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The Debian distribution is based on the Debian package management system,
dpkg. Thus, all packages in the Debian distribution must
be provided in the .deb file format.
A .deb package contains two sets of files: a set of files to
install on the system when the package is installed, and a set of files that
provide additional metadata about the package or which are executed when the
package is installed or removed. This second set of files is called
control information files. Among those files are the package
maintainer scripts and
control, the binary package control
file that contains the control fields for the package. Other control
information files include the
symbols file or
file used to store shared library dependency information and the
conffiles file that lists the package's configuration files
(described in Configuration files,
There is unfortunately a collision of terminology here between control
information files and files in the Debian control file format. Throughout this
document, a control file refers to a file in the Debian control file
format. These files are documented in Control
files and their fields, Chapter 5. Only files referred to specifically as
control information files are the files included in the control
information file member of the
.deb file format used by binary
packages. Most control information files are not in the Debian control file
Every package must have a name that's unique within the Debian archive.
The package name is included in the control field Package, the format of which is described in Package, Section 5.6.7. The package name is also included as a part of the file name of the .deb file.
Every package has a version number recorded in its Version control file field, described in Version, Section 5.6.12.
The package management system imposes an ordering on version numbers, so that it can tell whether packages are being up- or downgraded and so that package system front end applications can tell whether a package it finds available is newer than the one installed on the system. The version number format has the most significant parts (as far as comparison is concerned) at the beginning.
If an upstream package has problematic version numbers they should be converted to a sane form for use in the Version field.
In general, Debian packages should use the same version numbers as the upstream
sources. However, upstream version numbers based on some date formats
(sometimes used for development or "snapshot" releases) will not be
ordered correctly by the package management software. For example,
dpkg will consider "96May01" to be greater than
To prevent having to use epochs for every new upstream version, the date-based portion of any upstream version number should be given in a way that sorts correctly: four-digit year first, followed by a two-digit numeric month, followed by a two-digit numeric date, possibly with punctuation between the components.
Native Debian packages (i.e., packages which have been written especially for Debian) whose version numbers include dates should also follow these rules. If punctuation is desired between the date components, remember that hyphen (-) cannot be used in native package versions. Period (.) is normally a good choice.
Every package must have a maintainer, except for orphaned packages as described below. The maintainer may be one person or a group of people reachable from a common email address, such as a mailing list. The maintainer is responsible for maintaining the Debian packaging files, evaluating and responding appropriately to reported bugs, uploading new versions of the package (either directly or through a sponsor), ensuring that the package is placed in the appropriate archive area and included in Debian releases as appropriate for the stability and utility of the package, and requesting removal of the package from the Debian distribution if it is no longer useful or maintainable.
The maintainer must be specified in the Maintainer control field with their correct name and a working email address. The email address given in the Maintainer control field must accept mail from those role accounts in Debian used to send automated mails regarding the package. This includes non-spam mail from the bug-tracking system, all mail from the Debian archive maintenance software, and other role accounts or automated processes that are commonly agreed on by the project. If one person or team maintains several packages, they should use the same form of their name and email address in the Maintainer fields of those packages.
The format of the Maintainer control field is described in Maintainer, Section 5.6.2.
If the maintainer of the package is a team of people with a shared email address, the Uploaders control field must be present and must contain at least one human with their personal email address. See Uploaders, Section 5.6.3 for the syntax of that field.
An orphaned package is one with no current maintainer. Orphaned packages should have their Maintainer control field set to Debian QA Group <email@example.com>. These packages are considered maintained by the Debian project as a whole until someone else volunteers to take over maintenance.
Every Debian package must have a Description control field which contains a synopsis and extended description of the package. Technical information about the format of the Description field is in Description, Section 5.6.13.
The description should describe the package (the program) to a user (system administrator) who has never met it before so that they have enough information to decide whether they want to install it. This description should not just be copied verbatim from the program's documentation.
Put important information first, both in the synopsis and extended description. Sometimes only the first part of the synopsis or of the description will be displayed. You can assume that there will usually be a way to see the whole extended description.
The description should also give information about the significant dependencies and conflicts between this package and others, so that the user knows why these dependencies and conflicts have been declared.
Instructions for configuring or using the package should not be included (that is what installation scripts, manual pages, info files, etc., are for). Copyright statements and other administrivia should not be included either (that is what the copyright file is for).
The single line synopsis should be kept brief - certainly under 80 characters.
Do not include the package name in the synopsis line. The display software knows how to display this already, and you do not need to state it. Remember that in many situations the user may only see the synopsis line - make it as informative as you can.
Do not try to continue the single line synopsis into the extended description. This will not work correctly when the full description is displayed, and makes no sense where only the summary (the single line synopsis) is available.
The extended description should describe what the package does and how it relates to the rest of the system (in terms of, for example, which subsystem it is which part of).
The description field needs to make sense to anyone, even people who have no idea about any of the things the package deals with.
Every package must specify the dependency information about other packages that are required for the first to work correctly.
For example, a dependency entry must be provided for any shared libraries required by a dynamically-linked executable binary in a package.
Packages are not required to declare any dependencies they have on other packages which are marked Essential (see below), and should not do so unless they depend on a particular version of that package.
Sometimes, unpacking one package requires that another package be first unpacked and configured. In this case, the depending package must specify this dependency in the Pre-Depends control field.
