Happy Birthday Debian! And memories of an old-timer…

For Debian’s birthday, Francesca Ciceri of the Debian Publicity team suggested that developers “blog about their first experiences with Debian”. I found this a good idea so I’m going to share my own early experience. It’s quite different from what happens nowadays…

Before speaking of my early Debian experience, I have to set some context. In my youth, I have always been a Windows user and a fan of Bill Gates. That is until I got Internet at home… at that point, I got involved in Usenet and made some friends there. One of those made me discover Perl and it has been somewhat of a revelation for me who had only been programming in Visual Basic, Delphi or ObjectPal. Later the same friend explained me that Perl was working much better on Linux and that Debian Linux installs it by default so I should try this one.

I had no idea of what Linux was, but given how I loved Perl, I was eager to try his advice. So I got myself a Tri-Linux CD with Debian/RedHat/Slackware on it and started the installation process (which involved preparing boot floppies). But I did not manage to get the graphical interface working despite lots of fiddling with Xfree86’s configuration file. So I ended up installing RedHat and used it for a few months. But since many of the smart guys in my Usenet community were Debian users, I persisted and finally managed to get it to work!

After a few months of usage, I was amazed at everything that was available for free and I wanted to give back. I filed my first bug report in July 1998, I created my first Debian packages in August 1998 and I got accepted as an official Debian developer in September 1998 (after a quick chat over the phone with Martin Schulze or James Troup — I never understood the name of my interlocutor on the phone and I was so embarassed to have to use my rusty English over the phone that I never asked). That’s right, it took me less than 3 months to become a Debian developer (I was 19 years old back then).

I learned a lot during those months by reading and interacting with other Debian developers. Many of those went away from Debian in the mean time but some of them are still involved (Joey Hess, Manoj Srivastava, Ian Jackson, Martin Schulze, Steve McIntyre, Bdale Garbee, Adam Heath, John Goerzen, Marco D’Itri, Phil Hands, Lars Wirzenius, Santiago Vila, Matthias Klose, Dan Jacobowitz, Michael Meskes, …).

My initial Debian work was centered around Perl: I adopted dpkg-ftp (the FTP method for dselect) because it was written in Perl and had lots of outstanding bug reports. But I also got involved in more generic Quality Assurance work and tried to organize the nascent QA team. It was all really a lot of fun, I could take initiatives and it was clear to me that my work was appreciated.

I don’t know if you find this story interesting but I had some fun time digging through archives to find out the precise dates… if you want to learn more about what I did over the following years, I maintain a webpage for this purpose.

Looking back at 16 years of dpkg history with some figures

With Debian’s 19th anniversary approaching, I thought it would be nice to look back at dpkg’s history. After all, it’s one of the key components of any Debian system.

The figures in this article are all based on dpkg’s git repository (as of today, commit 9a06920). While the git repository doesn’t have all the history, we tried to integrate as much as possible when we created it in 2007. We have data going back to April 1996…

In this period between April 1996 and August 2012:

  • 146 persons contributed to dpkg (result of git log --pretty='%aN'|sort -u|wc -l)
  • 6948 commits have been made (result of git log --oneline | wc -l)
  • 3133612 lines have been written/modified (result of git log --stat|perl -ne 'END { print $c } $c += $1 if /(\d+) insertions/;')

Currently the dpkg source tree contains 28303 lines of C, 14956 lines of Perl and 6984 lines of shell (figures generated by David A. Wheeler’s ‘SLOCCount’) and is translated in 40 languages (but very few languages managed to translate everything, with all the manual pages there are 3997 strings to translate).

The top 5 contributors of all times (in number of commits) is the following (result of git log --pretty='%aN'|sort| uniq -c|sort -k1 -n -r|head -n 5):

  1. Guillem Jover with 2663 commits
  2. Raphaël Hertzog with 993 commits
  3. Wichert Akkerman with 682 commits
  4. Christian Perrier with 368 commits
  5. Adam Heath with 342 commits

I would like to point out that those statistics are not entirely representative as people like Ian Jackson (the original author of dpkg’s C reimplementation) or Scott James Remnant were important contributors in parts of the history that were recreated by importing tarballs. Each tarball counts for a single commit but usually bundles much more than one change. Also each contributor has its own habits in terms of crafting a work in multiple commits.

