Search Results: "Cyril Brulebois"

13 May 2012

Cyril Brulebois: D-I Wheezy Alpha1

Get it while it s hot: Debian Installer 7.0 Alpha1 release. See how yummy it is:

7 May 2012

Cyril Brulebois: Debian XSF News #12

Time for a DXN#11 follow-up.
  1. The recent xserver-xorg-input-synaptics rc4 upload solved a lot of issues, but the 1.6.0 release (just uploaded) should fix some more. Enjoy!
  2. I ve also uploaded a new xorg-server, merging from upstream server-1.12-branch to get many XI2.2 bug fixes, along with an infinite loop bug fix (also seen with synaptics).
  3. Many drivers can no longer work on ia64 due to the recent changes, so we requested they be removed, which happened promptly!
  4. All XSF-maintained packages build happily against X server 1.12, meaning users can get back to running apt-get dist-upgrade blindly without having to fear the consequences. Pro tip: when you see something like xserver-xorg go away during a dist-upgrade, think twice before confirming!
  5. xf86-input-mtrack was recently fixed; xf86-video-glamo and xf86-video-msm fail to build (#671028, #671806), so they stay uninstallable for now. Thankfully nothing appears to depend on them, so they can be temporarily removed from testing if needs be.
  6. In the meanwhile, xserver-xorg-video-intel 2.19 was released. It will probably land into experimental first, until the new server and its drivers make it into testing.
  7. Andreas Beckmann asked me to mention the status of the binary drivers, so here is my take about them: fglrx still doesn t support X server 1.12 (LOL!). The other, big fat blobby driver is installable, and supposed to work.

30 April 2012

Cyril Brulebois: Debian XSF News #11

Long time no see Summary Anyway, here are some quick news from the X packaging front, focussing on the past few weeks.
  1. While I was busy doing other things, Julien took care of uploading lots of libraries (making most of them multiarch-aware) along with our usual meta-packages (like x11-apps, x11-utils, etc.), preparing for the upcoming 7.7 katamari.
  2. Mesa 8.0.2 was finally uploaded to experimental, where it seems to be building fine, and working fine, at least for me.
  3. Accordingly, I m planning an upload to unstable very soon, and I won t be disabling wayland support this time, since wayland/weston reached their first milestone with a public release (0.85). There s nothing very interesting to see here, but since wayland support doesn t really hurt, I thought I d just keep it. That s why wayland hit unstable yesterday; weston should follow after mesa. (In case somebody is in a hurry, they have been in experimental for quite some time already.)
  4. Scrolling issues with the synaptics driver seem to be finally fixed thanks to rc4: #665004 was confirmed as fixed by many reporters (thanks everyone for the quick feedback after my ping). Accordingly, I ve pinged the release team to get an age-days 3 to make it migrate faster, and a kind RM added that hint to his file, so testing is getting the fixed package thanks to this midnight s britney run.
  5. libcairo2/server/EXA/ati/nouveau fun: will be added through an edition of this post. Executive summary: downgrade libcairo2 to testing s version if you re seeing text corruptions.
Upcoming X server transition X server 1.12 has been prepared in experimental for a while, from release candidates to the first stable release from server-1.12-branch. Since a bunch of drivers were uploaded to cope with that version when it shows up, we should be able to upload xorg-server 1.12 to unstable VERY SOON. What does that mean? Basically, that s a transition. In details:
  1. We upload xorg-server, and wait for it to be built everywhere, then we trigger binNMUs for all architectures at once when it s ready on all of them.
  2. Unlike shared libraries, there s no old and new library packages (old+new SONAME); instead, the server itself provides different packages (because of the different input and video ABI). That means that drivers won t be installable until they are rebuilt against the new server. Usually, we re talking about a few dinstall runs, meaning less than a day.
Frequently Yelled Phrases:
  1. Upgrades are broken! No, it just means you can t upgrade the server alone, you need the drivers too (see above).
  2. Installations are broken! Well, that s unstable, and you probably know installability-related issues are trivially solved by pulling packages from testing when needed. This is such a case.
Please don t report bugs on this topic, thanks already, and enjoy that new server.

22 April 2012

Gregor Herrmann: RC bugs 2012/16

this week I've started to look at the (not yet release critical) gcc 4.7 bugs. luckily there are still enough patches for them in the BTS but at the time of writing, at least 138 are not fixed & don't have a patch yet. so still some work ahead.

& for those who prefer to fix debian/rules files, lucas' last archive rebuild (where build-arch was used) still leaves enough work, & many bugs are not difficult to fix with a basic understanding of makefiles & debian build sytems.

19 April 2012

Raphaël Hertzog: People behind Debian: Samuel Thibault, working on accessibility and the Hurd