You should not specify a Pre-Depends entry for a package before this has been discussed on the debian-devel mailing list and a consensus about doing that has been reached.
The format of the package interrelationship control fields is described in Declaring relationships between packages, Chapter 7.
Sometimes, there are several packages which offer more-or-less the same functionality. In this case, it's useful to define a virtual package whose name describes that common functionality. (The virtual packages only exist logically, not physically; that's why they are called virtual.) The packages with this particular function will then provide the virtual package. Thus, any other package requiring that function can simply depend on the virtual package without having to specify all possible packages individually.
All packages should use virtual package names where appropriate, and arrange to create new ones if necessary. They should not use virtual package names (except privately, amongst a cooperating group of packages) unless they have been agreed upon and appear in the list of virtual package names. (See also Virtual packages - Provides, Section 7.5)
The latest version of the authoritative list of virtual package names can be
found in the debian-policy package. It is also available from the
Debian web mirrors at
The procedure for updating the list is described in the preface to the list.
The base system is a minimum subset of the Debian system that is installed before everything else on a new system. Only very few packages are allowed to form part of the base system, in order to keep the required disk usage very small.
The base system consists of all those packages with priority required or important. Many of them will be tagged essential (see below).
Essential is defined as the minimal set of functionality that must be available and usable on the system at all times, even when packages are in an unconfigured (but unpacked) state. Packages are tagged essential for a system using the Essential control field. The format of the Essential control field is described in Essential, Section 5.6.9.
Since these packages cannot be easily removed (one has to specify an extra
force option to
dpkg to do so), this flag must not be
used unless absolutely necessary. A shared library package must not be tagged
essential; dependencies will prevent its premature removal, and we
need to be able to remove it when it has been superseded.
Since dpkg will not prevent upgrading of other packages while an essential package is in an unconfigured state, all essential packages must supply all of their core functionality even when unconfigured. If the package cannot satisfy this requirement it must not be tagged as essential, and any packages depending on this package must instead have explicit dependency fields as appropriate.
Maintainers should take great care in adding any programs, interfaces, or functionality to essential packages. Packages may assume that functionality provided by essential packages is always available without declaring explicit dependencies, which means that removing functionality from the Essential set is very difficult and is almost never done. Any capability added to an essential package therefore creates an obligation to support that capability as part of the Essential set in perpetuity.
You must not tag any packages essential before this has been discussed on the debian-devel mailing list and a consensus about doing that has been reached.
The package installation scripts should avoid producing output which is
unnecessary for the user to see and should rely on
dpkg to stave
off boredom on the part of a user installing many packages. This means,
amongst other things, using the --quiet option on
Errors which occur during the execution of an installation script must be checked and the installation must not continue after an error.
Note that in general Scripts, Section 10.4 applies to package maintainer scripts, too.
You should not use
dpkg-divert on a file belonging to another
package without consulting the maintainer of that package first. When adding
or removing diversions, package maintainer scripts must provide the
--package flag to
dpkg-divert and must not use
All packages which supply an instance of a common command name (or, in general,
filename) should generally use
update-alternatives, so that they
may be installed together. If
update-alternatives is not used,
then each package must use Conflicts to ensure that other packages
are de-installed. (In this case, it may be appropriate to specify a conflict
against earlier versions of something that previously did not use
update-alternatives; this is an exception to the usual rule that
versioned conflicts should be avoided.)
Package maintainer scripts may prompt the user if necessary. Prompting must be
done by communicating through a program, such as
conforms to the Debian Configuration Management Specification, version 2 or
Packages which are essential, or which are dependencies of essential packages, may fall back on another prompting method if no such interface is available when they are executed.
The Debian Configuration Management Specification is included in the
debconf_specification files in the
package. It is also available from the Debian web mirrors at
Packages which use the Debian Configuration Management Specification may
contain the additional control information files
config is an additional maintainer script
used for package configuration, and
templates contains templates
used for user prompting. The
config script might be run before
preinst script and before the package is unpacked or any of
its dependencies or pre-dependencies are satisfied. Therefore it must work
using only the tools present in essential packages.
Packages which use the Debian Configuration Management Specification must allow
for translation of their user-visible messages by using a gettext-based system
such as the one provided by the
Packages should try to minimize the amount of prompting they need to do, and
they should ensure that the user will only ever be asked each question once.
This means that packages should try to use appropriate shared configuration
files (such as
debconf variables rather than each prompting for their
own list of required pieces of information.
It also means that an upgrade should not ask the same questions again, unless
the user has used dpkg --purge to remove the package's
configuration. The answers to configuration questions should be stored in an
appropriate place in
/etc so that the user can modify them, and
how this has been done should be documented.
If a package has a vitally important piece of information to pass to the user
(such as "don't run me as I am, you must edit the following configuration
files first or you risk your system emitting badly-formatted messages"),
it should display this in the
script and prompt the user to hit return to acknowledge the message. Copyright
messages do not count as vitally important (they belong in
/usr/share/doc/package/copyright); neither do
instructions on how to use a program (these should be in on-line documentation,
where all the users can see them).
Any necessary prompting should almost always be confined to the
postinst script. If it is done in the
postinst, it should be protected with a conditional so that
unnecessary prompting doesn't happen if a package's installation fails and the
postinst is called with abort-upgrade,
abort-remove or abort-deconfigure.
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Debian Policy Manualversion 22.214.171.124, 2012-09-19