Last but not least, I have generated this 3 minutes gource visualization of dpkg git’s history (I used Planet’s head pictures for dpkg maintainers where I could find it).

Watching this video made me realize that I have been contributing to dpkg for 5 years already. I’m looking forward to the next 5 years :-)

And what about you? You could be the 147th contributor… see this wiki page to learn more about the team and to start contributing.

How to use quilt to manage patches in Debian packages

Most Debian source packages are using the “3.0 (quilt)” format. This means that Debian changes to upstream files are managed in a quilt patch series. Knowledge of quilt is thus a must if you want to get involved in some serious packaging work. Don’t worry, this tutorial will teach you how to use quilt in the context of Debian packaging.

Pre-requisites

Install the packaging-dev package to get a decent set of packages to do Debian packaging. It includes the quilt package.

$ sudo apt-get install packaging-dev

What’s quilt?

Read the description of the Debian package:

Quilt manages a series of patches by keeping track of the changes each of them makes. They are logically organized as a stack, and you can apply, un-apply, update them easily by traveling into the stack (push/pop).

Quilt is good for managing additional patches applied to a package received as a tarball or maintained in another version control system. The stacked organization is proven to be efficient for the management of very large patch sets (more than hundred patches). As matter of fact, it was designed by and for Linux kernel hackers (Andrew Morton, from the -mm branch, is the original author), and its main use by the current upstream maintainer is to manage the (hundreds of) patches against the kernel made for the SUSE distribution.

The various files involved

Stack of files PictureTo better understand the various quilt commands, you should have a basic idea of how the tool works. The “stack of patches” is maintained in a dedicated directory (“patches” by default, but in Debian packages we override this value to “debian/patches”). This directory contains the patch files and a “series” file that gives an ordered list of patches to apply. Example:

$ ls debian/patches/
01_use_stdlib_htmlparser_when_possible.diff
02_disable-sources-in-sphinxdoc.diff
03_manpage.diff
06_use_debian_geoip_database_as_default.diff
series
$ cat debian/patches/series
01_use_stdlib_htmlparser_when_possible.diff
02_disable-sources-in-sphinxdoc.diff
03_manpage.diff
06_use_debian_geoip_database_as_default.diff

When quilt is used, it also maintains some internal files in a directory of its own (it’s named “.pc”). This directory is used to know what patches are currently applied (.pc/applied-patches) and to keep backup copies of files modified by the various patches.

Configuring quilt

Before going further, you should put this in your ~/.quiltrc file:

for where in ./ ../ ../../ ../../../ ../../../../ ../../../../../; do
    if [ -e ${where}debian/rules -a -d ${where}debian/patches ]; then
        export QUILT_PATCHES=debian/patches
        break
    fi
done

This ensures that quilt will always use “debian/patches” instead of “patches” when your current directory is within a Debian source package where debian/patches exists. If you only use quilt for debian packaging, then you can be more expedient and put a simple “export QUILT_PATCHES=debian/patches” in that file.

As a matter of personal preferences, I also have those lines in my ~/.quiltrc:

QUILT_PUSH_ARGS="--color=auto"
QUILT_DIFF_ARGS="--no-timestamps --no-index -p ab --color=auto"
QUILT_REFRESH_ARGS="--no-timestamps --no-index -p ab"
QUILT_DIFF_OPTS='-p'

It enables syntax coloring for the output of several commands and customizes the generated patches to get rid of useless information. I recommend you to use those settings too.

Applying and unapplying patches, navigating in the stack of patches

When you already have a patch series, you can navigate in the stack of patches so that any subset of consecutive patches (starting from the bottom) can be applied. quilt series will list all patches known by quilt.

You can apply all patches with quilt push -a or unapply them all with quilt pop -a. You can also verify what patches are applied (quilt applied) or unapplied (quilt unapplied). quilt push applies the next unapplied patch (i.e. the patch returned by quilt next) and quilt pop unapplies the last applied patch (i.e. the patch returned by quilt top). You can give a patch name as parameter to quilt push/pop and it will apply/unapply all the patches required until the given patch is on the top.

