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Debian Policy Manual
Chapter 4 - Source packages


4.1 Standards conformance

Source packages should specify the most recent version number of this policy document with which your package complied when it was last updated.

This information may be used to file bug reports automatically if your package becomes too much out of date.

The version is specified in the Standards-Version control field. The format of the Standards-Version field is described in Standards-Version, Section 5.6.11.

You should regularly, and especially if your package has become out of date, check for the newest Policy Manual available and update your package, if necessary. When your package complies with the new standards you should update the Standards-Version source package field and release it.[12]


4.2 Package relationships

Source packages should specify which binary packages they require to be installed or not to be installed in order to build correctly. For example, if building a package requires a certain compiler, then the compiler should be specified as a build-time dependency.

It is not necessary to explicitly specify build-time relationships on a minimal set of packages that are always needed to compile, link and put in a Debian package a standard "Hello World!" program written in C or C++. The required packages are called build-essential, and an informational list can be found in /usr/share/doc/build-essential/list (which is contained in the build-essential package).[13]

When specifying the set of build-time dependencies, one should list only those packages explicitly required by the build. It is not necessary to list packages which are required merely because some other package in the list of build-time dependencies depends on them.[14]

If build-time dependencies are specified, it must be possible to build the package and produce working binaries on a system with only essential and build-essential packages installed and also those required to satisfy the build-time relationships (including any implied relationships). In particular, this means that version clauses should be used rigorously in build-time relationships so that one cannot produce bad or inconsistently configured packages when the relationships are properly satisfied.

Declaring relationships between packages, Chapter 7 explains the technical details.


4.3 Changes to the upstream sources

If changes to the source code are made that are not specific to the needs of the Debian system, they should be sent to the upstream authors in whatever form they prefer so as to be included in the upstream version of the package.

If you need to configure the package differently for Debian or for Linux, and the upstream source doesn't provide a way to do so, you should add such configuration facilities (for example, a new autoconf test or #define) and send the patch to the upstream authors, with the default set to the way they originally had it. You can then easily override the default in your debian/rules or wherever is appropriate.

You should make sure that the configure utility detects the correct architecture specification string (refer to Architecture specification strings, Section 11.1 for details).

If you need to edit a Makefile where GNU-style configure scripts are used, you should edit the .in files rather than editing the Makefile directly. This allows the user to reconfigure the package if necessary. You should not configure the package and edit the generated Makefile! This makes it impossible for someone else to later reconfigure the package without losing the changes you made.


4.4 Debian changelog: debian/changelog

Changes in the Debian version of the package should be briefly explained in the Debian changelog file debian/changelog.[15] This includes modifications made in the Debian package compared to the upstream one as well as other changes and updates to the package. [16]

The format of the debian/changelog allows the package building tools to discover which version of the package is being built and find out other release-specific information.

That format is a series of entries like this:

     package (version) distribution(s); urgency=urgency
     	    [optional blank line(s), stripped]
       * change details
         more change details
     	    [blank line(s), included in output of dpkg-parsechangelog]
       * even more change details
     	    [optional blank line(s), stripped]
      -- maintainer name <email address>[two spaces]  date

package and version are the source package name and version number.

distribution(s) lists the distributions where this version should be installed when it is uploaded - it is copied to the Distribution field in the .changes file. See Distribution, Section 5.6.14.

urgency is the value for the Urgency field in the .changes file for the upload (see Urgency, Section 5.6.17). It is not possible to specify an urgency containing commas; commas are used to separate keyword=value settings in the dpkg changelog format (though there is currently only one useful keyword, urgency).

The change details may in fact be any series of lines starting with at least two spaces, but conventionally each change starts with an asterisk and a separating space and continuation lines are indented so as to bring them in line with the start of the text above. Blank lines may be used here to separate groups of changes, if desired.

If this upload resolves bugs recorded in the Bug Tracking System (BTS), they may be automatically closed on the inclusion of this package into the Debian archive by including the string: closes: Bug#nnnnn in the change details.[17] This information is conveyed via the Closes field in the .changes file (see Closes, Section 5.6.22).

The maintainer name and email address used in the changelog should be the details of the person who prepared this release of the package. They are not necessarily those of the uploader or usual package maintainer.[18] The information here will be copied to the Changed-By field in the .changes file (see Changed-By, Section 5.6.4), and then later used to send an acknowledgement when the upload has been installed.

