Volume boot record

A Volume Boot Record (also known as a volume boot sector or a partition boot sector, although the latter is not strictly correct) is a type of boot sector, stored in a disc volume on a hard disk, floppy disk, or similar data storage device, that contains code for booting programs (usually, but not necessarily, operating systems) stored in other parts of the volume. On non-partitioned storage devices, it is the first sector of the device. On partitioned devices, it is the first sector of an individual partition on the device, with the first sector of the entire device instead being a Master Boot Record (MBR).

The code in volume boot records is invoked either directly by the machine's firmware or indirectly by an MBR or a boot manager.

Invoking a VBR via a boot manager is known as chain loading. Some dual boot systems, such as NTLDR, take copies of the bootstrap code that individual operating systems install into a single partition's VBR and store them in disc files, loading the relevant VBR content from file after the boot loader has asked the user which operating system to bootstrap.

In certain file system formats, in addition to bootstrap code the VBR contains a BIOS parameter block that specifies the location and layout of the principal on-disc data structures for the file system.

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