The boot process
The procedure for booting a system image varies depending on the partition style of the mass storage device containing the image and the security features enforced during boot. The goal of the boot process is to bring up the system following power application and initialize the operating system, leaving the computer in a known state and ready to perform useful work.
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...