Content-type: text/html Man page of APT.CONF


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Updated: 10 December 2008
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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:

  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, each separated by a semicolon.

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

In general the sample configuration file in /usr/share/doc/apt/examples/apt.conf /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 part of the configuration tree. The specified element and all its descendents are erased.

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, codename or release version. Examples: 'stable', 'testing', 'unstable', 'lenny', 'squeeze', '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.


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 on.


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


Defines which package(s) 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 and the URI handlers.


Try to 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 timeout.

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 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, 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 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 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 section.


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 Pre-Install-Pkgs.


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 binaries.


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:

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(8).

Debug::IdentCdrom disables the inclusion of statfs data in CDROM IDs.

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-get(8).


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


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 queue.


Output status messages and errors related to verifying checksums and cryptographic signatures of downloaded files.


Output information about downloading and applying package index list diffs, and errors relating to package index list 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 downloads.


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 package is 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 space 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 version as the installed. section is the name of the section the package appears in.


Dump the default configuration to standard error on startup.


When invoking dpkg(8), output the precise command line with which it is being invoked, with arguments separated by a single space character.


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 dpkg(8).


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 /etc/apt/vendors.list.


/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).  


m[blue]APT bug pagem[][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 <[email protected]>

Initial documentation of Debug::*.


APT bug page




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Time: 04:16:04 GMT, September 24, 2010