment variable (if any)

        2. all files in Dir::Etc::Parts in alphanumeric ascending order which have either no or
           "conf" 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 Dir::Ignore-Files-Silently configuration
           list - in which case it will be silently ignored.

        3. the main configuration file specified by Dir::Etc::main

        4. all options set in the binary specific configuration subtree are moved into the root of
           the tree.

        5. the command line options are applied to override the configuration directives or to load
           even more configuration files.

SYNTAX
       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 APT::Get::Assume-Yes
       is an option within the APT tool group, for the Get tool. Options do not inherit from their
       parent groups.

       Syntactically the configuration language is modeled after what the ISC tools such as bind and
       dhcp use. Lines starting with // are treated as comments (ignored), as well as all text
       between /* and */, just like C/C++ comments. Lines starting with # are also treated as
       comments. Each line is of the form APT::Get::Assume-Yes "true";. 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:


           APT {
             Get {
               Assume-Yes "true";
               Fix-Broken "true";
             };
           };

       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.


           DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};

       In general the sample configuration file /usr/share/doc/apt/examples/configure-index is a
       good guide for how it should look.

       Case is not significant in names of configuration items, so in the previous example you could
       use dpkg::pre-install-pkgs.

       Names for the configuration items are optional if a list is defined as can be seen in the
       DPkg::Pre-Install-Pkgs 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.

       Two special commands are defined: #include (which is deprecated and not supported by
       alternative implementations) and #clear.  #include will include the given file, unless the
       filename ends in a slash, in which case the whole directory is included.  #clear 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.)

       The #clear 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 ::) will not 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.

       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 (APT::Get::Assume-Yes 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 :: to the name of the list. (As you might suspect, the
       scope syntax can't be used on the command line.)

       Note that appending items to a list using :: only works for one item per line, and that you
       should not use it in combination with the scope syntax (which adds :: implicitly). Using both
       syntaxes together will trigger a bug which some users unfortunately depend on: an option with
       the unusual name "::" which acts like every other option with a name. This introduces many
       problems; for one thing, users who write multiple lines in this wrong syntax in the hope of
       appending to a list will achieve the opposite, as only the last assignment for this option
       "::" 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.

THE APT GROUP
       This group of options controls general APT behavior as well as holding the options for all of
       the tools.

       Architecture
           System Architecture; sets the architecture to use when fetching files and parsing package
           lists. The internal default is the architecture apt was compiled for.

       Architectures
           All Architectures the system supports. For instance, CPUs implementing the amd64 (also
           called x86-64) instruction set are also able to execute binaries compiled for the i386
           (x86) instruction set. This list is used when fetching files and parsing package lists.
           The initial default is always the system's native architecture (APT::Architecture), and
           foreign architectures are added to the default list when they are registered via dpkg
           --add-architecture.

       Compressor
           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 .reversed file extension which it will
           pass to the command rev without additional commandline parameters for compression and
           uncompression:

               APT::Compressor::rev {
                    Name "rev";
                    Extension ".reversed";
                    Binary "rev";
                    CompressArg {};
                    UncompressArg {};
                    Cost "10";
               };

       Build-Profiles
           List of all build profiles enabled for build-dependency resolution, without the
           "profile." namespace prefix. By default this list is empty. The DEB_BUILD_PROFILES as
           used by dpkg-buildpackage(1) overrides the list notation.

       Default-Release
           Default release to install packages from if more than one version is available. Contains
           release name, codename or release version. Examples: 'stable', 'testing', 'unstable',
           'bookworm', 'trixie', '4.0', '5.0*'. See also apt_preferences(5).

       Snapshot
           Snapshot to use for all repositories configured with Snapshot: yes. See also
           sources.list(5), the --snapshot option that sets this value, and Acquire::Snapshots::URI
           below.

       Ignore-Hold
           Ignore held packages; this global option causes the problem resolver to ignore held
           packages in its decision making.

       Clean-Installed
           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.

       Immediate-Configure
           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(1) 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(1) 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.

           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.

