• with the instructions that follow we move a complete root system disk from bare partitions to a raid 1 software layer.
• all the work is done without putting the server off-line.
• only one reboot process is needed if the disks are already installed on the server.

We will move the system disk of a linux system from a standard partition scheme, to a raid 1 system withous

• /dev/sda: is the original disk from where the system boot
• /dev/sdb: is the second disk

• we need to create the correct partitions we need:
  • 100 MB for the boot partition
  • 2Gbyte for the swap partition (there's no need to put the swap partitions on a raid system)
  • rest of the space disk for the root and others partitions

start fdisk and follow these commands

 fdisk /dev/sdb
 n
 p
 1
 [enter]
 +100M
 n
 p
 2
 [enter]
 +2048M
 n
 p
 3
 [enter]
 [enter]
 t
 2
 82
 t
 3
 fd
 w

• now we need to create the raid 1 partitions for the boot and the other partitions
• /dev/md0 will be the first raid 1 partition used only by the /boot directory
• /dev/md1 will be the raid 1 disk used for everything else

<code> mdadm –create /dev/md0 –level=1 –raid-devices=2 missing /dev/sdb1 mdadm –create /dev/md1 –level=1 –raid-devices=2 missing /dev/sdb3