Search Results: "Colin Watson"

3 September 2012

Philipp Kern: IPv6 support in debian-installer

I tried to continue netcfg's journey to support IPv6 in debian-installer. Matt Palmer wrote a large patch set many moons ago (kudos!) and Colin Watson polished it and included it into Ubuntu. The reason for it not being merged into Debian first was ifupdown. Version 0.7 finally supports IPv6 and only entered Debian unstable by the end of May. Due to a bunch of changes to netcfg, one reason being a Summer of Code project on it, I had to forward-port those 50 patches and add two bug fixes on top. Hence it's possible that I introduced some breakage, even if the result works well for me (apart from one DHCPv6 oddity that cannot be seen from within KVM). The tree can be found in the people/pkern/ipv6 branch. I was unable to check if Ubuntu has introduced any additional patches on top of the old patch set, as I'm not used enough to bzr.

This mini.iso (detached signature) netinst image contains a debian-installer current as of today and two additional patched udebs: netcfg with the aforementioned IPv6 patch set and busybox with ping6 enabled. I'd appreciate if you could go and test it in one (or more) of the following environments: IPv4-only (DHCPv4 / static), wireless (IPv4 / IPv6 as desired, there has been some refactoring), stateless IPv6 autoconfiguration (it even supports RDNSS and DNSSL), stateless IPv6 autoconfiguration with stateless DHCPv6, and stateful DHCPv6. It will try to configure dual stack if possible. Please note that many Debian mirrors are not yet IPv6-enabled. Even prominent ftp.CC.debian.org hosts like ftp.de.debian.org still do not support it. So you'll have to pick one carefully if you want to try IPv6-only installation. (Which worked for me!)

If you have any feedback for me, please leave it here as a comment or mail me at pkern@d.o. Thanks!

12 August 2012

Gregor Herrmann: RC bugs 2012/32

this was a weird RCBW week for me. although we are not that far into the freeze yet, the amount of easy-enough-for-me-to-fix RC bugs on UDD is already rather low. besides the not very impressive list below, I at least tried to do some housekeeping on some bugreports (tagging, reassigning, forwarding, ).

Steve McIntyre: EFI installation progress

As promised last month at DebConf, I've been working on adding EFI support to debian-cd and debian-installer, hopefully to get it up and running. At the moment, this is basic support only for booting and setting up the installed system via UEFI. I'm not worrying about "Secure" (better named "Restricted"?) Boot yet - that comes later, and depends on the basic stuff working first. So, how is it going? Quite well, really. I've got a debian-cd branch that I'm working on locally, and with a relatively small amount of work there I've got a locally-built CD that boots in EFI mode, using grub-efi as a boot loader. I've borrowed a script called efi-image from Colin Watson which generates the necessary EFI boot image from bits out of the grub-efi-amd64-bin package. For some reason, this grub image isn't working with all the normal graphics code so I've not got a pretty branded startup screen yet. But, nonetheless, I do have a working EFI boot CD. Yay! Next step: the installer. At the moment, generic amd64 and i386 machines are assumed to use need dos-style partitioning, and then either lilo or grub as a bootloader. I've patched and rebuilt some of the d-i packages locally to add a new sub-architecture of "efi" for both amd64 and i386, alongside the existing "generic" and "mac" variants. Using that new sub-architecture, it's possible to add checks for amd/efi and i386/efi in various places to make the necessary changes: Why elilo? It's the default for current ia64 systems, and for EFI Macs. I tried to get grub-efi working with the grub-installer package, but with little success so far. I'll try again with grub-efi, but for now elilo is much simpler and (importantly!) it works for me. So, I have a netinst CD built that works for me in local testing in a qemu VM using James Bottomley's OVMF build of Tianocore. It's not pretty, but it works fine, covering all the normal Debian installation steps and giving me a UEFI system at the end of the process. I'm about to start testing on real hardware now, so I think it's worth sharing this netinst image with others too. Grab it from http://cdimage.debian.org/cdimage/unofficial/efi-development/upload1/ . The "bits" subdirectory contains all the tweaked d-i packages I've played with, in both source and binary form. If you have an EFI system and would like to help us get it supported well in Debian, please download this image and play with it! Feedback to the debian-cd and/or debian-boot lists, please!

