(It took me a while to come up with new CDBS packaging series post not because I stopped using CDBS just because I was procrastinating myself as busy) This is the second post in the CDBS packaging series. In this series I'm going to talk about package relationship management. The better example where this feature is useful is packages where build-depends and run-time dependencies overlap. Most of the Perl modules which have test suites have build-depend and run-time dependency intersection. So let me take example of a Perl module. First lets see control file of a Perl package which is not using CDBS and then let me explain how CDBS can help you improve the situation. I choose libxml-libxml-perl lets see part of control file which includes Build-Depends Depends Suggests Recommends. So 2 packages are both in Build-Depends and Depends field

1. libsax-xml-perl
2. libxml-namespacesupport-perl

So in this situation there is a possibility that we miss to add one or both of these packages into Depends field, I'm not saying we will surely miss but we might after all we are all human beings. So how can we improve the situation using CDBS? Let me go through step by step on what we need to do.

1. Create a file called control.in with same above contents but slight modification in Build-Depends and Depends section. I will display the diff below to avoid re-pasting entire file again and again.

1. Next we need to have something like below in the rule files

So basically we moved all Build-Depends and Depends to rules file. The common ones are placed in deps variable and assigned to both Build-Depends and Depends. CDBS uses following variables for package relationship management.

1. CDBS_BUILD_DEPENDS: This variable helps you manage Build-Depends field and all you need to do is in your control.in files Build-Depends field put place holder @cdbs@
2. CDBS_DEPENDS: This field can be used to manage Depends field of binary package for each binary package you need to have one CDBS_DEPENDS_pkgname variable with depends assigned to it. And in your control.in append $ cdbs:Depends to Depends field.
3. CDBS_PROVIDES, CDBS_BREAKS, CDBS_RECOMMENDS, CDBS_PREDEPENDS, CDBS_SUGGESTS, CDBS_REPLACES: all these does the job what you think it does :-).

Other than CDBS_BUILD_DEPENDS all other variables work using substvars i.e. CDBS will put the respective substitutions in pkgname.substvars file which will be used during deb creation to replace things in control file. So to make CDBS generate new control file run the below command Basically this command needs to be executed before starting build process if you miss your changes will not be reflected into debian/control. Additionally this feature is Maintainer Mode helper tool because Debian policy prohibits change of debian/control during normal package build. So what is the benefit of using this feature of CDBS? I've listed some of them which I felt are obvious.

1. When there is intersection in Build-Depends and Depends this feature from CDBS is helpful. As I shown above put all intersecting dependencies in common variable and appropriately assign them wherever it is required. Thus we can avoid possible missing of some of run-time dependencies due to human error.
2. It is also possible that newer version of package requires specific version of some package (mostly libraries) and we updated build dependencies but we might forget to do the same in Depends, by using this feature we can make sure we will not miss such minute details.

One last thing I want to point out is if you are NMUing a CDBS package

NMUs need not (but are encouraged to) make special use of these tools. In particular, the debian/control.in file can be completely ignored.

Before closing down the post, If you find some mistake in the post please let me know either through comments or through the email. Soon I will be back with new CDBS recipes till then cya.

Last year, I had a great time participating in the Google Summer of Code with the Debian project. I had a neat project with some rather interesting implications for helping developers to package and maintain their work. It s still a work-in-progress, of course, as many projects in open source are, but I was able to accomplish quite a bit and am proud of my work. I learned quite a bit about coding in C, working with Debian and met some very intelligent people. My student peers were also very intelligent and great to learn from. I enjoyed meeting them virtually and discussing our various projects on the IRC channel as the summer progressed and the Summer of Code kicked into full swing. The Debian project in particular also helps arrange travel grants for students to attend the Debian Conference (this year, DebConf10 is being held in New York City!). DebConf provides a great venue to learn from other developers (both in official talks but also unofficial hacking sessions). As the social aspect is particularly important to Debian, DebConf helps people meet those with whom they are working with the most, thereby creating lifelong friendships and making open source fun. I have had several interviews for internships, and the bit of my work experience most asked about is my time doing the Google Summer of Code. I really enjoyed seeing a project go from the proposal stage, setting a reasonable timeline with my mentor, exploring the state of the art, and most importantly, developing the software. I think this is the sort of indispensible industry-type experience we often lack in our undergrad education. We might have an honours thesis or presentation, but much of the work in the Google Summer of Code actually gets used in the field. Developing software for people rather than for marks is significant in a number of ways, but most importantly it means there are real stakeholders that must be considered at all stages. Proposing brilliant new ideas is important, however, without highlighting the benefits they can have for various users, the reality is that it simply will not gain traction. Learning how to write proposals effectively is an important skill and working with my prospective mentor (at the time he later mentored my project once it was accepted) to develop mine was tremendously useful for my future endeavours. The way I see the Google Summer of Code is, in many ways, similar to an academic grant (and the stipend is about the same as well). It provides a modest salary (this year it s US$5000) but more importantly, personal contact with a mentor. Mentors are typically veterans in software development or the Debian project and act in the same role as supervisors for post-graduate work: they help monitor your progress and propose new ideas to keep you on track. The Debian Project is looking for more students and proposals. We have a list of ideas as well as application instructions available on our Wiki. As I will be going on internship starting May, I have offered to be a mentor this year. I look forward to seeing your submissions (some really interesting ones have already begun to filter in as the deadline approaches).
Filed under: Computer Science, Peer Relationships, Software Engineering Tagged: Computer Science, Debian, Google Summer of Code, Support

not many closed bugs in the last two weeks, & not even one RC bug per day worked on. anyway, here's my recent list:

• #567144 libavg: "libavg FTBFS: python LOCALMODLIBS causes -lssl link failure"
  add a comment
• #568940 libswt-gtk-3.5-java: ""symlink /usr/share/java/swt.jar missing""
  add another comment to the bug report
• #569091 libvideo-capture-v4l-perl: "Uses obsolete V4L1 API"
  improve patch, run tests ... (pkg-perl)
• #569408 src:libdbix-class-perl: "libdbix-class-perl: FTBFS: tests failed"
  upload new upstream release prepared by jawnsy with a versioned build dependency (pkg-perl)
• #570160 nsd3: "nsd3: Installation fails because of missing /etc/nsd3/nsd.conf"
  apply patch from BTS, upload to DELAYED/2
• #570500 svn-workbench: "svn-workbench: crash on start: AttributeError: 'NoneType' object has no attribute 'lower'"
  grab fixed package from mentors.d.o, upload to DELAYED/2
• #572719 libx11-protocol-perl: "libx11-protocol-perl: perl X11 application does not launch"
  add a comment and tag unreproducible (co-maint)
• #573657 src:libfile-fu-perl: "libfile-fu-perl: FTBFS: tests failed"
  triage, comment (pkg-perl)
• #573661 src:libdbix-class-schema-loader-perl: "libdbix-class-schema-loader-perl: FTBFS: tests failed"
  add missing dependency and upload (pkg-perl)
• #573679 src:libwx-perl: "libwx-perl: FTBFS: xvfb-run: error: Xvfb failed to start"
  triage, comment (pkg-perl)