Hard Drives and MBR

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The MBR (Master Boot Record) resides on the first sector of the disk and is where control is passed to by the machine BIOS.

The MBR will be different from operating system to operating system, and each operating system will have a way of writing its own MBR.

For example, in Windows

Code:

 
fdisk /mbr

(google that for syntax) will write an MBR and on Solaris the

Code:

 
installboot

command will write an MBR.

If an MBR exists at all when the disk comes from the factory, that will just be from the manufacturing test process and probably won't be what you need for your O/S. When the O/S install routine runs it will install its MBR.

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LEARN ABOUT FREEBSD

zfsboot

ZFSBOOT(8)						    BSD System Manager's Manual 						ZFSBOOT(8)

NAME

     zfsboot -- bootcode for ZFS on BIOS-based computers

DESCRIPTION

     zfsboot is used on BIOS-based computers to boot from a filesystem in a ZFS pool.  zfsboot is installed in two parts on a disk or a partition
     used by a ZFS pool.  The first part, a single-sector starter boot block, is installed at the beginning of the disk or partition.  The second
     part, a main boot block, is installed at a special offset within the disk or partition.  Both areas are reserved by the ZFS on-disk specifi-
     cation for boot use.  If zfsboot is installed in a partition, then that partition should be made bootable using appropriate configuration and
     boot blocks described in boot(8).

BOOTING

     The zfsboot boot process is very similar to that of gptzfsboot(8).  One significant difference is that zfsboot does not currently support the
     GPT partitioning scheme.  Thus only whole disks and MBR partitions, traditionally referred to as slices, are probed for ZFS disk labels.  See
     the BUGS section in gptzfsboot(8) for some limitations of the MBR scheme support.

USAGE

     zfsboot supports all the same prompt and configuration file arguments as gptzfsboot(8).

FILES

     /boot/zfsboot  boot code binary
     /boot.config   parameters for the boot block (optional)
     /boot/config   alternative parameters for the boot block (optional)

EXAMPLES

     zfsboot is typically installed using dd(1).  To install zfsboot on the ada0 drive:

	   dd if=/boot/zfsboot of=/dev/ada0 count=1
	   dd if=/boot/zfsboot of=/dev/ada0 iseek=1 oseek=1024

     If the drive is currently in use, the GEOM safety will prevent writes and must be disabled before running the above commands:

	   sysctl kern.geom.debugflags=0x10

     zfsboot can also be installed in an MBR slice:

	   gpart create -s mbr ada0
	   gpart add -t freebsd ada0
	   gpart create -s BSD ada0s1
	   gpart bootcode -b /boot/boot0 ada0
	   gpart set -a active -i 1 ada0
	   dd if=/boot/zfsboot of=/dev/ada0s1 count=1
	   dd if=/boot/zfsboot of=/dev/ada0s1 iseek=1 oseek=1024

     Note that commands to create and populate a pool are not shown in the example above.

SEE ALSO

     dd(1), boot.config(5), boot(8), gptzfsboot(8), loader(8), zfsloader(8), zpool(8)

HISTORY

     zfsboot appeared in FreeBSD 7.3.

AUTHORS

     This manual page was written by Andriy Gapon <avg@FreeBSD.org>.

BUGS

     Installing zfsboot with dd(1) is a hack.  ZFS needs a command to properly install zfsboot onto a ZFS-controlled disk or partition.

BSD
								September 15, 2014							       BSD

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