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Unknown display

Posted: 2021/11/17 03:37:59
by fermiproxy
I installed CentOS-7 for a second time within two months (on two different desktops.) The first installation was on an old desktop (nearly ten years old), the second one, on a brand new one. These two desktops share the same display monitor through an HDMI KVM switch. The first installation detected my monitor with no problems, and set the screen resolution to the default 1920x1080 without even asking me. The second installation said "unknown display" and dropped me to a low 600x400 resolution. I tried to change the resolution after the first login using the display settings, but it gave me no option at all to change it. (Probably related to the "unknown display" message.)

I am not sure what caused this difference. I used the same USB stick to do installation in both cases. And I am using the same display monitor in both cases. Looks very strange to me. :o

How can I make CentOS-7 recognize my monitor and save my second installation? :?:

Thanks for your help. :)

Re: Unknown display

Posted: 2021/11/17 07:40:55
by jlehtone
Monitor is linked to GPU.

RHEL 7.9 was released Sep 2020. It has not and will not receive any feature updates, like support for new hardware, since then.
"Brand new" can very well have new GPU model too and hence no proper driver. That, I guess, might explain.

What GPU do you have? Check with lspci -nn

Re: Unknown display

Posted: 2021/11/17 17:09:03
by fermiproxy
I didn't think I had a GPU, but I ran 'lspci -nn' as you suggested. It listed a dozen lines of info for various devices. And there was no GPU.

Re: Unknown display

Posted: 2021/11/17 17:17:23
by TrevorH
lspci -nn | grep -i vga

Re: Unknown display

Posted: 2021/11/17 17:55:08
by fermiproxy
I ran "lspci -nn | grep -i vga" as you suggested. Here is the output:
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation TU117 [GeForce GTX 1650] [10de:1f82] (rev a1)

By the way, I want to add an important piece of information. While I was installing CentOS from the boot USB-stick, the screen resolution was normal. During the installation, I was not dropped into a low resolution screen.

Re: Unknown display

Posted: 2021/11/17 19:25:10
by jlehtone
The distro includes open source driver "nouveau" for NVidia cards, but it does not know how to use all features of the card.

NVidia's own driver does. It is easiest to get with:

Code: Select all

sudo yum install elrepo-release
sudo yum install nvidia-detect
sudo yum install $(nvidia-detect)
reboot
Check whether that can solve the resolution issue.

Re: Unknown display

Posted: 2021/11/17 20:11:24
by TrevorH
The installer uses the VESA driver which is slow but supports whatever resolutions the BIOS supports.

What is the output from uname -a

Re: Unknown display

Posted: 2021/11/24 00:59:44
by fermiproxy
Jlehtone: your solution worked very well thank you. I apologize that it took a while for me to reply and confirm, because I had to re-install CentOS-7 for a different unrelated issue. After the re-installation, I applied your fix, and it worked like a charm.