The strangest thing happened to my system. Suddenly, it seems Ubuntu wasn't able to recognize my monitor resolution, so I wasn't able to see the graphical system through my screen. It was like when the computer is off but the monitor is on, the monitor shows a standard message asking to verify connection with the computer and cables.
After verifying connections and etc, trying a few times through different methods, finally I was able to boot into the system and the screen was working, but monitor resolution was all messed up, it had somehow changed to 'Auto' and it was all widened up. I don't understand why this happened. I was working on the computer and went downstairs to get a coffee, when I came back this stuff was happening.
I honestly don't get it if the problem was with the screen or with Ubuntu, but anyway, when I was able to work with the system I decided to change resolution manually to 1920x1080. I guess I did something wrong there, because now when I try to log in to the system, the screen that asks for my user and password shows just fine, with the usual size and all, but when I enter the password and confirm, my monitor shows a message asking to verify the connection with the computer (this happens when the computer is off and monitor is on, or if there is a problem with the cables...). But it's not the case.
This would seem like a problem with the monitor itself, but it is not, since I am able to boot on and work with Ubuntu in recovery mode, using the same monitor.
Can anyone clarify what is happening here? How do I change my monitor settings back to auto, or something that makes me able to boot into my system sucessfully (outside of recovery mode). Monitor is connected through a RGB-PC cable and system is Ubuntu 18.04.2 LTS (Lubuntu).
I guess the only way to change the monitor resolution in my main system would be through the command line in recovery mode, so how should I do that? Anyway, sorry if it is a bit confuse, I am confused myself. I can clarify any points if necessary.