Rename container-linux modules to flatcar-linux

* CoreOS Container Linux was deprecated in v1.18.3
* Continue transitioning docs and modules from supporting
both CoreOS and Flatcar "variants" of Container Linux to
now supporting Flatcar Linux and equivalents

Action Required: Update the Flatcar Linux modules `source`
to replace `s/container-linux/flatcar-linux`. See docs for
examples

azure/flatcar-linux/kubernetes/workers/cl/worker.yaml

@@ -0,0 +1,117 @@
+---
+systemd:
+  units:
+    - name: docker.service
+      enabled: true
+    - name: locksmithd.service
+      mask: true
+    - name: wait-for-dns.service
+      enabled: true
+      contents: |
+        [Unit]
+        Description=Wait for DNS entries
+        Wants=systemd-resolved.service
+        Before=kubelet.service
+        [Service]
+        Type=oneshot
+        RemainAfterExit=true
+        ExecStart=/bin/sh -c 'while ! /usr/bin/grep '^[^#[:space:]]' /etc/resolv.conf > /dev/null; do sleep 1; done'
+        [Install]
+        RequiredBy=kubelet.service
+    - name: kubelet.service
+      enabled: true
+      contents: |
+        [Unit]
+        Description=Kubelet
+        Requires=docker.service
+        After=docker.service
+        Wants=rpc-statd.service
+        [Service]
+        Environment=KUBELET_IMAGE=quay.io/poseidon/kubelet:v1.19.3
+        Environment=KUBELET_CGROUP_DRIVER=${cgroup_driver}
+        ExecStartPre=/bin/mkdir -p /etc/kubernetes/cni/net.d
+        ExecStartPre=/bin/mkdir -p /etc/kubernetes/manifests
+        ExecStartPre=/bin/mkdir -p /opt/cni/bin
+        ExecStartPre=/bin/mkdir -p /var/lib/calico
+        ExecStartPre=/bin/mkdir -p /var/lib/kubelet/volumeplugins
+        ExecStartPre=/usr/bin/bash -c "grep 'certificate-authority-data' /etc/kubernetes/kubeconfig | awk '{print $2}' | base64 -d > /etc/kubernetes/ca.crt"
+        # Podman, rkt, or runc run container processes, whereas docker run
+        # is a client to a daemon and requires workarounds to use within a
+        # systemd unit. https://github.com/moby/moby/issues/6791
+        ExecStartPre=/usr/bin/docker run -d \
+          --name kubelet \
+          --privileged \
+          --pid host \
+          --network host \
+          -v /etc/kubernetes:/etc/kubernetes:ro \
+          -v /etc/machine-id:/etc/machine-id:ro \
+          -v /usr/lib/os-release:/etc/os-release:ro \
+          -v /lib/modules:/lib/modules:ro \
+          -v /run:/run \
+          -v /sys/fs/cgroup:/sys/fs/cgroup:ro \
+          -v /sys/fs/cgroup/systemd:/sys/fs/cgroup/systemd \
+          -v /var/lib/calico:/var/lib/calico:ro \
+          -v /var/lib/docker:/var/lib/docker \
+          -v /var/lib/kubelet:/var/lib/kubelet:rshared \
+          -v /var/log:/var/log \
+          -v /opt/cni/bin:/opt/cni/bin \
+          $${KUBELET_IMAGE} \
+          --anonymous-auth=false \
+          --authentication-token-webhook \
+          --authorization-mode=Webhook \
+          --bootstrap-kubeconfig=/etc/kubernetes/kubeconfig \
+          --cgroup-driver=$${KUBELET_CGROUP_DRIVER} \
+          --client-ca-file=/etc/kubernetes/ca.crt \
+          --cluster_dns=${cluster_dns_service_ip} \
+          --cluster_domain=${cluster_domain_suffix} \
+          --cni-conf-dir=/etc/kubernetes/cni/net.d \
+          --healthz-port=0 \
+          --kubeconfig=/var/lib/kubelet/kubeconfig \
+          --network-plugin=cni \
+          --node-labels=node.kubernetes.io/node \
+          %{~ for label in split(",", node_labels) ~}
+          --node-labels=${label} \
+          %{~ endfor ~}
+          --pod-manifest-path=/etc/kubernetes/manifests \
+          --read-only-port=0 \
+          --rotate-certificates \
+          --volume-plugin-dir=/var/lib/kubelet/volumeplugins
+        ExecStart=docker logs -f kubelet
+        ExecStop=docker stop kubelet
+        ExecStopPost=docker rm kubelet
+        Restart=always
+        RestartSec=5
+        [Install]
+        WantedBy=multi-user.target
+    - name: delete-node.service
+      enabled: true
+      contents: |
+        [Unit]
+        Description=Delete Kubernetes node on shutdown
+        [Service]
+        Environment=KUBELET_IMAGE=quay.io/poseidon/kubelet:v1.19.3
+        Type=oneshot
+        RemainAfterExit=true
+        ExecStart=/bin/true
+        ExecStop=/bin/bash -c '/usr/bin/docker run -v /var/lib/kubelet:/var/lib/kubelet:ro --entrypoint /usr/local/bin/kubectl $${KUBELET_IMAGE} --kubeconfig=/var/lib/kubelet/kubeconfig delete node $HOSTNAME'
+        [Install]
+        WantedBy=multi-user.target
+storage:
+  files:
+    - path: /etc/kubernetes/kubeconfig
+      filesystem: root
+      mode: 0644
+      contents:
+        inline: |
+          ${kubeconfig}
+    - path: /etc/sysctl.d/max-user-watches.conf
+      filesystem: root
+      mode: 0644
+      contents:
+        inline: |
+          fs.inotify.max_user_watches=16184
+passwd:
+  users:
+    - name: core
+      ssh_authorized_keys:
+        - "${ssh_authorized_key}"

