Talk:Volume boot record
|WikiProject Computing||(Rated Stub-class)|
GRUB as an MBR or VBR vs ordinary Volume Boot Records
I just finished 'undoing' an addition by User:Smwikicn2007 in which he called the VBR a 'virtual MBR' on non-partitioned devices. Later, this made me wonder what might have led him to make such a statement. Could it be the fact that GRUB (often found on computers running Linux) can actually be set up to act as either a Volume boot record or a partitioned device's Master boot record? If so, this may have led him to believe that any VBR code could also be thought of as an MBR on bootable devices that do not have a partition, such as floppy diskettes.
GRUB's 512-byte stage1 contents can perform either function, because it was not only created with executable code meant to run correctly after being loaded into memory at 0x7C00 by a master boot record, but also contains the usual 64-byte partition table that many utility programs expect to see in an MBR; especially those on hard disks with a bootable Microsoft operating system. Daniel B. Sedory 07:15, 22 September 2007 (UTC)
Please merge Volume boot record and boot sector. They both share the fate that they are certainly no master boot record with a partition table, but the first sector of a file system (FAT or whatever) in a partition or on a superfloppy.
They are also no "extended boot record", that's a pseudo-MBR in an extended partition, with an "extended" partition table containing one or two entries: One entry is the "logical disk", otherwise an ordinary partition starting with a volume boot record (but offsets relative to the "EBR", not the MBR in the first sector of the disk). The optional second entry in an "extended" partition table points to the next extended partition (with the next logical disk). The two or three remaining entries are empty (unused).
The code in a MBR is very different from the code in a VBR, all it ever does is to figure out which of the four partitions in its table is flagged as "active" (=> boot this). The code in a VBR is designed for an operating system and/or bootmanager scheme, e.g., it might know how to look for a file NTLDR on FAT or NTFS for a VBR starting a FAT or NTFS file system. And if it finds no NTLDR in this example the VBR code reports an error and gives up (the BIOS could then try the next boot device, or ask for a better floppy or CD). –184.108.40.206 (talk) 13:28, 18 July 2011 (UTC)
- This is only a description of a specific boot block program (originating from the partition support in PC DOS) that can be inserted in the MBR. I have a longer description in master boot record. Any boot code can be used in the MBR, including code that can also be used in a partition's VBR (for example, a GRUB boot block). The boot code in the MBR and a VBR on unpartitioned media are loaded identically by the BIOS, and the PC DOS MBR code also loads the partition VBR at the same address. Triskelios (talk)
The problem with boot sector is that it's a generic term but the current contents are specific to the IBM PC-compatible architecture described in master boot record (which I recently overhaulted) and volume boot record. As the VBR and MBR are very closely related and have similar constraints for boot code (the MBR specification is basically a specialisation of the VBR specification), it makes more sense to merge those two, or at least have a single description of bootstrapping. Triskelios (talk)
- The MBR article covering "partitions" is already complex enough, merging it with "VBR" would be a dubious plan. But "VBR" is still a stub; maybe I got the direction wrong, merge "VBR" into boot sector instead of the other way around? I'm looking at this zoo from the EBR article covering "extended partitions". Microsoft's boot vs. system partition terminology, where the system partition starts with a VBR, and the boot partition with the operating system might not be directly bootable at all, certainly does not help to explain these topics from a remotely "neutral" (non-MS) POV :-( –220.127.116.11 (talk) 05:43, 15 September 2011 (UTC)
Partition vs volume b
In my opinion(but I'm not so specialist), there are two little issues "to fix": 1)cause volume is not partition, VBR is not the same thing for PBR. Plenty of disk/data recovery tool refers to PBR and not to VPR 2) if you google PBR you can get more and more entries than VBR, so in my opinion it would be better if this page start from "Partion Boot Record" (PBR), with its acronym well focused and stop. After, you can report that there's also VBR, explaining the logical and physical difference- --Sistoiv (talk) 09:36, 27 December 2011 (UTC)