“3.0 (quilt)” is the most widely used Debian source package format

My goal with the “3.0 (quilt)” source format has always been to standardize the patch management in Debian source packages. This message seems to have been well understood. dbs and dpatch have been deprecated by their respective maintainers.

I made numerous efforts to make this source format useful in as many use cases as possible (but some improvements are still possible) and I have added hints to encourage maintainers to switch. Thanks to this, the adoption rate of this new source format has been very good and it’s now the most widely used source package format in Debian—only two years after its introduction in Debian unstable.

With 9829 source package using “3.0 (quilt)”, it surpassed the number of source package still using “1.0” (7368). (Those numbers have been taken from http://upsilon.cc/~zack/stuff/dpkg-v3/ on december 13th 2011.) The number of source packages using “3.0 (quilt)” doubled this year.

(Click on the picture to see it full size)

Of the 7368 packages using the old format, 6816 packages trigger the missing-debian-source-format lintian tag. This means that only 552 source packages have explicitly opted to keep using the old format and that the bulk of the remaining packages are rarely updated packages that have not been switched yet.

My Debian activities in July 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 (170 €, 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 passed by very quickly since I attended both the Libre Software Meeting / RMLL and the DebConf.

Libre Software Meeting / RMLL

I attended “only” 3 days out of the 6 but that was a deliberate choice since I was also attending DebConf for a full week later in the month.

During those 3 days I helped with the Debian booth that was already well taken care of by Frédéric Perrenot and Arnaud Gambonnet. Unfortunately we did not have any goodies to sell. We (as in Debian France) should do better in this regard next time.

One of the talks I attended presented EnVenteLibre. This website started as an online shop for two French associations (Ubuntu-fr, Framasoft). They externalize all the logistic to a company and only have to care about ordering goodies and delivering to the warehouse of the logistic company. They can also take some goodies from the warehouse and ship them for a conference, etc. We discussed a bit to see how Debian France could join, they are even ready to study what can be done to operate at the international level (that would be interesting for Debian with all the local associations that we have throughout the world).

Back to the LSM, while I had 3 good days in Strasbourg, it seems to mee that the event is slowly fading out… it’s far from being an international event and the number of talks doesn’t make for a better quality.

BTW, do you remember that Debconf 0 and Debconf 1 were associated to this event while it was in Bordeaux?

dpkg-source improvements

During my time in Strasbourg (and in particular the travel to go there and back!) I implemented some changes to “3.0 (quilt)” source format. It will now fail to build the source package if there are upstream changes that are not properly recorded in a quilt patch:

dpkg-source: info: local changes detected, the modified files are:
dpkg-source: info: you can integrate the local changes with dpkg-source --commit
dpkg-source: error: aborting due to unexpected upstream changes, see /tmp/2ping_1.1-1.diff.cki8YB

As the error message hints, there’s a new --commit command supported by dpkg-source that will generate the required quilt patch to fix this. In the process you will have to submit a name and edit the patch header (pre-formatted with DEP3 compatible fields). You can get back the old behavior with the --auto-commit option.

Build flags changes

Ever since we adopted the Ubuntu changes to let dpkg-buildpackage set some build related environment variables (see #465282), many Debian people expressed their concerns with this approach both because it broke some packages and because those variables are not set if you execute debian/rules directly.

In the end, the change was not quickly reverted and we fixed the package that this change broke. Despite this we later decided that the correct approach to inject build flags would be a new interface: dpkg-buildflags.

Before changing dpkg-buildpackage to no longer set the compilation flags, I wanted to ensure dpkg-buildflags had some decent coverage in the archive (to avoid breaking too many packages again). My criteria was that CDBS and dh (of debhelper) should be using it. With the recent debhelper change (see #544844) this has been reached so I changed dpkg-buildpackage accordingly.

Makefile snippets provided by dpkg

At the same time, I also wanted an easy way for maintainers not using dh or CDBS to be able to fix their package easily and go back to injecting the compilation flags in the environment but doing it from the rules files. Starting with the next version of dpkg, this will be possible with something like this:

include /usr/share/dpkg/default.mk

Without DPKG_EXPORT_BUILDFLAGS the variables are not exported in the environment and have no effect unless you use them somewhere.