Here are some examples of navigation in a quilt patch series

$ quilt series
02_disable-sources-in-sphinxdoc.diff
03_manpage.diff
06_use_debian_geoip_database_as_default.diff
$ quilt applied
No patches applied
$ quilt next
02_disable-sources-in-sphinxdoc.diff
$ quilt push
Applying patch 02_disable-sources-in-sphinxdoc.diff
patching file docs/conf.py

Now at patch 02_disable-sources-in-sphinxdoc.diff
$ quilt push
Applying patch 03_manpage.diff
patching file docs/man/django-admin.1

Now at patch 03_manpage.diff
$ quilt applied
02_disable-sources-in-sphinxdoc.diff
03_manpage.diff
$ quilt unapplied
06_use_debian_geoip_database_as_default.diff
$ quilt pop -a
Removing patch 03_manpage.diff
Restoring docs/man/django-admin.1

Removing patch 02_disable-sources-in-sphinxdoc.diff
Restoring docs/conf.py

No patches applied
$ quilt push 03_manpage.diff
Applying patch 02_disable-sources-in-sphinxdoc.diff
patching file docs/conf.py

Applying patch 03_manpage.diff
patching file docs/man/django-admin.1

Now at patch 03_manpage.diff
$ quilt top
03_manpage.diff

Creating a new patch

If there’s no quilt series yet, you want to create the “debian/patches” directory first.

If you already have one, you need to decide where to insert the new patch. Quilt will always add the new patch just after the patch which is currently on top. So if you want to add the patch at the end of the series, you need to run “quilt push -a” first.

Then you can use quilt new name-of-my-patch.diff to tell quilt to insert a new empty patch after the current topmost patch. In this operation quilt does almost nothing except updating the series file and recording the fact that the new patch is applied (even if still empty at this point!).

Now to add changes in this patch, you’re supposed to modify files but only after having informed quilt of your intent to modify those files. You do this with quilt add file-to-modify. At this point quilt will make a backup copy of that file so that it can generate the final patch when you’re done with your changes. It’s quite common to forget this step and to be unable to generate the patch afterward. That’s why I recommend you to use quilt edit file-to-modify which is a shorthand for doing quilt add and then opening the file in your favorite text editor.

If you want, you can review your work in progress with quilt diff.

When you’re done with the changes, you should call quilt refresh to generate the patch (or to update it if it was already existing). And since you’re a good packager, you call quilt header --dep3 -e to add DEP-3 meta-information to your patch header.

Importing an external patch

If someone else already prepared a patch, you can just import it right away with quilt import /tmp/the-patch. If you want to import it under a better name you can use the option “-P better-patch-name”. Like quilt new, it inserts the patch after the topmost patch.

Updating patches for a new upstream version

With some luck, your patches will still apply with some offsets in line numbers (quilt displays those offsets) and sometimes with some fuzz:

$ quilt push
[...]
Hunk #1 succeeded at 1362 (offset 11 lines).
Hunk #2 succeeded at 1533 with fuzz 1 (offset 4 lines).
[...]

While offsets are nothing to worry about (it means some lines were added and/or removed before the patched part), fuzz means that patch had to ignore some context lines to find the place where to apply the changes. In that case, you need to double check that patch did the right thing because it might have made changes somewhere where it shouldn’t. Also, you’ll have to update those patches because dpkg-source doesn’t accept any fuzz.

If you’re confident that all patches are correctly applied by quilt, you can refresh them to get rid of those warnings:

$ quilt pop -a
[...]
$ while quilt push; do quilt refresh; done

That was for the easy case. Now let’s deal with the case where some of the patches no longer apply. There’s one case that is usually nice to have:

$ quilt push
Applying patch 04_hyphen-manpage.diff
patching file docs/man/django-admin.1
Hunk #1 FAILED at 194.
1 out of 1 hunk FAILED -- rejects in file docs/man/django-admin.1
Patch 04_hyphen-manpage.diff can be reverse-applied

When the patch can be reverse-applied, it means that the upstream authors included the Debian patch (or that they made the same change even though you forgot to forward the patch). You can thus get rid of it:

$ quilt delete -r 04_hyphen-manpage.diff
Removed patch 04_hyphen-manpage.diff

Note that without the -r the patch is only dropped from the series file. With -r the patch file is also removed.

