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I have just installed CentOS 5.7 x86_64 on a new computer. The installation went on without any issues. But, after it finnished, the machine started to show an awkward behaviour: it restarts every time it tries to boot.

It happens after all the services have been started. The screen just goes black and it shows an error message from the monitor: Input not supported. And then it reboots.

I took a look at the logs, but I couldn't manage to find anything.

Any help?


Before doing the hardware diagnosis, as pointed out, I decided to make some tests.

First, I changed the runlevel to 3, adding the 3 parameter at the end of the kernel command. Then, after logging in in text mode, I checked the xorg.conf file out for some problems regarding the screen resolution. There was nothing unexpected set. Well, if there had to be a problem with it, I couldn't start the X server at the command line, right? So, I typed startx and Gnome started! So, probably, it's not an issue with the screen resolution, I suppose.

Then I selected the Log Out root... Gnome menu option and something odd happened: the screen went black, the Input not supported monitor error message was displayed and the system rebooted. Yes, the same problem I was having while trying to boot!

After that, I decided to try yet another test: I removed the rhgb quiet parameters from the kernel command to see if some error would show up. Well, to my surprise, the boot went on without problems! The Gnome login screen showed up, I logged in and the session started. But then I selected the Shut Down... menu option and guess what? Same problem: black screen, same monitor error and the system rebooted. Yes, it rebooted, it did not shut down.

I repeated both of the tests and the behaviours were the same. I really don't know what's going on. It seems to be an issue regarding the changing of the screen mode or something like that.

Any ideas? Could this be a hardware problem? Or does it seem to be something regarding the system configuration?

As I couldn't afford to lose any more time on this issue I installed Debian on this machine.

I really would like to thank you guys who took time to answer the question and tried to help!

Since this question is not going to provide any help for someone who bumps into it in the future, should I delete it?

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closed as too localized by Iain Jul 26 '12 at 8:21

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

The error message "Input not supported" usually means that your computer is sending an incompatible display mode to your monitor.

At what stage of the boot process do you get that error?

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Just right after the last daemon service, smartd, has started. Actually, I'm not quite sure if it really starts. I can see the message Starting smartd, but as soon as it appears, the screen goes black. Is there any way I could gather more information about this? Any log file I could take a look to find out more about the problem? – Wagner Maestrelli Sep 28 '11 at 15:01
You should boot in single-user mode and look through /var/log/Xorg*. After that you can edit or create your xorg.conf file and configure it to use lower resolution or refresh rate (the problem could be caused by any of these). – Vladimir Blaskov Sep 28 '11 at 15:34

Looks like you set resolution and/or refresh rate bigger than the monitor can handle. Boot to rescue mode, check your xorg.conf.

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You'll want to do some hardware testing on that machine. What you're describing sounds almost entirely like hardware failure. Test the hard drives and memory first (memtest86+ and probably the disk diagnostics from your manufacturer).

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I agree with the hardware diagnosis. Without knowing much about your environment, I would venture a guess that heat could be an issue here.

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Looks like you've narrowed it down to something that happens in your default run level but not in init level 3 so compare your init scripts for run level 3 with whatever your default is.

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I took this from the CentOS forum so you might want to try it out:

Boot to runlevel 3, AKA text mode, by
1) interrupting GRUB by typing a character such as "space",
2) invoking edit mode by typing "e",
3) appending to the kernel line by typing "a", backspacing through "rhgb quiet" and appending " 3".
4) typing "b" to boot.
Log in as root and run system-config-display.

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