           Before a big operation like dist-upgrade is run with this option disabled you should try
           to explicitly install the package APT is unable to configure immediately; but please make
           sure you also report your problem to your distribution and to the APT team with the bug
           link below, so they can work on improving or correcting the upgrade process.

       Force-LoopBreak
           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-Depends loop between two essential packages.  Such a loop should never
           exist and is a grave bug. This option will work if the essential packages are not tar,
           gzip, libc, dpkg, dash or anything that those packages depend on.

       Cache-Start, Cache-Grow, Cache-Limit
           APT uses since version 0.7.26 a resizable memory mapped cache file to store the available
           information.  Cache-Start 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.
           Cache-Grow 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 Cache-Start 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 Cache-Limit. The default of Cache-Limit
           is 0 which stands for no limit. If Cache-Grow is set to 0 the automatic growth of the
           cache is disabled.

       Build-Essential
           Defines which packages are considered essential build dependencies.

       Get
           The Get subsection controls the apt-get(8) tool; please see its documentation for more
           information about the options here.

       Cache
           The Cache subsection controls the apt-cache(8) tool; please see its documentation for
           more information about the options here.

       CDROM
           The CDROM subsection controls the apt-cdrom(8) tool; please see its documentation for
           more information about the options here.

       NeverAutoRemove
           Never autoremove packages that match the regular expression(s).

       Protect-Kernels
           This option tells apt autoremove that kernels are protected and defaults to true. In case
           kernels are not protected they are treated as any other package.

       VersionedKernelPackages
           Define the regular expression(s) for versioned kernel packages. Based on these
           expressions a rule set is injected into apt similar to APT::NeverAutoRemove regular
           expressions.

       NeverAutoRemove::KernelCount
           Keep a custom amount of kernels when autoremoving and defaults to 2, meaning two kernels
           are kept. Apt will always keep the running kernel and the latest one. If the latest
           kernel is the same as the running kernel, the second latest kernel is kept. Because of
           this, any value lower than 2 will be ignored. If you want only the latest kernel, you
           should set APT::Protect-Kernels to false.

THE ACQUIRE GROUP
       The Acquire group of options controls the download of packages as well as the various
       "acquire methods" responsible for the download itself (see also sources.list(5)).

       Check-Date
           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 Check-Valid-Until and verifying that the Date field of a
           release file is not in the future.

       Max-FutureTime
           Maximum time (in seconds) before its creation (as indicated by the Date header) that the
           Release file should be considered valid. The default value is 10. 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(5) entries by using the
           Date-Max-Future option there.

       Check-Valid-Until
           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 Valid-Until header, but if they don't or a stricter value
           is desired the Max-ValidTime option below can be used. The Check-Valid-Until option of
           sources.list(5) entries should be preferred to disable the check selectively instead of
           using this global override.

       Max-ValidTime
           Maximum time (in seconds) after its creation (as indicated by the Date header) that the
           Release file should be considered valid. If the Release file itself includes a
           Valid-Until header the earlier date of the two is used as the expiration date. The
           default value is 0 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(5) entries by using the Valid-Until-Max option
           there.

       Min-ValidTime
           Minimum time (in seconds) after its creation (as indicated by the Date header) that the
           Release 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 Valid-Until 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(5) entries by using the Valid-Until-Min
           option there.

       AllowTLS
           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.

       PDiffs
           Try to download deltas called PDiffs for indexes (like Packages files) instead of
           downloading whole ones. True by default. Preferably, this can be set for specific
           sources.list(5) entries or index files by using the PDiffs option there.

           Two sub-options to limit the use of PDiffs are also available: FileLimit can be used to
           specify a maximum number of PDiff files should be downloaded to update a file.  SizeLimit
           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.

       By-Hash
           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(5) entries or index
           files by using the By-Hash option there.

       Queue-Mode
           Queuing mode; Queue-Mode can be one of host or access which determines how APT
           parallelizes outgoing connections.  host means that one connection per target host will
           be opened, access means that one connection per URI type will be opened.

