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Old 03-09-2008, 03:30 AM   #1
concoran
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MBR and /dev/sda1? Are they same?


just curious.

is mbr the same as /dev/sda1?, (assuming SATA drive)
 
Old 03-09-2008, 04:01 AM   #2
bigrigdriver
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The MBR is the first sector on the hard drive - the first 512 bytes. The partition table is written there, as well as the first stage of the bootloader, which points to the location of the remainder of the bootloader's files.

/dev/dsa1 is the first partition on the hard drive, which can be any size, and does not include the first sector (the MBR).
 
Old 03-09-2008, 04:15 AM   #3
jschiwal
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Quote:
MBR and /dev/sda1? Are they same?
Asking about MBR and /dev/sda would have been a better question. If /dev/sda is the drive where the MBR was saved on, the first block of /dev/sda is the MBR. The first 244 bytes contain the boot portion and the magic byte. The rest is where the partition table is stored.

There is a wikipedia article on the MBR which is excellent.
 
Old 03-12-2008, 02:52 AM   #4
concoran
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so, if /dev/sda1 starts from very first possible sector, from the beginning of the disk as we call it, is it the first sector [bold]after[/bold] MBR, or is it same it MBR?

If MBR is not the same as first sector of /dev/sda1 which I assume is true, how far away from MBR can it start? I know there used to be a limit of some 1024 cylinders or something for the partition to be bootable. Is it still true?
 
Old 03-12-2008, 02:59 AM   #5
billymayday
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Since I thought I'd read it, here's the wikipedia link

http://en.wikipedia.org/wiki/Mbr
 
Old 03-12-2008, 03:26 AM   #6
konsolebox
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sda simply covers all your sda drive.. sda1 is just a part of.. actually a large part of it.. it's actually a partition..

doing 'cat /dev/sda' will print all of the contents of sda including your MBR, partition table and the partition sda1..

it's like this:
Code:
 -------------------- SDA --------------------------------
| MBR  and  |                    SDA1                     |
| OTHERS    |         (actually a lot more larger)        |
 ---------------------------------------------------------
Add:

You should be able to know where your sda1 resides from your first sector by looking at it with a partition tool like fdisk.. in fdisk you can use fdisk -l.. If i can remember it properly, the first sections (the mbr, partition table and others) allocate a head.. that's 255 sectors or 255*512 bytes.. 130,560 bytes..

Last edited by konsolebox; 03-12-2008 at 03:37 AM. Reason: scrambled
 
  


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