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apt.conf (5)

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NAME

apt.conf - Configuration file for APT

DESCRIPTION

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.

Syntacticly the configuration language is modeled after what the ISC tools such as bind and dhcp use. Lines starting with // are treated as comments (ignored). 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 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.

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.

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.

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

: 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.

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-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.

Cache-Limit

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

Build-Essential

: Defines which package(s) 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.

THE ACQUIRE GROUP

The Acquire group of options controls the download of packages and the URI handlers.

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

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.

ftp

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 subsitution 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 defaut 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

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

: GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv. gpgv::Options Additional options passed to gpgv.

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 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 prefered 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.

APT IN DSELECT

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

Updateoptions

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

HOW APT CALLS DPKG

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

options

: 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.

Pre-Install-Pkgs

: 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.

Run-Directory

: APT chdirs to this directory before invoking dpkg, 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.

DEBUG OPTIONS

Most of the options in the debug section are not interesting to the normal user, however Debug::pkgProblemResolver shows interesting output about the decisions dist-upgrade makes. Debug::NoLocking disables file locking so APT can do some operations as non-root and Debug::pkgDPkgPM will print out the command line for each dpkg invokation. Debug::IdentCdrom will disable the inclusion of statfs data in CDROM IDs. Debug::Acquire::gpgv Debugging of the gpgv method.