The boot process

The procedure for booting a system image varies, depending on the partition style of the mass storage device containing the image. Beginning in the early 1980s, the standard disk partition format was called the master boot record (MBR). An MBR partition has a boot sector located at the logical beginning of its storage space. The MBR boot sector contains information describing the device's logical partitions. Each partition contains a filesystem organized as a tree structure of directories and the files within them.

Due to the fixed format of MBR data structures, an MBR storage device can contain a maximum of four logical partitions and can be no larger than 2 TB in size, equal to 232 512-byte data sectors. These limits have become increasingly constraining as commercially available disk sizes grew beyond 2 TB. To resolve these issues, and in tandem with the development of UEFI, a new partition format called GUID partition table (GPT) (where GUID stands for...