Samuel Thibault is a French guy like me, but it took years until we met. He tends to keep a low profile, even though he s doing lots of good work that deserves to be mentioned. He focuses on improving Debian s accessibility and contributes to the Hurd. Who said he s a dreamer? :-) Checkout his interview to have some news of Wheezy s status on those topics. Raphael: Who are you? Samuel: I am 30 years old, and live in Bordeaux, France. During the workday, I teach Computer Science (Architecture, Networking, Operating Systems, and Parallel Programming, roughly) at the University of Bordeaux, and conduct researches in heterogeneous parallel computing. During the evening, I play the drums and the trombone in various orchestra (harmonic/symphonic/banda/brass). During the night, I hack on whatever fun things I can find, mainly accessibility and the Hurd at the moment, but also miscellaneous bits such as the Linux console support. I am also involved in the development of Aquilenet, an associative ISP around Bordeaux, and getting involved in the development of the network infrastructure in Bordeaux. I am not practicing Judo any more, but I roller-skate to work, and I like hiking in the mountains. I also read quite a few mangas. Saturday mornings do not exist in my schedule (Sunday mornings do, it s Brass Band rehearsal :) ). Raphael: How did you start contributing to Debian? Samuel: Bit by bit. I have been hacking around GNU/Linux since around 1998. I installed my first Debian system around 2000, as a replacement for my old Mandrake installation (which after all my tinkering was actually no longer looking like a Mandrake system any more!). That was Potato at the time, which somebody offered me through a set of CDs (downloading packages over the Internet was unthinkable at the time with the old modems). I have been happily reading and hacking around documentation, source code, etc. provided on them. Contribution things really started to take off when I went to the ENS Lyon high school in 2001: broadband Internet access in one s own student room! Since sending a mail was then really free, I started submitting bugs against various packages I was using. Right after that I started submitting patches along them, and then patches to other bugs. I did that for a long time actually. I had very little knowledge of all packaging details at the time, I was just a happy hacker submitting reports and patches against the upstream source code. At ENS Lyon, I met a blind colleague with very similar hacking tastes (of course we got friends) and he proposed me, for our student project, to work on a brlnet project (now called brlapi), a client/server protocol that lets applications render text on braille devices themselves. Along the way, I got to learn in details how a blind person can use a Unix system and the principles that should be followed when developing Accessibility. That is how I got involved in it. We presented our project at JDLL, and the Hurd booth happened to be next to our table, so I discussed with the Hurd people there about how the Hurd console could be used through braille. That is how I got into the Hurd too. From then on, I progressively contributed more and more to the upstream parts of both accessibility software and the Hurd. And then to the packaging part of them. Through patches in bug reports first, as usual, as well as through discussions on the mailing lists. But quickly enough people gave me commit access so I could just throw the code in. I was also given control over the Hurd buildds to keep them running. It was all good at that stage: I could contribute in all the parts I was caring about. People however started telling me that I should just apply for being a Debian Developer; both from accessibility and Hurd sides. I had also seen a bunch of my friends going through the process. I was however a bit scared (or probably it was just an excuse) by having to manage a gpg key, it seemed like a quite dangerous tool to me (even if I already had commit access to glibc at the time anyway ). I eventually applied for DM in 2008 so as to at least be able to upload some packages to help the little manpower of the Accessibility and Hurd teams. Henceforth I had already a gpg key, thus no excuse any more. And having it in the DM keyring was not enough for e.g. signing the hurd-i386 buildd packages. So I ended up going through NM in 2009, which went very fast, since I had already been contributing to Debian and learning all the needed stuff for almost 10 years! I now have around 50 packages in my QA page, and being a DD is actually useful for my work, to easily push our software to the masses :) So to sum it up, the Debian project is very easy to contribute to and open to new people. It was used during discussions at the GNU Hackers Meeting 2011 as an example of a very open community with public mailing lists and discussions. The mere fact that anybody can take the initiative of manipulating the BTS (if not scared by the commands) without having to ask anybody is an excellent thing to welcome contributions; it is notable tha the GNU project migrated to the Debbugs BTS. More generally, I don t really see the DD status as a must, especially now that we have the DM status (which is still a very good way to drag people into becoming DDs). For instance, I gave a talk at FOSDEM 2008 about the state of accessibility in Debian. People did not care whom I was, they cared that there was important stuff going on and somebody talking about it. More generally, decisions that are made through a vote are actually very rare. Most of the time, things just happen on the mailing lists or IRC channels where anybody can join the discussion. So I would recommend beginners to first use the software, then start reporting bugs, then start digging in the software to try fix the bugs by oneself, eventually propose patches, get them reviewed. At some point the submitted patches will be correct already most of the time. That s when the maintainers will start getting bored of just applying the patches, and simply provide with commit access, and voil , one has become a main contributor. Raphael: You re one of the main contributors to the Debian GNU/Hurd port. What motivates you in this project? Samuel: As I mentioned above, I first got real contact with the Hurd from the accessibility point of view. That initially brought me into the Hurd console, which uses a flexible design and nice interfaces to interact with it. The Hurd driver for console accessibility is actually very straightforward, way simpler than the Windows or Linux drivers. That is what caught me initially. I have continued working on it for several reasons. First, the design is really interesting for users. There are many things that are natural in the Hurd while Linux is still struggling to achieve them, such as UID isolation, recently mentioned in LWN. What I really like in the Hurd is that it excels at providing users with the same features as the administrator s. For instance, I find it annoying that I still can not mount an ISO image that I build on e.g. ries.debian.org. Linux now has FUSE which is supposed to permit that, but I have never seen it enabled on an ssh-accessible machine, only on desktop machines, and usually just because the administrator happens to be the user of the machine (who could as well just have used sudo ) For me, it is actually Freedom #0 of Free Software: let the user run programs for any purpose, that is, combining things together all the possible ways, and not being prevented from doing some things just because the design does not permit to achieve them securely. I had the chance to give a Hurd talk to explain that at GHM 2011, whose main topic was extensibility , I called it GNU/Hurd AKA Extensibility from the Ground, because the design of the Hurd is basically meant for extensibility, and does not care whether it is done by root or a mere user. All the tools that root uses to build a GNU/Hurd system can be used by the user to build its own GNU/Hurd environment. That is guaranteed by the design itself: the libc asks for things not to the kernel, but to servers (called translators), which can be provided by root, or by the user. It is interesting to see that it is actually also tried with varying success in GNU/Linux, through gvfs or Plash. An example of things I love being able to do is: $ zgrep foo ~/ftp://cdn.debian.net/debian/dists/sid/main/Contents-*.gz On my Hurd box, the ~/ftp: directory is indeed actually served by an ftpfs translator, run under my user uid, which is thus completely harmless to the system. Secondly and not the least, the Hurd provides me with interesting yet not too hard challenges. LWN confirmed several times that the Linux kernel has become very difficult to significantly contribute to, so it is no real hacking fun any more. I have notably implemented TLS support in the Hurd and the Xen and 64bit support in the GNU Mach kernel used by the Hurd. All three were very interesting to do, but were already done for Linux (at least for all the architectures which I actually know a bit and own). It happens that both TLS and Xen hacking experience became actually useful later on: I implemented TLS in the threading library of our research team, and the Xen port was a quite interesting line on my CV for getting a postdoc position at XenSource :) Lastly, I would say that I am used to lost causes :) My work on accessibility is sometimes a real struggle, so the Hurd is almost a kind of relief. It is famous for his vapourware reputation anyway, and so it is fun to just try to contribute to it nevertheless. An interesting thing is that the opinion of people on the Hurd is often quite extreme, and only rarely neutral. Some will say it is pure vapourware, while others will say that it is the hope of humanity (yes we do see those coming to #hurd, and they are not always just trolls!). When I published a 0.401 version on 2011 April 1st, the comments of people were very diverse, and some even went as far as saying that it was horrible of us to make a joke about the promised software :) Raphael: The FTPmasters want to demote the Hurd port to the debian-ports.org archive if it doesn t manage a stable release with wheezy. We re now at 2 months