27 May 2012

Colin Watson: OpenSSH 6.0p1

OpenSSH 6.0p1 was released a little while back; this weekend I belatedly got round to uploading packages of it to Debian unstable and Ubuntu quantal. I was a bit delayed by needing to put together an improvement to privsep sandbox selection that particularly matters in the context of distributions. One of the experts on seccomp_filter has commented favourably on it, but I haven't yet had a comment from upstream themselves, so I may need to refine this depending on what they say. (This is a good example of how it matters that software is often not built on the system that it's going to run on, and in particular that the kernel version is rather likely to be different. Where possible it's always best to detect kernel capabilities at run-time rather than at build-time.) I didn't make it very clear in the changelog, but using the new seccomp_filter sandbox currently requires UsePrivilegeSeparation sandbox in sshd_config as well as a capable kernel. I won't change the default here in advance of upstream, who still consider privsep sandboxing experimental.

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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15 April 2012

Gregor Herrmann: RC bugs 2012/15

another weekend, another RCBW report:

2 March 2012

Colin Watson: libpipeline 1.2.1 released

I've released libpipeline 1.2.1, and uploaded it to Debian unstable. This is a bug-fix release:

26 February 2012

Gregor Herrmann: RC bugs 2012/08

here comes my usual report about my work on RC bugs. this time a bit more "added a comment" or "sent a patch" but also some uploads.

