Appendix C: Master Boot Record Details

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C.1 MBR Structure

The Master Boot Record (MBR) defined in Section 2.1 occupies the first sector of a device (we assume that the size of a sector is always 512 bytes). Its structure is shown in Table 3 below.

Structure of a Master Boot Record

Table 3 - Structure of a Master Boot Record

C.2 Save and restore MBR

If you want to save a MBR, just copy the first sector of the first device in a file (keep a copy of that file on another media if you want to protect it from a device failure).

On Linux, type:

[xbas0:root] dd if=/dev/sda of=mbr.bin bs=512 count=1

If you want to restore the MBR replace the first sector with the saved file.

On Linux, type:

xbas0:root] dd if=mbr.bin of=/dev/sda bs=512 count=1

On Windows Server 2008, MBR can be restored even if not previously saved. Type:

C:\> bootrec /FixMbr