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Sometimes I am required to restart my Ubuntu machine and don't want to go through the BIOS then Grub. I remember that in windows we just need to hold down the Shift Key while clicking restart and trying the same procedure in Ubuntu without any success.

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This is a duplicate! See here: askubuntu.com/questions/152661/warm-reboot-directly-to-grub – Frantique Oct 3 '12 at 7:47
@Frantique No, I don't think my question is duplicate as the above link speaks about directly booting to Grub bypassing the BIOS and I am talking about bypassing all those thing BIOS and the GRUB too. I also want to restart from within my Ubuntu system might be with some modification and not making any changes to Firmware(Motherboard). – Namshum Oct 3 '12 at 8:04
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Could you please edit your question to include why you would want to restart the way you describe as opposed to doing a proper restart? – vasa1 Oct 3 '12 at 8:17
Ok, what about sudo kill -9 -1? – Frantique Oct 3 '12 at 8:42
@Frantique I used your code and it instantly makes the Screen dark just like expanded terminal (CUI) with a frozen cursor and had to restart my PC pressing the reset button. – Namshum Oct 4 '12 at 6:48

1 Answer

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On standard x86 PCs address 0x472 controls whether or not one does a cold or warm reboot. By writing 0x1234 to this address, the BIOS should do a warm reboot, and if zero is written to this address a cold reboot will occur.

This can be controlled with the kernel parameter reboot=w (warm) or reboot=c (cold). So using sudo and your favourite editor, edit /etc/default/grub and change

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash reboot=w"

and save. Then run:

sudo update-grub

and reboot. Hopefully, you should be doing warm reboots from now on. I've not tested this, but the code is there in the kernel to support this, see arch/x86/kernel/reboot.c in the kernel source and how reboot_type controls the reboot.

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lan king I have edit grub and then update but when I click restart it still goes through all the procedure bios, grub etc. and also ubuntu now restart immediately without waiting to close for any open application. – Namshum Oct 7 '12 at 12:22

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