30 January 2012

Colin Watson: APT resolver bugs

I've managed to go for eleven years working on Debian and nearly eight on Ubuntu without ever needing to teach myself how APT's resolver works. I get the impression that there's a certain mystique about it in general (alternatively, I'm just the last person to figure this out). Recently, though, I had a couple of Ubuntu upgrade bugs to fix that turned out to be bugs in the resolver, and I thought it might be interesting to walk through the process of fixing them based on the Debug::pkgProblemResolver=true log files. Breakage with Breaks The first was Ubuntu bug #922485 (apt.log). To understand the log, you first need to know that APT makes up to ten passes of the resolver to attempt to fix broken dependencies by upgrading, removing, or holding back packages; if there are still broken packages after this point, it's generally because it's got itself stuck in some kind of loop, and it bails out rather than carrying on forever. The current pass number is shown in each "Investigating" log entry, so they start with "Investigating (0)" and carry on up to at most "Investigating (9)". Any packages that you see still being investigated on the tenth pass are probably something to do with whatever's going wrong. In this case, most packages have been resolved by the end of the fourth pass, but xserver-xorg-core is causing some trouble. (Not a particular surprise, as it's an important package with lots of relationships.) We can see that each breakage is:
Broken xserver-xorg-core:i386 Breaks on xserver-xorg-video-6 [ i386 ] < none > ( none )
This is a Breaks (a relatively new package relationship type introduced a few years ago as a sort of weaker form of Conflicts) on a virtual package, which means that in order to unpack xserver-xorg-core each package that provides xserver-xorg-video-6 must be deconfigured. Much like Conflicts, APT responds to this by upgrading providing packages to versions that don't provide the offending virtual package if it can, and otherwise removing them. We can see it doing just that in the log (some lines omitted):
Investigating (0) xserver-xorg-core [ i386 ] < 2:1.7.6-2ubuntu7.10 -> 2:1.11.3-0ubuntu8 > ( x11 )
  Fixing xserver-xorg-core:i386 via remove of xserver-xorg-video-tseng:i386
Investigating (1) xserver-xorg-core [ i386 ] < 2:1.7.6-2ubuntu7.10 -> 2:1.11.3-0ubuntu8 > ( x11 )
  Fixing xserver-xorg-core:i386 via remove of xserver-xorg-video-i740:i386
Investigating (2) xserver-xorg-core [ i386 ] < 2:1.7.6-2ubuntu7.10 -> 2:1.11.3-0ubuntu8 > ( x11 )
  Fixing xserver-xorg-core:i386 via remove of xserver-xorg-video-nv:i386
OK, so that makes sense - presumably upgrading those packages didn't help at the time. But look at the pass numbers. Rather than just fixing all the packages that provide xserver-xorg-video-6 in a single pass, which it would be perfectly able to do, it only fixes one per pass. This means that if a package Breaks a virtual package which is provided by more than ten installed packages, the resolver will fail to handle that situation. On inspection of the code, this was being handled correctly for Conflicts by carrying on through the list of possible targets for the dependency relation in that case, but apparently when Breaks support was implemented in APT this case was overlooked. The fix is to carry on through the list of possible targets for any "negative" dependency relation, not just Conflicts, and I've filed a patch as Debian bug #657695. My cup overfloweth The second bug I looked at was Ubuntu bug #917173 (apt.log). Just as in the previous case, we can see the resolver "running out of time" by reaching the end of the tenth pass with some dependencies still broken. This one is a lot less obvious, though. The last few entries clearly indicate that the resolver is stuck in a loop:
Investigating (8) dpkg [ i386 ] < 1.15.5.6ubuntu4.5 -> 1.16.1.2ubuntu5 > ( admin )
Broken dpkg:i386 Breaks on dpkg-dev [ i386 ] < 1.15.5.6ubuntu4.5 -> 1.16.1.2ubuntu5 > ( utils ) (< 1.15.8)
  Considering dpkg-dev:i386 29 as a solution to dpkg:i386 7205
  Upgrading dpkg-dev:i386 due to Breaks field in dpkg:i386
Investigating (8) dpkg-dev [ i386 ] < 1.15.5.6ubuntu4.5 -> 1.16.1.2ubuntu5 > ( utils )
Broken dpkg-dev:i386 Depends on libdpkg-perl [ i386 ] < none -> 1.16.1.2ubuntu5 > ( perl ) (= 1.16.1.2ubuntu5)
  Considering libdpkg-perl:i386 12 as a solution to dpkg-dev:i386 29
  Holding Back dpkg-dev:i386 rather than change libdpkg-perl:i386
