I recently switched from Ubuntu to Lubuntu 17.10. I used Unbootin to create a startup flash drive and installed it over my previous OS (Lubuntu) on laptop hard drive (Dell D430). I remember booting up the first time had issues,like it boot up into a partition and didn't recognize it had an OS. I had to set the boot sequance in Bios menue to "previous" (the Bios menu seem to changed a bit after dealing with Unbootin installation). I'm pretty sure that after setting the Bios menu to "previous" (which got the computer to boot up to Lubuntu) the display changed. In the OS the display bar is set at max brightness, but the screen is still very dim. Please help.
I found the reason- Unbootin changed the bios menu and settings. Apparently there are now 2 relevant settings "brightness" and another one "ambient" which you can toggle on/off and also control the level of it. For some reason the ambient was toggle off and set to low level (aka dark display). Issue resolved.