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MBR include 3 parts: Master boot code, Partition table and disk signature. For example, I install Windows first and after linux. I don't know master boot code depend on boot loader? (NTLDR or Grub2). When I install linux after windows, how does master boot code change?

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migrated from Feb 28 '13 at 13:39

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Sorry, this question does not belong here, this place is about programming issues. – arkascha Feb 28 '13 at 8:45
Any one programming OS and Boot loader? So this is not programming? – thanhtv Feb 28 '13 at 8:48
Come on, you ask about installation of an operating system. That is not programming. If you would really implement boot loaders you would ask other questions. – arkascha Feb 28 '13 at 8:54

Windows is nasty. It will completely overwrite the MBR (master boot record), disregarding anything already there. With Linux, you can (and usually do, by default) choose to load grub or lilo or another bootloader into the MBR. When it does this, if there is already an OS bootloader there (such as with Windows), grub merely incorporates this disk image into its menu, thereby allowing you to choose which OS/disk image you want to boot.

That being said, the new UEFI bootloaders can be locked down on the hardware level to prevent the "secure booting" of any operating system whose bootloader has been tampered with. This is why there is a big issue in the Linux world nowadays, because with UEFI-enabled ("bootloader locked") versions of Windows, you can no longer let Linux overwrite the MBR (even preserving the installation image placed there), because Windows will refuse to boot, since the MBR/bootloader has been "tampered with". It's all very anti-competitive and evidence that Microsoft is beginning (or has begun) to fail to innovate. Once a corporation goes into litigation or market defense mode (usually via patents or hardware "lock-in" like UEFI), it's usually a sure sign that they've run out of good ideas. Microsoft is at that point in its life.

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