More than build flags, this will also provide a bunch of other variables that can be useful in a rules files: all the variables provided by dpkg-architecture, vendor related variables/macro and some basic package information (mainly version related).

dpkg-buildflags improvements

Given the renewed importance that dpkg-buildflags will take now that dpkg-buildpackage no longer sets the corresponding environment variables, I thought that I could give it some love by fixing all the open issues and implementing some suggestions I got.

I also had a chat with a few members of the technical committee to discuss how hardening build flags could be enabled in Debian and this also resulted in a few ideas of improvements.

In the end, here are the main changes implemented:

  • new “prepend” directive to inject flags at the start (see commit);
  • new “strip” directive to strip flags from the result returned by dpkg-buildflags (see commit);
  • new environment variables DEB_flag_MAINT_directive that can be set by the maintainer to adjust what dpkg-buildflags will return (see commit);
  • new --export=configure command to inject build flags on the ./configure command line (see commit);
  • new --dump command that is the default (see #603435).

Will all those changes, the complete set of compilation flags can be returned by dpkg-buildflags (before it would only return the default flags and it was expected that the Debian packaging would add whatever else is required afterwards). Now the maintainer just has to use the new environment variables to ensure the returned values correspond to what the package needs.

DebConf: rolling and hardening build flags

I spent a full week in DebConf (from Sunday 24th to Sunday 31th) and as usual, it’s been a pleasure to meet again all my Debian friends. It’s always difficult to find a good balance between attending talks, working in the hacklab and socializing but I’m pretty happy with the result.

I did not have any goal when I arrived, except managing the Rolling Bof (slides and video here) but all the discussions during talks always lead to a growing TODO list. This year was no exception. The technical committee BoF resulted in some discussions of some of the pending issues, in particular one that interests me: how to enable hardening build flags in Debian (see #552688).

We scheduled another discussion on the topic for Tuesday and the outcome is that dpkg-buildflags is the proper interface to inject hardening build flags provided that it offers a mean to drop unwanted flags and a practical way to inject them in the ./configure command line.

Given this I got to work and implemented those new features and worked with Kees Cook to prepare a patch that enables the hardening build flags by default. It’s not ready to be merged but it’s working already (see my last update in the bug log).

A few words about the Rolling BoF too. The room was pretty crowded: as usual the topic generates lots of interest. My goal with the BoF was very limited, I wanted to weigh the importance of the various opinions expressed in the last gigantic discussion on debian-devel.

It turns out a vast majority of attendants believe that testing is already usable. But when you ask them if we must advertise it more, answers are relatively mixed. When asked if we can sustain lots of testing/rolling users, few people feel qualified to reply but those that do tend to say yes.

More dpkg work

Lots of small things done:

  • I did again some bug triaging on Launchpad. But Brian Murray did a lot of it and the result is impressive, we’re down to 154 bugs (from more than 300 a month ago!).
  • I updated my multiarch branch multiple times. I was hoping to meet Guillem during DebConf to make some progress on this front but alas he did not attend. I have been asked a status update multiple times during my time in DebConf.
  • I fixed a regression in update-alternatives (#633627), a test-suite failure when run as root (#634961), a segfault in findbreakcycle. There have been a bunch of minor improvements too (#634510, #633539, #608260, #632937).

Package Tracking System and DEHS

Christoph Berg recently wrote a replacement for DEHS because the latter was not really reliable and not under control of the QA team. This is a centralized system that uses the watch files to detect new upstream versions of the software available in Debian.

I updated the Package Tracking System to use this new tool instead of DEHS. The new thing works well but we’re still lacking the mail notifications that DEHS used to send out. If someone wants to contribute it, that would be great!

Misc packaging work

I did some preliminary work to update the WordPress package to the latest upstream version (3.2). I still have to test the resulting package, replacing upstream shipped copies of javascript/PHP libraries is always a risk and unfortunately all of them had some changes in the integration process.

