I had the same problem (the system got upgraded from 19.04 to 19.10, nvidia-430 driver).
I noticed that nvidia drivers were loaded in the rescue mode - so they were likely not blacklisted properly. When I did not enter the rescue mode I had the following message displayed: "A start job is running for udev Wait for Complete Device Initialization (1min 3s/ 3min) /var/lib/gdm3/.local/share/xorg/Xorg.0.log contained the following (see the full file attached): [ 47.771] (==) ModulePath set to "/usr/lib/xorg/modules" [ 47.771] (II) The server relies on udev to provide the list of input devices. If no devices become available, reconfigure udev or disable AutoAddDevices. # ... [ 47.778] loading driver: nvidia [ 47.882] (==) Matched nvidia as autoconfigured driver 0 [ 47.882] (==) Matched nouveau as autoconfigured driver 1 [ 47.882] (==) Matched modesetting as autoconfigured driver 2 [ 47.882] (==) Matched fbdev as autoconfigured driver 3 [ 47.882] (==) Matched vesa as autoconfigured driver 4 [ 47.882] (==) Assigned the driver to the xf86ConfigLayout [ 47.882] (II) LoadModule: "nvidia" # ... [ 48.142] (II) Unloading vesa [ 48.142] (EE) modeset(G0): drmSetMaster failed: Permission denied [ 48.142] (EE) Fatal server error: [ 48.142] (EE) AddScreen/ScreenInit failed for gpu driver 0 -1 I removed the nvidia driver and got the system to the working state again and then installed it from scratch. Then I set up a trace point in prime-select here: https://github.com/tseliot/nvidia-prime/blob/cf757cc9585dfc032930379fc81effb3a3d59606/prime-select#L126-L138 Tracing showed that /lib/modprobe.d/blacklist-nvidia.conf and /lib/udev/rules.d/80-pm-nvidia.rules were created correctly this time: https://paste.ubuntu.com/p/2Dp5jgFQty/ cat /lib/modprobe.d/blacklist-nvidia.conf # Do not modify # This file was generated by nvidia-prime blacklist nvidia blacklist nvidia-drm blacklist nvidia-modeset alias nvidia off alias nvidia-drm off alias nvidia-modeset off I could then successfully reboot without hacking. ** Attachment added: "Xorg.0.log" https://bugs.launchpad.net/ubuntu/+source/nvidia-prime/+bug/1848326/+attachment/5302704/+files/Xorg.0.log -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to nvidia-prime in Ubuntu. https://bugs.launchpad.net/bugs/1848326 Title: error booting with prime-select intel Status in nvidia-prime package in Ubuntu: Confirmed Bug description: when I try to boot with the iGPU selected, DE won't boot, with nvidia selected, everithing is fine. I tried uninstalling nvidia driver and it allowed my to access without any problems and intel is working fine ProblemType: Bug DistroRelease: Ubuntu 19.10 Package: nvidia-prime 0.8.13 ProcVersionSignature: Ubuntu 5.3.0-18.19-generic 5.3.1 Uname: Linux 5.3.0-18-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.20.11-0ubuntu8 Architecture: amd64 CurrentDesktop: KDE Date: Wed Oct 16 12:41:26 2019 Dependencies: InstallationDate: Installed on 2019-09-25 (20 days ago) InstallationMedia: Kubuntu 19.10 "Eoan Ermine" - Beta amd64 (20190925) PackageArchitecture: all SourcePackage: nvidia-prime UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nvidia-prime/+bug/1848326/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp