Support VolumeConfig for EPHEMERAL partition

Author: dbackeus

app/controllers/machine_configs_controller.rb

@@ -24,6 +24,7 @@ def create
       :private_ip,
       :already_configured,
       :install_disk,
+      :ephemeral_disk_identifier,
     )
     @machine_config = MachineConfig.new(machine_config_params)
     @server = @machine_config.server

app/models/machine_config.rb

@@ -23,6 +23,7 @@ def initialize(message, output)
   validates_presence_of :private_ip
   validate :validate_private_ip_format
   validates_presence_of :install_disk
+  validate :validate_ephemeral_disk_identifier_format
 
   after_create :set_configured, if: :already_configured
 
@@ -97,7 +98,35 @@ def generate_config(output_type: server.talos_type)
     end
 
     # NOTE: This also gives us consistent 2 space indentation
-    talosconfig.to_yaml.delete_prefix("---\n")
+    config = talosconfig.to_yaml
+
+    # Add a VolumeConfig document if the server has an ephemeral disk identifier
+    if ephemeral_disk_identifier.present?
+      # id_type can be "wwid" or "uuid"
+      id_type, id = ephemeral_disk_identifier.split(":", 2)
+
+      # https://www.talos.dev/v1.10/talos-guides/configuration/disk-management/#disk-selector
+      disk_selector_cel =
+        if id_type == "wwid"
+          "disk.wwid == '#{id}'"
+        elsif id_type == "uuid"
+          "'dev/disk/by-uuid/#{id}' in disk.symlinks"
+        end
+
+      config += <<~YAML
+        ---
+        apiVersion: v1alpha1
+        kind: VolumeConfig
+        name: EPHEMERAL
+        provisioning:
+          diskSelector:
+            match: "#{disk_selector_cel}"
+          minSize: 10GB
+          grow: true
+      YAML
+    end
+
+    config
   end
 
   private
@@ -144,6 +173,14 @@ def validate_private_ip_format
     end
   end
 
+  def validate_ephemeral_disk_identifier_format
+    return if ephemeral_disk_identifier.blank?
+
+    unless ephemeral_disk_identifier.match?(/^(wwid|uuid):.+$/)
+      errors.add(:ephemeral_disk_identifier, "must be in the format 'wwid:<wwid>' or 'uuid:<uuid>'")
+    end
+  end
+
   def set_configured
     server.update!(
       last_configured_at: Time.now,

app/views/machine_configs/new.html.erb

@@ -5,9 +5,51 @@
 
   <%= f.text_field :hostname, required: true, placeholder: "worker-x", hint: "Will substitute ${hostname} in your config patches." %>
   <%= f.text_field :private_ip, required: true, placeholder: "10.0.x.x", label: "Private IP", hint: "Will substitute ${private_ip} in your config patches." %>
-  <%= f.text_field :install_disk, required: true, placeholder: "/dev/sda", hint: "Gets passed into the --install-disk argument for talosctl gen config." %>
+  <% if f.object.server.lsblk.present? %>
+    <%= f.text_field :install_disk, required: true, disabled: true, hint: "Gets passed into the --install-disk argument for talosctl gen config. Non modifiable: must use the same disk which was used for bootstrapping." %>
+    <%
+      # - RAID devices are listed as children of disks
+      # - UUID of disks containing RAID devices are actually the UUID of the RAID device
+      # Hence we reduce RAID disks to a single entry per RAID device, using their UUID as value.
+      disks = f.object.server.lsblk.fetch("blockdevices").select { |disk| disk.fetch("type") == "disk" }
+      raids, other = disks.partition { |disk| disk.fetch("children", []).any? { |child| child.fetch("type").start_with?("raid") } }
+      raids = raids
+        .group_by { |disk| disk.fetch("children").find { |child| child.fetch("type").start_with?("raid") }&.fetch("name") }
+        .map do |raid_name, disks|
+          raid = disks.first.fetch("children").find { |child| child.fetch("type").start_with?("raid") }
+          type = raid.fetch("type").upcase
+          label = "/dev/#{raid_name} (#{number_to_human_size(raid.fetch('size'))}) [#{type}]"
+          value = disks.first.fetch("uuid")
+
+          [label, "uuid:#{value}"]
+        end
+      other = other
+        .reject { |disk| disk.fetch("wwn") == f.object.server.bootstrap_disk_wwid }
+        .map do |disk|
+          partitions = disk.fetch("children", []).select { it.fetch("type").start_with?("part") }
+          suffix = partitions.empty? ? "" : "[#{partitions.length} existing partition#{'s' if partitions.length != 1}]"
+          label = "/dev/#{disk['name']} (#{number_to_human_size(disk['size'])}) #{suffix}"
+          value = disk.fetch("wwn")
+
+          [label, "wwid:#{value}"]
+        end
+      ephemeral_disk_options = (raids + other).sort_by(&:first)
+    %>
+    <%=
+      f.select(
+        :ephemeral_disk_identifier,
+        ephemeral_disk_options,
+        { include_blank: "Same as install disk" },
+        required: false,
+        label: "Ephemeral Disk (optional)",
+        hint: "If an ephemeral disk is selected, a VolumeConfig will be added to the server's MachineConfig to use the disk for Talos Linux's EPHEMERAL partition. RAID devices will be listed here but note that your Talos Factory Image must contain the <a href='https://github.com/siderolabs/extensions/tree/main/storage/mdadm' target='_blank' class='text-blue-500 hover:underline'>mdadm extension</a> for them to work.",
+      )
+    %>
+  <% else %>
+    <%= f.text_field :install_disk, required: true, placeholder: "/dev/nvme0n1", hint: "Gets passed into the --install-disk argument for talosctl gen config." %>
+  <% end %>
   <%= f.select :config_id, Config.pluck(:name, :id), { include_blank: true }, required: true %>
   <%= f.check_box :already_configured, class: "mr-1", hint: "Check to apply green status to the server immediately" %>
 
