Today I was removing KDE from my laptop, when I realized that kde-window-manager would not go away (even when it was automatically installed) since it provides x-window-manager, which is needed by gdm. I manually removed it, but that got me thinking that maybe I had other packages that were in this situation. So I picked aptitude and tried to build some search-fu. Here is the resulting query:

aptitude search '?for x:

 ?x:installed

 ?x:automatic

 ?x:provides(?virtual ?reverse-depends(?installed))

 ?not(?x:reverse-depends(?installed(?depends(?=x))))'

Now, lets go over the query. The first part ?for x: allows us to refer to the package currently being matched. See the documentation for details. We'll see later why we need this. Basically we are saying: give me all packages x that match the following pattern. The second and third parts are trivial: we only want automatically installed packages.
The fourth part, ?x:provides(?virtual ?reverse-depends(?installed)) was easy: find all packages that provide a virtual package that is depended upon by some other installed package.
The fifth and final part, ?not(?x:reverse-depends(?installed(?depends(?=x)))) is why we needed the bound variable x. We want to filter out (hence the ?not) the packages that have some reverse dependency that depends directly on the package x. That way, in my case, metacity won't show up since gnome-core directly depends on it and is installed.

Unfortunately, this query doesn't grok alternative dependencies. For example, if gnome-core depended on metacity x-window-manager then this query wouldn't show metacity, since it is depended upon by a package. If someone can make this query understand that so that it only eliminates packages directly depended upon with no alternatives dependencies, please let me know!Tags: aptitude, cleaning, tip, tips

It seems the current trend is to use short-form dh. Some people have even thought that dh has superseded CDBS. Since I prefer CDBS for my own packaging, I will say that no, CDBS is not being deprecated and in fact has been active. Packaging with CDBS is very simple. I'll try to explain how it works, and how to package with it. This may turn into a blog post series, but I won't promise anything.

CDBS is a set of makefiles that do several tasks that are common while packaging software, so that you don't have to repeat them over and over on each package. The makefiles are classified into 2 groups: classes and rules. Classes implement the rules required for building and installing software. These are classes because they can and do inherit from others. For example, there is the makefile class, and the autotools, qmake and cmake classes inherit from it, and the gnome and kde (which is for kde 3) classes inherits from the autotools class. Rules implement several other general purpose rules that don't depend on the toolchain used to build the package. For example, there is the debhelper rules file, which takes care of creating the debian package using the usual dh_* commands. There are several rules files which do all sorts of useful stuff, from running license checks to downloading new upstream releases. If this post transforms into a series, we may look into some of them. For now, I'll demonstrate how to use CDBS to package some simple software (only the debian/rules file, of course).

The first task while running creating debian/rules is determining which build system the software uses. I will use qutecsound package as a guide. So, first things first, we start using CDBS!

#!/usr/bin/make -f



# Uncomment this to turn on verbose mode.

#export DH_VERBOSE=1



include /usr/share/cdbs/1/rules/debhelper.mk

include /usr/share/cdbs/1/class/qmake.mk

Now this would be all that is required if qutecsound where a standard qmake package where nothing needs to be customized. Alas, this is not the case. First, there are some variables that need to be passed to qmake to appropriately configure the build. Also, the projects .pro file is not standard-named. How do we fix this? The CDBS way of overriding this kind of behavior is through the use of variables. Since we are using the qmake class, we will be overriding variables named DEB_QMAKE_*:

DEB_QMAKE_CONFIG_VAL += build64

DEB_QMAKE_ARGS = qcs.pro

We add a configuration value (because CDBS is setting other config values), and we set the extra arguments to qmake.

Now, there is a problem: the resulting binary is not created with the name we want. How do we change that? We could patch the source to avoid that, but it is far easier to add a rule to the makefile to do that. We will modify the build to rename the file at the end (and then clean it up on clean because the upstream makefile will not spot it):

build/qutecsound::

	[ -f bin/qutecsound ]   mv bin/qutecsound-d bin/qutecsound



clean::

	rm -f bin/qutecsound

So what did we just do? We extended the build and clean rules with extra stuff to do. In CDBS each package listed in debian/control gets a build/package rule (and several others at different stages of the build) so that one can add stuff specific to each package (this will be much more useful when dpkg finally learns about build-arch and build-indep).

For the final touch, we want to do a few more things. First, we want to ensure that we are using QT4's qmake, because the build will fail if QT3's is used. Second, since I created a manpage for the command, I want to install it. Finally, we want to use parallel building when the user has specified it, to build the project faster. How to do that? Again, via variables:

QMAKE = qmake-qt4

DEB_BUILD_PARALLEL = 1

DEB_INSTALL_MANPAGES_qutecsound = debian/qutecsound.1

CDBS creates several variables for each of the packages listed in debian/control, so we can customize each package build. In our case, this variable is passed to dh_installman from the debhelper rules file (CDBS will invoke the debhelper tools once for each binary package).

After all this we now have the complete debian/rules of a relatively simple package. How does it look like? Like this:

#!/usr/bin/make -f



# Uncomment this to turn on verbose mode.

#export DH_VERBOSE=1



include /usr/share/cdbs/1/rules/debhelper.mk

include /usr/share/cdbs/1/class/qmake.mk



QMAKE = qmake-qt4

DEB_QMAKE_CONFIG_VAL += build64

DEB_QMAKE_ARGS = qcs.pro

DEB_BUILD_PARALLEL = 1



DEB_INSTALL_MANPAGES_qutecsound = debian/qutecsound.1



build/qutecsound::

        [ -f bin/qutecsound ]   mv bin/qutecsound-d bin/qutecsound



clean::

        rm -f bin/qutecsound

Tags: cdbs, packaging

Now talk about good news.

The following developers got their Debian accounts in the last month:

• Adrian Perez (blackxored)
• Georges Khaznadar (georgesk)
• Felipe Sateler (fsateler)
• Thomas Goirand (zigo)

Congratulations!