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I have tested Ubuntu in i7, i5 but lower then 4 core/8 thread CPU. In two system which has i7 processor with 4 core/8 thread i have the same problem. After reboot it never reboot itself auto.

I need to physically turn it off (power out), and power on.

What is the way to reboot for such system? (less then 4 core/8 thread CPU its working nicely).

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Are you talking about laptops, off-the-shelf PCs from a supermarket/electronics discounter or self built computers? Laptops are known to have issues like this. What do you mean by "After reboot it never reboot itself auto." Does that mean you're still in the desktop? Are you getting logged out of your desktop session and does Ubuntu shut down? Do you see the POST (Power On Self Test)? Please provide more information like: - Ubuntu version - Brand and model number of the laptop or computer - Brand and model number of the motherboard for self built computer – LiveWireBT Mar 28 '12 at 23:18
Did you mean that the computer doesn't restart and stays off? or just it shut down and starts blank? – Prasad RD Mar 29 '12 at 2:40
Desktop PC i have two i7 processor with 4 core on them. Where if i submit init 6 or reboot using GUI. It shows a black screeen with all errors, after that nothing happens, completely a physical power off and on require. – YumYumYum Mar 29 '12 at 6:34

Well, there is always the terminal command sudo shutdown -r now are you just looking for a way to reboot the machine? We need more information, are you trying to restart for updates? Hitting restart in Gnome? Please provide more information of what you are trying to achieve.

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When rebooting, there might be an issue you might not see because of the plymouth splash, if the "ubuntu" with orange and white dots on a purple background appears, press as soon as you can the RIGHT ARROW key on your keyboard. If done properly, you will switch to a black screen with white text going on. Try to see if there shows any errors, usually on the bottom of the screen.

Putting your Ubuntu and kernel version, and if any propietary drivers are installed, might be value information to help you, good luck! ;)

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up vote 0 down vote accepted

This problem is resolved since i started using 11.10. (11.04 on i7 with 4 core/8 thread cause this issue)

I was able to reproduce this by :

1) having a system which has i7 processor and more core/threads like 2600 model
2) having 8GB RAM etc higher profile
3) 11.04 install and apply reboot

never properly rebooted back. Same system after putting 11.10, it just works perfectly.
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