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

       apt.conf - Configuration file for APT

       apt.conf 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 APT_CONFIG environment
       variable (if any) and then read the files in Dir::Etc::Parts then read
       the main configuration file specified by Dir::Etc::main then finally
       apply the command line options to override the configuration
       directives, possibly loading even more config 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 trailing semicolon is required and the quotes are optional. A new
       scope can be opened with curly braces, like:

           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 word enclosed in quotes followed
       by a semicolon. Multiple entries can be included, each separated by a

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

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

       The names of the configuration items are not case-sensitive. So in the
       previous example you could use dpkg::pre-install-pkgs.

       Two specials are allowed, #include and #clear #include will include the
       given file, unless the filename ends in a slash, then the whole
       directory is included.  #clear is used to erase a list of names.

       All of the APT tools take a -o option which allows an arbitrary
       configuration directive to be specified on the command line. The syntax
       is a full option name (APT::Get::Assume-Yes for instance) followed by
       an equals sign then the new value of the option. Lists can be appended
       too by adding a trailing :: to the list name.

       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.

           Default release to install packages from if more than one version
           available. Contains release name or release version. Examples:
           'stable', 'testing', 'unstable', '4.0', '5.0*'. Release codenames
           ('etch', 'lenny' etc.) are not allowed now. See also

           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.

           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.

           Never Enable this option unless you -really- know what you are
           doing. It permits APT to temporarily remove an essential package to
           break a Conflicts/Conflicts or Conflicts/Pre-Depend loop between
           two essential 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, bash or anything that those packages depend

           APT uses a fixed size memory mapped cache file to store the
           'available' information. This sets the size of that cache (in

           Defines which package(s) are considered essential build

           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 and the
       URI handlers.

           Try do download deltas called PDiffs for Packages or Sources files
           instead of downloading whole ones. True by default.

           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 URIs; http::Proxy is the default http proxy to use. 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. The
           http_proxy environment variable will override all settings.

           Three settings are provided for cache control with HTTP/1.1
           compliant proxy caches.  No-Cache tells the proxy to not use its
           cached response under any circumstances, Max-Age is sent only for
           index files and tells the cache to refresh its object if it is
           older than the given number of seconds. Debian updates its index
           files daily so the default is 1 day.  No-Store specifies that the
           cache should never store this request, it is only set for archive
           files. This may be useful to prevent polluting a proxy cache with
           very large .deb files. Note: Squid 2.0.2 does not support any of
           these options.

           The option timeout sets the timeout timer used by the method, this
           applies to all things including connection timeout and data

           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) Acquire::http::Pipeline-Depth can be a value from 0 to
           5 indicating how many outstanding requests APT should send. A value
           of zero MUST be specified if the remote host does not properly
           linger on TCP connections - otherwise data corruption will occur.
           Hosts which require this are in violation of RFC 2068.

           HTTPS URIs. Cache-control and proxy options are the same as for
           http method.  Pipeline-Depth option is not supported yet.

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

           FTP URIs; ftp::Proxy is the default proxy server to use. It is in
           the standard form of ftp://[[user][:pass]@]host[:port]/ and is
           overridden by the ftp_proxy environment variable. To use a 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 available are
           $(PROXY_USER) $(PROXY_PASS) $(SITE_USER) $(SITE_PASS) $(SITE) and
           $(SITE_PORT) Each is taken from it's respective URI component.

           The option timeout sets the timeout timer used by the method, this
           applies to all things including connection timeout and data

           Several settings are provided to control passive mode. Generally it
           is safe to leave passive mode on, it works in nearly every
           environment. However some situations require that passive mode be
           disabled and port mode ftp used instead. This can be done globally,
           for connections that go through a proxy or for a specific host (See
           the sample config file for examples).

           It is possible to proxy FTP over HTTP by setting the ftp_proxy
           environment variable to a http url - see the discussion of the http
           method above for syntax. You cannot set this in the configuration
           file and it is not recommended to use FTP over HTTP due to its low

           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 URIs; the only setting for CDROM URIs is the mount point,
           cdrom::Mount which must be the mount point for the CDROM 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 (such as an SMB mount and old mount packages). 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 URIs; the only option for GPGV URIs is the option to pass
           additional parameters to gpgv.  gpgv::Options Additional options
           passed to gpgv.

       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 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 their names to be blank. This
       will slow down startup but save disk space. It is probably preferred to
       turn off the pkgcache rather than the srcpkgcache. Like 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, 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
       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.

       When APT is used as a dselect(8) method several configuration
       directives control the default behaviour. 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 is passed to apt-get(8) as command
           line options when it is run for the install phase.

           The contents of this variable is 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(8) will always prompt to
           continue. The default is to prompt only on error.

       Several configuration directives control how APT invokes dpkg(8). These
       are in the DPkg section.

           This is a list of options to pass to dpkg. The options must be
           specified using the list notation and each list item is passed as a
           single argument to dpkg(8).

       Pre-Invoke, Post-Invoke
           This is a list of shell commands to run before/after invoking
           dpkg(8). 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. 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 to the commands on standard input the filenames of all
           .deb files it is going to install, one per line.

           Version 2 of this protocol dumps more information, including the
           protocol version, the APT configuration space and the packages,
           files and versions being changed. Version 2 is enabled by setting
           DPkg::Tools::options::cmd::Version to 2.  cmd is a command given to

           APT chdirs to this directory before invoking dpkg, the default is

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

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

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

       o    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.

       o    Debug::pkgDPkgPM prints out the actual command line each time that
           apt invokes dpkg(8).

       o    Debug::IdentCdrom disables the inclusion of statfs data in CDROM

       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.

           Dump the default configuration to standard output on startup.

           When invoking dpkg(8), 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(8) 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(8).

           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).

           Print information about the vendors read from

           Print information about each vendor.

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


       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 <dburrowsATdebian.org>
           Initial documentation of Debug::*.

        1. APT bug page

Linux                          10 December 2008                    APT.CONF(5)