of the freeze. How far are you from being releasable ? Samuel: Of course, I can not speak for the Debian Release team. The current progress is however encouraging. During Debconf11, Michael Banck and I discussed with a few Debian Release team members about the kind of goals that should be achieved, and we are near completion of that part. The Debian GNU/Hurd port can almost completely be installed from the official mirrors, using the standard Debian Installer. Some patches need some polishing, but others are just waiting for being uploaded Debian GNU/Hurd can start a graphical desktop and run office tools such as gnumeric, as well as the iceweasel graphical web browser, KDE applications thanks to Pino Toscano s care, and GNOME application thanks to Emilio Pozuelo Monfort s care. Of course, general textmode hacking with gcc/make/gdb/etc. just works smoothly. Thanks to recent work on ghc and ada by Svante Signell, the archive coverage has passed 76%. There was a concern about network board driver support: until recently, the GNU Mach kernel was indeed still using a glue layer to embed the Linux 2.2 or even 2.0 drivers (!). Finding a network board supported by such drivers had of course become a real challenge. Thanks to the GSoC work of Zheng Da, the DDE layer can now be used to embed Linux 2.6.32 drivers in userland translators, which was recently ACCEPTed into the archive, and thus brings way larger support for network boards. It also pushes yet more toward the Hurd design: network drivers as userland process rather than kernel modules. That said, the freeze itself is not the final deadline. Actually, freeze periods are rests for porters, because maintainers stop bringing newer upstream versions which of course break on peculiar architectures. That will probably be helpful to continue improving the archive coverage. Raphael: The kfreebsd port brought into light all the packages which were not portable between different kernels. Did that help the Hurd port or are the problems too different to expect any mutual benefit? Samuel: The two ports have clearly helped each other in many aspects. The hurd-i386 port is the only non-Linux one that has been kept working (at least basically) for the past decade. That helped to make sure that all tools (dpkg, apt, toolchain, etc.) were able to cope with non-Linux ports, and keep that odd-but-why-not goal around, and evidently-enough achievable. In return, the kFreeBSD port managed to show that it was actually releasable, at least as a technological preview, thus making an example. In the daily work, we have sometimes worked hand in hand. The recent porting efforts of the Debian Installer happened roughly at the same time. When fixing some piece of code for one, the switch-case would be left for the other. When some code could be reused by the other, a mail would be sent to advise doing so, etc. In the packaging effort, it also made a lot of difference that a non-Linux port is exposed as released architecture: people attempted by themselves to fix code that is Linuxish for no real reason. The presence of the kFreeBSD is however also sometimes a difficulty for the Hurd: in the discussions, it sometimes tends to become a target to be reached, even if the systems are not really comparable. I do not need to detail the long history of the FreeBSD kernel and the amount of people hacking on it, some of them full-time, while the Hurd has only a small handful of free-time hackers. The FreeBSD kernel stability has already seen long-term polishing, and a fair amount of the Debian software was actually already ported to the FreeBSD kernel, thanks to the big existing pure-FreeBSD hackerbase. These do not hold for the GNU/Hurd port, so the expectations should go along. Raphael: You re also very much involved in the Debian Accessibility team. What are the responsibilities of this team and what are you doing there? Samuel: As you would expect it, the Debian Accessibility team works on packaging accessibility-related packages, and helping users with them; I thus do both. But the goal is way beyond just that. Actual accessibility requires integration. Ideally enough, a blind user should be able to just come to a Debian desktop system, plug his braille device, or press a shortcut to enable speech synthesis, and just use the damn computer, without having to ask the administrator to install some oddly-named package and whatnot. Just like any sighted user would do. He should be able to diagnose why his system does not boot, and at worse be able to reinstall his computer all by himself (typically at 2am ). And that is hard to achieve, because it means discussing about integration by default of accessibility features. For instance, the Debian CD images now beep during at the boot menu. That is a precious feature that has been discussed between debian-boot and debian-accessibility for a few weeks before agreeing on how to do it without too much disturbance. Similarly, my proposition of installing the desktop accessibility engines has been discussed for some time before being commited. What was however surprisingly great is that when somebody brought the topic back for discussion, non-debian-accessibility people answered themselves. This is reassuring, because it means things can be done durably in Debian. On the installation side, our current status is that the stable Debian installer has a high contrast color theme, and several years ago, I have pushed toward making standard CD images automatically detect braille devices, which permits standalone installation. I have added to the Wheezy installer some software speech synthesis (which again brought discussion about size increase vs versatility etc.) for blind people who do not have a braille device. I find it interesting to work on such topic in Debian rather than another distribution, because Debian is an upstream for a lot of distributions. Hopefully they just inherit our accessibility work. It at least worked for the text installer of Ubuntu. Of course, the Accessibility team is looking for help, to maintain our current packages, but also introduce new packages from the TODO list or create some backports. One does not need to be an expert in accessibility: tools can usually be tested, at least basically, by anybody, without particular hardware (I do not own any, I contributed virtual ones to qemu). For new developments and ideas, it is strongly recommended to come and discuss on debian-accessibility, because it is easy to get on a wrong track that does not bring actual accessibility. We still have several goals to achieve: the closest one is to just fix the transition to gnome3, which has been quite bad for accessibility so far :/ On the longer run, we should ideally reach the scenario I have detailed above: desktop accessibility available and ready to be enabled easily by default. Raphael: What s the biggest problem of Debian? Samuel: Debian is famous for its heated debian-devel discussions. And some people eventually say this no fun any more . That is exemplified in a less extreme way in the debian-boot/accessibility discussions that I have mentioned above. Sometimes, one needs to have a real stubborn thick head to continue the discussion until finding a compromise that will be accepted for commit. That is a problem because people do not necessarily have so much patience, and will thus prefer to contribute to a project with easier acceptance. But it is also a quality: as I explained above, once it is there, it is apparently for good. The Ubuntu support of accessibility in its installer has been very diverse, in part due to quite changing codebase. The Debian Installer codebase is more in a convergence process. Its base will have almost not changed between squeeze and wheezy. That allowed the Debian Accessibility team to continue improving its accessibility support, and not have to re-do it. A wiki page explains how to test its accessibility features, and some non-debian-accessibility people do go through it. A problem I am much more frightened by is the manpower in some core teams. The Debian Installer, grub, glibc, Xorg, gcc, mozilla derivatives, When reading the changelogs of these, we essentially keep seeing the same very few names over and over. And when one core developer leaves, it is very often still the same names which appear again to do the work. It is hard to believe that there are a thousand DDs working on Debian. I fear that Debian does not manage to get people to work on core things. I often hear people saying that they do not even dare thinking about putting their hands inside Xorg, for instance. Xorg is complex, but it seems to me that it tends to be overrated, and a lot of people could actually help there, as well as all the teams mentioned above. And if nobody does it, who will? Raphael: Do you have wishes for Debian Wheezy? Samuel: That is an easy one :) Of course I wish that we manage to release the hurd-i386 port. I also wish that accessibility of gnome3 gets fixed enough to become usable again. The current state is worrying: so much has changed that the transition will be difficult for users already, the current bugs will clearly not help. I also hope to find the time to fix the qt-at-spi bridge, which should (at last!) bring complete KDE accessibility. Raphael: Is there someone in Debian that you admire for their contributions? Samuel: Given the concerns I expressed above, I admire all the people who do spend time on core packages, even when that is really not fun everyday. Just to alphabetically name a few people I have seen so often here and there in the areas I have touched in the last few years: Aur lien Jarno, Bastian Blank, Christian Perrier, Colin Watson, Cyril Brulebois, Frans Pop, J rg Jaspert, Joey Hess, Josselin Mouette, Julien Cristau, Matthias Klose, Mike Hommey, Otavio Salvador, Petr Salinger, Robert Millan, Steve Langasek. Man, so many things that each of them works on! Of course this list is biased towards the parts that I touched, but people working in others core areas also deserve the same admiration.
Thank you to Samuel for the time spent answering my questions. I hope you enjoyed reading his answers as I did. Note that older interviews are indexed on wiki.debian.org/PeopleBehindDebian.

