nvidia-331 selected but nouveau loads

The NVRM log messages stopped after reinstalling nvidia-331, but the system continued to use nouveau, and hence to crash (bug 1243557).

> modified.conffile..etc.modprobe.d.nvidia.331.hybrid.conf: [deleted]

I don't know how that (which blacklists nouveau) came to be missing, but purging and re-installing nvidia-331 put it back but didn't stop nouveau loading.

I've found out how /etc/modprobe.d/nvidia-331_hybrid.conf disappeared: nvidia-331's postrm explicitly deletes it, but as it's a conffile reinstalling nvidia-331 doesn't put it back. However, having it present doesn't fix the main bug.

Found how nouveau was being loaded while blacklisted: it's in the initramfs and nvidia-331_hybrid.conf wasn't.

This can be fixed by updating the initramfs (sudo update-initramfs -u, assuming the kernel you are currently running is the one you want to use nvidia-331 with), but my system also seems to have forgotten that nvidia-* needs the text-only splash screen (bug 1063969), causing it to drop into a low resolution graphics mode. This can be worked around by disabling the splash screen entirely (remove "splash" from the kernel command line in /etc/default/grub then run update-grub).

Status changed to 'Confirmed' because the bug affects multiple users.

Also affected on a Hewlett-Packard HP Compaq dc7800p Convertible Minitower/0AACh, BIOS 786F1 v01.32 07/21/2011 with nvidia GeForce GT 520 board.

Workarounds by Rebecca Palmer at #5 (many thanks!) did not entirely suffice: Had to additionally add "blacklist nouveau" to /etc/modprobe.d/blacklist.conf even after sudo apt-get remove nouveau as well as de- and reselecting the proprietary one from System Settings / Software & Updates / Additional Drivers - which (even while the system was actually using nouveau) had been shown all the time as "Using NVIDIA binary driver - version 311.38 from nvidia-331 (proprietary, tested)" with a green light for "NVIDIA Corporation: GF119 [GeForce GT 520" and as "1 proprietary driver in use."

Symptoms:

nvidia-settings shows only minimal menu with no information on monitor(s) or GPU.

prime-select query returns the string "unknown" rather than "nvidia".

/var/log/syslog is flooded with lines (dozens per second) to the tune of "kernel: [ 1195.548660] nouveau W[ PFIFO][0000:01:00.0] INTR 0x01000000: 0x00000005".

/var/log/syslog has these lines:
kernel: [ 11.695523] NVRM: The NVIDIA probe routine was not called for 1 device(s).
kernel: [ 11.695526] NVRM: This can occur when a driver such as:
kernel: [ 11.695526] NVRM: nouveau, rivafb, nvidiafb or rivatv
kernel: [ 11.695526] NVRM: was loaded and obtained ownership of the NVIDIA device(s).
kernel: [ 11.695529] NVRM: Try unloading the conflicting kernel module (and/or
kernel: [ 11.695529] NVRM: reconfigure your kernel without the conflicting
kernel: [ 11.695529] NVRM: driver(s)), then try loading the NVIDIA kernel module
kernel: [ 11.695529] NVRM: again.
kernel: [ 11.695532] NVRM: No NVIDIA graphics adapter probed!
kernel: [ 11.695850] NVRM: NVIDIA init module failed!

nouveau (or possibly just some of the related mode-switching) is deprecated due to resume issues in Ubuntu 14.04 LTS (of which this is a fresh install) http://ubuntuforums.org/showthread.php?t=2217536&s=da1e9ef7ae0c51c40110e1b8e1347b47&p=12993037#post12993037 which are resolved only for a few in threads such as https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1283938 (cf. #138 et seq. there) that like this one have been all too long-standing in an Unassigned state.

Remaining issue now that the proprietary nvidia driver finally loads is that Systems Settings / Sound / Play sound through: "HDMI / DisplayPort2: <i>GF119 HDMI Audio Controller</i>" works only intermittently and for 2 rather than 5.1 channels.
Any (auto-)tweak for the ELD (captured through the "Acquire EDID..." button from the DFP-1 menu of nvidia-settings) to be loaded from file (whichever comes in place of /etc/X11 these days) rather than by DDC would be very welcome.

The full workaround sequence is the one I posted in the updated description, not the comments. (There's no such package as just "nouveau", so sudo apt-get remove nouveau won't do anything, and the drivers dialog does a remove not the here-required purge.)

I also have the "nouveau W[ PFIFO][0000:01:00.0] INTR 0x01000000: 0x00000005" messages when running nouveau, sometimes ending in a crash (bug 1243557), and can't suspend with either driver (bug 1333417 / bug 1333431). I don't have HDMI sound so can't test that, but would suggest filing a separate bug for that problem.