System Partition and Boot Partition

System Partition And Boot Partition

In Microsoft Windows's descriptions, the system partition and boot partition refer to:

  • The system partition is a primary disk partition that contains the boot sector and files such as NTLDR that are needed for booting Windows XP and earlier. (Windows Vista and Windows Server 2008 use a newer boot loader called BOOTMGR that replaces NTLDR and is configured using BCDEDIT.EXE).
  • The boot partition is the disk partition, primary or logical, that contains the Windows operating system files and its support files, but not any files responsible for booting.

The system partition can be different from the boot partition, although they are often the same partition (drive C:). Windows setup places the initial system partition based on motherboard BIOS settings. Bitlocker requires a separate, unencrypted system partition for booting.

The Master Boot Record with its MBR partition table is located at physical sector 0, and the optional GUID partition table is located at physical sector 1. Both are therefore not contained inside any of the logical partitions or volumes.

Despite Microsoft's idiosyncratic terminology, it is possible to mark the boot partition as active and boot into it, if the partition is a primary partition, and the required files such as NTLDR and BOOT.INI for Windows XP or older Windows NT platforms exist on it. In a dual-boot scenario the system partition could be formatted with a FAT16 file system and contain an MS-DOS operating system and a Recovery Console. The old DOS boot sector of this partition is saved in a file BOOTSECT.DOS (or similar), and used as entry in the NTLDR BOOT.INI file. The new boot sector of this partition looks for and starts NTLDR, while the image of the old DOS boot sector looks for and starts DOS. Note, that DOS boot sectors look for different files depending on the original equipment manufacturer such as IBM for PC DOS or Microsoft for MS-DOS, or even have different calling conventions (f.e. DR-DOS), therefore these systems are booted through their respective boot sector image files rather than directly.

Generally, newer boot schemes support older schemes; this is the reason why Microsoft operating systems are typically installed in chronological order (oldest OS first, newest OS last), and why attempts to "repair" critical sectors with tools designed for older operating systems can cause havoc for newer operating systems.

The new Windows Vista startup process supports the same and additional features; its boot sector looks for the new boot manager instead of NTLDR. Old FIXMBR tools installing an NTLDR boot sector would destroy the newer boot sector, and therefore newer Windows versions typically use a separate system partition. The recommended layout consists of a primary hidden recovery partition followed by the primary NTFS system partition (marked as active for booting), and a separate boot partition (in Microsoft terminology), the latter could be either a primary partition or a logical disk in an extended partition mounted as drive C:. More convoluted layouts with an OEM partition, or simpler layouts with system = boot partition, are possible.

Read more about System Partition And Boot Partition:  Other Operating Systems

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