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2 March 2012

Sylvestre Ledru: Report from the BSP in Paris

From February 17 to 19th 2012, between 10 to 30 hackers met at IRILL's offices to squash as many bugs as possible for the Wheezy release. Besides about 42 pizzas, more than one hundred bugs (104 to be precise) have been fixed. Among them, 18 of them were fixed by removing old/unmaintained/deprecated packages from the Debian archive. In a great atmosphere, one of the most important achievements of this BSP was that Yada, a deprecated packaging helper, finally passed away thanks to the efforts of Cyril Brulebois. Thanks for all the contributors for making of this week end a success.

22 February 2012

Cyril Brulebois: Wrench days

Fixing hardware Thanks to the nice Debian Swiss Knives initiative! Fixing software Besides trying to maintain the whole X stack as usual, and preparing the funky wayland, mesa, and weston trio for experimental, I got myself into other areas. Debugging gzip Jakup Wilk noticed a while ago that some multiarchified packages couldn t be co-installed due to gzipped files being different between architectures. That was reported as #647522 against the gzip package. While some developers consider the lack of determinism (as in: it s not in the gzip specification, and the current implementation generates different packages anyway!) as a dead-end for the multiarch experiment, it didn t look like undebuggable or unfixable. And indeed, as confirmed by a quick analysis: a lack of clean-up when several files are processed at once can lead to different results, depending on the order in which files are specified on the command line; the patch for that is trivial, and was later made smaller and the need for it was explained. Working in the Release Team I reviewed/approved a few packages for squeeze, but also took care of handling or finishing a few transitions (as seen in my hints file), among which the funny iceweasel9/libmozjs ones; release tools are nice, but one gets to learn lots of stuff at once (which isn t a negative aspect). I hacked a tiny collision detector so that packages involved in several transitions can be easily spotted. Given the huge number of ongoing transitions we had lately, that didn t look overkill. Squashing bugs It had been a very long time since my last working on totally random RC bugs. The Bug Squashing Party organized at IRILL was a very nice opportunity to get back to totally crazy bugs in unknown packages, but also to meet with other Debian contributors; sponsoring maintainers with good patches on their first try was nice, but walking other contributors through their first patches sent to the BTS or through their first NMUs was nice too. Waving good bye to yada Back in the M rida QA meeting I attended in 2007, there were already jokes about how bad yada was, and how it should die in a fire etc. When I started looking at the RC bug list, I quickly switched to scrolling it backwards, and I wondered how much work was left. The details can be seen in #660548, and the result is: yada is gone! sanity++; packages.debian.org Both long descriptions and translations for packages in some suites disappeared after the switch to Description-md5. Thanks to a quick and reduced packages.debian.org setup (mostly: en+de for squeeze+sid+experimental), I managed to find my way through Perl and DB files to propose patches for #657557. I m still waiting for a confirmation, but in case it works fine, we could even get a fix for DDTP/DDTSS.

