Batch Diana on Headless Systems

Normally, Diana is configured to run on systems with an X server, using OpenGL for accelerated rendering of maps and data. When running Diana in batch mode with the bdiana tool, nothing is displayed on the screen via the X server, but the user is often running bdiana on a system with an X server present. When building Diana normally, the bdiana tool that is produced is linked to the X libraries on the system and can be run by users on workstations without problems.

On servers, where it is not desirable to run an X server, we cannot use the bdiana tool produced by the normal Diana build without some kind of X server. Traditionally, Xvfb has been used to provide the support that this version of bdiana needs to run. However, this was not always a reliable solution, so we have used an alternative configuration of Diana to produce a version of bdiana that runs without an X server. This does two things to avoid dependencies on X:

1. It uses a custom build of the Qt libraries that do not depend on X libraries.
2. It provides a wrapper that redirects OpenGL calls to Qt, rendering products entirely in software. Only the subset of OpenGL functions that Diana uses are wrapped.

We build an alternative set of Qt libraries using the standard Qt 4.8 sources (4.8.1 and 4.8.3 will work fine), applying some patches and using an “embedded” configuration to remove the dependency on X.

The patches we use are part of the Debian packaging we use to build packages for Ubuntu 12.04. These can be obtained from a git repository:

git clone https://projects.met.no/~davidb/projects/qt4-headless/git qt4-headless

The standard Debian package building process involves applying the patches found in the debian/patches directory to the Qt 4.8 sources then running the configure script in the way described in the debian/rules file.

If you are building on a Debian derived distribution, you can simply copy the debian directory from the qt4-headless directory into the Qt 4.8 source directory, enter the source directory and run debuild:

debuild -sa -uc -us

Note that, if you use the distribution's own source package, you will need to unpatch the sources first by running the debhelper script, dh_quilt_unpatch.

The result should be a package in the parent directory you can install using dpkg or aptitude.

If you are building on another distribution, you will need to patch the files by hand. Enter the Qt 4.8 source directory and run a command of the following form on each of the patches in ascending numerical order; for example:

patch -p1 < ../qt4-headless/debian/patches/metno_00_remove_qpicture_checksum.diff
patch -p1 < ../qt4-headless/debian/patches/metno_01_identitymodel_feature_fix.diff
patch -p1 < ../qt4-headless/debian/patches/metno_02_wms_configuration.diff
patch -p1 < ../qt4-headless/debian/patches/metno_03_dummy_screen.diff
patch -p1 < ../qt4-headless/debian/patches/metno_04_qpa.diff

You can then run the configure script using the command given in the debian/rules file:

./configure -confirm-license -depths 16,32 -qpa dummy -qconfig wms \
            -exceptions -fast -glib -iconv -largefile -nis \
            -no-accessibility -no-audio-backend -no-cups -no-dbus \
            -no-declarative -no-declarative-debug -no-gfx-linuxfb \
            -no-gfx-multiscreen -no-javascript-jit -nomake demos \
            -nomake docs -nomake examples -nomake tests -nomake tools \
            -no-multimedia -no-opengl -no-phonon -no-phonon-backend \
            -no-qt3support -no-script -no-scripttools \
            -no-separate-debug-info -no-sql-ibase -no-sql-sqlite2 \
            -no-webkit -xmlpatterns -opensource -openssl \
            -optimized-qmake -pch -prefix-install -prefix /opt/qt4-headless \
            -release -rpath -shared -stl -svg -system-freetype \
            -no-libjpeg -no-libmng -system-libpng -no-libtiff -system-zlib

If this fails then you will need to provide the appropriate dependencies for your system.

Once configured, build and install in the usual way:

make
sudo make install

Note: This is a work in progress. More details to be added.