Some RAID Controllers, many fake RAID controllers and software raid put a signature on both the beginning and/or ending of the space on a hard drives. This many times creates problems when reformatting the drives or reloading the system after removing the hard drives.

Disconnect all external firewire, flash and usb devices (except keyboard and monitor)

Boot the system using a Centos 7 Net Install CD

When prompted, select “Troubleshooting” then “Rescue a Centos System”

When prompted with Continue/Read-Only/Skip select “Skip”

When you get to the # prompt type

lsblk -io NAME,TYPE,SIZE | grep disk

you should get something like

sda     disk 200G
sdb     disk 190G

(the sizes will vary depending on the size of your disk drives)

Some systems may come up with hda or other terms

Execute both of the following lines replacing sd* with sda, sdb, etc for each hard drive you have. Replace sda with hda if the above test indicates the drive name is that.

Note the second command has two entries for sdX!!! Also make sure you use the “back tick”  (`) character in the second command and not the “single quote” (‘) character

dd if=/dev/zero of=/dev/sd* bs=512 count=2
dd if=/dev/zero of=/dev/sd* bs=512 count=2 seek=$((`blockdev --getsz /dev/sd*` - 2))

Repeat for each hard disk

Reboot and install Centos

Note – this will remove your ability to access any data on the drives modified. Dont do this on any drives that you want to retain the data. (Recovery is possible but outside the realm of this document)