diff --git a/docs/user/metal/install_upi.md b/docs/user/metal/install_upi.md
index 7faedd0ecec..4f2d0ea75bf 100644
--- a/docs/user/metal/install_upi.md
+++ b/docs/user/metal/install_upi.md
@@ -196,6 +196,8 @@ TODO RHEL CoreOS does not have assets for bare-metal.
 
 * `rd.neednet=1`: [CoreOS Installer][coreos-installer] needs internet access to fetch the OS image that needs to be installed on the machine.
 
+* `coreos.inst.image_url`: Required for versions <= 4.5 only; should be the URL to a CoreOS "metal" image.  In 4.6+ the metal image is included in the Live images.
+
 * CoreOS Installer [arguments][coreos-installer-args] are required to be configured to install RHCOS and setup the Ignition config file for that machine.
 
 ## Watching your installation
diff --git a/upi/metal/config.tf b/upi/metal/config.tf
index b6435fdb8c0..9ad60e7b2a2 100644
--- a/upi/metal/config.tf
+++ b/upi/metal/config.tf
@@ -132,13 +132,13 @@ EOF
 
 }
 
-variable "pxe_os_image_url" {
+variable "pxe_kernel_args" {
   type = string
+  default = ""
 
   description = <<EOF
-URL to the OS image for RHCOS that should be installed on machines.
-
-For more info: https://github.com/coreos/coreos-installer#kernel-command-line-options-for-coreos-installer-running-in-the-initramfs
+Arbitrary kernel arguments, space delimited ie:
+coreos.inst.image_url=http://example.com/image.gz coreos.color=blue
 EOF
 
 }
diff --git a/upi/metal/main.tf b/upi/metal/main.tf
index 915166bcacb..46b81f589a7 100644
--- a/upi/metal/main.tf
+++ b/upi/metal/main.tf
@@ -15,8 +15,6 @@ locals {
 
     # "rd.break=initqueue"
     "coreos.inst=yes",
-
-    "coreos.inst.image_url=${var.pxe_os_image_url}",
     "coreos.inst.install_dev=sda",
     "coreos.inst.skip_media_check",
   ]
@@ -52,6 +50,7 @@ resource "matchbox_profile" "master" {
   args = concat(
     local.kernel_args,
     ["coreos.inst.ignition_url=${var.matchbox_http_endpoint}/ignition?cluster_id=${var.cluster_id}&role=master"],
+    [var.pxe_kernel_args],
   )
 
   raw_ignition = file(var.master_ign_file)
@@ -68,6 +67,7 @@ resource "matchbox_profile" "worker" {
   args = concat(
     local.kernel_args,
     ["coreos.inst.ignition_url=${var.matchbox_http_endpoint}/ignition?cluster_id=${var.cluster_id}&role=worker"],
+    [var.pxe_kernel_args],
   )
 
   raw_ignition = file(var.worker_ign_file)
@@ -134,7 +134,10 @@ module "bootstrap" {
 
   pxe_kernel             = local.pxe_kernel
   pxe_initrd             = local.pxe_initrd
-  pxe_kernel_args        = local.kernel_args
+  pxe_kernel_args        = concat(
+    local.kernel_args,
+    [var.pxe_kernel_args],
+  )
   matchbox_http_endpoint = var.matchbox_http_endpoint
   igntion_config_content = file(var.bootstrap_ign_file)
 
diff --git a/upi/metal/terraform.tfvars.example b/upi/metal/terraform.tfvars.example
index ea3a4faa5c0..c4ce5dab347 100644
--- a/upi/metal/terraform.tfvars.example
+++ b/upi/metal/terraform.tfvars.example
@@ -8,7 +8,7 @@ bootstrap_ign_file = ""
 cluster_domain = ""
 
 // The number of control plane machines required.
-// 
+//
 // Since etcd is colocated on control plane machines, suggested number is 3 or 5.
 // Default: 1
 master_count = "1"
@@ -17,22 +17,22 @@ master_count = "1"
 master_ign_file = ""
 
 // Client certificate used to authenticate with the matchbox RPC API.
-// 
+//
 // For more info: https://github.com/coreos/matchbox/blob/master/Documentation/api.md
 matchbox_client_cert = "matchbox/tls/client.crt"
 
 // Client certificate's key used to authenticate with the matchbox RPC API.
-// 
+//
 // For more info: https://github.com/coreos/matchbox/blob/master/Documentation/api.md
 matchbox_client_key = "matchbox/tls/client.key"
 
 // HTTPS endpoint for matchbox. This must include the scheme
-// 
+//
 // For more info: https://github.com/coreos/matchbox/blob/master/Documentation/api.md
 matchbox_http_endpoint = ""
 
 // RPC endpoint for matchbox.
-// 
+//
 // For more info: https://godoc.org/github.com/coreos/matchbox/matchbox/client
 matchbox_rpc_endpoint = ""
 
@@ -46,22 +46,24 @@ packet_project_id = ""
 public_r53_zone = ""
 
 // URL to the initrd image that should be used to PXE machines.
-// 
+//
 // This can be a fully-qualified URL or URL relative to matchbox_http_endpoint to use Matchbox assets (https://github.com/coreos/matchbox/blob/master/Documentation/matchbox.md#assets).
 pxe_initrd_url = ""
 
 // URL to the kernel image that should be used to PXE machines.
-// 
+//
 // This can be a fully-qualified URL or URL relative to matchbox_http_endpoint to use Matchbox assets (https://github.com/coreos/matchbox/blob/master/Documentation/matchbox.md#assets).
 pxe_kernel_url = ""
 
-// URL to the OS image for RHCOS that should be installed on machines.
-// 
+// PXE Boot Kernel args
+// Note, earlier versions of this code relied on a url via pxe_os_image_url, this has been replaced
+// with arbitrary kernel arguments which can include coreos.inst.image_url
+//
 // For more info: https://github.com/coreos/coreos-installer#kernel-command-line-options-for-coreos-installer-running-in-the-initramfs
-pxe_os_image_url = ""
+pxe_kernel_args = "coreos.inst.image_url=https://example.com/image.gz "
 
 // The number of worker machines required.
-// 
+//
 // Default: 1
 worker_count = "1"