scripting mdadm when a component device may contain ext2 file system already
I want to script the striping of the two ephemeral storage devices on m1.large EC2 instances using mdadm (apparently amis don't always include device information, so i can't just create a new ami once the array is started).

The problem is, ephemeral storage on EC2 instances generally comes preformatted with a file system, causing mdadm to say:


    mdadm: /dev/sdb appears to contain an ext2fs file system
        size=440366080K  mtime=Mon Jan  2 20:32:06 2012
    mdadm: /dev/sdc appears to contain an ext2fs file system
        size=440366080K  mtime=Wed Dec 31 19:00:00 1969
    Continue creating array? 

And wait for input.  I'm sure there's a way to auto answer yes for these types of prompts in mdadm for non interactive situations (like in fsck -y for example) but I can't seem to figure it out (it's not --force).  I know I could just zero out the devices using dd but that seems a rather sledgehammer-ey solution to something I'm sure is easily done.

scripting mdadm when a component device may contain ext2 file system already
===

I want to script the striping of the two ephemeral storage devices on m1.large EC2 instances using mdadm (apparently amis don't always include device information, so i can't just create a new ami once the array is started).

The problem is, ephemeral storage on EC2 instances generally comes preformatted with a file system, causing mdadm to say:


    mdadm: /dev/sdb appears to contain an ext2fs file system
        size=440366080K  mtime=Mon Jan  2 20:32:06 2012
    mdadm: /dev/sdc appears to contain an ext2fs file system
        size=440366080K  mtime=Wed Dec 31 19:00:00 1969
    Continue creating array? 

And wait for input.  I'm sure there's a way to auto answer yes for these types of prompts in mdadm for non interactive situations (like in fsck -y for example) but I can't seem to figure it out (it's not --force).  I know I could just zero out the devices using dd but that seems a rather sledgehammer-ey solution to something I'm sure is easily done.