7 February 2012

Raphaël Hertzog: Dpkg with multiarch support available in Debian experimental

As I announced on debian-devel, Guillem Jover uploaded a snapshot of dpkg s multiarch branch to experimental (version 1.16.2~wipmultiarch). Beware: There will
likely be some small interface changes between this version and the version that will be released later in unstable (possibly in the output of dpkg --get-selections, dpkg --list, maybe other commands). multiarch allows you to install packages from different architectures on the same machine. This can be useful if your computer can run programs from 2 architectures (eg. x86 CPU supporting i386 and amd64), or if you often need to cross-compile software and thus need the libraries of your target architecture. Test dpkg with multiarch support If you want to test multiarch support in dpkg, install the package from experimental (apt-get install dpkg/experimental assuming you have experimental in your sources.list). Then you can add a supplementary architecture to your system by doing sudo dpkg --add-architecture <arch> (e.g. i386 if you are on amd64, and vice-versa). APT will automatically pick up the new architecture and start downloading the Packages file for the new architecture (it uses dpkg --print-foreign-architectures to know about them). From there on you can install packages from the foreign architectures with apt-get install foo:<arch> . Many packages will not be installable because some of their dependencies have not yet been updated to work with in a multiarch world (libraries must be installed in a multiarch-compliant path so as to be co-installable, and then marked Multi-Arch: same ). Other dependencies might need to be marked Multi-Arch: foreign . See wiki.debian.org/Multiarch/Implementation for more HOWTO-like explanations. Now is a good time to see if you can install the foreign packages that you could need in such a setup and to help to convert the required libraries. You can also read Cyril Brulebois article which quickly shows how to hunt for the problematic packages which have not been converted to multiarch (in his sample, ucf is not ready. Since it s an Architecture: all package which can run on any architecture, it means that it s lacking a Multi-Arch: foreign field). Report bugs If you discover any bug in dpkg s multiarch implementation, please report it to the Bug Tracking System (against dpkg with the version 1.16.2~wipmultiarch ). If you notice important libraries or packages which are not yet multiarch ready, please open wishlist bug reports requesting the conversion and point the maintainers towards the wiki page linked above. Even better, prepare patches and submit those with your bug reports. Again, you can follow the lead of Cyril Brulebois who filed 6 bugs! Review the multiarch implementation If you re a C programmer and have some good knowledge of dpkg (or are willing to learn more of it), we would certainly benefit from more eyes reviewing the multiarch branch. If you want to discuss some design issues of the multiarch implementation in dpkg (or have questions related to your review), please get in touch via debian-dpkg@lists.debian.org. The latest version of the branch is pu/multiarch/master in Guillem s personal repository. I have my own version of the branch (pu/multiarch/full) which is usually a snapshot of Guillem s branch with my own submitted fixes.
$ git clone git://git.debian.org/dpkg/dpkg.git
$ cd dpkg
$ git remote add guillem git://git.hadrons.org/git/debian/dpkg/dpkg.git
$ git remote add buxy git://git.debian.org/~hertzog/dpkg.git
$ git fetch guillem && git fetch buxy
If you followed the instructions above, the relevant branches are thus guillem/pu/multiarch/master and buxy/pu/multiarch/full. Both branches are regularly rebased on top of master where Guillem merges progressively the commits from the multi-arch branch as his review progresses. Thank you in advance for your help bringing multiarch in shape for Debian Wheezy,

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6 February 2012

Cyril Brulebois: dpkg with multiarch, a new hope

dpkg was uploaded to experimental a few times lately, let s sum it up quickly:
  1. It started with my NMU on 2012-01-31, since I hadn t received any reasons not to upload (except NACK , which doesn t count as such in my book).
  2. It got reverted a few minutes after that.
  3. Since this was getting nowhere, the Debian Technical Committee finally got involved, and voted in a few days only (wow, thanks!) for an it s time to experiment decision.
  4. A new dpkg upload to experimental finally happened. One shall note the prominent This is a WIP release, command line interfaces will change. notice.
I ve updated my previous dpkg with multiarch page accordingly, only keeping the interesting bits. Playing around with grep-aptavail -F Multi-Arch $i -sPackage (with $i being same or foreign), I found some bugs: Also, some wishlist bugs (keeping the prominent notice in mind): Finally, one dpkg improvement and one possible dpkg bug:

1 February 2012

Rapha&#235;l Hertzog: My Debian Activities in January 2012

This is my monthly summary of my Debian related activities. If you re among the people who made a donation to support my work (213.68 , thanks everybody!), then you can learn how I spent your money. Otherwise it s just an interesting status update on my various projects. Dpkg The biggest change I made is a small patch that brings to an end years and years of recurring discussions about the build-arch and build-indep targets of debian/rules (see #229357). Last year the technical committee took this issue in its hands (see #629385) but it failed to take any resolution. Fortunately thanks to this we got some concrete numbers on the colateral damages inflicted on the archive for each possible approach. In the end, Guillem and I managed to agree on the way forward. The remaining of what I did as dpkg maintainer has not much to do with coding. I reviewed the work of Gianluca Ciccarelli on dpkg-maintscript-helper who is trying to provide helper functions to handle migration between directories and symlinks. I also reviewed a 2000-lines patch from Patrick Schoenfeld who s trying to provide a perl API to parse dpkg log files and extract meaningful data out of them. I updated the dpkg-architecture manual page to document the Makefile snippet /usr/share/dpkg/architecture.mk and to drop information that s no longer releveant nowadays. I reviewed a huge patch prepared by Russ Alberry to update the Debian policy and document the usage of symbols files for libraries. As the author of dpkg-gensymbols, I was keen to see it properly documented at the policy level. I brought up for discussion a detail that was annoying me for quite some time: some copyright notices were embedded in translatable strings and updating them resulted in useless work for translators. In the end we decided to drop those notices and to keep them only at the source level. I updated my multiarch branch on top of Guillem s branch several times, all the fixes that were in my branch have been integrated (often in a modified form). Unfortunately even if the code works quite well, Guillem doesn t want to release anything to Debian until he has finished to review everything and many people are annoyed by the unreasonable delay that it imposes. Cyril Brulebois tried to release a snapshot of the current multiarch branch to experimental but Guillem has been prompt to revert this upload. I m somewhat at a loss in this situation. I offered my help to Guillem multiple times but he keeps doing his work in private, he doesn t share many details of his review except some comments in commit logs or when it affects the public interface. I complained once more of this sad situation. Debian Package Maintenance Hub That s the codename I use for a new infrastructure that I would like to develop to replace the Package Tracking System and the DDPO and several other services. I started to draft a Debian Enhancement Proposal (DEP), see DEP-2, and requested some comments within the QA team. For now, it looks like that nobody had major objections on the driving idea behind this project. Those who commented were rather enthusiastic. I will continue to improve this DEP within the QA team and at some point I will bring the discussion to a larger audience like debian-devel@lists.debian.org. Package Tracking System Even if I started to design its replacement, the PTS will still be used for quite some time so I implemented two new features that I deemed important: displaying a TODO notice when there is (at least) one open bug related to a release goal, displaying a notice when the package is involved in an ongoing or upcoming transition. Misc packaging tasks I created and uploaded the dh-linktree package which is a debhelper addon to create symlink trees (useful to replace embedded copies of PHP/JavaScript libraries by symlinks to packaged copies of those files). I packaged quilt 0.50. I helped the upstream authors to merge a Debian patch that had been forwarded by Martin Quinson (a quilt s co-maintainer). I packaged a security release of WordPress (3.3.1) and a new upstream release of feed2omb and gnome-shell-timer. I prepared a new Debian release of python-django with a patch cherry-picked from the upstream SVN repository to fix the RC bug #655666. Book update We re again making decent progress in the translation of the Debian Administrator s Handbook, about 12 chapters are already translated. The liberation campaign is also (slowly) going forward. We re at 72% now (thanks to 63 new supporters!) while we were only at 67% at the start of January. Thanks See you next month for a new summary of my activities.

