&apt-author.jgunthorpe; &apt-author.team; Daniel Burrows Initial documentation of Debug::*. dburrows@debian.org &apt-email; &apt-product; 10 December 2008
apt.conf
5

# 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.

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 semicolon.

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

In general the sample configuration file in `&docdir;examples/apt.conf` &configureindex; 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.

## 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.

Default-Release

  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;.

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; tool, please see its documentation for more information about the options here.

Cache

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

CDROM

  The CDROM subsection controls the &apt-cdrom; 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.

PDiffs

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

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.

https

  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

  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 &configureindex; 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

  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 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`.

## APT in DSelect

When APT is used as a &dselect; 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; as command line options when it is run for the install phase.

Updateoptions

  The contents of this variable is passed to &apt-get; as command line options when it is run for the update phase.

PromptAfterUpdate

  If true the [U]pdate operation in &dselect; 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;. 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;.

Pre-Invoke
Post-Invoke

  This is a list of shell commands to run before/after 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.

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; when compiling packages, the default is to disable signing and produce all binaries.

## Periodic and Archives options

`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.

## Debug options

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

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

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

- `Debug::pkgDPkgPM` prints out the actual command line each time that `apt` invokes &dpkg;.

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

A full list of debugging options to apt follows.

`Debug::Acquire::cdrom`

  Print information related to accessing `cdrom://` sources.

`Debug::Acquire::ftp`

  Print information related to downloading packages using FTP.

`Debug::Acquire::http`

  Print information related to downloading packages using HTTP.

`Debug::Acquire::https`

  Print information related to downloading packages using HTTPS.

`Debug::Acquire::gpgv`

  Print information related to verifying cryptographic signatures using `gpg`.

`Debug::aptcdrom`

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

`Debug::BuildDeps`

  Describes the process of resolving build-dependencies in &apt-get;.

`Debug::Hashes`

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

`Debug::IdentCDROM`

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

`Debug::NoLocking`

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

`Debug::pkgAcquire`

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

`Debug::pkgAcquire::Auth`

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

`Debug::pkgAcquire::Diffs`

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

`Debug::pkgAcquire::RRed`

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

`Debug::pkgAcquire::Worker`

  Log all interactions with the sub-processes that actually perform downloads.

`Debug::pkgAutoRemove`

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

`Debug::pkgDepCache::AutoInstall`

  Generate debug messages describing which packages are being automatically installed to resolve dependencies. This corresponds to the initial auto-install pass performed in, e.g., `apt-get install`, and not to the full `apt` dependency resolver; see `Debug::pkgProblemResolver` for that.

`Debug::pkgDepCache::Marker`

  Generate debug messages describing which 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.

`Debug::pkgInitConfig`

  Dump the default configuration to standard output on startup.

`Debug::pkgDPkgPM`

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

`Debug::pkgDPkgProgressReporting`

  Output all the data received from &dpkg; on the status file descriptor and any errors encountered while parsing it.

`Debug::pkgOrderList`

  Generate a trace of the algorithm that decides the order in which `apt` should pass packages to &dpkg;.

`Debug::pkgPackageManager`

  Output status messages tracing the steps performed when invoking &dpkg;.

`Debug::pkgPolicy`

  Output the priority of each package list on startup.

`Debug::pkgProblemResolver`

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

`Debug::pkgProblemResolver::ShowScores`

  Display a list of all installed packages with their calculated score used by the pkgProblemResolver. The description of the package is the same as described in `Debug::pkgDepCache::Marker`

`Debug::sourceList`

  Print information about the vendors read from `/etc/apt/vendors.list`.

`Debug::Vendor`

  Print information about each vendor.

## Examples

&configureindex; is a configuration file showing example values for all possible options.

## Files

`/etc/apt/apt.conf`

## See Also

&apt-cache;, &apt-config;, &apt-preferences;.

&manbugs;