MBR Total Size
446 + 64 + 2 = 512
446 bytes - Bootstrap. 64 bytes - Partition table. 2 bytes - Signature.
512 vs 446 Bytes
dd command to copy MBR (identically sized partitions only) Type dd command as follows:
# dd if=/dev/sda of=/dev/sdb bs=512 count=1
Above command will copy 512 bytes (MBR) from sda to sdb disk. This will only work if both discs have identically sized partitions. dd command for two discs with different size partitions
# dd if=/dev/sda of=/tmp/mbrsda.bak bs=512 count=1
Now to restore the image to any sdb:
# dd if=/tmp/mbrsda.bak of=/dev/sdb bs=446 count=1
The above commands will preserve the partitioning schema. Linux sfdisk Command Example
Linux sfdisk command can make a backup of the primary and extended partition table as follows. It creates a file that can be read in a text editor, or this file can be used by sfdisk to restore the primary/extended partition table. To back up the partition table /dev/sda, enter:
# sfdisk -d /dev/sda > /tmp/sda.bak
To restore, enter:
# sfdisk /dev/sda < /tmp/sda.bak
The above command will restore extended partitions.
Task: Backup MBR and Extended Partitions Schema Backup /dev/sda MBR, enter:
# dd if=/dev/sda of=/tmp/backup-sda.mbr bs=512 count=1
Next, backup entries of the extended partitions:
# sfdisk -d /dev/sda > /tmp/backup-sda.sfdisk
Copy /tmp/backup-sda.sfdisk and /tmp/backup-sda.mbr to USB pen or somewhere else safe over the network based nas server.
Task: Restore MBR and Extended Partitions Schema To restore the MBR and the extended partitions copy backup files from backup media and enter:
# dd if=backup-sda.mbr of=/dev/sda # sfdisk /dev/sda < backup-sda.sfdisk