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Fedora 28 My triple monitor works initial install and LiveUSB, but not after performing dnf update/upgrade.

asked 2018-09-20 00:29:07 -0500

So I install Fedora 28 and was happy that my triple monitor setup works right from the start. I install it locally and as a dual boot with Windows 10. Works after initial install. All three of my 1080p monitors are displaying and doing it correctly. I do what I normally do for new OS installs from media, I go straight to updating. After rebooting, my triple monitor display only becomes a dual monitor. It is as if my third monitor isn't receiving a signal. But it works in POST, UEFI bios, and in windows 10.

I have an AMD Radeon RX 570 if that helps any.

I have also checked display and Fedora 28 isn't listing the third monitor at all.

I am a total newbie in the linux world and trying to ween away from Windows.

Here is what I have attempted:

I have attempted a reinstall. Solo OS with just Fedora 28, just Windows 10, and looked for answers across the internets. I'm not really sure where to start, but any help is appreciated.

Steps to get to my issue:

1 Install Fedora 28 via USB 2 Open up terminal after initial user creation 3 type 'dnf upgrade --refresh' or update, I can't remember which 4 restart 5 Login

Before the log in screen appears, my third monitor turns off as if no signal is being received. Anytime before that, all screens are displaying correctly.

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Hi, welcome to Ask Fedora. Edit your question and add to it output of inxi -SGxxxz command. After you paste it into the editor, select the text and use Ctrl+K to format it in a more readable way.

Using dnf history info 2 you should see what has been updated during the initial update.

In future you can use updated ISO images available here: That way live booted system is more up to date and also right after installation there are way fewer updates to install.

ozeszty gravatar imageozeszty ( 2018-09-20 08:05:43 -0500 )edit

I suspect that with update you got newer kernel version which enables AMD's new DC (display code) and might have caused the regression.

ozeszty gravatar imageozeszty ( 2018-09-20 12:06:33 -0500 )edit

Try booting withamdgpu.dc=0 kernel parameter to confirm whether it's the case.

ozeszty gravatar imageozeszty ( 2018-09-22 05:54:48 -0500 )edit

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answered 2018-09-20 06:35:48 -0500

keponk gravatar image

hey, not an expert here but it sounds like there's no issue with the HW if the livecd & fresh install works well.

During initial install some config files are populated based on what you do during the livecd installation (this is normal) so during an update some package may have replaced those config files with a "fresh" one. Your livecd probably populated it with the 3rd monitor detected but a fresh config file most probably doesn't have that written down by default.

Anyway, all that just to say that you might want to find the file where the 3 monitors are configured on a fresh install and save it. After an update put the file back (and notice if it changed). Which and where that file is-at idk. I think it's different for wayland vs Xorg.

Some breacrumbs: use xrandr to get some info. I would assume some gsettings could also shed some light.

Hope this helps!

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Asked: 2018-09-20 00:26:40 -0500

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Last updated: Sep 20 '18