I just upgraded to 18.04, and I am experiencing this very annoying problem.
If I disable through PRIME the Nvidia card, when I reboot a get to a black screen that flashes the boot operations, that is too fast to be read.
I have to login in a tty and re-set the Nvidia card as PRIME card in order to login. Please note that the system does not stay stabily in the chosen tty, it randomly goes back to tty1 where the boot operations are randomly flashing.
lspci -k
00:00.0 Host bridge: Intel Corporation 3rd Gen Core processor DRAM Controller (rev 09)
Subsystem: Dell 3rd Gen Core processor DRAM Controller
Kernel driver in use: ivb_uncore
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor PCI Express Root Port (rev 09)
Kernel driver in use: pcieport
Kernel modules: shpchp
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
Subsystem: Dell 3rd Gen Core processor Graphics Controller
Kernel driver in use: i915
Kernel modules: i915
00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller (rev 04)
Subsystem: Dell 7 Series/C210 Series Chipset Family USB xHCI Host Controller
Kernel driver in use: xhci_hcd
00:16.0 Communication controller: Intel Corporation 7 Series/C216 Chipset Family MEI Controller #1 (rev 04)
Subsystem: Dell 7 Series/C216 Chipset Family MEI Controller
Kernel driver in use: mei_me
Kernel modules: mei_me
00:1a.0 USB controller: Intel Corporation 7 Series/C216 Chipset Family USB Enhanced Host Controller #2 (rev 04)
Subsystem: Dell 7 Series/C216 Chipset Family USB Enhanced Host Controller
Kernel driver in use: ehci-pci
00:1b.0 Audio device: Intel Corporation 7 Series/C216 Chipset Family High Definition Audio Controller (rev 04)
Subsystem: Dell 7 Series/C216 Chipset Family High Definition Audio Controller
Kernel driver in use: snd_hda_intel
Kernel modules: snd_hda_intel
00:1c.0 PCI bridge: Intel Corporation 7 Series/C216 Chipset Family PCI Express Root Port 1 (rev c4)
Kernel driver in use: pcieport
Kernel modules: shpchp
00:1c.3 PCI bridge: Intel Corporation 7 Series/C216 Chipset Family PCI Express Root Port 4 (rev c4)
Kernel driver in use: pcieport
Kernel modules: shpchp
00:1c.5 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 6 (rev c4)
Kernel driver in use: pcieport
Kernel modules: shpchp
00:1d.0 USB controller: Intel Corporation 7 Series/C216 Chipset Family USB Enhanced Host Controller #1 (rev 04)
Subsystem: Dell 7 Series/C216 Chipset Family USB Enhanced Host Controller
Kernel driver in use: ehci-pci
00:1f.0 ISA bridge: Intel Corporation HM77 Express Chipset LPC Controller (rev 04)
Subsystem: Dell HM77 Express Chipset LPC Controller
Kernel driver in use: lpc_ich
Kernel modules: lpc_ich
00:1f.2 RAID bus controller: Intel Corporation 82801 Mobile SATA Controller [RAID mode] (rev 04)
Subsystem: Dell 82801 Mobile SATA Controller [RAID mode]
Kernel driver in use: ahci
Kernel modules: ahci
00:1f.3 SMBus: Intel Corporation 7 Series/C216 Chipset Family SMBus Controller (rev 04)
Subsystem: Dell 7 Series/C216 Chipset Family SMBus Controller
Kernel modules: i2c_i801
02:00.0 3D controller: NVIDIA Corporation GF117M [GeForce 610M/710M/810M/820M / GT 620M/625M/630M/720M] (rev a1)
Subsystem: Dell GeForce GT 630M
Kernel driver in use: nvidia
Kernel modules: nvidiafb, nouveau, nvidia
07:00.0 Network controller: Intel Corporation Centrino Wireless-N 2230 (rev c4)
Subsystem: Intel Corporation Centrino Wireless-N 2230 BGN
Kernel driver in use: iwlwifi
Kernel modules: iwlwifi
09:00.0 Ethernet controller: Qualcomm Atheros AR8161 Gigabit Ethernet (rev 10)
Subsystem: Dell AR8161 Gigabit Ethernet
Kernel driver in use: alx
Kernel modules: alx
Any help on how to save some energy when using my laptop?