But there’s a less desirable case where the patch is still relevant but it doesn’t apply any longer:

$ quilt push
Applying patch 01_disable_broken_test.diff
patching file tests/regressiontests/test_utils/tests.py
Hunk #1 FAILED at 422.
1 out of 1 hunk FAILED -- rejects in file tests/regressiontests/test_utils/tests.py
Patch 01_disable_broken_test.diff does not apply (enforce with -f)

In that case, you should follow quilt’s advice to force the patch application, manually apply the parts of the patch that were rejected, and then refresh the patch.

$ quilt push -f
Applying patch 01_disable_broken_test.diff
patching file tests/regressiontests/test_utils/tests.py
Hunk #1 FAILED at 422.
1 out of 1 hunk FAILED -- saving rejects to file tests/regressiontests/test_utils/tests.py.rej
Applied patch 01_disable_broken_test.diff (forced; needs refresh)
$ vim tests/regressiontests/test_utils/tests.py    
$ quilt refresh
Refreshed patch 01_disable_broken_test.diff

Other quilt commands

You should probably read quilt’s manual page too to learn about the various other commands and options that exist.

There’s at least quilt rename new-name that you can also find useful to rename the topmost patch (you can use “-P patch-to-rename” to rename a patch which is not currently at the top).

Feedback

Please leave comments if you have suggestions of improvements, or if there are some tips that are good to know. I might incorporate them in this article.

Feel free to share this article with newbie packagers which are struggling with quilt. For your convenience, you can also refer to this article with this URL: http://raphaelhertzog.com/go/quilt

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My Debian Activities in July 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 (72.65 €, thanks everybody!), then you can learn how I spent your money. Otherwise it’s just an interesting status update on my various projects.

This month has been a short one since I have been away for 2 weeks of vacation.

Dpkg

My dpkg work encompasses a bunch of small tasks:

  • I uploaded dpkg 1.16.7 with an important bugfix for a regression.
  • I initiated a new round of discussions about how we were going to solve the problem that source packages with “Multi-Arch: same” binary packages can’t be individually bin-nmued.
  • Following that discussion, I opened a bunch of bugs to plan/discuss the transition of changelog/copyright files within the package metadata (#681289 on debian-policy, #681293 on apt-listchanges, #681295 on www.debian.org for packages.debian.org).
  • I also filed #681292 on sbuild to get it to use dpkg’s new syntax for bin-nmus. It will allow us to do binary-only rebuilds with arbitrary versions (instead of only “+b1″ suffixes). Ubuntu could use this for their +rebuild1, we could use this to build backports which do not require source changes (and share the common source package instead of duplicating it). It can also be useful if we ever get to the situation where transitions are prepared in external repositories and where we want bin-nmus in those repositories to have unique versions (even though the same package might be bin-nmued in multiple repositories in case of concurrent transitions).
  • I filed an unblock request for dpkg once it was almost 10 days old.
  • I did reconsider the bug #316521 where dpkg looses track of some shared directories with manually created files and proposed an updated patch. No words from Guillem on the patch yet. Fixing this would help to fix a bunch of piuparts issues.
  • And just before my vacation, I filed many bugs against dpkg itself, effectively moving some of the items that accumulated in my TODO in a public place where others can help (I’ll be happy to mentor anyone who wants to tackle one of these):
    • #681443: dpkg-source –commit should be able to merge changes in an existing patch
    • #681470: dpkg-shlibdeps: should also scan Build-Depends-Arch for minimal versions
    • #681474: Dpkg::Vendor: should support /etc/os-release and /etc/os-release.d/*
    • #681477: dpkg-vendor: implement –select-closest command
    • #681480: base-files: Provide HOME_URL, SUPPORT_URL and BUG_REPORT_URL in /etc/os-release
    • #681489: base-files: Add /etc/os-release.d/debian and make it easy to provide supplementary /etc/os-release.d/* files
  • In #595112 we discussed the specifics of a new dpkg-mainstscript-helper feature to move a conffile from one package to another.

