16.04 GUI comes up as garbled text

[rsteinmetz70112]

I have 16.04 on one computer. Recently the GUI stopped working right. If I reboot the machine the boot up messages scroll through as usual and a login prompt appears. Very shortly after that the screen goes blank as if preparing the GUI and but after a few minutes I get an screen with garbled text characters. The screen contains a login prompt and I can login but I can't read anything on the screen. I can also login from any other machine using ssh and that works fine. Obviously some sort of video problem but I don't know what.

[TheFu]

bad cable?
bad PSU?
bad GPU?

Were any GPU drivers recently updated? Does the Xorg.0.log have anything inside it? Probably need to ssh in from a different machine to check that.

[rsteinmetz70112]

I suspect a messed up configuration. I just have to figure it out.

bad cable?

Unlikely the unit is on a KVM and the other machines work just fine and since the screen is in text mode - I can login in but just can't read anything on the screen.
I can try swapping the the cables arounf on the KVM to test them

bad PSU?

I don't see how, it simply seems to refuse to go into graphics mode, everything else seems to work as expected.

bad GPU?

Possibly I'll try a live session when I can take it down.

Were any GPU drivers recently updated?

Don't know. I am supposed to use the nouveau driver, if an update caused this I would expect a number os similar reports. I haven't found any thing that seems to march but I have a difficult time clearly describing what is happening.

Does the Xorg.0.log have anything inside it? Probably need to ssh in from a different machine to check that.

There is the

[    46.350] (II) NVIDIA(0): Validated MetaModes:
[    46.350] (II) NVIDIA(0):     "CRT-0:nvidia-auto-select"
[    46.350] (II) NVIDIA(0): Virtual screen size determined to be 1280 x 1024
[    46.353] (WW) NVIDIA(0): Unable to support custom viewPortOut 1280 x 720 +0 +152
[    46.353] (--) NVIDIA(0): DPI set to (116, 123); computed from "UseEdidDpi" X config
[    46.353] (--) NVIDIA(0):     option
[    46.353] (II) UnloadModule: "nouveau"
[    46.353] (II) Unloading nouveau
[    46.353] (II) UnloadModule: "modesetting"
[    46.353] (II) Unloading modesetting
[    46.353] (II) UnloadModule: "fbdev"
[    46.353] (II) Unloading fbdev
[    46.353] (II) UnloadSubModule: "fbdevhw"
[    46.353] (II) Unloading fbdevhw
[    46.353] (II) UnloadModule: "vesa"
[    46.353] (II) Unloading vesa
[    46.353] (--) Depth 24 pixmap format is 32 bpp
[    46.359] (II) NVIDIA(0): Setting mode "CRT-0:nvidia-auto-select"
[    46.453] (EE)
[    46.456] (EE) Backtrace:
[    46.456] (EE) 0: /usr/lib/xorg/Xorg (xorg_backtrace+0x52) [0x5d2bb2]
[    46.456] (EE) 1: /usr/lib/xorg/Xorg (0x431000+0x1a6022) [0x5d7022]
[    46.456] (EE) 2: (vdso) (__kernel_rt_sigreturn+0x0) [0xb7795c20]
[    46.456] (EE) 3: /usr/lib/i386-linux-gnu/xorg/extra-modules/nvidia_drv.so (0xb416f000+0x7b5e00) [0xb4924e00]
[    46.456] (EE)
[    46.456] (EE) Segmentation fault at address 0x248
[    46.456] (EE)
Fatal server error:
[    46.456] (EE) Caught signal 11 (Segmentation fault). Server aborting
[    46.456] (EE)

Looks like it's trying to use the NVIDIA driver, it looks like nvidia-304 was installed at some point. I will try to remove all of the NVIDIA driver, probably left over from a previous

[rsteinmetz70112]

OK - ran

sudo apt remove nvidia*
sudo reboot

No more giberish, only a black screen
Xorg.0.log shows NOUVEAU configured OK
Ran

dpkg-reconfigure lightdm
select gdm3
sudo shutdown

Power cycle power supply
Graphic login comes up
Login
Desktop comes up.

Need to do some more testing but it looks like its OK.