I also updated nautilus-dropbox to version 0.6.8 released upstream. I also uploaded the previous version (that was in testing at that time) to squeeze-backports. So there’s now an official package in all the Debian distributions (Squeeze, Wheezy, Sid and Experimental)!


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

3 ways to not clutter your Debian source package with autogenerated files

It’s quite common that the upstream build system generates/updates some files but does not clean them up properly when you call make clean. In that case, when you rebuild the package a second time in the same tree, the generated Debian source package will contain those changes.

You usually don’t want those changes. They make your package harder to review because they contain unneeded modifications (either directly in the .diff.gz with the old source format, or in a new patch in debian/patches/debian-changes-<ver> with the “3.0 (quilt)” source format).

I’ll show you 3 ways to avoid this problem. They are all workarounds, the proper fix would be to improve the upstream build system to really clean up the generated files. This is usually possible for files that are “created”, but it’s much more cumbersome for files that are “updated” (you would have to keep a backup of the original file so that you can restore it).

The traditional fix

Instead of relying on the upstream build system to do the work, we modify the clean target in debian/rules to remove the files that are left-over. Since “debian/rules clean” is always called before a source package is built, those generated files are not included as changes compared to what upstream provided.

A common work-around: always build from a clean state

As you have noted, the problem only happens when you build (source and binaries) twice in a row in the same tree. Some VCS-helper tools always build the Debian package in a temporary tree which is exported from the VCS. This is the case of svn-buildpackage by default and of git-buildpackage if you use its --git-export-dir option.

I don’t like this solution because it solves the problem only for the maintainer. Anyone else who is working on top of the package without using the same VCS-helper tool would be affected by the problem.

A new way to avoid the problem

Since it’s now possible to store dpkg-source options in the source package itself, we can conveniently have everybody use the --extend-diff-ignore option. It tells dpkg-source to ignore some files when checking whether we have made changes to upstream files.

For example if you want to ignore changes made on the files “config.sub”, “config.guess” and “Makefile” you could put this in debian/source/options:

# Don't store changes on autogenerated files
extend-diff-ignore = "(^|/)(config\.sub|config\.guess|Makefile)$"

You need to know a bit about Perl regular expressions since that’s what is used by dpkg-source to match the filenames to exclude.

Note that this approach always works, even when you can’t remove the file. So it saves you having to make a backup of the unmodified file just to be able to restore it before the next build.

Found it useful? Be sure to not miss other packaging tips (or lessons), click here to subscribe to my free newsletter and get new articles by email.

Howto to rebuild Debian packages

Being able to rebuild an existing Debian package is a very useful skill. It’s a prerequisite for many tasks that an admin might want to perform at some point: enable a feature that is disabled in the official Debian package, rebuild a source package for another suite (for example build a Debian Testing package for use on Debian Stable, we call that backporting), include a bug fix that upstream developers prepared, etc. Discover the 4 steps to rebuild a Debian package.

1. Download the source package

The preferred way to download source packages is to use APT. It can download them from the source repositories that you have configured in /etc/apt/sources.list, for example:

deb-src http://ftp.debian.org/debian unstable main contrib non-free
deb-src http://ftp.debian.org/debian testing main contrib non-free
deb-src http://ftp.debian.org/debian stable main contrib non-free

Note that the lines start with “deb-src” instead of the usual “deb”. This tells APT that we are interested in the source packages and not in the binary packages.

After an apt-get update you can use apt-get source publican to retrieve the latest version of the source package “publican”. You can also indicate the distribution where the source package must be fetched with the syntax “package/distribution“. apt-get source publican/testing will grab the source package publican in the testing distribution and extract it in the current directory (with dpkg-source -x, thus you need to have installed the dpkg-dev package).