Packaging

I updated nautilus-dropbox to version 1.4.0 and python-django-registration to version 0.8. Both have been uploaded to unstable and I initially wanted to request an unblock for the latter, but it turns out it has gained reverse dependencies and version 0.8 introduces API changes so it’s not an option at this point of the freeze.

QA work

I investigated and fixed #678356 where it had been reported that the PTS static news were no longer working as expected.

At the start of the month, I also unblocked the mostly-unknown but important “mole” service… it was out of date of several weeks and several people were annoyed that the information about new upstream versions was no longer up-to-date.

Vacation

Almost no Debian work during my vacation but the lack of Wifi nearby made me look for solutions to connect my computer through my Nokia N900 3G/GPRS connection. I discovered the “Mobile Hotspot” application (homepage) and it worked like a charm (although it required Maemo’s non-default devel repository to be able to install the alternative kernel “for power users”).

The Debian Handbook

Michal Čihař proposed us to host a Weblate instance to help translate the book with a web interface. He kindly agreed to implement some improvements to better suit my requirements. Those have been completed and the weblate instance is now live at debian.weblate.org.

There’s no requirement to use Weblate for translations teams but for those that do, it sure makes it easier to recruit volunteers who have no prior knowledge of Git and PO files. If you want to help, please checkout this page first though, you should not start using Weblate without getting in touch with the respective translations teams.

Apart from translations, I also had the pleasure to merge some patches from Philipp Kern who improved the section covering IPv6 and a few other parts. We can make the book even better if more people share their expertise in the part of the book where they know better than me and Roland. :-)

Thanks

See you next month for a new summary of my activities.

My Debian Activities in June 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 (168.12 €, thanks everybody!), then you can learn how I spent your money. Otherwise it’s just an interesting status update on my various projects.

Dpkg

This month, I resumed my work on dpkg. I concentrated my efforts on some “polishing” of the “3.0 (quilt)” format. With the latest version (1.16.6 — which was uploaded to unstable shortly before the freeze), dpkg-source restores the source tree in a clean state after a failed patch application (#652970), doesn’t overwrite the patch header from the pre-existing automatic patch, updates automatically debian/source/include-binaries during dpkg-source –commit, and supports a new –no-unapply-patches option for those who dislike the auto-unapplication at the end of the process when the patches were not applied at the start.

I wanted to go further and offer a new feature that could insert the automatic patch at the bottom of the quilt series but I have been short on time to complete this feature. I just managed to factorize all the quilt handling in a dedicated Perl module (Dpkg::Source::Quilt) to have cleaner code in the module handling the source format (Dpkg::Source::Package::V3::quilt).

For those who wonder, this feature is meant primarily for the X Strike Force team which maintains packages in Git and are doings lots of upstream cherry-picks (to fix regressions, etc.). But they also use quilt on top of that tree to keep some lasting Debian specific changes. With the 1.0 format, the “automatic diff” is a bit messy but at least it gets smaller automatically when a new upstream release gets out, there’s nothing to clean out. I’d like them to be able to use “3.0 (quilt)” while keeping their workflow. I’m leaning towards allowing “--auto-commit=first:cherry-picks” that would name the automatic patch “cherry-picks” and put it in the first position in the quilt series. (Opinions welcome on that feature, BTW)

Packaging

There’s been quite some packaging in this last month before the freeze:

  • I packaged CppUTest (a test framework for C/C++), and I wrote an article about it.
  • I prepared a stable update of Publican to fix a missing dependency. I also updated the unstable version to include a backport of a fix that some user requested me to include.
  • I updated dh-linktree to improve its documentation (following a discussion that happened on debian-devel) and to deal properly with trailing slashes in its input (#673408).
  • I sponsored dblatex 0.3.4-1 and ledgersmb 1.3.18-1.
  • I updated gnome-shell-timer to a new upstream snapshot that was tagged as compatible with GNOME 3.4 (#6776516).
  • I packaged wordpress 3.4 and spent a whole day triaging the old bugs that accumulated. A few days later I developed a new infrastructure to properly manage plugins/themes/language files. The canonical directory where the user is expected to drop his custom plugins/themes is now in /var/lib/wordpress/wp-content/ and the official plugins/themes are “installed” there with symlinks pointing back to /usr/share/wordpress/wp-content/ where they actually reside.
  • I wanted to commit 2 patches for the developers-reference but then I noticed that some translations were complete and were waiting for an upload. So I cleaned the packaging (switch to dh) and I uploaded version 3.4.8 before committing the patches for #678710 and #678712.