   <%= f.submit "Configure" %>
-<% end %>
+<% end %>

db/migrate/20250804112912_add_ephemeral_disk_identifier_to_machine_configs.rb

@@ -0,0 +1,5 @@
+class AddEphemeralDiskIdentifierToMachineConfigs < ActiveRecord::Migration[8.0]
+  def change
+    add_column :machine_configs, :ephemeral_disk_identifier, :string
+  end
+end

db/schema.rb

@@ -1,6 +1,6 @@
 default:
   name: default
-  endpoint: http://kubernetes.example.com:6443
+  endpoint: https://kubernetes.example.com:6443
   secrets: |
     cluster:
         id: d4ztP13Cr27K_0eTNQmM0I1_k50EHxci7bT_KROwxrI=

spec/fixtures/clusters.yml

@@ -1,4 +1,22 @@
 RSpec.describe MachineConfig do
+  it "validates format of ephemeral_disk_identifier" do
+    machine_config = MachineConfig.new
+    machine_config.validate
+    expect(machine_config.errors[:ephemeral_disk_identifier]).to be_empty
+
+    machine_config.ephemeral_disk_identifier = "wwid:1234567890abcdef"
+    machine_config.validate
+    expect(machine_config.errors[:ephemeral_disk_identifier]).to be_empty
+
+    machine_config.ephemeral_disk_identifier = "uuid:12345678-1234-5678-1234-567812345678"
+    machine_config.validate
+    expect(machine_config.errors[:ephemeral_disk_identifier]).to be_empty
+
+    machine_config.ephemeral_disk_identifier = "invalid_format"
+    machine_config.validate
+    expect(machine_config.errors[:ephemeral_disk_identifier]).to include("must be in the format 'wwid:<wwid>' or 'uuid:<uuid>'")
+  end
+
   describe "#generate_config" do
     it "raises an error if hostname is blank" do
       server = Server.new(name: "worker-1")
@@ -12,7 +30,7 @@
       expect { machine_config.generate_config }.to raise_error "can't generate config before assigning private_ip"
     end
 
-    it "generates a config" do
+    it "generates a config including substitution variables: bootstrap_disk_wwid, hostname, public_ip, private_ip and vlan" do
       hetzner_vswitch = HetznerVswitch.new(name: "vswitch", vlan: 1337)
       cluster = Cluster.create!(
         name: "cluster",
@@ -69,6 +87,7 @@
         server:,
       )
       expect(machine_config.generate_config).to eq <<~YAML
+        ---
         version: v1alpha1
         debug: false
         persist: true
@@ -147,5 +166,59 @@
               service: {}
       YAML
     end
+
+    context "with an ephemeral_disk_identifier" do
+      it "generates a config including a VolumeConfig for the ephemeral disk with different matchers for uuid and wwid" do
+        server = servers(:cloud_botstrapped)
+
+        config = Config.new(
+          name: "config",
+          install_image: "ghcr.io/siderolabs/installer:v1.10.6",
+          kubernetes_version: "1.33.3",
+          kubespan: true,
+          patch: "",
+        )
+        machine_config = MachineConfig.new(
+          hostname: server.name,
+          private_ip: "10.0.1.2",
+          install_disk: "/dev/nvme0n1",
+          ephemeral_disk_identifier: "wwid:eui.36344630528029720025384500000002",
+          config:,
+          server:,
+        )
+
+        generated_config = machine_config.generate_config
+        expect(YAML.load_stream(generated_config).length).to eq 2 # sanity check that YAML is valid
+
+        volume_config = generated_config.split("---\n").last # expect on raw String to ensure good formatting
+        expect(volume_config).to eq <<~YAML
+          apiVersion: v1alpha1
+          kind: VolumeConfig
+          name: EPHEMERAL
+          provisioning:
+            diskSelector:
+              match: "disk.wwid == 'eui.36344630528029720025384500000002'"
+            minSize: 10GB
+            grow: true
+        YAML
+
+        machine_config.ephemeral_disk_identifier = "uuid:12345678-1234-5678-1234-567812345678"
+
+        generated_config = machine_config.generate_config
+        expect(YAML.load_stream(generated_config).length).to eq 2 # sanity check that YAML is valid
+
+        volume_config = generated_config.split("---\n").last # expect on raw String to ensure good formatting
+        expect(volume_config).to eq <<~YAML
+          apiVersion: v1alpha1
+          kind: VolumeConfig
+          name: EPHEMERAL
+          provisioning:
+            diskSelector:
+              match: "'dev/disk/by-uuid/12345678-1234-5678-1234-567812345678' in disk.symlinks"
+            minSize: 10GB
+            grow: true
+        YAML
+      end
+    end
   end
 end