I noticed in journalctl that gnome-shell was core dumping. yum reinstall gnome-shell fixed my displays problem. So I am back to my first premise that the 'yum update' did not complete properly for some reason. Is there any way I can check the integrity of the packages installed? What could cause 'yum upgrade' to say 'Nothing to do' and not install the latest 305 kernel? Alan -- Alan McRae On 05/06/2021 15:30, Alan McRae via CentOS wrote: > The yum upgrade from 8.3 to 8.4 on my main machine looked as if it > was working fine so I went to have a coffee. > > When I came back the screens were blank so I don't know what happened. > On rebooting the screens are still blank. > > I have two graphics cards running three displays. > > I have a "rescue" system on the same machine that upgraded from 8.3 to > 8.4 fine. The 3 screens work fine on this. > > I am not sure the upgrade completed properly. For example the new kernel: > > vmlinuz-4.18.0-305.3.1.el8.x86_64 > > was not present in /boot. Even worse, "yum upgrade" said there was > nothing to do and would not install it. I installed the kernel package > manually. /etc/redhat-release says CentOS Linux release 8.4.2105 > > > My main question is: Where are the config files for the screen(s). > This used to be something like /etc/X11/xorg.conf. > > Since I have a working rescue system my current plan is to > compare/copy the config files. > > Suggestions please as to where I should start. It is difficult to work > without a GUI. I have ssh access to the machine. > > Thanks > > Alan >