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These boot sectors expect the FDISK partition table scheme to be in use and scans the list of partitions in the MBR's embedded partition table to find the only one that is marked with the active flag. [24] It then loads and runs the volume boot record (VBR) of the active partition.
fdisk version 1.0 can create one FAT12 partition, delete it, change the active partition, or display partition data. fdisk writes the master boot record , which supports up to four partitions. The other three were intended for other operating systems such as CP/M-86 and Xenix , which were expected to have their own partitioning utilities.
The partition type (or partition ID) in a partition's entry in the partition table inside a master boot record (MBR) is a byte value intended to specify the file system the partition contains or to flag special access methods used to access these partitions (e.g. special CHS mappings, LBA access, logical mapped geometries, special driver access, hidden partitions, secured or encrypted file ...
Each partition then appears to the operating system as a distinct "logical" disk that uses part of the actual disk. System administrators use a program called a partition editor to create, resize, delete, and manipulate the partitions. [3] Partitioning allows the use of different filesystems to be installed for different kinds of files.
The MBR sector may contain code to locate the active partition and invoke its volume boot record. A volume boot record (VBR) is the first sector of a data storage device that has not been partitioned, or the first sector of an individual partition on a data storage device that has been partitioned. It may contain code to load an operating ...
On GPT-based devices, the sectors hold the actual partition table, necessitating the use of an extra partition. On MBR-partitioned disks, boot loaders are usually implemented so the portion of their code stored within the MBR, which cannot hold more than 512 bytes, operates as a first stage that serves primarily to load a more sophisticated ...
Like MBR, GPT uses logical block addressing (LBA) in place of the historical cylinder-head-sector (CHS) addressing. The protective MBR is stored at LBA 0, and the GPT header is in LBA 1, with a backup GPT header stored at the final LBA. The GPT header has a pointer to the partition table (Partition Entry Array), which is typically at LBA 2 ...
If the first partition is the active partition the proposed case of a combined MBR + VBR would also contain code for this job, e.g., find a FAT32 or NTFS file such as NTLDR in the active partition, check plausibility + load + run it, or report trouble (NTLDR missing or compressed or whatever). 320 bytes are quite a lot.