While doing all this packaging work, I found 2 possible improvements that I filed as bug reports:

  • #676606: debcommit should be able to identify alone that a new release is prepared (when the distribution field of the changelog changes from UNRELEASED to something else).
  • #679132: lintian outputs false positives for the tag package-uses-local-diversion when neither –local nor –package is given on the dpkg-divert command line.

Debian France Booth at Solutions Linux

From June 19th to June 21th, I manned the Debian France booth at Solutions Linux together with Carl Chenet, Tanguy Ortolo and other members of the association. We answered lots of questions, sold all t-shirts and umbrellas that Carl imported from Germany and Switzerland (we really need to get our own merchandising stuff produced in France!), got people to join the association. We also presented a printed copy of the Debian Administrator’s Handbook and of the corresponding French book.

You can see Carl, me and Tanguy on this picture (click on it to see a bigger picture, thanks to Sébastien Dubois of Evolix for this one!):

I know lots of people are preparing for Debconf but I decided to not attend this year, the price of the air plane ticket was a bit too hefty for me and it was also in partial conflict with our family vacations. I thought about attending the Libre Software Meeting instead but alas I won’t go there either (but Roland Mas will be there!), I have too much work to complete before my own vacation in 2 weeks.

Thanks

See you next month for a new summary of my activities.

Test Driven Development with CppUTest, now in Debian

I have recently read Test Driven Development with Embedded C by James W. Grenning and published by Pragmatic Programmers.

I really enjoyed the book: while I was aware of the huge benefits of having a comprehensive test suite, I never studied seriously the principles behind Test Driven Development (TDD) and this book makes a good introduction to the topic. At the same time it focuses on the C language and contains lots of examples on how you can create tests even for projects which have to interact with hardware or other unpredictable components (the key is to create many abstractions) using all the possibilities that C offers.

The author convincingly argues that developing code with TDD forces you to create a modular design that is easier to evolve when the underlying requirements change. He also highlights how the tests serve as reference documentation of the API.

James W. Grenning recommends CppUTest as his xUnit test framework of choice. When I wanted to try this test framework, I discovered that it was not available in Debian. I decided to package it because it has some interesting features not offered by the contenders (at least not to my knowledge). It’s now available in Debian and in Ubuntu.

First, it doesn’t require any explicit registration of tests and has a very lightweight syntax. The small downside is that CppUTest requires the usage of C++ for the tests. But C++ is compatible with C so it doesn’t matter much if you have a C++ compiler for your target. On the contrary, usage of variables and methods scoped to the test group makes it easy to write clear tests. Here’s a short sample of test code:

extern "C" {
#include "timer.h"
#include "timefn.h"
}
 
#include "CppUTest/TestHarness.h"
 
static Time the_time;
static const int start_sec = 123;
static const int start_nsec = 456789000;
static const int delay_sec = 8;
static const int delay_nsec = 111111000; // start_nsec + delay_nsec < 10^9
 
TEST_GROUP(Timer)
{
    /* Class variables available to all tests in the group */
    Timer timer;
    Delay remaining;
 
    /* Standard setup/teardown methods of xUnit tests */
    void setup() {
        timer = timer_new();
        time_set(&the_time, start_sec, start_nsec);
        /* [...] */
    }
 
    void teardown() {
        timer_free(timer);
        /* [...] */
    }
 
    /* Helper functions specific to the test group */
    void start_timer_with_delay(long sec, long nsec)
    {
        timer_set_real_delay(timer, sec, nsec);
        timer_start(timer);
    }
 
    void ensure_remaining_is(long sec, long nsec)
    {
        CHECK_EQUAL(sec, delay_get_seconds(remaining));
        CHECK_EQUAL(nsec, delay_get_nanoseconds(remaining));
    }
};
 
