On Wed, Aug 22, 2018 at 03:57:51PM +0100, Luca Boccassi wrote: > > Because I suspect something on your system is causing some packages to > be picked from backports and some from stable. That's what's breaking. > So try and remove any custom configuration you have for apt and then it > should work. >
I broke down and read apt_preferences(5) again and found this: If the target release has been specified then APT uses the following algorithm to set the priorities of the versions of a package. Assign: ... priority 990 to the versions that belong to the target release. The highest of those priorities whose description matches the version is assigned to the version. So I think my apt configuration is ok. I did the experiment (comment out default-release setting) but it still falls over: # apt-cache policy nvidia-driver nvidia-driver: Installed: (none) Candidate: 384.130-1 Version table: 390.77-1~bpo9+1 200 200 http://debian-archive.atnf.csiro.au:9999/debian stretch-backports/non-free amd64 Packages 384.130-1 500 500 http://debian-archive.atnf.csiro.au:9999/debian stretch/non-free amd64 Packages # apt-get install nvidia-driver Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: nvidia-driver : Depends: nvidia-driver-libs (= 384.130-1) but it is not going to be installed or nvidia-driver-libs-nonglvnd (= 384.130-1) but it is not going to be installed E: Unable to correct problems, you have held broken packages. This preferences tweak kind of fixes the issue for me # cat /etc/apt/preferences.d/backports Explanation: Low priority to avoid installation unless explicitly required Package: * Pin: release a=stretch-backports Pin-Priority: 200 Explanation: Negative priority; mixing stable & backports not supported Package: nvidia* libnvidia* libegl* libgl* glx-* Pin: release a=stretch-backports Pin-Priority: -1 # apt-cache policy nvidia-driver nvidia-driver: Installed: (none) Candidate: 384.130-1 Version table: 390.77-1~bpo9+1 -1 100 http://debian-archive.atnf.csiro.au:9999/debian stretch-backports/non-free amd64 Packages 384.130-1 990 990 http://debian-archive.atnf.csiro.au:9999/debian stretch/non-free amd64 Packages # apt-get install nvidia-driver Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: glx-alternative-mesa glx-alternative-nvidia glx-diversions libegl-nvidia0 libegl1-glvnd-nvidia libgl1-glvnd-nvidia-glx libgl1-nvidia-glvnd-glx libglvnd0-nvidia libglx-nvidia0 libglx0-glvnd-nvidia libnvidia-eglcore libnvidia-glcore libnvidia-ml1 nvidia-alternative nvidia-driver-bin nvidia-driver-libs nvidia-egl-common nvidia-egl-icd nvidia-installer-cleanup nvidia-kernel-common nvidia-kernel-dkms nvidia-kernel-support nvidia-legacy-check nvidia-modprobe nvidia-support nvidia-vdpau-driver update-glx xserver-xorg-video-nvidia Recommended packages: nvidia-settings nvidia-persistenced nvidia-driver-libs-i386 libopengl0 | libopengl0-glvnd-nvidia libgles-nvidia1 libgles-nvidia2 libnvidia-cfg1 nvidia-egl-wayland-icd nvidia-vulkan-icd The following NEW packages will be installed: glx-alternative-mesa glx-alternative-nvidia glx-diversions libegl-nvidia0 libegl1-glvnd-nvidia libgl1-glvnd-nvidia-glx libgl1-nvidia-glvnd-glx libglvnd0-nvidia libglx-nvidia0 libglx0-glvnd-nvidia libnvidia-eglcore libnvidia-glcore libnvidia-ml1 nvidia-alternative nvidia-driver nvidia-driver-bin nvidia-driver-libs nvidia-egl-common nvidia-egl-icd nvidia-installer-cleanup nvidia-kernel-common nvidia-kernel-dkms nvidia-kernel-support nvidia-legacy-check nvidia-modprobe nvidia-support nvidia-vdpau-driver update-glx xserver-xorg-video-nvidia 0 upgraded, 29 newly installed, 0 to remove and 8 not upgraded. Need to get 29.7 MB of archives. After this operation, 119 MB of additional disk space will be used. Do you want to continue? [Y/n] n Abort. Thanks for your help with this Vince