This post is about how (and why) I recently produced my own Debian packages for a recent upstream release of Mesa to work around a bug on my own machine. Though the specifics are not specifically interesting, you may extrapolate my story to a more general guide of what to do when you need to run an upstream software release that's too recent to be packaged by Debian, and too complex to be easy to install by hand with make install.

I recently tried to figure out the source of weird crashes on my machine, which runs Debian testing. I understood from /var/log/syslog that I was probably affected by Bug #771045. From the linked discussions it seemed that a patch in Mesa had a good chance of fixing the problem. The patch was part of version 10.3.4 of Mesa, but Debian testing only had 10.3.2-1, judging from the output of:

dpkg-query -l | grep -i mesa

So, if I wanted the patch, I needed to install manually a newer version of Mesa.

A first thing to check was whether it was not packaged in Debian unstable. I have the unstable repository set up and pinned at a lower priority with the following in /etc/apt/preferences.d/prefs:

Package: *
Pin: release a=testing
Pin-Priority: 650

Package: *
Pin: release a=unstable
Pin-Priority: 600

I use this to manually install a recent version of iceweasel from unstable. Could it be the case that a recent Mesa was packaged in unstable? Alas, no, checking on a random mesa package among those at version 10.3.2-1:

apt-cache policy libegl1-mesa

libegl1-mesa:   
  Installed: 10.3.2-1
  Candidate: 10.3.2-1
  Version table:
 *** 10.3.2-1 0
        650 http://debian.proxad.net/debian/ testing/main amd64 Packages
        600 http://cdn.debian.net/debian/ unstable/main amd64 Packages
        100 /var/lib/dpkg/status

So here is how I manually compiled a more recent version. I was surprised to see how simple it turned out to be, in fact: precious little manual intervention is required.

Of course, a word of warning applies: make sure you will know how to fix your system if it gets broken by the home-made packages that you installed or by anything else you did.

I'm assuming that your machine's architecture is amd64, otherwise what I say later about compiling for i386 may make no sense.

You may need to start by installing some packages such as build-essential if you don't have them. Then, issue:

sudo apt-get build-dep libegl1-mesa

This will install¹ the packages needed to compile Mesa.

Then, go to a fresh folder and download the sources for Mesa:

mkdir -p ~/mesa
cd ~/mesa
apt-get source libegl1-mesa

The source for the packaged version (10.3.2-1) should be downloaded. You could then go in the source tree and run uscan from the devscripts package:

cd mesa-10.3.2
uscan

This would automatically search for a newer release on the Mesa website and download it. However, it would pick the latest version (10.4.1 as of this writing) for which the packaging wouldn't work as is. So instead, download directly Mesa 10.3.4, the version that we want, from the official website, and symlink it to the conventions used by the Debian tools.

cd ~/mesa
wget ftp://ftp.freedesktop.org/pub/mesa/older-versions/10.x/10.3.4/MesaLib-10.3.4.tar.gz
ln -s MesaLib-10.3.4.tar.gz mesa_10.3.4.orig.tar.gz

Now we can go back in the source tree for the old version, and use uupdate to unpack the new version and migrate the Debian-specific stuff. Then go to the new source tree thus created:

cd mesa-10.3.2
uupdate ../mesa_10.3.4.orig.tar.gz
cd ../mesa-10.3.4

Now we are ready to start the compilation process:

debuild -us -uc

This should compile everything and take 10-30 minutes. If a problem occurs, you should have copious output to try to understand what went wrong. Otherwise, if all goes well, all the deb packages for the new version will have been generated in the parent folder. That was easy!² :)

That's all nice and well, but then I realized that I needed the i386 version of the packages, because I use Skype, whose "multiarch" package is actually i386. How to cross-compile the packages? In fact, it's quite easy. We will use pbuilder to create a chroot where the compilation can take place, but everything is automatic:

sudo apt-get install pbuilder
sudo pbuilder --create --architecture i386

Now go in the source tree and issue³:

sudo pbuilder --build ../mesa_10.3.4-1.dsc

This should take care of everything. The packages will be produced in /var/cache/pbuilder/result.

Now you just have to figure out which packages you need to install (using dpkg-query -l) and install them with sudo dpkg -i, then correct any dependency problems with sudo apt-get -f install. Alternatively, you can just issue sudo debi -u from the source tree, which should do those steps automatically. However, I haven't tested it. Of course to install the i386 packages in this way you will need to move them, or let debi know where to find them.

Note that to avoid problems it looks like it is safer to install all packages at once. If you run into file conflicts between the i386 and amd64 packages, a solution may be to apt-get remove all the old versions and then install the new ones. Of course, this will probably remove a bunch of useful packages on your system that depend on Mesa; if you do this should make sure that you have kept a trace of the packages that you will want to reinstall afterwards, and also that you are confident using a tty or ssh if your graphical environment breaks.

And, well, that's it. If you have installed the packages successfully, you can just reboot. Then you can check in dpkg-query that you are indeed using the newer version of the packages, and double-check using:

glxinfo | grep -i version

Of course, if something went bad, maybe your system will not boot (or at least not boot graphically) and then it will be up to you to investigate. Hopefully removing the new packages and installing back the Debian ones should make things work again. :)

One last thing: hopefully, as the version numbers of your home-made Mesa packages correspond to the actual version number of the release, apt-get upgrade should move you to the more recent versions as soon as they start getting packaged by Debian.