Chapter 4. Source packages

Table of Contents

4.1. Standards conformance
4.2. Package relationships
4.3. Changes to the upstream sources
4.4. Debian changelog: debian/changelog
4.5. Copyright: debian/copyright
4.6. Error trapping in makefiles
4.7. Time Stamps
4.8. Restrictions on objects in source packages
4.9. Main building script: debian/rules
4.9.1. debian/rules and DEB_BUILD_OPTIONS
4.10. Variable substitutions: debian/substvars
4.11. Optional upstream source location: debian/watch
4.12. Generated files list: debian/files
4.13. Convenience copies of code
4.14. Source package handling: debian/README.source

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This information may be used to file bug reports automatically if your package becomes too much out of date.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 Section 5.6.11, “Standards-Version.

You should regularly, and especially if your package has become out of date, check for the newest Policy Manual available and update your package, if necessary.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. [13]

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). [14]

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. [15]

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.

Chapter 7, Declaring relationships between packages 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 Section 11.1, “Architecture specification strings” for details).

If your package includes the scripts config.sub and config.guess, you should arrange for the versions provided by the package autotools-dev be used instead (see autotools-dev documentation for details how to achieve that). This ensures that these files can be updated distribution-wide at build time when introducing new architectures.

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. [16] This includes modifications made in the Debian package compared to the upstream one as well as other changes and updates to the package. [17]

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 Section 5.6.14, “Distribution.

urgency is the value for the Urgency field in the .changes file for the upload (see Section 5.6.17, “Urgency). 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. [18] This information is conveyed via the Closes field in the .changes file (see Section 5.6.22, “Closes).

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. [19] The information here will be copied to the Changed-By field in the .changes file (see Section 5.6.4, “Changed-By), and then later used to send an acknowledgement when the upload has been installed.

The date has the following format [20] (compatible and with the same semantics of RFC 2822 and RFC 5322):

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

where:

  • day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun

  • dd is a one- or two-digit day of the month (01-31)

  • month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec

  • yyyy is the four-digit year (e.g. 2010)

  • hh is the two-digit hour (00-23)

  • mm is the two-digit minutes (00-59)

  • ss is the two-digit seconds (00-60)

  • +zzzz or -zzzz is the time zone offset from Coordinated Universal Time (UTC). "+" indicates that the time is ahead of (i.e., east of) UTC and "-" indicates that the time is behind (i.e., west of) UTC. The first two digits indicate the hour difference from UTC and the last two digits indicate the number of additional minutes difference from UTC. The last two digits must be in the range 00-59.

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 Section 12.7, “Changelog files”.

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 Section 12.5, “Copyright information” for further details). Also see Section 2.3, “Copyright considerations” 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. [21]

4.8. Restrictions on objects in source packages

The source package may not contain any hard links, [22] device special files, sockets or setuid or setgid files. [23]

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.

For packages in the main archive, no required targets may attempt network access.

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. [24]

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

The build-arch target must perform all the configuration and compilation required for producing all architecture-dependent 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. [25]

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, 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. [26]

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).

The clean target cannot be used to remove files in the source tree that are not compatible with the DFSG. This is because the files would remain in the upstream tarball, and thus in the source package, so the source package would continue to violate DFSG. Instead, the upstream source should be repacked to remove those files.

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 Section 4.14, “ Source package handling: debian/README.source.

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. The target architecture is the architecture of the packages that the compiler currently being built will generate. 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), building a cross-compiler (a compiler package that will generate objects for one architecture, built on a machine of a different architecture) or a Canadian cross-compiler (a compiler that will generate objects for one architecture, built on a machine of a different architecture, that will run on yet a different architecture).

