Templates

A Template is a collection of tasks that are executed sequentially. Each Task is a collection of actions that are executed sequentially on a specific worker. Actions are the individual unit of work, such as streaming an image to a disk, writing a file, or partitioning a disk.

Templates are specified as a Kubernetes custom resource definition (CRD).

apiVersion: tinkerbell.org/v1alpha1
kind: Template
metadata:
  name: ubuntu
  namespace: tink-system
spec:
  data: ""

Tasks

While the spec.data field in the Template CRD is of type string, it has an expected data structure. This structure is defined in the workflow spec under the status field. It’s structure is as follows:

name: ""
version: "0.1"
global_timeout: 3600
tasks: []

name string: A string that describes the template. It must be a string > 0 and < 200 characters. It should be unique among Tasks in the Template. Required.
version string: A string that describes the version of the template. It must be “0.1”. Note that it is deprecated and not used in the implementation. Required.
global_timeout int: An integer that describes the global timeout in seconds for the template.
tasks []task: A list of task objects. Required.

The Go struct for Tasks is found here and the Kubernetes custom resource definition here. The spec can also be explored here.

Task

A Task describes a list of actions. A Task can define volumes and environment variables that will be available to all action containers. Multiple Tasks can be defined. Each Task can define a worker to run on. The same worker can be used for multiple tasks. Task names must be unique within a template.

tasks:
- name: "installation"
  environment:
    GLOBAL_VALUE: "my global value"
  volumes:
  - /dev:/dev
  - /lib/firmware:/lib/firmware:ro
  worker: "{{.device_1}}"
  actions: []
- name: "post installation"
  environment:
    GLOBAL_VALUE: "my global value"
  volumes:
  - /dev:/dev
  - /lib/firmware:/lib/firmware:ro
  worker: "{{.device_2}}"
  actions: []

name string: A string that describes the task. It should be unique among tasks in the template. Required.
worker string: A string that is a Go template value that is used to match a worker. Required.
volumes []string: A list of strings that are used to mount volumes into all action containers. The format for each string should be source:destination.
environment map[string]string: A map of strings that are used to set environment variables in all action containers.
actions []action: A list of actions that are executed sequentially. Required.

Actions

Actions are the list of Action objects to be executed. Action objects will be executed sequentially at runtime and are all executed on the worker specified in the Task.

actions:
  - environment:
      COMPRESSED: "true"
      DEST_DISK: /dev/vda
      IMG_URL: http://192.168.2.112:8080/jammy-server-cloudimg-amd64.raw.gz
    image: quay.io/tinkerbell-actions/image2disk:v1.0.0
    name: stream ubuntu image
    timeout: 9600
  - environment:
      CONTENTS: |
        datasource:
          Ec2:
            metadata_urls: ["http://192.168.2.112:50061"]
            strict_id: false
        manage_etc_hosts: localhost
        warnings:
          dsid_missing_source: off        
      DEST_DISK: /dev/vda1
      DEST_PATH: /etc/cloud/cloud.cfg.d/10_tinkerbell.cfg
      DIRMODE: "0700"
      FS_TYPE: ext4
      GID: "0"
      MODE: "0600"
      UID: "0"
    image: quay.io/tinkerbell-actions/writefile:v1.0.0
    name: add-cloud-init-config
    timeout: 90
  - environment:
      CONTENTS: |
        datasource: Ec2        
      DEST_DISK: /dev/vda1
      DEST_PATH: /etc/cloud/ds-identify.cfg
      DIRMODE: "0700"
      FS_TYPE: ext4
      GID: "0"
      MODE: "0600"
      UID: "0"
    image: quay.io/tinkerbell-actions/writefile:v1.0.0
    name: add-tink-cloud-init-ds-config
    timeout: 90
  - image: quay.io/tinkerbell-actions/writefile:v1.0.0
    name: write-netplan
    timeout: 90

Action

An Action is an individual units of work, such as streaming an image to a disk, writing a file, or partitioning a disk.

name: stream ubuntu image
image: quay.io/tinkerbell-actions/image2disk:v1.0.0
timeout: 9600
command: ["echo", "override", "entrypoint", "in", "container", "image", "here"]
on-timeout: ["echo", "timeout"]
on-failure: ["echo", "failure"]
volumes: ["/var/run/data":"/data"]
pid: "host"
environment:
  COMPRESSED: "true"
  DEST_DISK: /dev/vda
  IMG_URL: http://192.168.2.112:8080/jammy-server-cloudimg-amd64.raw.gz

name string: A string that describes the action. It should be unique among actions in the task. Required.
image string: A string that describes the fully qualified location to a container image to be used for the action. Required.
timeout int: An integer that describes the timeout in seconds for the action.
command []string: A list of strings that are used to override the entrypoint in the container image.
on-timeout []string: A list of strings that are used to override the entrypoint in the container image when the action times out.
on-failure []string: A list of strings that are used to override the entrypoint in the container image when the action fails.
volumes []string: A list of strings that are used to mount volumes into the action container. The format for each string should be source:destination.
pid string: A string that describes the pid mode for the action. Generally it is either “host” or not defined.
environment map[string]string: A map of strings that are used to set environment variables in the action container.