Investigating (9) dpkg [ i386 ] < 1.15.5.6ubuntu4.5 -> 1.16.1.2ubuntu5 > ( admin )
Broken dpkg:i386 Breaks on dpkg-dev [ i386 ] < 1.15.5.6ubuntu4.5 -> 1.16.1.2ubuntu5 > ( utils ) (< 1.15.8)
  Considering dpkg-dev:i386 29 as a solution to dpkg:i386 7205
  Upgrading dpkg-dev:i386 due to Breaks field in dpkg:i386
Investigating (9) dpkg-dev [ i386 ] < 1.15.5.6ubuntu4.5 -> 1.16.1.2ubuntu5 > ( utils )
Broken dpkg-dev:i386 Depends on libdpkg-perl [ i386 ] < none -> 1.16.1.2ubuntu5 > ( perl ) (= 1.16.1.2ubuntu5)
  Considering libdpkg-perl:i386 12 as a solution to dpkg-dev:i386 29
  Holding Back dpkg-dev:i386 rather than change libdpkg-perl:i386
The new version of dpkg requires upgrading dpkg-dev, but it can't because of something wrong with libdpkg-perl. Following the breadcrumb trail back through the log, we find:
Investigating (1) libdpkg-perl [ i386 ] < none -> 1.16.1.2ubuntu5 > ( perl )
Broken libdpkg-perl:i386 Depends on perl [ i386 ] < 5.10.1-8ubuntu2.1 -> 5.14.2-6ubuntu1 > ( perl )
  Considering perl:i386 1472 as a solution to libdpkg-perl:i386 12
  Holding Back libdpkg-perl:i386 rather than change perl:i386
Investigating (1) perl [ i386 ] < 5.10.1-8ubuntu2.1 -> 5.14.2-6ubuntu1 > ( perl )
Broken perl:i386 Depends on perl-base [ i386 ] < 5.10.1-8ubuntu2.1 -> 5.14.2-6ubuntu1 > ( perl ) (= 5.14.2-6ubuntu1)
  Considering perl-base:i386 5806 as a solution to perl:i386 1472
  Removing perl:i386 rather than change perl-base:i386
Investigating (1) perl-base [ i386 ] < 5.10.1-8ubuntu2.1 -> 5.14.2-6ubuntu1 > ( perl )
Broken perl-base:i386 PreDepends on libc6 [ i386 ] < 2.11.1-0ubuntu7.8 -> 2.13-24ubuntu2 > ( libs ) (>= 2.11)
  Considering libc6:i386 -17473 as a solution to perl-base:i386 5806
  Added libc6:i386 to the remove list
Investigating (0) libc6 [ i386 ] < 2.11.1-0ubuntu7.8 -> 2.13-24ubuntu2 > ( libs )
Broken libc6:i386 Depends on libc-bin [ i386 ] < 2.11.1-0ubuntu7.8 -> 2.13-24ubuntu2 > ( libs ) (= 2.11.1-0ubuntu7.8)
  Considering libc-bin:i386 10358 as a solution to libc6:i386 -17473
  Removing libc6:i386 rather than change libc-bin:i386
So ultimately the problem is something to do with libc6; but what? As Steve Langasek said in the bug, libc6's dependencies have been very carefully structured, and surely we would have seen some hint of it elsewhere if they were wrong. At this point ideally I wanted to break out GDB or at the very least experiment a bit with apt-get, but due to some tedious local problems I hadn't been able to restore the apt-clone state file for this bug onto my system so that I could attack it directly. So I fell back on the last refuge of the frustrated debugger and sat and thought about it for a bit. Eventually I noticed something. The numbers after the package names in the third line of each of these log entries are "scores": roughly, the more important a package is, the higher its score should be. The function that calculates these is pkgProblemResolver::MakeScores() in apt-pkg/algorithms.cc. Reading this, I noticed that the various values added up to make each score are almost all provably positive, for example:
         Scores[I->ID] += abs(OldScores[D.ParentPkg()->ID]);
The only exceptions are an initial -1 or -2 points for Priority: optional or Priority: extra packages respectively, or some values that could theoretically be configured to be negative but weren't in this case. OK. So how come libc6 has such a huge negative score of -17473, when one would normally expect it to be an extremely powerful package with a large positive score? Oh. This is computer programming, not mathematics ... and each score is stored in a signed short, so in a sufficiently large upgrade all those bonus points add up to something larger than 32767 and everything goes haywire. Bingo. Make it an int instead - the number of installed packages is going to be on the order of tens of thousands at most, so it's not as though it'll make a substantial difference to the amount of memory used - and chances are everything will be fine. I've filed a patch as Debian bug #657732. I'd expected this to be a pretty challenging pair of bugs. While I certainly haven't lost any respect for the APT maintainers for dealing with this stuff regularly, it wasn't as bad as I thought. I'd expected to have to figure out how to retune some slightly out-of-balance heuristics and not really know whether I'd broken anything else in the process; but in the end both patches were very straightforward.

