Ubuntu 18.10 boots only if one monitor is connected dual monitor setup stalls boot

[mas192]

Hi I am a mac user migrating to Ubuntu, please need help.
I have custom built machine, with 2xGTX 970.
Ubuntu 18.10 is installed in a separate hard drive alongside window 10(also in separate hard drive).
I have a bug, where Ubuntu boots normally only when 1 monitor is connected (HDMI or Display port doesn't matter).
But if I boot with two monitors connected Ubuntu boots with splash screen but after a moment goes into show activities of the boot sequence and stops progress and doesn't boot.
I have tried the Nvidia driver but that destroys the boot and Ubuntu does not even boot with one screen , I had to go into recovery and purge Nvidia driver to get Ubuntu to boot again.

This is my primary work computer, please someone help me to troubleshoot this.

Thank you very much

[oldfred]

How are you installing Ubuntu driver? From Ubuntu repository using ppa?
Do not install using nVidia's .run file.

What brand/model motherboard?
Do you need two video cards to run two monitors? I thought one video card could run several monitors, but never have needed that.

If primary work computer probably better to use 18.04LTS since long term support. Only if bleeding edge motherboard/chip may you need 18.10 for newer kernel & support software.

[mas192]

"How are you installing Ubuntu driver? From Ubuntu repository using ppa?"
I am not installing it through the nVidia/s.run file, however, I did not use the PPA.
I changed it in the software&Updates ->Additional Drivers->Using Nvidia Driver instead of the X.org.Xserver - nouveau display driver.

"What brand/model motherboard?
Do you need two video cards to run two monitors? I thought one video card could run several monitors, but never have needed that"

My motherboard is Gigabyte G7 Z170X, I have GTX870 in SLI.

"If primary work computer probably better to use 18.04LTS since long term support. Only if bleeding edge motherboard/chip may you need 18.10 for newer kernel & support software"
Oh okay, do you recommend I wipe and install 18.04?

[mas192]

Do you need more info? Thanks for helping

[oldfred]

My motherboard is Gigabyte Z170N-Gaming 5, but I only use the Intel internal video.

On another older system I have Asus Z97 with an older nVidia card just for port. Older monitor only had DVI & VGA and motherboard has HDMI & display port. So need nVidia only for DVI out.

But both have some settings in UEFI on which video is used. Have not checked Gigabyte manual to see what settings it has.

[mas192]

Hi Olfred, thanks for the reply, since Ill be using this system for data analysis and photo editing, I need to use the GPU, unfortunately, cannot rely on the integrated GPU

[oldfred]

But do you have video settings on motherboard's UEFI to enable the correct video mode.

My manual has this:

& Initial Display Output
Specifies the first initiation of the monitor display from the installed PCI Express graphics card or the onboard
graphics.
IGFX

Sets the onboard graphics as the first display.
PCIe

1 Slot
Sets the graphics card on the PCIEX16 slot as the first display. (Default)

Internal Graphics
Enables or disables the onboard graphics function. (Default: Auto

[mas192]

Yes, My UEFI settings are PCIe slot 1 is set as the initial display and IGFX is enabled and set to auto

[mas192]

So, I took your advice and installed Ubuntu LTS 18.4, all look good, only one question, I had to fix my grub using boot-repair, now how do I delete the backup bootloader files, that was generated by boot-repair which shows up every time I boot Ubuntu, is there a way to remove the backup files?

[oldfred]

What backup boot files?

Boot-Repair does copy Windows files as many users do not have any backup.
It also adds a lot of entries to grub menu in a new grub /etc/grub.d/25_custom which can be edited or deleted.