Provided by: apt_1.0.10.2ubuntu1_i386 bug


       apt.conf - Configuration file for APT


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


       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. 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.gz 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

       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.


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

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

           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

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

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

           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.

           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 buglink below, so they can work on improving or correcting the
           upgrade process.

           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

           Defines which packages are considered essential build dependencies.

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

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

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


       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)).

           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.

           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

           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.

           Try to download deltas called PDiffs for indexes (like Packages
           files) instead of downloading whole ones. True by default.

           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.

           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.

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

           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::Proxy sets the default proxy to use for HTTP URIs. It is in
           the standard form of http://[[user][:pass]@]host[:port]/. Per host
           proxies can also be specified by using the form http::Proxy::<host>
           with the special keyword DIRECT meaning to use no proxies. If no
           one of the above settings is specified, http_proxy environment
           variable will be used.

           Three settings are provided for cache control with HTTP/1.1
           compliant proxy caches.  No-Cache tells the proxy not to use its
           cached response under any circumstances.  Max-Age sets the allowed
           maximum age (in seconds) of an index file in the cache of the
           proxy.  No-Store specifies that the proxy should not store the
           requested archive files in its cache, which can be used to prevent
           the proxy from polluting its cache with (big) .deb files.

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

           The setting Acquire::http::Pipeline-Depth can be used to enable
           HTTP pipelining (RFC 2616 section which can be beneficial
           e.g. on high-latency connections. It specifies how many requests
           are sent in a pipeline. Previous APT versions had a default of 10
           for this setting, but the default value is now 0 (= disabled) to
           avoid problems with the ever-growing amount of webservers and
           proxies which choose to not conform to the HTTP/1.1 specification.

           Acquire::http::AllowRedirect controls whether APT will follow
           redirects, which is enabled by default.

           The used bandwidth can be limited with Acquire::http::Dl-Limit
           which accepts integer values in kilobytes per second. The default
           value is 0 which deactivates the limit and tries to use all
           available bandwidth. Note that this option implicitly disables
           downloading from multiple servers at the same time.

           Acquire::http::User-Agent 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.

           Acquire::http::Proxy-Auto-Detect can be used to specify an external
           command to discover the http proxy to use. Apt expects the command
           to output the proxy on stdout in the style http://proxy:port/. This
           will override the generic Acquire::http::Proxy but not any specific
           host proxy configuration set via Acquire::http::Proxy::$HOST. See
           the squid-deb-proxy-client(1) package for an example implementation
           that uses avahi. This option takes precedence over the legacy
           option name ProxyAutoDetect.

           The Cache-control, Timeout, AllowRedirect, Dl-Limit and proxy
           options work for HTTPS URIs in the same way as for the http method,
           and default to the same values if they are not explicitly set. The
           Pipeline-Depth option is not yet supported.

           CaInfo suboption specifies place of file that holds info about
           trusted certificates.  <host>::CaInfo is the corresponding per-host
           option.  Verify-Peer boolean suboption determines whether or not
           the server's host certificate should be verified against trusted
           certificates.  <host>::Verify-Peer is the corresponding per-host
           option.  Verify-Host boolean suboption determines whether or not
           the server's hostname should be verified.  <host>::Verify-Host is
           the corresponding per-host option.  SslCert determines what
           certificate to use for client authentication.  <host>::SslCert is
           the corresponding per-host option.  SslKey determines what private
           key to use for client authentication.  <host>::SslKey is the
           corresponding per-host option.  SslForceVersion overrides default
           SSL version to use. It can contain either of the strings 'TLSv1' or
           'SSLv3'.  <host>::SslForceVersion is the corresponding per-host

           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.gz 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.

           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

               /cdrom/::Mount "foo";

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

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

           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
           bzip2, lzma and gzip 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:

               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 - default 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 bzip2 and lzma. If
           lzma should be preferred over gzip and bzip2 the configure setting
           should look like this:

               Acquire::CompressionTypes::Order { "lzma"; "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, 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 useable for local

           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.

           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").

           When downloading, force to use only the IPv4 protocol.

           When downloading, force to use only the IPv6 protocol.


       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-getdpkg-sourcedpkg-buildpackage and apt-cache specify the
       location of the respective programs.

