Hope somebody can help me with my confusion regarding the boot loader, boot sector (aka dos boot sector or DBS aks volume boot record or VBR), boot record, and boot manager.

MBR: As I understand it, there is only one MBR on a system, the MBR is loaded first, then it vectors control to the boot sector (or boot loader?). I have read that the boot loader, and partition table, are in the MBR, but that doesn't make sense to me. As I understand it, the MBR is only about 512 bytes.

DBS/VBR: As I understand it, these are located on individual bootable partitions. There can be sevral on single HDD. Does the DBS/VBR actually load the OS? Or is the OS loaded by the boot loader? What about on a floppy?

boot loader: GRUB and LILO are boot loaders, right? Or are GRUB and LILO boot managers? Or both? Is it the boot loader that finally loads the OS? So, the boot loader runs *after* the DBS/VBR?

boot sector: As I understand it, a bootable floppy doesn't have an MBR, because a floppy can not be partitioned. Does a boot floppy have a boot loader? I suppose a boot floppy *can* have a boot loader, since LILO can be put on a floppy. But, what about a floppy to boot MS-DOS, would that have a boot loader?

boot manager: is that the part of LILO or GRUB that lets you decide which OS/kernel to boot?

"I have read that the boot loader, and partition table, are in the MBR"

The boot loader is located in a file in /boot. The partition table begins immediately after the MBR.

"the MBR is loaded first, then it vectors control to the boot sector (or boot loader?)"

Yes. One of the things that happens when you install the bootloader to the MBR is that the address of the bootloader file in /boot is inserted into the MBR.

"DBS/VBR: As I understand it, these are located on individual bootable partitions."

What is a DBS/VBR?

"boot loader: GRUB and LILO are boot loaders, right? Or are GRUB and LILO boot managers? Or both? Is it the boot loader that finally loads the OS?"

The portion of lilo or grub on the MBR boots the rest of the bootloader from a file in /boot. Each OS contains its own boot loader. grub and lilo figure out which OS to load and then start up the bootloader of that OS.
"
"Does a boot floppy have a boot loader?"
Yes. This is the same grub or lilo boot loader that on a hard drive is located in /boot.

"what about a floppy to boot MS-DOS, would that have a boot loader?"
Yes. It would have the MS-DOS boot loader and nothing from lilo or grub.

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Steve Stites

This:
Technically, it *could* run lilo or grub which chainloaded the MS-DOS (or other) bootloader.

--Jonas

As already mentioned, I have seen boot sector refered to as dos boot sector or DBS aks volume boot record or VBR.

I wish I had been more clear about that. Because the most confusing aspect of all this is: what actually, finally, loads the OS? The boot loader, or the sector?

Well, the sector is just a hunk of space on your hard disk. The contents of the sector (i.e. the bootloader) loads the OS.

hth --Jonas