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Extended Partition Boot Record

Definition: EPBR: Extended Partition Boot Record:

Like the MBR, this sector contains a partition table. But unlike the MBR, the EPBR can be anywhere on the disk.
An Extended Boot Record (EBR), or Extended Partition Boot Record (EPBR), It is a descriptor for a logical partition under the common DOS disk drive partitioning system. In that system, when one (and only one) partition record entry in the Master Boot Record (MBR) is designated an "extended partition," then that partition can be subdivided into a number of logical drives. The actual structure of that extended partition is described by one or more EBRs, which are located inside the extended partition. The first EBR will always be located on the very first sector of the extended partition.

Unlike primary partitions, which are all described by a single partition table within the MBR, and thus limited in number, each EBR precedes the logical partition it describes. If another logical partition follows, then the first EBR will contain an entry pointing to the next EBR; thus, multiple EBRs form a sort of chain from the first to the next, and finally to the last one. This means the number of logical drives that can be formed within an extended partition is limited only by the amount of available disk space.

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