I'm having the weirdest issue. We use SL7.2 and have a network home directory and AD + SSSD for auth. This means I can go to different computers and get a consistent home dir as well as UID/GID etc. I have a physical KVM to set up computers more easily.
I started having an issue where my workstation would stop displaying X to my monitor. The monitor will say "No Signal" It would work fine until I switched away via the KVM to another computer, when I switched back X would not display. I could connect via Bomgar and see my X session, it was fine. I could ctrl-alt-F3 and the virtual terminal would display, but the only way to get X back was to reboot.
I thought it might be the KVM, so I connected the monitor via DVI directly to the workstation. No change.
I thought it was an issue with the hardware or the OS install, so I set up a brand new Lenovo P510 with a new SL7.2 install. Now it will loose X if I just don't use it for a while (I think it's the screen locking?).
I thought it might be the monitor - maybe it's old and loosing signal, or the new Display port to DVI adapter can be funky, so I installed a brand new BENQ GW2765, connected directly via Display Port to the nVidia card (this card only has Display Port connectors - 4x). No change.
So now I'm thinking - it HAS to be software, and it has to be something in my configuration. But I don't really even know where to start looking - /var/log/messages and /var/log/Xorg.0.log don't show anything that's obvious to me.
How can I fix X not coming back?
EDIT: I have confirmed that it only happens when I turn off the monitor. I left my new monitor on overnight - and X did not die. The problem with this is SL7.2 never actually turns off the monitor's backlight so I think it's bad for the monitors longevity.