TEST(Timer, NewIsNotStarted)
{
    CHECK(!timer->started);
}
/* [...] */
TEST(Timer, GetRemainingTimeWithNanosecondPrecision_ShiftOfSeconds)
{
    start_timer_with_delay(delay_sec, delay_nsec);
    time_set(&the_time, start_sec + delay_sec - 5, start_nsec + delay_nsec + 1000);
 
    remaining = timer_get_remaining_time(timer);
 
    ensure_remaining_is(4, 999999000);
}

To run those tests, you just need this boilerplate code in a main.cpp:

#include "CppUTest/CommandLineTestRunner.h"
 
int main(int argc, char** argv)
{
   return CommandLineTestRunner::RunAllTests(argc, argv);
}

Another interesting feature is its integrated memory leak detection system. Any test that hasn’t released allocated memory at the end of the “teardown” process will be marked as failed.

The upstream developers have made some unusual choices (static library only, installation in a private directory) but this will likely change with the switch to an automake and autoconf-based build system. I have reported the oddities that I found and I requested them to provide a pkg-config file to make it easier to compile and link unit tests exploiting CppUTest.

I already used CppUTest to develop a small application running on an embedded Linux. At some point, I might try to use CppUTest for dpkg development. I believe that it makes for a good fit. dpkg is already C++ ready since dselect is written in C++ and reuses a good part of dpkg’s code.

In any case, if you like Test Driven Development and are writing C or C++ based applications, I invite you to try CppUTest.

My Debian Activities in May 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 (338.26 €, thanks everybody!), then you can learn how I spent your money. Otherwise it’s just an interesting status update on my various projects.

Dpkg

Like last month, I did almost nothing concerning dpkg. This will probably change in June now that the book is out…

The only thing worth noting is that I have helped Carey Underwood who was trying to diagnose why btrfs was performing so badly when unpacking Debian packages (compared to ext4). Apparently this already resulted in some btrfs improvements.

But not as much as what could be hoped. The sync_file_range() calls that dpkg are doing only force the writeback of the underlying data and not of the meta-data. So the numerous fsync() that follow still create many journal transactions that would be better handled as one big transaction. As a proof of this, replacing the fsync() with a sync() brings the performance on par with ext4.

(Beware this is my own recollection of the discussion, while it should be close to the truth, it’s probably not 100% accurate when speaking of the brtfs behaviour)

Packaging

I uploaded new versions of smarty-gettext and smarty-validate because they were uninstallable after the removal of smarty. The whole history of smarty in Debian/Ubuntu has been a big FAIL since the start.

Once upon a time, there was a smarty package and some plugins. Everything was great except that the files were installed in a way that differs from the upstream recommendations. So Ubuntu changed the path in their version of the package and did not check whether it broke anything else (and it did break all the plugins). Despite the brokenness of the plugins, this divergence survived for years. So several packages that were using Smarty were modified to use dpkg-vendor to use the correct path depending on whether it was built on Debian or Ubuntu.

In 2010, Smarty 3.0 has been released and instead of upgrading the smarty package to this version, one of the smarty co-maintainers introduced a smarty3 package that used yet another path (despite the fact that smarty 3 had a mode to be compatible with smarty 2).
At some point, I informed him that he had to handle the migration of users of smarty to smarty3… he acknowledged and then lost interest in smarty (“I’m no longer using it”) and did nothing.

After some more bitrot, smarty has been forcefully orphaned in August 2011 by a member of the security team. And in March this year, it has been removed from unstable despite the fact that it still had reverse dependencies (usually removals only happen when they impact no other packages, I don’t know why this wasn’t the case here).

At least the brokenness attracted some attention to the situation and Mike Gabriel contacted me about it. I offered him to take over the various packages since they all needed a real maintainer and he accepted. I sponsored his uploads of all smarty related packages (bringing in the latest upstream versions at the same time).

In the end, the situation is looking better now, except that there’s no migration path from users who rely on smarty in Squeeze. They will discover that they need smarty3 in Wheezy and that the various paths have to be adjusted. It’s probably acceptable since the new upstream versions are no longer backwards compatible with smarty 2…

The Debian Administrator’s Handbook

At the start of the month, I was busy preparing the release of the book. I introduced the publican-debian package to unstable, it’s a Publican brand (aka a set of CSS and XSL stylesheets to tailor the output of Publican) using the Debian colors and using the Debian logo. This brand is used by the book.

