MBRBackup
Backing up the Master Boot Record:
Save the MBR with dd:
dd if=/dev/sda of=backup-sda.mbr count=1 bs=512
It will produce a very small, but very important file: 512 bytes of data. Now, we will save entries of the extended partitions:
sfdisk -d /dev/sda > backup-sda.sf
Restoring partition entries from the backup:
First, restore the Master Boot Record:
dd if=backup-sda.mbr of=/dev/sda
Restore extended partitions entries:
sfdisk /dev/sda < backup-sda.sf
Reboot.