Allow Flatcar Linux os_channel on bare-metal

* Choose the Container Linux derivative Flatcar Linux on
bare-metal by setting os_channel to flatcar-stable, flatcar-beta
or flatcar-alpha
* As with Container Linux from Red Hat, the version (os_version)
must correspond to the channel being used
* Thank you to @dongsupark from Kinvolk

bare-metal/container-linux/kubernetes/cl/install.yaml.tmpl

@@ -31,7 +31,7 @@ storage:
         inline: |
           #!/bin/bash -ex
           curl --retry 10 "${ignition_endpoint}?{{.request.raw_query}}&os=installed" -o ignition.json
-          coreos-install \
+          ${os_flavor}-install \
             -d ${install_disk} \
             -C ${os_channel} \
             -V ${os_version} \

bare-metal/container-linux/kubernetes/groups.tf

@@ -2,7 +2,8 @@ resource "matchbox_group" "install" {
   count = "${length(var.controller_names) + length(var.worker_names)}"
 
   name    = "${format("install-%s", element(concat(var.controller_names, var.worker_names), count.index))}"
-  profile = "${var.cached_install == "true" ? element(matchbox_profile.cached-container-linux-install.*.name, count.index) : element(matchbox_profile.container-linux-install.*.name, count.index)}"
+
+  profile = "${local.flavor == "flatcar" ? element(matchbox_profile.flatcar-install.*.name, count.index) : var.cached_install == "true" ? element(matchbox_profile.cached-container-linux-install.*.name, count.index) : element(matchbox_profile.container-linux-install.*.name, count.index)}"
 
   selector {
     mac = "${element(concat(var.controller_macs, var.worker_macs), count.index)}"

bare-metal/container-linux/kubernetes/profiles.tf

@@ -1,5 +1,6 @@
 locals {
   # coreos-stable -> coreos flavor, stable channel
+  # flatcar-stable -> flatcar flavor, stable channel
   flavor  = "${element(split("-", var.os_channel), 0)}"
   channel = "${element(split("-", var.os_channel), 1)}" 
 }
@@ -33,6 +34,7 @@ data "template_file" "container-linux-install-configs" {
   template = "${file("${path.module}/cl/install.yaml.tmpl")}"
 
   vars {
+    os_flavor           = "${local.flavor}"
     os_channel          = "${local.channel}"
     os_version          = "${var.os_version}"
     ignition_endpoint   = "${format("%s/ignition", var.matchbox_http_endpoint)}"
@@ -75,6 +77,7 @@ data "template_file" "cached-container-linux-install-configs" {
   template = "${file("${path.module}/cl/install.yaml.tmpl")}"
 
   vars {
+    os_flavor           = "${local.flavor}"
     os_channel          = "${local.channel}"
     os_version          = "${var.os_version}"
     ignition_endpoint   = "${format("%s/ignition", var.matchbox_http_endpoint)}"
@@ -87,6 +90,29 @@ data "template_file" "cached-container-linux-install-configs" {
   }
 }
 
+// Flatcar Linux install profile (from release.flatcar-linux.net)
+resource "matchbox_profile" "flatcar-install" {
+  count = "${length(var.controller_names) + length(var.worker_names)}"
+  name  = "${format("%s-flatcar-install-%s", var.cluster_name, element(concat(var.controller_names, var.worker_names), count.index))}"
+
+  kernel = "http://${local.channel}.release.flatcar-linux.net/amd64-usr/${var.os_version}/flatcar_production_pxe.vmlinuz"
+
+  initrd = [
+    "http://${local.channel}.release.flatcar-linux.net/amd64-usr/${var.os_version}/flatcar_production_pxe_image.cpio.gz",
+  ]
+
+  args = [
+    "initrd=flatcar_production_pxe_image.cpio.gz",
+    "flatcar.config.url=${var.matchbox_http_endpoint}/ignition?uuid=$${uuid}&mac=$${mac:hexhyp}",
+    "flatcar.first_boot=yes",
+    "console=tty0",
+    "console=ttyS0",
+    "${var.kernel_args}",
+  ]
+
+  container_linux_config = "${element(data.template_file.container-linux-install-configs.*.rendered, count.index)}"
+}
+
 // Kubernetes Controller profiles
 resource "matchbox_profile" "controllers" {
   count                  = "${length(var.controller_names)}"

bare-metal/container-linux/kubernetes/variables.tf

@@ -12,12 +12,12 @@ variable "matchbox_http_endpoint" {
 
 variable "os_channel" {
   type        = "string"
-  description = "Channel for a Container Linux derivative (coreos-stable, coreos-beta, coreos-alpha)"
+  description = "Channel for a Container Linux derivative (coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha)"
 }
 
 variable "os_version" {
   type        = "string"
-  description = "Version for a Container Linux derivative to PXE and install (coreos-stable, coreos-beta, coreos-alpha)"
+  description = "Version for a Container Linux derivative to PXE and install (coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha)"
 }
 
 # machines