Solaris11.4 - no X11

After some problems, I have installed Solaris 11.4. The warnings said

WARNING: /pci@0,0/.....
(xhci1): Connecting device on port 5 failed
WARNING: /pci@0,0/.....
(xhci1): Connecting device on port 6 failed

Preparing image for use
Unable to mount media
Requesting System Maintenance Mode
(See /lib/svc/share/README for more information)
Console login service(s) cannot run

The problem was that I had inserted the USB stick into a USB3 port. I instead used a USB2 port and could finally install Solaris 11.4. So for future reference, if anyone fails to install with these error messages, I have recorded the solution here.

Now I have a problem. I cannot get to X11. I see the splash screen, so I have graphics. But when I try to start X11, it does not work. How can I get X11 graphics?

After installation, I added the desktop package:

# pkg install solaris-desktop

But still there is no X11. I reboot the PC, and see some error messages. Can anyone help me solve this problem? I have reinstalled the nvidia driver, I am using version 387.34 which is the one NVidia web site gave me.

I have a Supermicro X10SAT, E3-1245 cpu and a NVidia Geforce 1070Ti.

The error messages say:

WARNING: Signature verification of module /kernel/drv/amd64/nvidia failed
WARNING: Signature verification of module /kernel/drv/amd64/nvidia_modeset failed
Loading NVIDIA Kernel Mode Setting Driver for UNIX platforms 387.34
nvidia_modeset: Unloading
krtld: WARNING: Signature verification of module /kernel/drv/amd64/nvidia failed
krtld: WARNING: Signature verification of module /kernel/drv/amd64/nvidia_modeset failed
nvidia_modeset: Loading NVIDIA Kernel Mode Setting Driver for UNIX platforms

And then I try to do “svcadm enable gdm” and after that I do “startx” and see these error messages:

xauth: file /export/home/root/.serverauth.1374 does not exist
X.org X Server 1.19.5
Release Date: 2017-10-12
X Protocol Version 11, Revision 0
Build Operating System: SunOS 5.11 i86pc
Current Operating System: SunOS 5.11 11.4.0.15.0 i86pc
Solaris ABI: 64-bit
Current version of pixman: 0.34.0
Before reporting problems, check https://support.oracle.com/ to make sure you have the latest version
(==) Log file: "/var/log/Xorg.0.log"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
(EE)
Fatal server error:
(EE) no screens found(EE)
(EE)
Please consult the Oracle corporation, based on X.Org Foundation sources support
(EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information
(EE)
(EE) Server terminated with error (1). Closing log file
xinit: giving up
xinit: unable to connect to X server: Connection refused
xinit: server error

So I get no X11. No GUI. How can I start X11?

Question, is Geforce GTX 1070 Ti supported???