       Retries
           Number of retries to perform. If this is non-zero APT will retry failed files the given
           number of times.

       Source-Symlinks
           Use symlinks for source archives. If set to true then source archives will be symlinked
           when possible instead of copying. True is the default.

       http https
           The options in these scopes configure APT's acquire transports for the protocols HTTP and
           HTTPS and are documented in the apt-transport-http(1) and apt-transport-https(1) manpages
           respectively.

       ftp
           ftp::Proxy sets the default proxy to use for FTP URIs. It is in the standard form of
           ftp://[[user][:pass]@]host[:port]/. Per host proxies can also be specified by using the
           form ftp::Proxy::<host> with the special keyword DIRECT meaning to use no proxies. If no
           one of the above settings is specified, ftp_proxy environment variable will be used. To
           use an FTP proxy you will have to set the ftp::ProxyLogin script in the configuration
           file. This entry specifies the commands to send to tell the proxy server what to connect
           to. Please see /usr/share/doc/apt/examples/configure-index for an example of how to do
           this. The substitution variables representing the corresponding URI component are
           $(PROXY_USER), $(PROXY_PASS), $(SITE_USER), $(SITE_PASS), $(SITE) and $(SITE_PORT).

           The option timeout sets the timeout timer used by the method; this value applies to the
           connection as well as the data timeout.

           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).

           It is possible to proxy FTP over HTTP by setting the ftp_proxy 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.

           The setting ForceExtended controls the use of RFC2428 EPSV and EPRT 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.

       cdrom
           For URIs using the cdrom method, the only configurable option is the mount point,
           cdrom::Mount, which must be the mount point for the CD-ROM (or DVD, or whatever) drive as
           specified in /etc/fstab. 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

               /cdrom/::Mount "foo";

           within the cdrom block. It is important to have the trailing slash. Unmount commands can
           be specified using UMount.

       gpgv
           For GPGV URIs the only configurable option is gpgv::Options, which passes additional
           parameters to gpgv.

       CompressionTypes
           List of compression types which are understood by the acquire methods. Files like
           Packages can be available in various compression formats. By default the acquire methods
           can decompress and recompress many common formats like xz and gzip; with this scope the
           supported formats can be queried, modified as well as support for more formats added (see
           also APT::Compressor). The syntax for this is:

               Acquire::CompressionTypes::FileExtension "Methodname";

           Also, the Order 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.

               Acquire::CompressionTypes::Order:: "gz";

           can be used to prefer gzip compressed files over all other compression formats. If xz
           should be preferred over gzip and bzip2 the configure setting should look like this:

               Acquire::CompressionTypes::Order { "xz"; "gz"; };

           It is not needed to add bz2 to the list explicitly as it will be added automatically.

           Note that the Dir::Bin::Methodname 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 bzip2 method (the inbuilt) setting is:

               Dir::Bin::bzip2 "/bin/bzip2";

           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.

           The special type uncompressed 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.

       GzipIndexes
           When downloading gzip 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.

       Languages
           The Languages subsection controls which Translation 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
           Translation files for every language - the long language codes are especially rare.

           The default list includes "environment" and "en". "environment" has a special meaning
           here: it will be replaced at runtime with the language codes extracted from the
           LC_MESSAGES environment variable. It will also ensure that these codes are not included
           twice in the list. If LC_MESSAGES is set to "C" only the Translation-en file (if
           available) will be used. To force APT to use no Translation file use the setting
           Acquire::Languages=none. "none" is another special meaning code which will stop the
           search for a suitable Translation 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").

               Acquire::Languages { "environment"; "de"; "en"; "none"; "fr"; };

           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
           /var/lib/apt/lists/ will be added to the end of the list (after an implicit "none").

       ForceIPv4
           When downloading, force to use only the IPv4 protocol.

       ForceIPv6
           When downloading, force to use only the IPv6 protocol.

       MaxReleaseFileSize
           The maximum file size of Release/Release.gpg/InRelease files. The default is 10MB.

       EnableSrvRecords
           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".

