How to split a source Debian package into several smaller binary packages

Do not forget to read the bibliography.

Please examine the php-java-bridge /debian/* files, as this source package contains many tricks and hints leveraging debhelper scripts and avoiding pitfalls.

Ideas collected from other package sources, discussion lists, debian-mentors hints and guidance, Debian Policy, maintainers guide, man pages.

Special attention to /debian/rules and subpackage_name.* files, like php-java-bridge-j2ee.install , php-java-bridge-j2ee.dirs and so on.

The approach used is a fine grained control, specifying each control file and its contents.

Also, see the README.Debian file, containing many hints and instructions.

Please, note that this source package is a dynamic work in progress, constantly evolving. All suggestions are welcome at the php-java-bridge-users mailing list.

This text concept is explaining from bottom to up abstraction level building the packages.

= Readings =

Splitting a Debian source package into several smaller binary packages is not trivial.

Before you start, you must read the essential guides [1] to [7], [10] to [12], [19], [29], [30] and feeling already comfortable creating single binary packages.

= Variables in rules makefile =


You must remember that /debian/rules is a makefile. It is not a shell batch script.

Read the following code:

  • * Variables MUST be set outside target rules
  • * Target rules MUST start at column 1, then followed by ":"
  • * Actions MUST start after a TAB, not blank spaces

The BUILDDIR was set to allow use of dh_install for .war files.

The Debian package makefile must be fully relocatable.

The build directory must be at a package tool discretion (usually at some source temporary subdirectory) and must not need root privileges.

For the installation, the destination directory MUST NOT be hard coded into the source.

If the upstream source has hardcoded directories, you must apply patches even before the configure target rule.

You must know the different types of makefile variables reading [20].

The effects of using a simply expanded variable ( := ) or a recursively expanded variable ( = ) are very different in a rules makefile.

At our example we want the simply expanded variable behaviour.

= Shell command output into rules makefile =

We want also collect some shell command output into some variables. [21]

There are some misconceptions that you should avoid [27].

= Leveraging dpatch =

dpatch is a clever development tool. Its use is not limited nor specific to multiple binary packages. You could use it for single binary packages too. This topic could be safely skipped if you do not intend to modify upstream code.

If you must have to apply some modifications to the upstream code before packaging for Debian, then one of the easiest modes is to use dpatch.

When you execute dpatch in a shell prompt, it opens a session and from now on until you exit the session, all you do will be recorded and converted to a patch for your upstream code into /debian/patches directory.

A good practice is to create small patches with clear, self explanatory and different names.
For example, 10_relocate_build , 20_relocate_install, 30_correct_env_variable.

You must read the dpatch man page.

The following code snippet will apply the patches to source, walking through all patches into /debian/patches directory in the ascendant patchnamefile order.

And then stamp the configure step.

= Cleaning and deapplying patches =

You must have a clean rule.
Also, if you applied patches, you must deapply them in reverse order.

The dpatch helper will take care of this if you created the patches in a planned naming convention.

= Compiling the binaries =

The rule calls the "configure" rule and then test if it is at the correct directory for the step and if the /debian/control file exists. 
Finally, touch the build-stamp file.


= The phony targets =

You must read the Make Manual, about phony targets [28].

Here, we intend to use them as like "subroutines".


= The relocatable install =

Now we will use the "dirs" file and some inline commands to install into the relocated tree.

The "dirs" file is applicable to the default package, the first target rule.
The debhelper dh_installdirs will create the listed directories if they not exist.

Please, note the -k option for dh_clean. It keeps the files between binary packages generations. Study the man page for this and other options.


This "installini" rule will be used to install some files in desired directories.

This rule could be substituded by a suitable "binary_package_name.install" file, used by dh_install.

Note the absence of leading "/" (for relocation) and one per line to avoid jumping to next rule (a debhelper behaviour of this version).

= The spliting begins =

The compiled code is installed (almost) as the original upstream code intended.

It was sanely relocated.

Now you will distribute the installed files inside the multiple binary packages.

== The first binary independent target ==

/debian/php-java-bridge-j2ee.dirs file

/debian/ file

/debian/php-java-bridge-j2ee.install file for some file almost moved "by hand" after the make install. You use this file with dh_install instead a mv or cp.

Note the -p$@ to use target name package files in /debian as parameters. [24]

Note the inline dh_install using dynamic variables referring to some directory configured at the begining of the rule file. [23]

Note the use of -i option, indicating a binary architecture independent package.

The inline code does not have a leading "/" for relocating.

See how debhelper apps is leveraged, executing the hard detailed work for you.

Also, the /debian/control file must have some special variables for use here. [22] If they are not used, only a warning will be issued. They do not make harm. For sake of future builds, place them on the control file.


== The second binary independent target ==

/debian/ file

/debian/php-java-bridge-devel.examples file for the debhelper placing at the correct directory.

pitfall-> packages may have "-" in their name. Do not create intermediate (phony) rules with this character or things may go really weird and unexpected (as of april 2007 versions).

See how variables are used at dh_install to point to directories that may be different as different related packages are released (php5).[23], [20]


== The third binary independent package ==

/debian/ file

The trick here is to reuse a phony rule and specify desired files at the specific configuration file.

== The fourth binary independent package ==

/debian/ file

See the reusable phony rules. We use build and installbasic and then, the installdocs phony rule becomes reusable too.

== The first binary dependent package ==

The package name is implicit. We reuse other phony rules to reduce rule size.

Close attention to the execution path and realize why we do not have a dh_install at this rule.

Note the use of -a option, indicating a binary architecture dependent package.


= The closing: defining the binary rules =

Here you define the whole thing. It is the top level abstraction rule.

That is it. You have a complete set of files and rules ready for building your first multiple binary packages software.

= External useful links =

*[0] php-java-bridge source tree
*[1] Debian policy
*[2] Debian develpers reference
*[3] Debian new maintainers guide
*[4] Debian developers manuals
*[5] Create Debian Linux packages
*[6] Debian Binary Package Building HOWTO
*[7] How to backports packages to your version
*[8] Debian Mentors site
*[9] debian-mentors mailing list
*[10] Debian packaging tutorial
*[11] How to package for Debian
*[12] Debian Packaging
*[13] Collaborative Maintenance
*[14] Debian for Developers Tutorial
*[15] The Debconf Programmer's Tutorial
*[16] DEBCONF man page
*[17] DEBCONF-DEVEL man page
*[18] DEBCONF.CONF man page
*[19] DEBHELPER man page
*[20] Make manual - variables flavours
*[21] Make manual - shell function
*[22] substitution variables ${misc:Depends}, ${python:Depends}, ${perl:Depends} and package_name.substvars and control files
*[23] thread: how pass variables from files for dh_install into rules?
*[24] thread: arguments of some dh_* into rules
*[25] some debhelper clever examples /usr/share/doc/debhelper/examples
*[26] debhelper homepage
*[27] thread: variables from shell output in rules makefile
*[28] Make manual - the phony targets
*[29] Autobook - GNU autoconf, automake, libtool book (online and paper)
*[30] Learning the GNU development tools

= Up to date version of this document =

You can find a colectively maintained version of this how-to at
You can find an updated version of the Debian files of the package used at this example at [0].