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Cyril Brulebois: dpkg with multiarch

(This page was edited a few times, details are available.) Grab it while it s hot! Thanks to the hard work of dpkg developers and many (generations of) developers, multiarch is becoming a reality. If you want to give it a try, install dpkg from experimental, add a foreign architecture, and start trying to install packages. Example on amd64:
# dpkg --add-architecture i386
# dpkg --print-foreign-architectures
i386
# apt-get update
[ lots of amd64 and i386 Packages files get downloaded ]
# apt-get install mksh:i386
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  ed:i386
The following NEW packages will be installed:
  mksh:i386
0 upgraded, 1 newly installed, 0 to remove and 9 not upgraded.
Need to get 414 kB of archives.
After this operation, 707 kB of additional disk space will be used.
Get:1 http://ftp.fr.debian.org/debian/ sid/main mksh i386 40.4-2 [414 kB]
Fetched 414 kB in 0s (664 kB/s)
Selecting previously unselected package mksh.
(Reading database ... 171933 files and directories currently installed.)
Unpacking mksh (from .../archives/mksh_40.4-2_i386.deb) ...
Processing triggers for menu ...
Processing triggers for man-db ...
Setting up mksh (40.4-2) ...
update-alternatives: using /bin/mksh to provide /bin/ksh (ksh) in auto mode.
Processing triggers for menu ...
# mksh
$ ldd $(which mksh)
linux-gate.so.1 =>  (0xf779c000)
libc.so.6 => /lib/i386-linux-gnu/i686/cmov/libc.so.6 (0xf75d6000)
libgcc_s.so.1 => /lib/i386-linux-gnu/libgcc_s.so.1 (0xf75b9000)
/lib/ld-linux.so.2 (0xf779d000)
Of course, installing an i386 mksh package isn t exactly what multiarch is about. Dozens of packages have been patched already to add Multi-Arch fields, but until their (recursive) dependencies have been multiarch-ified, foreign packages can be uninstallable, as can be seen below, with the usual why is it uninstallable? hunt (shortened output):
# apt-get install psutils:i386
The following packages have unmet dependencies:
 psutils:i386 : Depends: libpaper1:i386 but it is not going to be installed
# apt-get install libpaper1:i386
The following packages have unmet dependencies:
 libpaper1:i386 : Depends: ucf:i386 (>= 0.28) but it is not installable
                  Recommends: libpaper-utils:i386 but it is not going to be installed
# apt-get install ucf:i386
E: Package 'ucf:i386' has no installation candidate
Another example, successful handling of the installation of a foreign package, while it s already installed with the host architecture:
# apt-get install xz-utils:i386
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  liblzma5:i386
Suggested packages:
  xz-lzma:i386
The following packages will be REMOVED:
  xz-utils
The following NEW packages will be installed:
  liblzma5:i386 xz-utils:i386
0 upgraded, 2 newly installed, 1 to remove and 9 not upgraded.
Need to get 440 kB of archives.
After this operation, 410 kB of additional disk space will be used.
Do you want to continue [Y/n]?
Get:1 http://ftp.fr.debian.org/debian/ sid/main liblzma5 i386 5.1.1alpha+20110809-3 [205 kB]
Get:2 http://ftp.fr.debian.org/debian/ sid/main xz-utils i386 5.1.1alpha+20110809-3 [235 kB]
Fetched 440 kB in 0s (478 kB/s)
dpkg: xz-utils: dependency problems, but removing anyway as you requested:
 dpkg depends on xz-utils.
 xz-lzma depends on xz-utils.
 dpkg-dev depends on xz-utils.
(Reading database ... 171952 files and directories currently installed.)
Removing xz-utils ...
Processing triggers for man-db ...
Selecting previously unselected package liblzma5:i386.
(Reading database ... 171908 files and directories currently installed.)
Unpacking liblzma5:i386 (from .../liblzma5_5.1.1alpha+20110809-3_i386.deb) ...
Selecting previously unselected package xz-utils.
Unpacking xz-utils (from .../xz-utils_5.1.1alpha+20110809-3_i386.deb) ...
Processing triggers for man-db ...
Setting up liblzma5:i386 (5.1.1alpha+20110809-3) ...
Setting up xz-utils (5.1.1alpha+20110809-3) ...
# dpkg -l xz-utils xz-utils:i386 'liblzma*:*'
[   ]
un  xz-utils            <none>
ii  xz-utils            5.1.1alpha+20110809-3
ii  liblzma5:amd64      5.1.1alpha+20110809-3
ii  liblzma5:i386       5.1.1alpha+20110809-3
# ldd $(which xz)
    linux-gate.so.1 =>  (0xf776b000)
    liblzma.so.5 => /usr/lib/i386-linux-gnu/liblzma.so.5 (0xf7724000)
    librt.so.1 => /lib/i386-linux-gnu/i686/cmov/librt.so.1 (0xf771b000)
    libpthread.so.0 => /lib/i386-linux-gnu/i686/cmov/libpthread.so.0 (0xf7701000)
    libc.so.6 => /lib/i386-linux-gnu/i686/cmov/libc.so.6 (0xf75a4000)
    /lib/ld-linux.so.2 (0xf776c000)
# zgrep -a '_("Activities")' gnome-shell-3.2.2.1.tar.xz
        this._label = new St.Label(  text: _("Activities")  );
zgrep is a shell script, but it calls xz, which is from the i386 package, and everything runs just fine. Running it through strace -f -e '', I discovered those messages, which I had never seen before:
[ Process PID=8900 runs in 32 bit mode. ]
[ Process PID=8899 runs in 64 bit mode. ]
[ Process PID=8900 runs in 32 bit mode. ]
[ Process PID=8899 runs in 64 bit mode. ]
 
What s next? We re late! It s time to check what happens with that dpkg package, report bugs, and convert more libraries! Please think of the kittens, and coordinate with the release team to make sure you don t delay a transition when uploading a shiny, multiarch-ified package. In a nutshell, if you received a patch from Steve Langasek or Riku Voipio, it s a good indication your package will be helpful quickly when it s multiarchified. Since zlib is directly depended on by 2000+ packages, #569697 was pinged right after the dpkg upload; but many other packages will need patches and heavy testing. Hurry up, the freeze is coming, we need to shake it up as soon as possible!