The date has the following format[19] (compatible and with the same semantics of RFC 2822 and RFC 5322):

     day-of-week, dd month yyyy hh:mm:ss +zzzz

where:

The first "title" line with the package name must start at the left hand margin. The "trailer" line with the maintainer and date details must be preceded by exactly one space. The maintainer details and the date must be separated by exactly two spaces.

The entire changelog must be encoded in UTF-8.

For more information on placement of the changelog files within binary packages, please see Changelog files, Section 12.7.


4.5 Copyright: debian/copyright

Every package must be accompanied by a verbatim copy of its copyright information and distribution license in the file /usr/share/doc/package/copyright (see Copyright information, Section 12.5 for further details). Also see Copyright considerations, Section 2.3 for further considerations related to copyrights for packages.


4.6 Error trapping in makefiles

When make invokes a command in a makefile (including your package's upstream makefiles and debian/rules), it does so using sh. This means that sh's usual bad error handling properties apply: if you include a miniature script as one of the commands in your makefile you'll find that if you don't do anything about it then errors are not detected and make will blithely continue after problems.

Every time you put more than one shell command (this includes using a loop) in a makefile command you must make sure that errors are trapped. For simple compound commands, such as changing directory and then running a program, using && rather than semicolon as a command separator is sufficient. For more complex commands including most loops and conditionals you should include a separate set -e command at the start of every makefile command that's actually one of these miniature shell scripts.


4.7 Time Stamps

Maintainers should preserve the modification times of the upstream source files in a package, as far as is reasonably possible.[20]


4.8 Restrictions on objects in source packages

The source package may not contain any hard links[21], device special files, sockets or setuid or setgid files.[22]


4.9 Main building script: debian/rules

This file must be an executable makefile, and contains the package-specific recipes for compiling the package and building binary package(s) from the source.

It must start with the line #!/usr/bin/make -f, so that it can be invoked by saying its name rather than invoking make explicitly. That is, invoking either of make -f debian/rules args... or ./debian/rules args... must result in identical behavior.

The following targets are required and must be implemented by debian/rules: clean, binary, binary-arch, binary-indep, build, build-arch and build-indep. These are the targets called by dpkg-buildpackage.

Since an interactive debian/rules script makes it impossible to auto-compile that package and also makes it hard for other people to reproduce the same binary package, all required targets must be non-interactive. It also follows that any target that these targets depend on must also be non-interactive.

The targets are as follows:

build (required)

The build target should perform all the configuration and compilation of the package. If a package has an interactive pre-build configuration routine, the Debian source package must either be built after this has taken place (so that the binary package can be built without rerunning the configuration) or the configuration routine modified to become non-interactive. (The latter is preferable if there are architecture-specific features detected by the configuration routine.)

For some packages, notably ones where the same source tree is compiled in different ways to produce two binary packages, the build target does not make much sense. For these packages it is good enough to provide two (or more) targets (build-a and build-b or whatever) for each of the ways of building the package, and a build target that does nothing. The binary target will have to build the package in each of the possible ways and make the binary package out of each.

The build target must not do anything that might require root privilege.

The build target may need to run the clean target first - see below.

When a package has a configuration and build routine which takes a long time, or when the makefiles are poorly designed, or when build needs to run clean first, it is a good idea to touch build when the build process is complete. This will ensure that if debian/rules build is run again it will not rebuild the whole program.[23]

build-arch (required), build-indep (required)

The build-arch target must perform all the configuration and compilation required for producing all architecture-dependant binary packages (those packages for which the body of the Architecture field in debian/control is not all). Similarly, the build-indep target must perform all the configuration and compilation required for producing all architecture-independent binary packages (those packages for which the body of the Architecture field in debian/control is all). The build target should either depend on those targets or take the same actions as invoking those targets would perform.[24]

The build-arch and build-indep targets must not do anything that might require root privilege.

binary (required), binary-arch (required), binary-indep (required)

The binary target must be all that is necessary for the user to build the binary package(s) produced from this source package. It is split into two parts: binary-arch builds the binary packages which are specific to a particular architecture, and binary-indep builds those which are not.

binary may be (and commonly is) a target with no commands which simply depends on binary-arch and binary-indep.

