Ubuntu
grub2 package

Proper Ubuntu 10.10 install with windows 7

Asked by David M Turner

So I have tried once before. I am using a 1TB drive. Windows on a primary, plus its 100mb system reserved partition using about half of the drive. The other half is unallocated and I intend to use it for Ubuntu 10.10. I followed this procedure before. I manually selected the unallocated space for the linux install. The option for "alongside windows' makes it sound like it will split the windows partition, so I avoided it. Linux installed fine (except for the uppercase user issue which drove me insane). However I could no longer boot into Windows. Grub never gave me any options, straight to linux everytime. I deleted the linux partition thinking it would also eliminate grub. After that I could not boot into anything at all. So now windows is reinstalled. Could someone explain where grub is installed, and what it does with ntloader when it does install? Perhaps if I had a clearer understanding of the process I could make my dual boot dreams come true haha. Thanks, ciao.

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actionparsnip (andrew-woodhead666) said : 		#1

Try:

sudo apt-get install os-prober; sudo os-prober; sudo update-grub

This will add windows to the grub config

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delance (olivier-delance) said : 		#2

The boot process is a little complicated, due to "legacy".
When you boot PC, the BIOS search first bootable device in order you specified.
For internal/external hard disk/flash memory, it use firstly DOS partition scheme.
Yes, DOS. As I said it's legacy.
This partition table is at end of first disk sector (512 bytes) and can hold up to four primary partition table.
Before this partition table, there are few hundreds of blocks which contains boot code.
And in the 32kB at start of disk, there is also code for booting purposes.
Sometimes MBR designate only first sector, and sometimes the first 64 sectors.
When you install Grub2, it overwrite both the first sector and the following 63 sector with a predefined code.
And it add inside first sector code address of partition which contains the "/boot" folder.
The following 63 sectors are used to read disk file system (for /boot) and to use keyboard and mouse (and other things I don't know).
This code will read the displayed menu in /boot folder, and the way to launch operating systems, including Windows one.
In this case, for what I understand, it loads a Windows bootloader, which will load a Windows OS.
When you reinstalled Windows, you reinstalled its MBR (64 first sectors), and if you want to use Ubuntu, you will have to reinstall Grub2:
   https://help.ubuntu.com/community/Grub2#Reinstalling%20from%20LiveCD
During this process, it will try to detect Windows OS and configure their loading.
A good news is that it works best when reinstalling from CD than at end of Ubuntu's installation.
If it continue to fail, it can be done manually.

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