16 January 2012

Rapha&#235;l Hertzog: Review of my Debian related goals for 2011

Last year I shared my Debian related goals for 2011 . I tend to put more goals than what I can reasonably complete alone and this year was no exception. Let s have a look.
  1. Translate my Debian book into English: PARTLY DONE
    It took more time than expected to prepare and to run the fundraising campaign but it has been successful and the translation is happening right now.
  2. Finish multiarch support in dpkg: DONE BUT NOT ENTIRELY MERGED YET
    Yes, multiarch support was already in the pipe last year in January. I completed the development between January and April (it was sponsored by Linaro) and since then it has mostly been waiting on Guillem to review it, tweak it, and integrate it.
  3. Make deb files use XZ compression by default: TRIED BUT ABANDONED
    After discussing the issue with Colin Watson and Joey Hess during debconf, I came to the conclusion that it was not really desirable at this point. The objections were that debian-installer was not ready for it and that it adds a new dependency on xz for debootstrap to work on non-Debian systems. I believe that the debian-installer side is no longer a problem since unxz is built in busybox-udeb (since version 1:1.19.3-2). For the other side, there s not much to do except ensuring that xz is portable to all the other OS we care about. DAK has been updated too (see #556407).
  4. Be more reactive to review/merge dpkg patches: PARTLY DONE
    I don t think we had any patch that received zero input. We still have a backlog of patches, and the situation is far from ideal but the situation improved.
  5. Implement the rolling distribution proposed as part of the CUT project and try to improve the release process: NOT DONE
    We had a BoF during debconf, we discussed it at length on debian-devel, but in the end we did nothing out of it. Except Josselin Mouette who wrote a proof of concept for his idea. For me testing is already what people are expecting from a rolling distribution. It s just a matter of documenting how to effectively use testing, and of some marketing by defining rolling as alias to testing.
  6. Work more regularly on the developers-reference: PARTLY DONE
    I did contribute some new material to the document but not as much as I could have hoped. On the other hand, I have been rather reactive to ensure that sane patches got merged. We need more people writing new parts and updating the existing content.
  7. Write a 10-lesson course called Smart Package Management : NOT DONE
  8. Create an information product (most likely an ebook or an online training) and sell it on my blog: NOT DONE
    This was supposed to happen after the translation of the Debian Administrator s Handbook. Since the translation is not yet over, I did not start to work on this yet.
  9. By the end of the year, have at least 1/3 of my time funded by donations and/or earnings of my information products: NOT REACHED
    My target was rather aggressive with 700 each month, and given that I did not manage to complete any information product, I m already very pleased to have achieved a mean amount of 204 of donations each month (min: 91 , max: 364 ). It s more than two times better than in 2010. Thank you! Note that those figures do not take into account the revenues of the fundraising of the Debian Administrator s Handbook since they will be used for its translation.
That makes quite a lot of red (for things that I did not achieve) on the other hand I completed projects that I did not foresee and did not plan. For instance improving dpkg-buildflags and then merging Kees Cook work on hardened build flags was an important step for Debian. This was waiting for so long already

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15 January 2012

Gregor Herrmann: RC bugs 2012/02

while working on RC bugs, I noticed that some DDs sent patches to the BTS in the last weeks (yeah!) but did not upload the fixes in NMUs. short request: could you please either state the reason for not uploading, or just go ahead and dput/dupload the fixed packages?

& here's my list:

10 December 2011

Tim Retout: SFTP default umask

So I was about to configure an FTP server to let a friend upload content for a website... and then I came to my senses and remembered sftp exists. It's supported by the same graphical clients, and avoids me having to figure out SSL certificates and so on. Next problem: we want to both edit the site. Okay, so I create a group, make it the default group for both users... and now I need to set the umask to 002 so that all group members can edit all files. There's no option in the client... Skimming Debian bug #496843 (closed Apr 2010, thanks Colin Watson!) we can set this in sshd_config these days - no need to mess about with wrapper scripts. Very easy:
Subsystem sftp /usr/lib/openssh/sftp-server -u 002
Now all content created through the sftp client is group-writable, and owned by the default group of each user! See 'man (8) sftp-server'.

5 December 2011

Ana Beatriz Guerrero Lopez: RCBSaturday

On Saturday evening I started talking with M nica about Bug Squashing Parties and how they work. I am not sure how it happened, we started doing one. Then it was too fun to stop :P NMUs by M nica: Funny, there were a couple of NMUs by others uploading patchs by M nica. NMUs by Ana: I also closed #646449 (libosip2) that has been fixed in a new release upload, sponsored a NMU to Sven Joachim who had a patch sitting in the BTS for a month NMU-fixing #646147 (lie), sponsored dbus-c++ and reviewed for sponsoring a new version inspircd.

