After an unsuccessful install of the Nvidia drivers , I decided to remove them and go
back to Nouveau. This is a Debian testing (Jessie) amd64 system.
However, just purging the package nvidia-driver did not work. All kind of rubbish remained in various
system config directories. To able to reach the graphical login manager it was necessary to remove
anything that had nvidia name in it explicitely: "aptitude purge ~nnvidia" .
But, this still leaves me with broken OpenGL support (For example, 'glxgears' are not running and 'glxinfo' returns the error "couldn't find RGB GLX visual or fbconfig").
Any ideas how to restore 3D acceleration?
To be totally accurate, the 2D functionality was restored before purging ~nnvidia , when I manually removed the nvidia junk from /etc/modprobe.d and anything nvidia related from /etc/alternatives. Perhaps I was overzealous in removing the alternatives entries, but I did reinstall glx-diversions and mesa alternatives afterwards.