apt.conf(5)
NAME
apt.conf - Configuration file for APT
DESCRIPTION
/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. all options set in the binary specific configuration subtree are
moved into the root of the tree.
5. the command line options are applied to override the configuration
directives or to load even more configuration files.
SYNTAX
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
semicolon.)
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.
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.
Architectures
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
--add-architecture.
Compressor
This scope defines which compression formats are supported, how
compression and decompression can be performed if support for this
format isn't built into apt directly and a cost-value indicating
how costly it is to compress something in this format. As an
example the following configuration stanza would allow apt to
download and uncompress as well as create and store files with the
low-cost .reversed file extension which it will pass to the command
rev without additional commandline parameters for compression and
uncompression:
Build-Profiles
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
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-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
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.
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-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
disabled.
Build-Essential
Defines which packages 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 as well as the various "acquire methods" responsible for the download itself (see also sources.list(5)). Check-Valid-Until 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. The Check-Valid-Until option of sources.list(5) entries should be preferred to disable the check selectively instead of using this global override. Max-ValidTime 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 name. Preferably, the same can be achieved for specific sources.list(5) entries by using the Valid-Until-Max option there. Min-ValidTime 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. Preferably, the same can be achieved for specific sources.list(5) entries by using the Valid-Until-Min option there. PDiffs Try to download deltas called PDiffs for indexes (like Packages files) instead of downloading whole ones. True by default. Preferably, this can be set for specific sources.list(5) entries or index files by using the PDiffs option there. 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. By-Hash Try to download indexes via an URI constructed from a hashsum of the expected file rather than downloaded via a well-known stable filename. True by default, but automatically disabled if the source indicates no support for it. Usage can be forced with the special value "force". Preferably, this can be set for specific sources.list(5) entries or index files by using the By-Hash option there. 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::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 8.1.2.2) which can be beneficial e.g. on high-latency connections. It specifies how many requests are sent in a pipeline. APT tries to detect and workaround misbehaving webservers and proxies at runtime, but if you know that yours does not conform to the HTTP/1.1 specification pipelining can be disabled by setting the value to 0. It is enabled by default with the value 10. 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. The first and only parameter is an URI denoting the host to be contacted to allow for host-specific configuration. APT expects the command to output the proxy on stdout as a single line in the style http://proxy:port/ or the word DIRECT if no proxy should be used. No output indicates that the generic proxy settings should be used. Note that auto-detection will not be used for a host if a host-specific proxy configuration is already 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. https 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 option. ftp 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. cdrom 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 put /cdrom/::Mount "foo"; within the cdrom block. It is important to have the trailing slash. Unmount commands can be specified using UMount. gpgv For GPGV URIs the only configurable option is gpgv::Options, which passes additional parameters to gpgv. CompressionTypes 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 and recompress many common formats like xz and gzip; with this scope the supported formats can be queried, modified as well as support for more formats added (see also APT::Compressor). 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 - 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 all other compression formats. If xz should be preferred over gzip and bzip2 the configure setting should look like this: Acquire::CompressionTypes::Order { "xz"; "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 and support for this format isn't directly built into apt, 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 mirrors. GzipIndexes 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. Languages 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"). ForceIPv4 When downloading, force to use only the IPv4 protocol. ForceIPv6 When downloading, force to use only the IPv6 protocol. MaxReleaseFileSize The maximum file size of Release/Release.gpg/InRelease files. The default is 10MB. EnableSrvRecords This option controls if apt will use the DNS SRV server record as specified in RFC 2782 to select an alternative server to connect to. The default is "true". AllowInsecureRepositories Allow update operations to load data files from repositories without sufficient security information. The default value is "false". Concept, implications as well as alternatives are detailed in apt-secure(8). AllowWeakRepositories Allow update operations to load data files from repositories which provide security information, but these are deemed no longer cryptographically strong enough. The default value is "false". Concept, implications as well as alternatives are detailed in apt- secure(8). AllowDowngradeToInsecureRepositories Allow that a repository that was previously gpg signed to become unsigned during an update operation. When there is no valid signature for a previously trusted repository apt will refuse the update. This option can be used to override this protection. You almost certainly never want to enable this. The default is false. Concept, implications as well as alternatives are detailed in apt- secure(8). Changelogs::URI scope Acquiring changelogs can only be done if an URI is known from where to get them. Preferable the Release file indicates this in a 'Changelogs' field. If this isn't available the Label/Origin field of the Release file is used to check if a Acquire::Changelogs::URI::Label::LABEL or Acquire::Changelogs::URI::Origin::ORIGIN option exists and if so this value is taken. The value in the Release file can be overridden with Acquire::Changelogs::URI::Override::Label::LABEL or Acquire::Changelogs::URI::Override::Origin::ORIGIN. The value should be a normal URI to a text file, except that package specific data is replaced with the placeholder @CHANGEPATH@. The value for it is: 1. if the package is from a component (e.g. main) this is the first part otherwise it is omitted, 2. the first letter of source package name, except if the source package name starts with 'lib' in which case it will be the first four letters. 3. The complete source package name. 4. the complete name again and 5. the source version. The first (if present), second, third and fourth part are separated by a slash ('/') and between the fourth and fifth part is an underscore ('_'). The special value 'no' is available for this option indicating that this source can't be used to acquire changelog files from. Another source will be tried if available in this case.