$ apt-get source publican/testing
Reading package lists... Done
Building dependency tree       
Reading state information... Done
NOTICE: 'publican' packaging is maintained in the 'Git' version control system at:
Need to get 727 kB of source archives.
Get:1 http://nas/debian/ squeeze/main publican 2.1-2 (dsc) [2253 B]
Get:2 http://nas/debian/ squeeze/main publican 2.1-2 (tar) [720 kB]
Get:3 http://nas/debian/ squeeze/main publican 2.1-2 (diff) [4728 B]
Fetched 727 kB in 0s (2970 kB/s)  
dpkg-source: info: extracting publican in publican-2.1
dpkg-source: info: unpacking publican_2.1.orig.tar.gz
dpkg-source: info: unpacking publican_2.1-2.debian.tar.gz
$ ls -dF publican*
publican-2.1/                 publican_2.1-2.dsc
publican_2.1-2.debian.tar.gz  publican_2.1.orig.tar.gz

If you don’t want to use APT, or if the source package is not hosted in an APT source repository, you can download a complete source package with dget -u dsc-url where dsc-url is the URL of the .dsc file representing the source package. dget is provided by the devscripts package. Note that the -u option means that the origin of the source package is not verified before extraction.

2. Install the build-dependencies

Again APT can do the grunt work for you, you just have to use apt-get build-dep foo to install the build-dependencies for the last version of the source package foo. It supports the same syntactic sugar than apt-get source so that you can run apt-get build-dep publican/testing to install the build-dependencies required to build the testing version of the publican source package.

If you can’t use APT for this, enter the directory where the source package has been unpacked and run dpkg-checkbuilddeps. It will spit out a list of unmet build dependencies (if there are any, otherwise it will print nothing and you can go ahead safely). With a bit of copy and paste and a “apt-get install” invocation, you’ll install the required packages in a few seconds.

3. Do whatever changes you need

I won’t detail this step since it depends on your specific goal with the rebuild. You might have to edit debian/rules, or to apply a patch.

But one thing is sure, if you have made any change or have recompiled the package in a different environment, you should really change its version number. You can do this with “dch --local foo” (again from the devscripts package), replace “foo” by a short name identifying you as the supplier of the updated version. It will update debian/changelog and invite you to write a small entry documenting your change.

4. Build the package

The last step is also the simplest one now that everything is in place. You must be in the directory of the unpacked source package.
Now run either “debuild -us -uc” (recommended, requires the devscripts package) or directly “dpkg-buildpackage -us -uc”. The “-us -uc” options avoid the signature step in the build process that would generate a (harmless) failure at the end if you have no GPG key matching the name entered in the top entry of the Debian changelog.

$ cd publican-2.1
$ debuild -us -uc
 dpkg-buildpackage -rfakeroot -D -us -uc
dpkg-buildpackage: export CFLAGS from dpkg-buildflags (origin: vendor): -g -O2
dpkg-buildpackage: export CPPFLAGS from dpkg-buildflags (origin: vendor): 
dpkg-buildpackage: export CXXFLAGS from dpkg-buildflags (origin: vendor): -g -O2
dpkg-buildpackage: export FFLAGS from dpkg-buildflags (origin: vendor): -g -O2
dpkg-buildpackage: export LDFLAGS from dpkg-buildflags (origin: vendor): 
dpkg-buildpackage: source package publican
dpkg-buildpackage: source version 2.1-2rh1
dpkg-buildpackage: source changed by Raphaël Hertzog 
 dpkg-source --before-build publican-2.1
dpkg-buildpackage: host architecture i386
dpkg-deb: building package `publican' in `../publican_2.1-2rh1_all.deb'.
 dpkg-genchanges  >../publican_2.1-2rh1_i386.changes
dpkg-genchanges: not including original source code in upload
 dpkg-source --after-build publican-2.1
dpkg-buildpackage: binary and diff upload (original source NOT included)
Now running lintian...
Finished running lintian.

The build is over, the updated source and binary packages have been generated in the parent directory.

$ cd ..
$ ls -dF publican*
publican-2.1/                    publican_2.1-2rh1.dsc
publican_2.1-2.debian.tar.gz     publican_2.1-2rh1_i386.changes
publican_2.1-2.dsc               publican_2.1-2rh1_source.changes
publican_2.1-2rh1_all.deb        publican_2.1.orig.tar.gz

Do you want to read more tutorials like this one? Click here to subscribe to my free newsletter, you can opt to receive future articles by email.