27 January 2012

Rapha&#235;l Hertzog: People Behind Debian: Josselin Mouette, founder of the Debian GNOME team

Josselin Mouette is one the leaders of the pkg-gnome team, he takes sound technical decisions and doesn t fear writing code to work-around upstream issues. He deserves kudos for the work he has put into packaging GNOME over the years. He can also be very sarcastic (sometimes he even enjoys participating to flamewars on debian lists), and there are quite a few topics where we have long agreed to disagree. But this kind of diversity is also what makes Debian a so interesting place Read on to learn more about the pkg-gnome team, its plans for Wheezy, Josselin s opinion on the GNOME 3 switch, and much more. Raphael: Who are you? Josselin: I am a 31 years old Linux systems engineer. I started in life with physics, which I studied at the ENS Lyon. I started a thesis on experimental and numerical models for optoelectronics, but when it became clear that research was not for me, I abandoned it and accepted a job at the CEA, which holds the largest computing center in Europe. Working on these machines has been the most awesome job ever (except for it being near Paris). After that I worked a bit on system monitoring technologies. I am married, currently living in Lyon, and working for EDF (the French historical electricity company) on scientific workstations using Debian. EDF is using Debian on more than a thousand workstations and holds the fastest Debian supercomputer in the world (200 Tflops), which makes it another obvious place for Debian developers. Raphael: How did you start contributing to Debian? Josselin: I discovered Debian in 1999 while studying at the ENS, which is one of the biggest nests of Debian developers while being a small place, it is producing almost one Debian developer per year on average. After wondering for a while what it could be useful for, hacking on a slink snapshot made me think that it was for, well, everything except for gaming. Later, in 2002, when I was working on optoelectronics computing codes, I started to package them for Debian in order to make them easier to install, for us as well as other labs over the world. I started the NM process, and it was going smoothly but also going to take time. However, at that moment, the frozen-bubble game went out and made quite some buzz. Since I knew a guy who knew the game s developer, he asked me to package it. The package found 3 sponsors in a very short time and was fast-tracked into the archive at a speed that was unseen before. After which the NM process was completed very quickly. At that time, I was a heavy WindowMaker user, but I didn t like the direction the project was taking (actually, I wonder if there was one). GNOME was starting to become attractive, but its packaging in Debian was very ineffective, with many inconsistent packages maintained by people who didn t ever talk to each other some of them didn t speak English, and some of them didn t talk at all. Together with awesome people, among which Jordi Mallach, Gustavo Noronha Silva, JHM Dassen, Ross Burton and S bastien Bacher, we started the GNOME team in 2003, introducing consistent packaging practices, and initiating synchronized uploads. Releasing a completely integrated GNOME 2.8 in sarge was a considerable achievement; proving (together with the Perl team) that a team was the best way to maintain large package sets changed the way people work on Debian.
Proving [ ] that a team was the best way to maintain large package sets changed the way people work on Debian.
Raphael: You re one of the most active contributors of the team which is packaging GNOME for Debian. What would you suggest to a new contributor who would like to help the team? Josselin: There are several ways to contact the team, but the recommended one has always been IRC. We hang on #debian-gnome on the OFTC network, so just come around and ask for us. The real question is what you want to do in the team. Of course, most new volunteers want to help packaging the latest and greatest version of GNOME into unstable as soon as possible, but unless they already have Debian background, this is not the easiest task. Since there are already people working on this, the big packages are usually waiting on dependencies. I used to direct newcomers towards bug triage, but it is a tedious task and I m now convinced that our huge bug backlog will never be dealt with. The most useful thing to do for newcomers now is probably to find a GNOME or GNOME-related package that needs improvement or is lagging behind, and simply try to work on it. You can also come and fix the bugs you find annoying. Find a patch on the GNOME bugzilla, or cook it yourself, propose it, and if it s worthy enough you ll soon get commit access.
Our huge bug backlog will never be dealt with.
At this point I feel worth mentioning that if no one answers in 10 minutes, it doesn t mean that no one will answer in 2 hours, so please stay on the channel after asking. Raphael: There s been some controversy about GNOME 3 and the direction that the project is taking. What s your personal stance on GNOME 3? And what s the position of the pkg-gnome team? Josselin: The controversy is not new to GNOME 3, but the large-scale changes made with it have put it more prominently. The criticism usually boils down to a few categories:
  1. General lack of configurability
  2. Strange design decisions
  3. Red Hat centric development
  4. Hardware requirements
  5. Change resistance
The lack of configuration options has been an ongoing criticism since GNOME 2.0 has decided to rip off most of them. Of course, when the control center was redesigned again for 3.0, there was a surge of horrified exclamations from people who missed their favorite buttons. On this topic, I fully concur with GNOME developers. The configuration option that is useful for you is not necessarily useful for someone else. Of course, sometimes developers go a bit too far, but the general direction is right. At work, we found that only a minority of users actually configure anything on their desktops: they just want something that works to launch their applications. Apple and Google have sold millions of devices by making them the simplest possible and without any configuration. Design decisions are, on the contrary, individual decisions, and each of them, while having reasons behind it, can be questioned. I remember seeing a lot of complaints when the OK and Cancel buttons were reversed in dialog boxes, something that nobody questions anymore. GNOME Shell is full of such changes; some are easy to get accustomed with, some others just make eyebrows raise. The most obvious example is the user menu in GNOME 3.2, which contains an entry to configure your Google account, but no entry to shutdown the computer. Both decisions were taken independently, each of them with (good or bad) reasons, but the result is simply ridiculous. The default configuration in Debian will contain an extension to make it a bit better, but on the whole we don t intend to diverge from the upstream design, on which a lot of good work has been done.
On the whole we don t intend to diverge from the upstream design, on which a lot of good work has been done.
Point 3 is more complex. Red Hat being the company spending the most on GNOME, it is obvious that their employees work on making things work for their distribution. An example is the recurring discussions about relying on system services that are currently only implemented by systemd. Since there is a lot of (mostly unjustified) resistance against systemd in Debian, and since it won t work on kFreeBSD anyway, someone needs to develop an alternative implementation of these services for upstart and sysvinit. Everything is in place for someone else to do the job but it has to be done, and this can be frustrating. Especially since it can also be hard to integrate changes needed for other distributions . Hardware requirements are mostly a consequence of the previous criticism: there s hardware that most distributions just don t want to bother supporting. We ve seen it in squeeze with the introduction of a hard dependency on PulseAudio. The Debian GNOME team (together with the Gentoo maintainers) made this dependency optional, carrying heavy patches, in order to cover the cases where it does not work. Now that it has gained more maturity, making this effort obsolete, the new tendency is to require 3D acceleration. For various reasons, it is not available to everyone . On this matter, the position of the Debian GNOME team has always been to support as much different configurations as possible with reasonable effort. Thanks to efforts from the incredible Vincent Untz, upstream supports a so-called fallback mode , which is the GNOME panel from 2.x with a lot of its bugs fixed. We intend to support this mode for as long as reasonably possible in Debian, possibly even after upstream ends up dropping it. However, other applications are going to require 3D because GStreamer is moving to clutter too, affecting video playback performance on non-accelerated systems . For epiphany this is not a problem; only embedded video will be affected. But for totem, this is a major issue; because of that we will probably keep totem 3.0 in wheezy. Finally, there is a natural human tendency to dislike change (I have it too), and it applies a lot to desktop users habits. Needless to say a change of such a scale as introducing GNOME Shell can trigger reactions. However, I don t think it is reasonable, because of this resistance, to keep gnome-panel 2.x in Debian. This would be a lot of work on obsolete technology, and would prevent the upcoming removal of a lot of deprecated libraries. This time is much better spent improving gnome-panel 3.x in Debian and keeping the fallback mode great. One of the change that was made in Debian was to make it easier to find, being available as GNOME Classic directly from the login manager, instead of having to find it in an obscure configuration panel. In all cases, I would recommend to actually try GNOME Shell for a few hours before ditching it. I had never been accustomed to a new environment as quickly ever before.
In all cases, I would recommend to actually try GNOME Shell for a few hours before ditching it.
Having seen several of my GDM patches reverted without a warning, I know we are not finished with carrying patches in Debian packages.
Scientific workstations are a non-trivial example, since there is a measurable effect of using 3D in the window manager on heavy 3D applications.
On the other hand, on accelerated systems, this feature should end up improving performance a lot. Raphael: What are your plans for Debian Wheezy? Josselin: The first goal of the GNOME team is, of course, to provide again a great desktop environment to work on. For wheezy it will probably be based on GNOME 3.4. There also needs to be some work on package management interfaces. Upstream bases everything on PackageKit, but it is not as featureful as the aptdaemon Ubuntu technology. If I have time, I would also like to improve HTTP proxy support, since currently it is based on a stack of terrible hacks. Raphael: If you could spend all your time on Debian, what would you work on? Josselin: Obviously I would like to make GNOME in Debian even better. That would imply working on underneath dependencies (what we now like to call plumbing) to make sure everything is working great. This would also imply working more as GNOME upstream to make it more suitable for our needs. I would also work on large-scale improvements on the distribution, like conditional recommends which I d love to see implemented , or automatic build-dependency generation. I would also work on the installer to make it better for desktops machines. The idea is to automatically install language packs, or glues between two packages when both packages are installed. Raphael: What s the biggest problem of Debian? Josselin: The obvious answer is the same as the one most people you interviewed before gave: not enough members in core teams. A lot of developers join Debian to work on a small number of pet packages, and don t necessarily want to be involved with existing teams. It is probably still not obvious enough that the primary way to start contributing to Debian is to join an existing team. But if there is one thing that is preventing Debian from gaining more momentum now, it is a completely different one: the too short support timeframe. 3 years is really not enough for corporate users. One year to migrate from one version to another is too short, and it is not possible to skip a release. It is definitely possible to change that with reasonable effort: the long-term support after 3 years doesn t have to cover the same perimeter as the short-term one. For example, we could upgrade the kernel to the version in the current stable release, and stop fixing all non-remote security holes. The important thing is to cover the most basic needs: companies are ready to take the risk of having less support if it allows skipping a version, but not the risk of having no support at all. And even more important is to say that you do something. Red Hat says they support a release for 10 years, but of course after 5 years the supported perimeter is extremely small.
3 years [of support] is really not enough for corporate users.
Long-term support will not magically fix all problems in Debian, but it will bring more corporate users into the picture. And with corporate users come paid Debian developers, who can work on critical pieces of the system. Debian was built on the synergy between individuals and companies, and in recent years perhaps as a reaction against what happened with Ubuntu we ve kind of forgot the latter. A lot of individuals have joined the project, and they are actively working, for example, on shortening the release cycle, which goes against the interest of professionals. We should embrace again such users and developers, and that means adapting to the current needs of larger entities. Raphael: You re the maintainer of python-support, a packaging helper that was competing with python-central. Both helpers are now deprecated in favor of dh_python2. Does this mean that the situation of Python in Debian is now sane? Or are there remaining problems? Josselin: dh_python2 (and the Python3 version, dh_python3) has a sane enough design. It fixes a lot of issues in python-central and also python-support, at the expense of somehow reduced functionality for developers. However, just like the previous tools, it merely works around design mistakes in the Python interpreter. For example it is not possible to split binary modules, pure-Python modules and byte-compiled modules in different directory trees, like Perl does although PEP 3147 introduces a way to do so. There is still no sane and standardized way to deal with module versions. There is no difference made between the module (which is a part of language semantics) and the file containing it (an information which depends on the implementation). Developers heavily rely on introspection features and make assumptions based on the implementation, that make it impossible to work around problems with module files. Such problems are not restricted to Python. Those who fought against Ruby gems could tell even worse stories. While introducing GObject introspection packages in Debian (they can be used in JavaScript and Python to provide modules based on GObject libraries), I was pleased to see a clear distinction between file and module, but I was again struck by the fact you are not forced to declare API versions in your Python/JS code. In all cases, there is no reliable way to detect runtime dependencies in a given Python or JavaScript file, which leaves the maintainer to declare them by hand, and of course, often be wrong about them. Add to that the fact that most errors cannot be detected before runtime. For all these reasons, and while still being fond of Python for scripts and prototyping, I ve become really skeptical of using purely interpreted languages to write real applications. Some GNOME developers are moving away from Python and JavaScript, mostly towards Vala; I can only approve of that move and hope the same happens to other projects. Raphael: Is there someone in Debian that you admire for their contributions? Of course there is the never-sleeping, never-stopping, Michael Biebl who can upload a whole GNOME release in a single week-end. But there are a lot of awesome people who make Debian something that simply works. I could talk about Cyril Brulebois from the X strike force, Julien Cristau from the release team, Sjoerd Simons for his sound advice and work on plumbing, Luca Falavigna who is so fast at processing NEW, to quote only a few of those I work with frequently. And of course, Jordi and Sam for their humor.
Thank you to Josselin for the time spent answering my questions. I hope you enjoyed reading his answers as I did. Note that you can find older interviews on http://wiki.debian.org/PeopleBehindDebian.