Full example

This is a full example of a Template for installing Ubuntu and configuring it to use cloud-init.

apiVersion: tinkerbell.org/v1alpha1
kind: Template
metadata:
  name: ubuntu
  namespace: tink-system
spec:
  data: |
    global_timeout: 9800
    tasks:
      - name: "os installation"
        worker: "{{.device_1}}"
        volumes:
          - /dev:/dev
          - /dev/console:/dev/console
          - /lib/firmware:/lib/firmware:ro
        environment:
          GLOBAL_VALUE: "my global value"
        actions:
          - name: "stream image"
            image: quay.io/tinkerbell-actions/image2disk:v1.0.0
            timeout: 9600
            environment:
              DEST_DISK: {{ index .Hardware.Disks 0 }}
              IMG_URL: "http://{{ .artifact_server_ip_port }}/jammy-server-cloudimg-amd64.raw.gz"
              COMPRESSED: true
          - name: "add cloud init config"
            image: quay.io/tinkerbell-actions/writefile:v1.0.0
            timeout: 90
            environment:
              CONTENTS: |
                datasource:
                  Ec2:
                    metadata_urls: ["http://{{ .hegel_ip_port }}"]
                    strict_id: false
                manage_etc_hosts: localhost
                warnings:
                  dsid_missing_source: off
              DEST_DISK: {{ formatPartition ( index .Hardware.Disks 0 ) 1 }}
              DEST_PATH: /etc/cloud/cloud.cfg.d/10_tinkerbell.cfg
              DIRMODE: "0700"
              FS_TYPE: ext4
              GID: "0"
              MODE: "0600"
              UID: "0"
          - name: "add cloud-init ds config"
            image: quay.io/tinkerbell-actions/writefile:v1.0.0
            timeout: 90
            environment:
              DEST_DISK: {{ formatPartition ( index .Hardware.Disks 0 ) 1 }}
              FS_TYPE: ext4
              DEST_PATH: /etc/cloud/ds-identify.cfg
              UID: 0
              GID: 0
              MODE: 0600
              DIRMODE: 0700
              CONTENTS: |
                datasource: Ec2
          - name: "write netplan"
            image: quay.io/tinkerbell-actions/writefile:v1.0.0
            timeout: 90
            environment:
              DEST_DISK: {{ formatPartition ( index .Hardware.Disks 0 ) 1 }}
              FS_TYPE: ext4
              DEST_PATH: /etc/netplan/config.yaml
              CONTENTS: |
                network:
                  version: 2
                  renderer: networkd
                  ethernets:
                    id0:
                      match:
                        name: en*
                      dhcp4: true
              UID: 0
              GID: 0
              MODE: 0644
              DIRMODE: 0755

Templating a Template

A Template spec can contain Go template values, for example {{ .device_1 }}. The values come from a workflow spec that references the Template. For example, given the following template and workflow, the {{ .device_1 }} in the Template will be evaluated to 02:00:00:00:00:01 as defined in the Workflow spec at spec.hardwareMap.device_1. The spec.hardwareMap in the Workflow takes arbitrary key/value pairs.

apiVersion: tinkerbell.org/v1alpha1
kind: Template
metadata:
  name: ubuntu
  namespace: tink-system
spec:
  data: |
    global_timeout: 9800
    tasks:
      - name: "os installation"
        worker: "{{.device_1}}"
        volumes:
          - /dev:/dev
        actions:
          - name: "stream image"
            image: quay.io/tinkerbell-actions/image2disk:v1.0.0
            timeout: 9600
            environment:
              DEST_DISK: {{ index .Hardware.Disks 0 }}
              IMG_URL: "http://{{ .artifact_server_ip_port }}/jammy-server-cloudimg-amd64.raw.gz"
              COMPRESSED: true

apiVersion: tinkerbell.org/v1alpha1
kind: Workflow
metadata:
  name: ubuntu-install
  namespace: tink-system
spec:
  templateRef: ubuntu
  hardwareRef: hardware-1
  hardwareMap:
    device_1: 02:00:00:00:00:01

Available template arguments

Key names that are defined by a User in the Workflow spec at spec.hardwareMap:

source	output
`{{ .device_1 }}`	`02:00:00:00:00:01`
`{{ .key_name }}`	`value`

Values from the Hardware spec (currently, only Disks are available):

source	output
`{{ .Hardware.Disks }}`	`[ /dev/nvme0n1, /dev/sda ]`

Available template functions

Standard Go template functions:

source	output
`{{ .device_1 \| printf "%s" }}`	`02:00:00:00:00:01`
`{{ if eq .device_1 "02:00:00:00:00:01" }}`	`true`
`{{ index .Hardware.Disks 0 }}`	`/dev/nvme0n1`

Tinkerbell custom functions:

source	output
`{{ formatPartition ( index .Hardware.Disks 0 ) 1 }}`	`/dev/nvme0n1p1`
`{{ contains .device_1 "02:00:00:00:00:01" }}`	`true`
`{{ hasPrefix .device_1 "02:00:00" }}`	`true`
`{{ hasSuffix .device_1 "00:01" }}`	`true`

Other Resources

v1alpha1 Spec

Services that use the Template spec

Tink Controller