When I first installed Ubuntu a couple years ago, I set it up with a software RAID using the Ubuntu alternate install disk. I have two 500 GB drives in the RAID.

A few days ago, one of the drives failed. I had to switch the boot order of the drives in the computer's BIOS, but other than that, the computer kept on truckin'. All my data is safe on the remaining drive.

I bought a new drive to replace the defective one, and it is installed in my computer. If I look at it with gParted Partition Manager, I can see it's there with all its space unallocated.

How do I get Ubuntu to see it as part of the RAID and begin mirroring the other drive?

dave@homebase:~$ sudo fdisk -lu



Disk /dev/sda: 500.1 GB, 500107862016 bytes

255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00078955



   Device Boot      Start         End      Blocks   Id  System

/dev/sda1   *          63    39070079    19535008+  fd  Linux raid autodetect

/dev/sda2        39070080    46877669     3903795   fd  Linux raid autodetect

/dev/sda3        46877670   781449794   367286062+  fd  Linux raid autodetect

/dev/sda4       781449795   976768064    97659135   83  Linux



Disk /dev/sdb: 500.1 GB, 500107862016 bytes

255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000



Disk /dev/sdb doesn't contain a valid partition table



Disk /dev/md2: 376.1 GB, 376084365312 bytes

2 heads, 4 sectors/track, 91817472 cylinders, total 734539776 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000



Disk /dev/md2 doesn't contain a valid partition table



Disk /dev/md1: 3997 MB, 3997368320 bytes

2 heads, 4 sectors/track, 975920 cylinders, total 7807360 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000



Disk /dev/md1 doesn't contain a valid partition table



Disk /dev/md0: 20.0 GB, 20003749888 bytes

2 heads, 4 sectors/track, 4883728 cylinders, total 39069824 sectors

Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000



Disk /dev/md0 doesn't contain a valid partition table

dave@homebase:~$ df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/md0               19G  4.5G   13G  26% /

none                  1.8G  708K  1.8G   1% /dev

none                  1.8G  752K  1.8G   1% /dev/shm

none                  1.8G  332K  1.8G   1% /var/run

none                  1.8G     0  1.8G   0% /var/lock

/dev/sda4              92G  211M   87G   1% /tmp

/dev/md2              345G  237G   91G  73% /home

192.168.0.12:/home/mythbuntu

                      651G  174G  444G  29% /home/dave/Mythbuntu

dave@homebase:~$ cat /proc/mdstat

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 

md0 : active raid1 sda1[1]

      19534912 blocks [2/1] [_U]



md1 : active (auto-read-only) raid1 sda2[1]

      3903680 blocks [2/1] [_U]



md2 : active raid1 sda3[1]

      367269888 blocks [2/1] [_U]



unused devices: <none>