2 December 2011

Rapha&#235;l Hertzog: My Debian Activities in November 2011

This is my monthly summary of my Debian related activities. If you re among the people who made a donation to support my work (310.73 , thanks everybody!), then you can learn how I spent your money. Otherwise it s just an interesting status update on my various projects. Dpkg: Multi-Arch Saga I know lots of people are waiting the landing of multiarch in Debian unstable, and so am I. Things are progressing, though not as quickly as I hoped. Guillem merged about half of the branch between the 24th October and the 6th of November. After that most of the work happened on his personal repository in his pu/multiarch/master branch. I verify this repository from time to time because Guillem does not inform me when he has made progress. I noticed changes on his repository on the 10th, 19th, 23th, 28th of November and on the 1th of December. He announced a long time ago that he had some interface changes and up to now only wrote about the switch from the command-line option --foreign-architecture (to put in /etc/dpkg/dpkg.cfg) to the explicit command dpkg --add-architecture that only needs to be called once (see mail here). As of today (December 2th), the promised email for the other interface changes is still not here. On November 23th, I reviewed Guillem s work and tried to run the code in his branch. I spent the whole day chasing up regressions and submitted lots of fixes to Guillem. Thanks to the extensive test-suite I wrote when I developed my branch, it has been fairly easy to track them all down. All the issues I reported have been fixed in the latest version of Guillem s branch although the fixes are often slightly different from those that I submitted. Dpkg: Squeeze Backport At the start of the month, I uploaded what I expected to be a fairly uncontroversial backport of dpkg 1.16.1.1. It turns out I was wrong. After some discussion, I think we came to an agreement that it was acceptable to backport dpkg-dev and libdpkg-perl only. My goal was not to bring the latest dpkg to users but to make it easier for package maintainers to backport packages using new features provided by dpkg-dev >= 1.16 (such as hardening build flags, the makefile snippets provided in /usr/share/dpkg/, or the improved dpkg-buildflags interface). Thus I modified the source package uploaded to squeeze-backports to build only dpkg-dev and libdpkg-perl. It has been uploaded on November 23th and it s waiting in the NEW queue for a backports admin to process it. Misc Dpkg Work I merged a patch of Colin Watson to be able to verify build-dependencies for a foreign architecture (taking into account the Multi-Arch status of each package listed). I released dpkg 1.16.1.2 with two minor fixes that were sitting in the sid branch. I wanted to get rid of this so that the path is clear for a 1.16.2 upload with multiarch. The package just migrated to testing so we re fine. I spent another day doing dpkg bug triaging on Launchpad, we re now down to 77 bugs with many of them tagged as incomplete and likely to expire in 2 months. The Debian Administrator s Handbook eBookWe released a sample chapter so that it s easier to have an idea of the quality of the book. The chapter covers the APT tools quite extensively. I bet that even you could learn something about apt-get/aptitude The crowfunding campaign on Ulule ended on November 28th.
With 675 supporters, we raised 24385 EUR. Of those, 14935 EUR have been put in the liberation fund and the rest corresponds to the various pre-orders and rewards offered. This means that the translation will happen (we just started) but that the book is currently not going to be released under a free license. Don t despair As planned, the liberation campaign is carried on until the 25 K target is reached! Instead of being hosted on Ulule, this permanent campaign is on the project website at debian-handbook.info/liberation/. Note that any contribution of 10 EUR or more means that you get a copy of the ebook as soon as it s available (even if the liberation target is not reached). Package Tracking System At the start of the month, I filed two ideas of improvements for the PTS in the bug tracking system: #647258 is about showing outstanding bugs that relate to a release goal and #647901 is about warning maintainers that the package is affected by a current transition. If you re a coder and want to start contributing to Debian and its QA team, those bugs could be interesting targets for a start. :-) In both cases, I have been in contact with members of the release team because those ideas require some structured data from the release team as input. Thanks to Meddi Dohguy and Niels Thykier for their help. Later in the month, the topic of relocating the PTS once again came up. For historical reasons, the PTS was hosted on master.debian.org together with the BTS. Nowadays the BTS has its own host and it made no sense anymore to have the PTS separate from the rest of the QA services hosted on qa.debian.org (currently quantz.debian.org). So together with Martin Zobel Helas we took care to plan the migration and on November 19th we executed the plan. It worked like a charm and almost nobody noticed (only one undocumented dependency was missed, which broke the SOAP interface). Misc Packaging Work WordPress was broken in Ubuntu and it was also not properly synchronized with Debian due to an almost useless change on their side. Thus I requested a sync so that the working version from Debian gets imported in Ubuntu. I sponsored the docbook-xsl 1.76.1 upload that I needed for Publican. Then I updated Publican just to discover that the test-suite triggers a new bug in fop (filed as #649476). I disabled the test-suite temporarily and uploaded Publican 2.8 to unstable. BTW, I also filed 2 upstream bugs with patches for issues I discovered while trying to generate the sample chapter of my book (see here and here). I uploaded a version 0.7.1 of nautilus-dropbox and fixed #648215 at the same time. I made an NMU of bison to fix a long-standing release critical bug that hit me once more during an upgrade (see #645038). I uploaded to experimental a new version of gnome-shell-timer compatible with GNOME 3.2. I took the opportunity to install from experimental the few GNOME 3.2 packages which are not yet in unstable Thanks See you next month for a new summary of my activities.

