Today I was trying to install CentOS6 on a server put together from bits and pieces I had lying about. The CentOS installer would not include either of the disks I’d used because it claimed they had BIOS RAID metadata that didn’t appear to be part of an existing RAID partition.
Initially I tried using “dd” to write a load of zeros to the start of the disk to see if that would clear whatever information had been left on the disks from their previous life but no dice, so I had to do things the hard way…
Eventually I found that the following command (run for each disk device in turn) cleared the data and allowed me to use the disks for installing the OS:
dmraid -r -E /dev/sda
The easiest way I found to run it from the CentOS installer was to use Alt-F2 to flip to a shell once the GUI installer had started, run it there and then Alt-F7 to flip back to the installer screen.