       AllowInsecureRepositories
           Allow update operations to load data files from repositories without sufficient security
           information. The default value is "false". Concept, implications as well as alternatives
           are detailed in apt-secure(8).

       AllowWeakRepositories
           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 "false". Concept, implications as well as alternatives are detailed in apt-
           secure(8).

       AllowDowngradeToInsecureRepositories
           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 false. Concept, implications
           as well as alternatives are detailed in apt-secure(8).

       Changelogs::URI scope
           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
           Acquire::Changelogs::URI::Label::LABEL or Acquire::Changelogs::URI::Origin::ORIGIN option
           exists and if so this value is taken. The value in the Release file can be overridden
           with Acquire::Changelogs::URI::Override::Label::LABEL or
           Acquire::Changelogs::URI::Override::Origin::ORIGIN. The value should be a normal URI to a
           text file, except that package specific data is replaced with the placeholder
           @CHANGEPATH@. The value for it is: 1. if the package is from a component (e.g.  main)
           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 'lib' 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 ('/') and between the fourth and fifth part is an underscore ('_').
           The special value 'no' 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.

       Snapshots::URI scope
           Like changelogs, snapshots can only be acquired if an URI is known from where to get
           them. Preferable the Release file indicates this in a 'Snapshots' field. If this isn't
           available the Label/Origin field of the Release file is used to check if a
           Acquire::Snapshots::URI::Label::LABEL or Acquire::Snapshots::URI::Origin::ORIGIN option
           exists and if so this value is taken. The value in the Release file can be overridden
           with Acquire::Snapshots::URI::Override::Label::LABEL or
           Acquire::Snapshots::URI::Override::Origin::ORIGIN. The value should be a normal URI to a
           directory, except that the snapshot ID replaced with the placeholder @SNAPSHOTID. The
           special value 'no' is available for this option indicating that this source cannot be
           used to acquire snapshots from. Another source will be tried if available in this case.

BINARY SPECIFIC CONFIGURATION
       Especially with the introduction of the apt 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 APT::Get::Show-Versions effect apt-get as well as apt.

       Setting an option for a specific binary only can be achieved by setting the option inside the
       Binary::specific-binary scope. Setting the option APT::Get::Show-Versions for the apt only
       can e.g. by done by setting Binary::apt::APT::Get::Show-Versions instead.

       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.

DIRECTORIES
       The Dir::State section has directories that pertain to local state information.  lists is the
       directory to place downloaded package lists in and status is the name of the dpkg(1) status
       file.  preferences is the name of the APT preferences file.  Dir::State contains the default
       directory to prefix on all sub-items if they do not start with / or ./.

       Dir::Cache contains locations pertaining to local cache information, such as the two package
       caches srcpkgcache and pkgcache as well as the location to place downloaded archives,
       Dir::Cache::archives. Generation of caches can be turned off by setting pkgcache or
       srcpkgcache to "". This will slow down startup but save disk space. It is probably preferable
       to turn off the pkgcache rather than the srcpkgcache. Like Dir::State the default directory
       is contained in Dir::Cache

       Dir::Etc contains the location of configuration files, sourcelist gives the location of the
       sourcelist and main is the default configuration file (setting has no effect, unless it is
       done from the config file specified by APT_CONFIG).

       The Dir::Parts 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.

       Binary programs are pointed to by Dir::Bin.  Dir::Bin::Methods specifies the location of the
       method handlers and gzip, bzip2, lzma, dpkg, apt-get dpkg-source dpkg-buildpackage and
       apt-cache specify the location of the respective programs.

       The configuration item RootDir has a special meaning. If set, all paths will be relative to
       RootDir, even paths that are specified absolutely. So, for instance, if RootDir is set to
       /tmp/staging and Dir::State::status is set to /var/lib/dpkg/status, then the status file will
       be looked up in /tmp/staging/var/lib/dpkg/status. If you want to prefix only relative paths,
       set Dir instead.