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27 November 2011

Gregor Herrmann: RC bugs 2011/47

after the rather intensive last week, this week was more business as usual. here's the list:

20 November 2011

Gregor Herrmann: RC bugs 2011/46

as expected this week was characterised by fixing bugs around the perl 5.14 transition. besides that I've also uploaded a couple of NMUs with patches kindly provided in the BTS by some tireless bug fixers.

6 November 2011

Gregor Herrmann: RC bugs 2011/44

this week showed an interesting mixture of RC bug fixes: applying patches from others, writing one on my one, adjusting build dependencies, & also closing some bugs that did not occur anymore during the last Grid'5000 run & are also unreproducible locally (thanks to Lucas for the hint).

24 October 2011

Colin Watson: Quality in Ubuntu 12.04 LTS

As is natural for an LTS cycle, lots of people are thinking and talking about work focused on quality rather than features. With Canonical extending LTS support to five years on the desktop for 12.04, much of this is quite rightly focused on the desktop. I'm really not a desktop hacker in any way, shape, or form, though. I spent my first few years in Ubuntu working mainly on the installer - I still do, although I do some other things now too - and I used to say only half-jokingly that my job was done once X started. Of course there are plenty of bugs I can fix, but I wanted to see if I could do something with a bit more structure, so I got to thinking about projects we could work on at the foundations level that would make a big difference. Image build pipeline One difficulty we have is that quite a few of our bugs - especially installer bugs, although this goes for some other things too - are only really caught when people are doing coordinated image testing just before a milestone release. Now, it takes a while to do all the builds and then it takes a while to test them. The excellent work of the QA team has meant that testing is much quicker now than it used to be, and a certain amount of smoke-testing is automated (particularly for server images). On the other hand, the build phase has only got longer as we've added more flavours and architectures, particularly as some parts of the process are still serialised per architecture or subarchitecture so ARM builds in particular take a very long time indeed. Exact timings are a bit difficult to get for various reasons, but I think the minimum time between a developer uploading a fix and us having a full set of candidate images on all architectures including that fix is currently somewhere north of eight hours, and that's with people cutting corners and pulling strings which is a suboptimal thing to have to do around release time. This obviously makes us reluctant to respin for anything short of showstopper bugs. If we could get things down to something closer to two hours, respins would be a much less horrible proposition and so we might be able to fix a few bugs that are serious but not showstoppers, not to mention that the release team would feel less burned out. We discussed this problem at the release sprint, and came up with a laundry list of improvements; I've scheduled this for discussion at UDS in case we can think of any more. Please come along if you're interested! One thing in particular that I'm working on is refactoring Germinate, a tool which dates right back to our first meeting before Ubuntu was even called Ubuntu and whose job is to expand dependencies starting from our lists of "seed" packages; we use this, among other things, to generate Task fields in the archive and to decide which packages to copy into our images. This was acceptably quick in 2004, but now that we run it forty times (eight flavours multiplied by five architectures) at the end of every publisher run it's actually become rather a serious performance problem: cron.germinate takes about ten minutes, which is over a third of the typical publisher runtime. It parses Packages files eight times as often as it needs to, Sources files forty times as often as it needs to, and recalculates the dependency tree of the base system five times as often as it needs to. I am confident that we can significantly reduce the runtime here, and I think there's some hope that we might be able to move the publisher back to a 30-minute cycle, which would increase the velocity of Ubuntu development in general. Maintaining the development release Our release cycle always starts with syncing