       The configuration item RootDir has a special meaning. If set, all paths
       in Dir:: 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.

       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 end with .disabled, ~, .bak or
       .dpkg-[a-z]+ is silently ignored. As seen in the last default value
       these patterns can use regular expression syntax.


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

           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.

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

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

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


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

           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).

       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.

           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 dumps more information, including the
           protocol version, the APT configuration space and the packages,
           files and versions being changed. Version 3 adds the architecture
           and MultiArch flag to each version being dumped.

           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.

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

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

   dpkg trigger usage (and related options)
       APT can call dpkg(1) in such a way as to let it make aggressive use of
       triggers over multiple calls of dpkg(1). Without further options
       dpkg(1) will use triggers once each time it runs. Activating these
       options can therefore decrease the time needed to perform the install
       or upgrade. Note that it is intended to activate these options per
       default in the future, but as it drastically changes the way APT calls
       dpkg(1) it needs a lot more testing.  These options are therefore
       currently experimental and should not be used in production
       environments.  It also breaks progress reporting such that all
       front-ends will currently stay around half (or more) of the time in the
       100% state while it actually configures all packages.

       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(1) for help could also be useful for
       debugging proposes, see e.g.  dpkg --audit. A defensive option
       combination would be

           DPkg::NoTriggers "true";
           PackageManager::Configure "smart";
           DPkg::ConfigurePending "true";
           DPkg::TriggersPending "true";

           Add the no triggers flag to all dpkg(1) calls (except the
           ConfigurePending call). See dpkg(1) if you are interested in what
           this actually means. In short: dpkg(1) 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(1) - now APT will also add this flag to the unpack and remove

           Valid values are "all", "smart" and "no". The default value is
           "all", which causes APT to configure all packages. The "smart" way
           is to configure only packages which need to be configured before
           another package can be unpacked (Pre-Depends), and let the rest be
           configured by dpkg(1) with a call generated by the ConfigurePending
           option (see below). On the other hand, "no" will not configure
           anything, and totally relies on dpkg(1) for configuration (which at
           the moment will fail if a Pre-Depends is encountered). Setting this
           option to any value other than all will implicitly also activate
           the next option by default, as otherwise the system could end in an
           unconfigured and potentially unbootable state.

           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 automatically per default if the previous
           option is not set to all, but deactivating it 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.

           Useful for the smart configuration as a package which has pending
           triggers is not considered as installed, and dpkg(1) treats them as
           unpacked currently which is a showstopper for Pre-Dependencies (see
           debbugs #526774). Note that this will process all triggers, not
           only the triggers needed to configure this package.

           Essential packages (and their dependencies) should be configured
           immediately after unpacking. It is a good idea to do this quite
           early in the upgrade process as these configure calls also
           currently require DPkg::TriggersPending which will run quite a few
           triggers (which may not be needed). Essentials get per default a
           high score but the immediate flag is relatively low (a package
           which has a Pre-Depends is rated higher). These option and the
           others in the same group can be used to change the scoring. The
           following example shows the settings with their default values.

               OrderList::Score {
                    Delete 500;
                    Essential 200;
                    Immediate 10;
                    PreDepends 50;


       APT::Periodic and APT::Archives groups of options configure behavior of
       apt periodic updates, which is done by the /etc/cron.daily/apt script.
       See the top of this script for the brief documentation of these


       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

       ·   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

       A full list of debugging options to apt follows.

           Print information related to accessing cdrom:// sources.

           Print information related to downloading packages using FTP.

           Print information related to downloading packages using HTTP.

           Print information related to downloading packages using HTTPS.

           Print information related to verifying cryptographic signatures
           using gpg.

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

           Describes the process of resolving build-dependencies in apt-

           Output each cryptographic hash that is generated by the apt

           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.

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

           Log when items are added to or removed from the global download

           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 diffs.

           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

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

           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.

           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

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

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

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

           Output status messages tracing the steps performed when invoking

           Output the priority of each package list on startup.

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

           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

           Print information about the vendors read from

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


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


           APT configuration file. Configuration Item: Dir::Etc::Main.

           APT configuration file fragments. Configuration Item:


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


       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.


       Jason Gunthorpe

       APT team

       Daniel Burrows <>
           Initial documentation of Debug::*.


        1. APT bug page