azure/flatcar-linux/kubernetes/workers/variables.tf

@@ -0,0 +1,99 @@
+variable "name" {
+  type        = string
+  description = "Unique name for the worker pool"
+}
+
+# Azure
+
+variable "region" {
+  type        = string
+  description = "Must be set to the Azure Region of cluster"
+}
+
+variable "resource_group_name" {
+  type        = string
+  description = "Must be set to the resource group name of cluster"
+}
+
+variable "subnet_id" {
+  type        = string
+  description = "Must be set to the `worker_subnet_id` output by cluster"
+}
+
+variable "security_group_id" {
+  type        = string
+  description = "Must be set to the `worker_security_group_id` output by cluster"
+}
+
+variable "backend_address_pool_id" {
+  type        = string
+  description = "Must be set to the `worker_backend_address_pool_id` output by cluster"
+}
+
+# instances
+
+variable "worker_count" {
+  type        = number
+  description = "Number of instances"
+  default     = 1
+}
+
+variable "vm_type" {
+  type        = string
+  description = "Machine type for instances (see `az vm list-skus --location centralus`)"
+  default     = "Standard_DS1_v2"
+}
+
+variable "os_image" {
+  type        = string
+  description = "Channel for a Container Linux derivative (flatcar-stable, flatcar-beta, flatcar-alpha, flatcar-edge)"
+  default     = "flatcar-stable"
+}
+
+variable "priority" {
+  type        = string
+  description = "Set priority to Spot to use reduced cost surplus capacity, with the tradeoff that instances can be evicted at any time."
+  default     = "Regular"
+}
+
+variable "snippets" {
+  type        = list(string)
+  description = "Container Linux Config snippets"
+  default     = []
+}
+
+# configuration
+
+variable "kubeconfig" {
+  type        = string
+  description = "Must be set to `kubeconfig` output by cluster"
+}
+
+variable "ssh_authorized_key" {
+  type        = string
+  description = "SSH public key for user 'core'"
+}
+
+variable "service_cidr" {
+  type        = string
+  description = <<EOD
+CIDR IPv4 range to assign Kubernetes services.
+The 1st IP will be reserved for kube_apiserver, the 10th IP will be reserved for coredns.
+EOD
+  default     = "10.3.0.0/16"
+}
+
+variable "node_labels" {
+  type        = list(string)
+  description = "List of initial node labels"
+  default     = []
+}
+
+# unofficial, undocumented, unsupported
+
+variable "cluster_domain_suffix" {
+  description = "Queries for domains with the suffix will be answered by coredns. Default is cluster.local (e.g. foo.default.svc.cluster.local) "
+  type        = string
+  default     = "cluster.local"
+}
+

