Recently I have installed Ubuntu Mate 15.10 on my Dell Inspiron 5720. This laptop (like many others) uses optimus technology and nvidia GeForce GT 630M GPU. My driver version is 358.09 from http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu .
When I switch to Intel card in nvidia-settings and restart my PC everything is fine, but when I try to restart it again with only intel enabled, then nvidia GPU disappears. Normally I can see it in the results of lspci:
$ lspci | grep 3D 01:00.0 3D controller: NVIDIA Corporation GF117M [GeForce 610M/710M/810M/820M / GT 620M/625M/630M/720M] (rev a1)
But after restart it disappears. The error from nvidia-settings is “Active graphics card: unknown”. The only way to bring it back is to power off the computer and then start it again - normal reboots don’t solve the problem.
This is very annoying problem, because I cannot use tools like bumblebee to switch these cards dynamically - it won’t work after restart. I wouldn’t mind using only nvidia, but it has this ugly tearing problem that is not fixed yet (https://devtalk.nvidia.com/default/topic/775691/linux/vsync-issue-nvidia-prime-ux32vd-with-gt620-m-/1). I have attached log files generated by nvidia-bug-report.sh. When nvidia card is gone, this shell script is also unavailable, I have prepared the log file using a copy of this script.
Previously I had Ubuntu 14.04 with many different versions of the driver and during 1.5 years of using it this problem happened once - but I just ignored it. On the new system it happens after every restart.
Normal start with nvidia gpu enabled: http://pastebin.com/mydiZVBV
First start on intel card (nvidia is still available): http://pastebin.com/XbgFZz00
Second start (nvidia is gone): http://pastebin.com/j1fd3ctt
Thanks in advance.