Here is a list of supported make variables:

  • DEB_*_ARCH (the Debian architecture)

  • DEB_*_ARCH_CPU (the Debian CPU name)

  • DEB_*_ARCH_BITS (the Debian CPU pointer size in bits)

  • DEB_*_ARCH_ENDIAN (the Debian CPU endianness)

  • DEB_*_ARCH_OS (the Debian System name)

  • DEB_*_GNU_TYPE (the GNU style architecture specification string)

  • DEB_*_GNU_CPU (the CPU part of DEB_*_GNU_TYPE)

  • DEB_*_GNU_SYSTEM (the System part of DEB_*_GNU_TYPE)

where * is either BUILD for specification of the build architecture, HOST for specification of the host architecture or TARGET for specification of the target 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. [27] 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.

nodoc

This tag says to skip any build steps that only generate package documentation. Files required by other sections of Debian Policy, such as copyright and changelog files, must still be generated and put in the package, but other generated documentation such as help2man-generated pages, Doxygen-generated API documentation, or info pages generated from Texinfo sources should be skipped if possible. This option does not change the set of binary packages generated by the source package, but documentation-only binary packages may be nearly empty when built with this option.

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. [28] 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) [29] 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. [30] 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. [31]

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 Section 4.9, “Main building script: debian/rules.

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

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

  4. 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).



[13] See the file upgrading-checklist for information about policy which has changed between different versions of this document.

[14] Rationale:

  • This allows maintaining the list separately from the policy documents (the list does not need the kind of control that the policy documents do).

  • Having a separate package allows one to install the build-essential packages on a machine, as well as allowing other packages such as tasks to require installation of the build-essential packages using the depends relation.

  • The separate package allows bug reports against the list to be categorized separately from the policy management process in the BTS.

[15] The reason for this is that dependencies change, and you should list all those packages, and only those packages that you need directly. What others need is their business. For example, if you only link against libimlib, you will need to build-depend on libimlib2-dev but not against any libjpeg* packages, even though libimlib2-dev currently depends on them: installation of libimlib2-dev will automatically ensure that all of its run-time dependencies are satisfied.

[16] Mistakes in changelogs are usually best rectified by making a new changelog entry rather than "rewriting history" by editing old changelog entries.

[17] Although there is nothing stopping an author who is also the Debian maintainer from using this changelog for all their changes, it will have to be renamed if the Debian and upstream maintainers become different people. In such a case, however, it might be better to maintain the package as a non-native package.

[18] To be precise, the string should match the following Perl regular expression:

/closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i

Then all of the bug numbers listed will be closed by the archive maintenance software (dak) using the version of the changelog entry.

[19] In the case of a sponsored upload, the uploader signs the files, but the changelog maintainer name and address are those of the person who prepared this release. If the preparer of the release is not one of the usual maintainers of the package (as listed in the Maintainer or Uploaders control fields of the package), the first line of the changelog is conventionally used to explain why a non-maintainer is uploading the package. The Debian Developer's Reference (see Section 1.4, “Related documents”) documents the conventions used.

[20] This is the same as the format generated by date -R.

[21] The rationale is that there is some information conveyed by knowing the age of the file, for example, you could recognize that some documentation is very old by looking at the modification time, so it would be nice if the modification time of the upstream source would be preserved.

[22] This is not currently detected when building source packages, but only when extracting them.

Hard links may be permitted at some point in the future, but would require a fair amount of work.

[23] Setgid directories are allowed.

[24] Another common way to do this is for build to depend on build-stamp and to do nothing else, and for the build-stamp target to do the building and to touch build-stamp on completion. This is especially useful if the build routine creates a file or directory called build; in such a case, build will need to be listed as a phony target (i.e., as a dependency of the .PHONY target). See the documentation of make for more information on phony targets.

[25] This split allows binary-only builds to not install the dependencies required for the build-indep target and skip any resource-intensive build tasks that are only required when building architecture-independent binary packages.

[26] The fakeroot package often allows one to build a package correctly even without being root.

[27] Some packages support any delimiter, but whitespace is the easiest to parse inside a makefile and avoids ambiguity with flag values that contain commas.

[28] Packages built with make can often implement this by passing the -jn option to make.

[29] files.new is used as a temporary file by dpkg-gencontrol and dpkg-distaddfile - they write a new version of files here before renaming it, to avoid leaving a corrupted copy if an error occurs.

[30] For example, parts of the GNU build system work like this.

[31] Having multiple copies of the same code in Debian is inefficient, often creates either static linking or shared library conflicts, and, most importantly, increases the difficulty of handling security vulnerabilities in the duplicated code.