       The Ignore-Files-Silently list can be used to specify which files APT should silently ignore
       while parsing the files in the fragment directories. Per default a file which ends with
       .disabled, ~, .bak or .dpkg-[a-z]+ is silently ignored. As seen in the last default value
       these patterns can use regular expression syntax.

APT IN DSELECT
       When APT is used as a dselect(1) method several configuration directives control the default
       behavior. These are in the DSelect section.

       Clean
           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.

       options
           The contents of this variable are passed to apt-get(8) as command line options when it is
           run for the install phase.

       Updateoptions
           The contents of this variable are passed to apt-get(8) as command line options when it is
           run for the update phase.

       PromptAfterUpdate
           If true the [U]pdate operation in dselect(1) will always prompt to continue. The default
           is to prompt only on error.

HOW APT CALLS DPKG(1)
       Several configuration directives control how APT invokes dpkg(1). These are in the DPkg
       section.

       options
           This is a list of options to pass to dpkg(1). The options must be specified using the
           list notation and each list item is passed as a single argument to dpkg(1).

       Path
           This is a string that defines the PATH environment variable used when running dpkg. It
           may be set to any valid value of that environment variable; or the empty string, in which
           case the variable is not changed.

       Pre-Invoke, Post-Invoke
           This is a list of shell commands to run before/after invoking dpkg(1). Like options this
           must be specified in list notation. The commands are invoked in order using /bin/sh;
           should any fail APT will abort.

       Pre-Install-Pkgs
           This is a list of shell commands to run before invoking dpkg(1). Like options this must
           be specified in list notation. The commands are invoked in order using /bin/sh; 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.

           Version 2 of this protocol sends more information through the requested file descriptor:
           a line with the text VERSION 2, the APT configuration space, and a list of package
           actions with filename and version information.

           Each configuration directive line has the form key=value. Special characters (equal
           signs, newlines, nonprintable characters, quotation marks, and percent signs in key and
           newlines, nonprintable characters, and percent signs in value) are %-encoded. Lists are
           represented by multiple key::=value lines with the same key. The configuration section
           ends with a blank line.

           Package action lines consist of five fields in Version 2: package name (without
           architecture qualification even if foreign), old version, direction of version change (<
           for upgrades, > 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 - < 1.23.4). 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.

           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.

           The version of the protocol to be used for the command cmd can be chosen by setting
           DPkg::Tools::options::cmd::Version 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.

           The file descriptor to be used to send the information can be requested with
           DPkg::Tools::options::cmd::InfoFD which defaults to 0 for standard input and is available
           since version 0.9.11. Support for the option can be detected by looking for the
           environment variable APT_HOOK_INFO_FD which contains the number of the used file
           descriptor as a confirmation.

       Run-Directory
           APT chdirs to this directory before invoking dpkg(1), the default is /.

       Build-options
           These options are passed to dpkg-buildpackage(1) when compiling packages; the default is
           to disable signing and produce all binaries.

       DPkg::ConfigurePending
           If this option is set APT will call dpkg --configure --pending to let dpkg(1) 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.

PERIODIC AND ARCHIVES OPTIONS
       APT::Periodic and APT::Archives groups of options configure behavior of apt periodic updates,
       which is done by the /usr/lib/apt/apt.systemd.daily script. See the top of this script for
       the brief documentation of these options.

DEBUG OPTIONS
       Enabling options in the Debug:: section will cause debugging information to be sent to the
       standard error stream of the program utilizing the apt libraries, or enable special program
       modes that are primarily useful for debugging the behavior of apt. Most of these options are
       not interesting to a normal user, but a few may be:

       •   Debug::pkgProblemResolver enables output about the decisions made by dist-upgrade,
           upgrade, install, remove, purge.

       •   Debug::NoLocking disables all file locking. This can be used to run some operations (for
           instance, apt-get -s install) as a non-root user.

       •   Debug::pkgDPkgPM prints out the actual command line each time that apt invokes dpkg(1).

       •   Debug::IdentCdrom disables the inclusion of statfs data in CD-ROM IDs.

       A full list of debugging options to apt follows.