and merging packages from Debian unstable (or testing in the case of LTS cycles). The vast majority of packages in Ubuntu arrive this way, and generally speaking if we didn't do this we would fall behind in ways that would be difficult to recover from later. However, this does mean that we get a "big bang" of changes at the start of the cycle, and it takes a while for the archive to be usable again. Furthermore, even once we've taken care of this, we have a long-established rhythm where the first part of the cycle is mainly about feature development and the second part of the cycle is mainly about stabilisation. As a result, we've got used to the archive being fairly broken for the first few months, and we even tell people that they shouldn't expect things to work reliably until somewhere approaching beta. This makes some kind of sense from the inside. But how are you supposed to do feature development that relies on other things in the development release? In the first few years of Ubuntu, this question didn't matter very much. Nearly all the people doing serious feature development were themselves serious Ubuntu developers; they were capable of fixing problems in the development release as they went along, and while it got in their way a little bit it wasn't all that big a deal. Now, though, we have people focusing on things like Unity development, and we shouldn't assume that just because somebody is (say) an OpenGL expert or a window management expert that they should be able to recover from arbitrary failures in development release upgrades. One of the best things we could do to help the 12.04 desktop be more stable is to have the entire system be less unstable as we go along, so that developers further up the stack don't have to be distracted by things wobbling underneath them. Plus, it's just good software engineering to keep the basics working as you go along: it should always build, it should always install, it should always upgrade. Ubuntu is too big to do something like having everyone stop any time the build breaks, the way you might do in a smaller project, but we shouldn't let things slide for months either. I've been talking to Rick Spencer and the other Ubuntu engineering leads at Canonical about this. Canonical has a system of "rotations", where you can go off to another team for a while if you're in need of a change or want to branch out a bit; so I proposed that we allow our engineers to spend a month or two at a time on what I'm calling the +1 Maintenance Team, whose job is simply to keep the development release buildable, installable, and upgradeable at all times. Rick has been very receptive to this, and we're going to be running this as a trial throughout the 12.04 cycle, with probably about three people at a time. As well as being professional archive gardeners, these people will also work on developing infrastructure to help us keep better track of what we need to do. For instance, we could deploy better tools from Debian QA to help us track uninstallable packages, or we could enhance some of our many existing reports to have bug links and/or comment facilities, or we could spruce up the weather report; there are lots of things we could do to make our own lives easier. By 12.04, I would like, in no particular order: Of course, this overlaps to a certain extent with the kinds of things that the MOTU team have been doing for years, not to mention with what all developers should be doing to keep their own houses in reasonable order, and I'd like us to work together on this; we're trying to provide some extra hands here to make Ubuntu better for everyone, not take over! I would love this to be an opportunity to re-energise MOTU and bring some new people on board. I've registered a couple of blueprints (priorities, infrastructure) for discussion at UDS. These are deliberately open-ended skeleton sessions, and I'll try to make sure they're scheduled fairly early in the week, so that we have time for break-out sessions later on. If you're interested, please come along and give your feedback!

16 October 2011

Gregor Herrmann: RC bugs 2011/41

here's my list of recent RC bug fixes, again comprising bugs which already had a patch in the BTS:

9 October 2011

Gregor Herrmann: RC bugs 2011/40

another week, another list of fixed RC bugs, again most of them with patches from ubuntu. &, as zack said today, the next freeze is not really imminent but it's getter closer.

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