Error while installing RHCOS using ISO

Hi,

I am trying to setup OpenShift cluster on baremetal user defined infrastructure. I am getting error at below step,

https://docs.openshift.com/container-platform/4.6/installing/installing_bare_metal/installing-bare-metal.html#installation-user-infra-machines-iso_installing-bare-metal

Permission Denied error after running coreos-installer command.

Full error:
Error: Parsing Arguments
caused by: getting sector size of /dev/sda
caused by: opening /dev/sda
caused by: Permission denied (os error 13)