Both binary-* targets should depend on the build target, or on the appropriate build-arch or build-indep target, if provided, so that the package is built if it has not been already. It should then create the relevant binary package(s), using dpkg-gencontrol to make their control files and dpkg-deb to build them and place them in the parent of the top level directory.

Both the binary-arch and binary-indep targets must exist. If one of them has nothing to do (which will always be the case if the source generates only a single binary package, whether architecture-dependent or not), it must still exist and must always succeed.

The binary targets must be invoked as root.[25]

clean (required)

This must undo any effects that the build and binary targets may have had, except that it should leave alone any output files created in the parent directory by a run of a binary target.

If a build file is touched at the end of the build target, as suggested above, it should be removed as the first action that clean performs, so that running build again after an interrupted clean doesn't think that everything is already done.

The clean target may need to be invoked as root if binary has been invoked since the last clean, or if build has been invoked as root (since build may create directories, for example).

get-orig-source (optional)

This target fetches the most recent version of the original source package from a canonical archive site (via FTP or WWW, for example), does any necessary rearrangement to turn it into the original source tar file format described below, and leaves it in the current directory.

This target may be invoked in any directory, and should take care to clean up any temporary files it may have left.

This target is optional, but providing it if possible is a good idea.

patch (optional)

This target performs whatever additional actions are required to make the source ready for editing (unpacking additional upstream archives, applying patches, etc.). It is recommended to be implemented for any package where dpkg-source -x does not result in source ready for additional modification. See Source package handling: debian/README.source, Section 4.14.

The build, binary and clean targets must be invoked with the current directory being the package's top-level directory.

Additional targets may exist in debian/rules, either as published or undocumented interfaces or for the package's internal use.

The architectures we build on and build for are determined by make variables using the utility dpkg-architecture. You can determine the Debian architecture and the GNU style architecture specification string for the build architecture as well as for the host architecture. The build architecture is the architecture on which debian/rules is run and the package build is performed. The host architecture is the architecture on which the resulting package will be installed and run. These are normally the same, but may be different in the case of cross-compilation (building packages for one architecture on machines of a different architecture).

Here is a list of supported make variables:

where * is either BUILD for specification of the build architecture or HOST for specification of the host architecture.

Backward compatibility can be provided in the rules file by setting the needed variables to suitable default values; please refer to the documentation of dpkg-architecture for details.

It is important to understand that the DEB_*_ARCH string only determines which Debian architecture we are building on or for. It should not be used to get the CPU or system information; the DEB_*_ARCH_CPU and DEB_*_ARCH_OS variables should be used for that. GNU style variables should generally only be used with upstream build systems.


4.9.1 debian/rules and DEB_BUILD_OPTIONS

Supporting the standardized environment variable DEB_BUILD_OPTIONS is recommended. This variable can contain several flags to change how a package is compiled and built. Each flag must be in the form flag or flag=options. If multiple flags are given, they must be separated by whitespace.[26] flag must start with a lowercase letter (a-z) and consist only of lowercase letters, numbers (0-9), and the characters - and _ (hyphen and underscore). options must not contain whitespace. The same tag should not be given multiple times with conflicting values. Package maintainers may assume that DEB_BUILD_OPTIONS will not contain conflicting tags.

The meaning of the following tags has been standardized:

nocheck

This tag says to not run any build-time test suite provided by the package.

noopt

The presence of this tag means that the package should be compiled with a minimum of optimization. For C programs, it is best to add -O0 to CFLAGS (although this is usually the default). Some programs might fail to build or run at this level of optimization; it may be necessary to use -O1, for example.

nostrip

This tag means that the debugging symbols should not be stripped from the binary during installation, so that debugging information may be included in the package.

parallel=n

This tag means that the package should be built using up to n parallel processes if the package build system supports this.[27] If the package build system does not support parallel builds, this string must be ignored. If the package build system only supports a lower level of concurrency than n, the package should be built using as many parallel processes as the package build system supports. It is up to the package maintainer to decide whether the package build times are long enough and the package build system is robust enough to make supporting parallel builds worthwhile.

Unknown flags must be ignored by debian/rules.

The following makefile snippet is an example of how one may implement the build options; you will probably have to massage this example in order to make it work for your package.

