Juno and higher versions of Ironic:

nova flavor-key my-baremetal-flavor set cpu_arch=$ARCH

Associate the deploy ramdisk and deploy kernel images to the node’s driver_info (pxe_ipmitool driver used in the example below):

ironic node-create -d pxe_ipmitool \
-i pxe_deploy_kernel=$DEPLOY_VMLINUZ_UUID \
-i pxe_deploy_ramdisk=$DEPLOY_INITRD_UUID \
-i ipmi_address=<IPaddress> \
-i ipmi_username=<username> \
-i ipmi_password=<password> \
-i pxe_root_gb=<root partition size> \
-p cpus=$CPU -p memory_mb=$RAM_MB -p local_gb=$DISK_GB -p cpu_arch=$ARCH