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

CHANGES.md

@@ -4,6 +4,7 @@ Notable changes between versions.
 
 ## Latest
 
+* Add [Flatcar Linux](https://docs.flatcar-linux.org/) (Container Linux derivative) as an option for AWS and bare-metal (thanks @kinvolk folks)
 * Allow bearer token authentication to the Kubelet ([#216](https://github.com/poseidon/typhoon/issues/216))
   * Require Webhook authorization to the Kubelet
   * Switch apiserver X509 client cert org to satisfy new authorization requirement
@@ -12,21 +13,22 @@ Notable changes between versions.
 
 #### AWS
 
-* Allow preemptible workers via spot instances ([#202](https://github.com/poseidon/typhoon/pull/202))
+* Allow Flatcar Linux by setting `os_image` to flatcar-stable (default), flatcar-beta, flatcar-alpha ([#211](https://github.com/poseidon/typhoon/pull/211))
-  * Add `worker_price` to allow worker spot instances. Default to empty string for the worker autoscaling group to use regular on-demand instances.
-  * Add `spot_price` to internal `workers` module for spot [worker pools](https://typhoon.psdn.io/advanced/worker-pools/)
-* Allow Container Linux derivative [Flatcar Linux](https://docs.flatcar-linux.org/) by setting `os_image` to `flatcar-stable`, `flatcar-beta`, `flatcar-alpha`.
 * Replace `os_channel` variable with `os_image` to align naming across clouds
-  * Please change values `stable`, `beta`, or `alpha` to `coreos-stable`, `coreos-beta`, `coreos-alpha` (action required!)
+  * Please change values stable, beta, or alpha to coreos-stable, coreos-beta, coreos-alpha (**action required!**)
+* Allow preemptible workers via spot instances ([#202](https://github.com/poseidon/typhoon/pull/202))
+  * Add `worker_price` to allow worker spot instances. Default to empty string for the worker autoscaling group to use regular on-demand instances
+  * Add `spot_price` to internal `workers` module for spot [worker pools](https://typhoon.psdn.io/advanced/worker-pools/)
 
 #### Bare-Metal
 
+* Allow Flatcar Linux by setting `os_channel` to flatcar-stable, flatcar-beta, flatcar-alpha ([#220](https://github.com/poseidon/typhoon/pull/220))
 * Replace `container_linux_channel` variable with `os_channel`
-  * Please change values `stable`, `beta`, or `alpha` to `coreos-stable` (default), `coreos-beta`, `coreos-alpha` (action required!)
+  * Please change values stable, beta, or alpha to coreos-stable, coreos-beta, coreos-alpha (**action required!**)
 * Replace `container_linux_version` variable with `os_version`
 * Add `network_ip_autodetection_method` variable for Calico host IPv4 address detection
   * Use Calico's default "first-found" to support single NIC and bonded NIC nodes 
-  * Allow [alternative](https://docs.projectcalico.org/v3.1/reference/node/configuration#ip-autodetection-methods) methods for multi NIC nodes, like `can-reach=IP` or `interface=REGEX`
+  * Allow [alternative](https://docs.projectcalico.org/v3.1/reference/node/configuration#ip-autodetection-methods) methods for multi NIC nodes, like can-reach=IP or interface=REGEX
 * Deprecate `container_linux_oem` variable
 
 #### Addons

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

docs/cl/bare-metal.md

@@ -353,7 +353,7 @@ Check the [variables.tf](https://github.com/poseidon/typhoon/blob/master/bare-me
 |:-----|:------------|:--------|
 | cluster_name | Unique cluster name | mercury |
 | matchbox_http_endpoint | Matchbox HTTP read-only endpoint | http://matchbox.example.com:port |
-| os_channel | Channel for a Container Linux derivative | coreos-stable, coreos-beta, coreos-alpha |
+| os_channel | Channel for a Container Linux derivative | coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha |
 | os_version | Version for a Container Linux derivative to PXE and install | 1632.3.0 |
 | k8s_domain_name | FQDN resolving to the controller(s) nodes. Workers and kubectl will communicate with this endpoint | "myk8s.example.com" |
 | ssh_authorized_key | SSH public key for user 'core' | "ssh-rsa AAAAB3Nz..." |
@@ -369,7 +369,7 @@ Check the [variables.tf](https://github.com/poseidon/typhoon/blob/master/bare-me
 
 | Name | Description | Default | Example |
 |:-----|:------------|:--------|:--------|
-| cached_install | Whether machines should PXE boot and install from the Matchbox `/assets` cache. Admin MUST have downloaded Container Linux images into the cache to use this | false | true |
+| cached_install | Whether machines should PXE boot and install from the Matchbox `/assets` cache. Admin MUST have downloaded Container Linux images into the cache to use this (coreos only for now) | false | true |
 | install_disk | Disk device where Container Linux should be installed | "/dev/sda" | "/dev/sdb" |
 | networking | Choice of networking provider | "calico" | "calico" or "flannel" |
 | network_mtu | CNI interface MTU (calico-only) | 1480 | - |