Re: GLX, (xserver-)xorg(-dev), and nvidia-driver under jessie(-backports)

["Rebecca N. Palmer" <rebecca_palmer@zoho.com>]

The Skype problem is a known issue: skype is 32-bit, so you need 
libgl1-nvidia-glx:i386 installed. 
https://wiki.debian.org/skype#Frequently_Ask_Questions_.28F.A.Q..29_for_Jessie_64_bits

Where did you obtain afni from?  There is no such package in Debian 
itself: do you have any other sources in /etc/apt/sources.list(.d)?

> qobi@tlamachilistli>ls -l /usr/lib/x86_64-linux-gnu/libGL.so
> lrwxrwxrwx 1 root root 48 Jun 16 16:16 /usr/lib/x86_64-linux-gnu/libGL.so -> /etc/alternatives/glx--libGL.so-x86_64-linux-gnu
> qobi@tlamachilistli>ls -l /etc/alternatives/glx--libGL.so-x86_64-linux-gnu
> lrwxrwxrwx 1 root root 48 Jun 16 16:16 /etc/alternatives/glx--libGL.so-x86_64-linux-gnu -> /usr/lib/mesa-diverted/x86_64-linux-gnu/libGL.so

> qobi@tlamachilistli>ls -l /usr/lib/x86_64-linux-gnu/libGL.so.1
> lrwxrwxrwx 1 root root 50 Jun 16 16:16 /usr/lib/x86_64-linux-gnu/libGL.so.1 -> /etc/alternatives/glx--libGL.so.1-x86_64-linux-gnu
> qobi@tlamachilistli>ls -l /etc/alternatives/glx--libGL.so.1-x86_64-linux-gnu
> lrwxrwxrwx 1 root root 43 Jun 16 16:17 /etc/alternatives/glx--libGL.so.1-x86_64-linux-gnu -> /usr/lib/x86_64-linux-gnu/nvidia/libGL.so.1

i.e. libGL.so points to mesa (libgl1-mesa-dev) but libGL.so.1 points to 
nvidia.  This is intentional, to make applications compiled against 
libGL.so portable to other graphics hardware: 
https://sources.debian.net/src/glx-alternatives/0.7.3/debian/glx-diversions.README.Debian/#L90

Use of libGL.so (without .1) at run time (as opposed to compile time) is 
considered a bug in the application.