azure/flatcar-linux/kubernetes/workers/versions.tf

@@ -0,0 +1,14 @@
+# Terraform version and plugin versions
+
+terraform {
+  required_version = ">= 0.12.26, < 0.14.0"
+  required_providers {
+    azurerm  = "~> 2.8"
+    template = "~> 2.1"
+
+    ct = {
+      source  = "poseidon/ct"
+      version = "~> 0.6.1"
+    }
+  }
+}

azure/flatcar-linux/kubernetes/workers/workers.tf

@@ -0,0 +1,111 @@
+locals {
+  # flatcar-stable -> Flatcar Linux Stable
+  channel = split("-", var.os_image)[1]
+}
+
+# Workers scale set
+resource "azurerm_linux_virtual_machine_scale_set" "workers" {
+  resource_group_name = var.resource_group_name
+
+  name      = "${var.name}-worker"
+  location  = var.region
+  sku       = var.vm_type
+  instances = var.worker_count
+  # instance name prefix for instances in the set
+  computer_name_prefix   = "${var.name}-worker"
+  single_placement_group = false
+  custom_data            = base64encode(data.ct_config.worker-ignition.rendered)
+
+  # storage
+  os_disk {
+    storage_account_type = "Standard_LRS"
+    caching              = "ReadWrite"
+  }
+
+  # Flatcar Container Linux
+  source_image_reference {
+    publisher = "Kinvolk"
+    offer     = "flatcar-container-linux-free"
+    sku       = local.channel
+    version   = "latest"
+  }
+
+  plan {
+    name      = local.channel
+    publisher = "kinvolk"
+    product   = "flatcar-container-linux-free"
+  }
+
+  # Azure requires setting admin_ssh_key, though Ignition custom_data handles it too
+  admin_username = "core"
+  admin_ssh_key {
+    username   = "core"
+    public_key = var.ssh_authorized_key
+  }
+
+  # network
+  network_interface {
+    name                      = "nic0"
+    primary                   = true
+    network_security_group_id = var.security_group_id
+
+    ip_configuration {
+      name      = "ip0"
+      primary   = true
+      subnet_id = var.subnet_id
+
+      # backend address pool to which the NIC should be added
+      load_balancer_backend_address_pool_ids = [var.backend_address_pool_id]
+    }
+  }
+
+  # lifecycle
+  upgrade_mode = "Manual"
+  # eviction policy may only be set when priority is Spot
+  priority        = var.priority
+  eviction_policy = var.priority == "Spot" ? "Delete" : null
+}
+
+# Scale up or down to maintain desired number, tolerating deallocations.
+resource "azurerm_monitor_autoscale_setting" "workers" {
+  resource_group_name = var.resource_group_name
+
+  name     = "${var.name}-maintain-desired"
+  location = var.region
+
+  # autoscale
+  enabled            = true
+  target_resource_id = azurerm_linux_virtual_machine_scale_set.workers.id
+
+  profile {
+    name = "default"
+
+    capacity {
+      minimum = var.worker_count
+      default = var.worker_count
+      maximum = var.worker_count
+    }
+  }
+}
+
+# Worker Ignition configs
+data "ct_config" "worker-ignition" {
+  content  = data.template_file.worker-config.rendered
+  strict   = true
+  snippets = var.snippets
+}
+
+# Worker Container Linux configs
+data "template_file" "worker-config" {
+  template = file("${path.module}/cl/worker.yaml")
+
+  vars = {
+    kubeconfig             = indent(10, var.kubeconfig)
+    ssh_authorized_key     = var.ssh_authorized_key
+    cluster_dns_service_ip = cidrhost(var.service_cidr, 10)
+    cluster_domain_suffix  = var.cluster_domain_suffix
+    cgroup_driver          = local.channel == "edge" ? "systemd" : "cgroupfs"
+    node_labels            = join(",", var.node_labels)
+  }
+}
+