       Debug::Acquire::cdrom
           Print information related to accessing cdrom:// sources.

       Debug::Acquire::ftp
           Print information related to downloading packages using FTP.

       Debug::Acquire::http
           Print information related to downloading packages using HTTP.

       Debug::Acquire::https
           Print information related to downloading packages using HTTPS.

       Debug::Acquire::gpgv
           Print information related to verifying cryptographic signatures using gpg.

       Debug::aptcdrom
           Output information about the process of accessing collections of packages stored on
           CD-ROMs.

       Debug::Hashes
           Output each cryptographic hash that is generated by the apt libraries.

       Debug::IdentCDROM
           Do not include information from statfs, namely the number of used and free blocks on the
           CD-ROM filesystem, when generating an ID for a CD-ROM.

       Debug::NoLocking
           Disable all file locking. For instance, this will allow two instances of “apt-get update”
           to run at the same time.

       Debug::pkgAcquire
           Log when items are added to or removed from the global download queue.

       Debug::pkgAcquire::Auth
           Output status messages and errors related to verifying checksums and cryptographic
           signatures of downloaded files.

       Debug::pkgAcquire::Diffs
           Output information about downloading and applying package index list diffs, and errors
           relating to package index list diffs.

       Debug::pkgAcquire::RRed
           Output information related to patching apt package lists when downloading index diffs
           instead of full indices.

       Debug::pkgAcquire::Worker
           Log all interactions with the sub-processes that actually perform downloads.

       Debug::pkgAutoRemove
           Log events related to the automatically-installed status of packages and to the removal
           of unused packages.

       Debug::pkgDepCache::AutoInstall
           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., apt-get install, and not to the full apt dependency resolver; see
           Debug::pkgProblemResolver for that.

       Debug::pkgDepCache::Marker
           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 MarkKeep, MarkDelete or MarkInstall followed by package-name
           <a.b.c -> d.e.f | x.y.z> (section) where a.b.c is the current version of the package,
           d.e.f is the version considered for installation and x.y.z 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.  section is the name of the
           section the package appears in.

       Debug::pkgDPkgPM
           When invoking dpkg(1), output the precise command line with which it is being invoked,
           with arguments separated by a single space character.

       Debug::pkgDPkgProgressReporting
           Output all the data received from dpkg(1) on the status file descriptor and any errors
           encountered while parsing it.

       Debug::pkgOrderList
           Generate a trace of the algorithm that decides the order in which apt should pass
           packages to dpkg(1).

       Debug::pkgPackageManager
           Output status messages tracing the steps performed when invoking dpkg(1).

       Debug::pkgPolicy
           Output the priority of each package list on startup.

       Debug::pkgProblemResolver
           Trace the execution of the dependency resolver (this applies only to what happens when a
           complex dependency problem is encountered).

       Debug::pkgProblemResolver::ShowScores
           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
           Debug::pkgDepCache::Marker

       Debug::sourceList
           Print information about the vendors read from /etc/apt/vendors.list.

       Debug::RunScripts
           Display the external commands that are called by apt hooks. This includes e.g. the config
           options DPkg::{Pre,Post}-Invoke or APT::Update::{Pre,Post}-Invoke.

EXAMPLES
       /usr/share/doc/apt/examples/configure-index is a configuration file showing example values
       for all possible options.

FILES
       /etc/apt/apt.conf
           APT configuration file. Configuration Item: Dir::Etc::Main.

       /etc/apt/apt.conf.d/
           APT configuration file fragments. Configuration Item: Dir::Etc::Parts.

SEE ALSO
       apt-cache(8), apt-config(8), apt_preferences(5).

BUGS
       APT bug page[1]. If you wish to report a bug in APT, please see
       /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command.

AUTHORS
       Jason Gunthorpe

       APT team

       Daniel Burrows <dburrows AT debian.org>
           Initial documentation of Debug::*.

NOTES
        1. APT bug page
           https://bugs.debian.org/src:apt

APT 2.8.3                                 21 February 2024                               APT.CONF(5)