     CFLAGS = -Wall -g
     INSTALL = install
     INSTALL_FILE    = $(INSTALL) -p    -o root -g root  -m  644
     INSTALL_PROGRAM = $(INSTALL) -p    -o root -g root  -m  755
     INSTALL_SCRIPT  = $(INSTALL) -p    -o root -g root  -m  755
     INSTALL_DIR     = $(INSTALL) -p -d -o root -g root  -m  755
     
     ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
         CFLAGS += -O0
     else
         CFLAGS += -O2
     endif
     ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
         INSTALL_PROGRAM += -s
     endif
     ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
         NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
         MAKEFLAGS += -j$(NUMJOBS)
     endif
     
     build:
     	# ...
     ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
     	# Code to run the package test suite.
     endif

4.10 Variable substitutions: debian/substvars

When dpkg-gencontrol generates binary package control files (DEBIAN/control), it performs variable substitutions on its output just before writing it. Variable substitutions have the form ${variable}. The optional file debian/substvars contains variable substitutions to be used; variables can also be set directly from debian/rules using the -V option to the source packaging commands, and certain predefined variables are also available.

The debian/substvars file is usually generated and modified dynamically by debian/rules targets, in which case it must be removed by the clean target.

See deb-substvars(5) for full details about source variable substitutions, including the format of debian/substvars.


4.11 Optional upstream source location: debian/watch

This is an optional, recommended configuration file for the uscan utility which defines how to automatically scan ftp or http sites for newly available updates of the package. This is used Debian QA tools to help with quality control and maintenance of the distribution as a whole.


4.12 Generated files list: debian/files

This file is not a permanent part of the source tree; it is used while building packages to record which files are being generated. dpkg-genchanges uses it when it generates a .changes file.

It should not exist in a shipped source package, and so it (and any backup files or temporary files such as files.new[28]) should be removed by the clean target. It may also be wise to ensure a fresh start by emptying or removing it at the start of the binary target.

When dpkg-gencontrol is run for a binary package, it adds an entry to debian/files for the .deb file that will be created when dpkg-deb --build is run for that binary package. So for most packages all that needs to be done with this file is to delete it in the clean target.

If a package upload includes files besides the source package and any binary packages whose control files were made with dpkg-gencontrol then they should be placed in the parent of the package's top-level directory and dpkg-distaddfile should be called to add the file to the list in debian/files.


4.13 Convenience copies of code

Some software packages include in their distribution convenience copies of code from other software packages, generally so that users compiling from source don't have to download multiple packages. Debian packages should not make use of these convenience copies unless the included package is explicitly intended to be used in this way.[29] If the included code is already in the Debian archive in the form of a library, the Debian packaging should ensure that binary packages reference the libraries already in Debian and the convenience copy is not used. If the included code is not already in Debian, it should be packaged separately as a prerequisite if possible. [30]


4.14 Source package handling: debian/README.source

If running dpkg-source -x on a source package doesn't produce the source of the package, ready for editing, and allow one to make changes and run dpkg-buildpackage to produce a modified package without taking any additional steps, creating a debian/README.source documentation file is recommended. This file should explain how to do all of the following:

  1. Generate the fully patched source, in a form ready for editing, that would be built to create Debian packages. Doing this with a patch target in debian/rules is recommended; see Main building script: debian/rules, Section 4.9.

  1. Modify the source and save those modifications so that they will be applied when building the package.

  1. Remove source modifications that are currently being applied when building the package.

  1. Optionally, document what steps are necessary to upgrade the Debian source package to a new upstream version, if applicable.

This explanation should include specific commands and mention any additional required Debian packages. It should not assume familiarity with any specific Debian packaging system or patch management tools.

This explanation may refer to a documentation file installed by one of the package's build dependencies provided that the referenced documentation clearly explains these tasks and is not a general reference manual.

debian/README.source may also include any other information that would be helpful to someone modifying the source package. Even if the package doesn't fit the above description, maintainers are encouraged to document in a debian/README.source file any source package with a particularly complex or unintuitive source layout or build system (for example, a package that builds the same source multiple times to generate different binary packages).


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Debian Policy Manual

version 3.9.6.1, 2014-11-22

The Debian Policy Mailing List