I know you said that it's not a hardware problem, but there is a lot of hardware on a computer. Hear me out.

Try these suggestions, just to see if one of them works for you:

1) Attach a flat screen monitor, or even any video screen, and see if you can get dependable performance, without the problems you are experiencing.
2) Plug in a USB flash drive. It could be any usb flash or external hd, but stay away from usb devices like a printers or bluetooth. This might bypass a possible faulty motherboard circuit, and cause the video to start working again.
3) Try running on just battery power. Again, faulty circuits could be bypassed by not using the A/C circuits.

If suggestion 1) works, it's possibly a bad video backlight inverter. I used to repair computers for a living, and I repaired a couple of these. The screen goes completely dark, intermittently, but you can actually see what's on the screen if you shine a flashlight onto the screen.

Take a look at this video, which shows how to replace the backlight inverter:
https://www.youtube.com/watch?v=ucaJA324hbg

I thought about the monitor, but i dont have one. arranging one is also not possible

There are no external devices connected.

Using USB to install CentOS, this same USB was used to boot to Knoppix 7.2 so the USB drive is fine, display is fine, RAM is fine. I have booted into Knoppix with highest resolution possible and changed it other options using the boot option. All just worked fine.

The laptop does not has a battery.

Also this Laptop was running SME Server 9.2 and it just worked fine. It always booted in Text Mode.

I want to try my hands on CentOS and this Laptop is my only hope.

From what i have understood here is - Somehow i just to need to get the kernel understand NOT to load any video drivers and boot up in pure command line mode, like in Rescue mode.

I don't see anybody else responding to your post, so I guess you're stuck with me.

You could try this link:
https://www.supergrubdisk.org/2020/0...0-73-released/

Watch the video on Rescatux. It might be just what you need. There are a lot of configuration options with this software, including options to adjust the video resolution. Whether or not you can control loading of video drivers, I'm not sure.

Best wishes. I hope this helps.

I would just boot to whatever run level systemd has that does not load the graphical target. Since I do not use anything with systemd, this link my be helpful. https://www.thegeekdiary.com/centos-...-with-systemd/

So i found the reason, it is ACPI. I turned it off in Kernel Boot Options acpi=off and that stopped the Laptop from going into Sleep.

I understand ACPI is in place for a reason but for now i have turned it off and double checked that the problem does not occur.

Older version like 6.3 does not do this, why i chose 6.3, because i had its .iso file. In the recent versions i think 7 onwards some changes have happened related to ACPI.

I found a very informative link for Linux Kernel Parameters (for me - especially video & ACPI )
http://distro.ibiblio.org/fatdog/web...t-options.html

coderlen - Thank you for your time, I learnt about Rescatux, which looks like a good tool.

sevendogsbsd - Thank you for your time, the link you shared about systemd was really informative.

I'm glad you got it working. It was a pleasure working with you. I learned a few things myself.

Take care.
coderlen