I also created the debian-handbook package and setup the public Git repository on alioth.debian.org.

I was ready or so I thought. A few hours after the announce, the website became unusable because the numerous visitors were exhausting the maximum number of client connections. And I could not increase the limit due to Apache’s memory usage (with PHP and WordPress). We quickly off-loaded most of the static files traffic to another machine and we setup bittorrent. The problem was solved for the short term. Thousands of persons downloaded the ebook and to this date, 135 copies of the paperback have been sold.

Then I took a one-week vacation. Even though I had no Internet at the place I was, I wandered in the street to find a “Freewifi” wifi network (customers of the Free ISP can use those freely) to stay on top of incoming email. We quickly received some bug reports and I dealt with the easy ones (typos and the like) on the fly.

When I came back at home, I manually placed 54 lulu orders for the people who opted for the paperback as reward during the fundraising campaign. A bit tedious but it had to be done (if only Lulu supported a way to batch many orders at once…).

I also wanted a long term solution to avoid the use of an external host to serve static files (should a new traffic spike arrive…). So I installed nginx as a front-end. It serves static files directly, as well as WordPress pages which have been cached by wp-super-cache. Apache is still here listening on a local port and responding to the remaining queries forwarded by nginx. Once I’ll migrate to wheezy, I might completely ditch apache in favor of php5-fpm to handle the PHP pages.

Last but not least, I wanted to bootstrap the various translations that people offered to contribute. I wrote some documentation for interested translators and blogged about it. It’s shaping up nicely… check it out if you’re interested to help!

Thanks

See you next month for a new summary of my activities.

The Debian Administrator’s Handbook is available

The Debian Administrator's Handbook CoverI am so glad that we managed to complete this project. Roland and I have spent countless hours on this book since December, both for the translation itself and also for all the things that we tend to forget: a nice book cover, a great book layout for the print version, coordinating the work of reviewers, registering as an editor to get an ISBN, etc. I think I will come back to this in a future article because some parts of the story are interesting.

In the mean time, enjoy the DFSG-free Debian Administrator’s Handbook:

  • get it from unstable with apt-get install debian-handbook;
  • browse the online version;
  • get the paperback or the ebook (available as PDF, EPUB, MOBI);
  • grab the sources with git clone git://anonscm.debian.org/debian-handbook/debian-handbook.git and contribute a translation :-)

Check out the official announce (there’s a discount for early buyers of the paperback).

My Debian Activities in April 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 (186.38 €, thanks everybody!), then you can learn how I spent your money. Otherwise it’s just an interesting status update on my various projects.

Dpkg News

For the first time since several years, there has been a dpkg release (1.16.3) where the changelog doesn’t contain any entry of my own. The 3-4 commits I did were not really worthy of a changelog entry. I must admit that it was easy to put dpkg aside given Guillem’s message and given how busy I have been with my other projects.

Keeping a low-profile for a while certainly doesn’t hurt. But I don’t intend to stop contributing to dpkg. Quite on the contrary in fact, it’s something that I (usually) enjoy doing.

Packaging News

I packaged a new upstream release of SQL-Ledger (3.0.0) and later in the month I sponsored the upload of LedgerSMB, a fork of SQL-Ledger which — unlike the former — is maintained like a typical free software project.

I also uploaded version 0.56 of Zim and updated WordPress to version 3.3.2 with its slew of security fixes.

The Debian Administrator’s Handbook

Like several months now, most of my time has been directed towards the Debian Administrator’s Handbook. The big news is that the liberation fund has been completed… this means that the book will be published under DFSG-free licenses from the start (GPL-2+ / CC-BY-SA 3.0).

We hope to publish the book next week (i.e. between May 7th and May 11th). The PDF output for the printed book is almost ready. There’s some work left for the HTML/EPUB output and we have to prepare for the release of the sources as well…

Hopefully everything will work out like planned. Stay tuned!

Thanks

See you next month for a new summary of my activities.

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 voilà, 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: Aurélien Jarno, Bastian Blank, Christian Perrier, Colin Watson, Cyril Brulebois, Frans Pop, Jörg 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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