BINARY SPECIFIC CONFIGURATION
Especially with the introduction of the apt binary it can be useful to set certain options only for a specific binary as even options which look like they would effect only a certain binary like APT::Get::Show-Versions effect apt-get as well as apt. Setting an option for a specific binary only can be achieved by setting the option inside the Binary::specific-binary scope. Setting the option APT::Get::Show-Versions for the apt only can e.g. by done by setting Binary::apt::APT::Get::Show-Versions instead. Note that as seen in the DESCRIPTION section further above you can't set binary-specific options on the commandline itself nor in configuration files loaded via the commandline.
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(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-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 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. If you want to prefix only relative paths, set Dir instead. 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.
APT IN DSELECT
When APT is used as a dselect(1) method several configuration directives control the default behavior. 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 are passed to apt-get(8) as command line options when it is run for the install phase. Updateoptions The contents of this variable are 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(1) will always prompt to continue. The default is to prompt only on error.
HOW APT CALLS DPKG(1)
Several configuration directives control how APT invokes dpkg(1). These are in the DPkg section. options 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. Pre-Install-Pkgs 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 sends more information through the requested file descriptor: a line with the text VERSION 2, the APT configuration space, and a list of package actions with filename and version information. Each configuration directive line has the form key=value. Special characters (equal signs, newlines, nonprintable characters, quotation marks, and percent signs in key and newlines, nonprintable characters, and percent signs in value) are %-encoded. Lists are represented by multiple key::=value lines with the same key. The configuration section ends with a blank line. Package action lines consist of five fields in Version 2: package name (without architecture qualification even if foreign), old version, direction of version change (< for upgrades, > for downgrades, = for no change), new version, action. The version fields are "-" for no version at all (for example when installing a package for the first time; no version is treated as earlier than any real version, so that is an upgrade, indicated as - < 1.23.4). The action field is "**CONFIGURE**" if the package is being configured, "**REMOVE**" if it is being removed, or the filename of a .deb file if it is being unpacked. In Version 3 after each version field follows the architecture of this version, which is "-" if there is no version, and a field showing the MultiArch type "same", "foreign", "allowed" or "none". Note that "none" is an incorrect typename which is just kept to remain compatible, it should be read as "no" and users are encouraged to support both. 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. Run-Directory APT chdirs to this directory before invoking dpkg(1), 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. DPkg::ConfigurePending 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 by default, but deactivating it could be useful if you want to run APT multiple times in a row - e.g. in an installer. In this scenario you could deactivate this option in all but the last run.
PERIODIC AND ARCHIVES OPTIONS
APT::Periodic and APT::Archives groups of options configure behavior of apt periodic updates, which is done by the /usr/lib/apt/apt.systemd.daily script. See the top 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(1).
* Debug::IdentCdrom disables the inclusion of statfs data in CD-ROM
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(8).
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 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
in.
Debug::pkgDPkgPM
When invoking dpkg(1), 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(1) 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(1).
Debug::pkgPackageManager
Output status messages tracing the steps performed when invoking
dpkg(1).
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::RunScripts
Display the external commands that are called by apt hooks. This
includes e.g. the config options DPkg::{Pre,Post}-Invoke or
APT::Update::{Pre,Post}-Invoke.
EXAMPLES
/usr/share/doc/apt/examples/configure-index.gz is a configuration file showing example values for all possible options.
FILES
/etc/apt/apt.conf
APT configuration file. Configuration Item: Dir::Etc::Main.
/etc/apt/apt.conf.d/
APT configuration file fragments. Configuration Item:
Dir::Etc::Parts.
SEE ALSO
apt-cache(8), apt-config(8), apt_preferences(5).
BUGS
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.
AUTHORS
Jason Gunthorpe
APT team
Daniel Burrows <dburrows@debian.org>
Initial documentation of Debug::*.
NOTES
1. APT bug page
http://bugs.debian.org/src:apt
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