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1 January 2012

Cyril Brulebois: X server 1.12 RC1

It s this time of the year again: a new X release approaches. The upstream schedule has been delayed a tiny bit so that the multitouch changes could land in master during this merge window. Which is what happened, a few days before Christmas. The other components involved in XI2.2 (aka. multitouch ) were packaged in experimental while the server side was getting prepared: Given we reached the 1.12 RC1 stage, it s a good idea to start building drivers against the new server to make it possible for users to perform some tests. And as usual, a new server means bumped input and video ABI, meaning a rebuild for the drivers to pick new dependencies. Some of them also needed a few fixes to make them build against the new server. Nothing that can t be fixed with a few merges from upstream master branches. The usual set of major drivers was uploaded to experimental: Significant change on the intel side: a snapshot of the current master branch was created, and packaged with SNA support enabled. SandyBridge's New Acceleration has apparently reached a point where it can be published to the masses, so here we go. Some details about it can be found in the initial commit. Also, for those wondering about the xorg-server FTBFS on some architectures, fixes are pending. Happy new year.

12 December 2011

Cyril Brulebois: Fixing synaptics on powerpc

(It s a new day, it s a new bug ) A regression appeared in the synaptics input driver, between the 1.4.1 and the 1.5.0 release, as reported in Debian #649002 by many users. Basically, no more touchpad on PowerPC (hi, iBook G4 users!). :-( What follows is how I tracked it down. The upstream bug report is fdo#43728. Anyone could have done so, there s no black magic involved. A little hint maybe: git bisect is really easy on X drivers, since one can build and test without the Debian packaging bits. 1st step: Getting started You need sources and build dependencies, nothing fancy. Since packages might be named a bit differently, there s a reference to the relevant upstream repositories in debian/watch for X packages.
# You need git here:
debcheckout xserver-xorg-input-synaptics synaptics.git
cd synaptics.git
# Let s get the upstream tags and branches:
cat debian/watch
git remote add upstream git://anongit.freedesktop.org/xorg/driver/xf86-input-synaptics
git fetch --all
# Let s install build dependencies:
sudo apt-get build-dep xserver-xorg-input-synaptics
2nd step: Reproducing It was said 1.5.0 was the first known buggy version, so let s make sure:
# Get the appropriate tag:
git checkout xf86-input-synaptics-1.5.0
# Prepare the build system:
autoreconf -vfi
# X finds its modules under /usr, not /usr/local:
./configure --prefix=/usr
# Build and install:
make && sudo make install
Now time to restart the display manager, and confirm that the pointer is not moving bug reproduced. Now let s check the 1.4.1 release isn t affected:
# Clean everything:
git clean -xdf
git checkout xf86-input-synaptics-1.4.1
autoreconf -vfi
./configure --prefix=/usr
make && sudo make install
And after a display manager restart, the pointer is moving again, good! For reference, the log has very different lines about appletouch, so it can be used to programmatically learn about the status (good or bad). 3rd step: Narrowing it down So, we have a known good version and a known bad version. Time for a binary search to find the guilty commit which introduced that regression!
git bisect start
git bisect good xf86-input-synaptics-1.4.1
git bisect bad  xf86-input-synaptics-1.5.0
You don t even need to know that 1.4.x and 1.5.x live in different branches, git figures that out for you:
Bisecting: a merge base must be tested
[de0dfb76444ad4160468d00515876c91a9fa20bf] synaptics 1.4.0
It s just a matter of running autoreconf && ./configure && make && sudo make install && sudo /etc/init.d/xdm restart every step of the way, so it s pretty easy. No wonder, 1.4.0 was working OK, so it can be recorded as such through git bisect good, and the binary search goes between that commit and 1.5.0. After a few iterations of git bisect good and git bisect bad, we get to the commit reported on the upstream bug. As an extra bonus, mentioning the upstream bug number/URL in the Debian bug means it can be marked as forwarded there and we ll receive automatic notifications when its status changes, thanks to bts-link. Now, if you want to provide a patch for this bug, you may want to try and revert this commit. 4th step: Providing a patch Let s go back to the affected release and try to revert the guilty commit:
git checkout xf86-input-synaptics-1.5.0
git revert 13543b156d78bc4d01a19844a5ee8f283269621b
Unfortunately, some later commits modified the affected areas so we re running into conflicts:
error: could not revert 13543b1... eventcomm: replace synaptics-custom TEST_BIT with server's BitIsOn.
hint: after resolving the conflicts, mark the corrected paths
hint: with 'git add <paths>' or 'git rm <paths>'
hint: and commit the result with 'git commit'
Let s try to understand what the offending commit did: it replaced a set of macros with a single one, taken from the server. Both the old TEST_BIT() and the new BitIsOn() take 2 arguments, but the order is reversed. Reverting it should only be a matter of introducing the TEST_BIT() macro again (along with the two other ones it needs), and using it. The problem is replacing all BitIsOn(foo,bar) with TEST_BIT(bar,foo): foo and bar might not be trivial, they could be complex C expressions, and a replacement in your favourite editor might not get all occurrences right. Thankfully, there s a nice tool to handle such things, called coccinelle. I won t go into details, just show how it can help here. Basically you just need to craft a tiny patch, called a semantic patch, which describes what I wrote in the previous paragraph. You only need to declare two expressions, say a and b, and declare that all BitIsOn(a,b) must be replaced with TEST_BIT(b,a). Here s the syntax:
@@
expression a,b;
@@
-BitIsOn(a,b)
+TEST_BIT(b,a)
Save it under testbit.cocci and apply it through spatch (from the coccinelle package), asking it to perform in-place replacement (we re in a git checkout copy, remember):
# Apply:
spatch -sp_file testbit.cocci -in_place .
# Profit:
git diff
Then you can run git commit -s, write a nice commit message, send it upstream, and enjoy the rest of the night. Coming soon to a mirror near you: fixing commit. As mentioned on the upstream bug report, I got the Debian reference wrong in the commit message, I really meant #649002.

11 December 2011

Cyril Brulebois: Fixing libdrm for intel

If you re having issues with video playback in unstable on Intel hardware, this post is for you. Some buffer freeing code was added in libdrm 2.4.28 to try and fix exhaustion of per-process limits. Some safeguards (assert()) were put in place to see whether some other components needed fixing (like unbalanced map()/unmap()). It s hard to miss those, since the server crashes when something s wrong. Good news: for affected users, downgrading to libdrm 2.4.27 (currently available in testing) should restore a functional setup. So far, patches have floated around for libva[1], xserver-xorg-video-intel[1,2] and libdrm[1,2,3] itself. Since libdrm has already been exposed to a wide audience for a while, a new upstream release is planned in a few days, disabling those assert()s. Other packages will then have some extra time to get new releases with the appropriate patches.

28 August 2011

Cyril Brulebois: Everybody be cool

this is not a robbery, only a regular X server branch switch, from 1.10 to 1.11. That means X drivers (for input and video) need to be rebuilt against the new server, which is happening through binNMUs. That also means the X stack from sid might be uninstallable for a few hours, but impatient people can still use the stack from wheezy in the meanwhile. Please refrain from reporting uninstallability bugs. That s expected, can t be avoided, and only for a few hours (assuming no driver starts to Fail To Build From Source). Many thanks to the following people, who joined the let s do a pre-upload crash test effort:

19 August 2011

Cyril Brulebois: Squeeze backports for Xorg

It took some time but it finally happened! NEW queue for backports Rule of thumb: if you're happy with Squeeze s X, stick to it. If you need a newer driver, for example for Intel Sandy Bridge, then give squeeze-backports a shot, and cross fingers! As usual, x.debian.net contains the relevant documentation. Hopefully, the short squeeze-backports instructions will be sufficient. If you encounter some issues, feel free to contact debian-x@.

20 July 2011

Cyril Brulebois: Smile of the day

It s been a while since my last patches for GNU/kFreeBSD, and Christoph kindly took over the kfreebsd-* build daemons from me some time ago, but still: smile of the day. Thanks, Russ.

17 July 2011

Cyril Brulebois: Thoughts on multiple webcams

Keeping an eye on something with a webcam is really easy: just a matter of setting up for example (c)vlc to multicast from /dev/videoX to the network, and done. Example:
# Streaming:
cvlc v4l2:///dev/video0 --no-audio --sout "#transcode vcodec=mp2v,vb=3072 :std access=udp,mux=ts,dst=224.0.0.1 "
# Playing, possibly on a remote machine:
vlc udp://@224.0.0.1:1234
Notes: Possible problems: Where to go from here:

26 June 2011

Cyril Brulebois: Hack orola (1)

Disclaimer: This post only describes what I ve been hacking on those days, and why. I haven t finished yet, and that might be too long of a story for a blog/planet. I m therefore duplicating the problem and the context, and mentioning the parts already documented on the page dedicated to that hack. Challenge: How to send commands to a computer without using an input device? Context: While it s not frequent, I sometimes run into situations where no input devices would work. That can happen because of a new X server with no compatible input devices; or while running a sample Wayland compositor on a console with X still running (not exactly sure what the problem was exactly); or because running gdb on X from within X is a bad idea; etc. Simple, non-bulletproof solutions: Alternative, viable solution 1: Buying a tiny, open, programmable device, like the Arduino Nano, a few components like a selector and a push button might do the trick. Then, some bits of programming with the open source Arduino environment should make it possible to connect that device to a USB port using a mini-B cable. Some bits going through a serial console and a daemon listening on it would make it possible to trigger a predefined set of actions just by selecting a position and hitting the button. Tada! No drawback for that solution, except the need for thinking about bringing that device everywhere. :) Alternative, viable solution 2: While I m by no means a phone addict, I tend to have it with me more or less all the time, and it can be connected through a mini-B USB cable. Oh, but then, maybe I could turn it into a suitable device as described above? That s a Motorola RAZR V3, it runs Java applications, and there s a SDK available for Linux (32 bits) through the Motorola developer network. That might be enough, so I decided to jump through some hoops to see whether that s indeed feasible. Not because I like it much better than the Arduino-based solution, just because I can. My hack orola page explains how I went from the maybe it s possible idea to the yes, now I know how to build, upload, and run a custom application certitude. It still lacks the actual Java code running on the phone, as well as its Unix daemon counterpart, but for a good reason: they need be written! At the moment the following sections are available:

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