Kubernetes Template Management

Overview

CSE uses customized VM templates (Kubernetes templates) as building blocks for deployment of Kubernetes clusters. These templates are crucial for CSE to function properly. This document describes the various aspects of these Kubernetes templates including their life cycle management.

Kubernetes Templates

CSE 2.5 supports deploying Kubernetes clusters from multiple Kubernetes templates. Templates vary by guest OS (e.g. PhotonOS, Ubuntu), as well as, software versions, like Kubernetes, Docker, or Weave. Each template name is uniquely constructed based on the flavor of guest OS, Kubernetes version, and the Weave software version. The definitions of different templates reside in an official location hosted at a remote repository URL. The CSE sample config file, out of the box, points to the official location of those templates definitions. The remote repository is officially managed by maintainers of the CSE project.

Creating Kubernetes Templates

During CSE server installation, CSE provides the option to create Kubernetes templates from all template definitions available at the remote repository URL specified in the config file. Alternatively, Service Providers have the option to install CSE server with --skip-template-creation flag, if specified CSE does not create any Kubernetes templates during installation. Once CSE server installation is complete, Service Providers can create selective Kubernetes templates using the following command.

cse template list
cse template install TEMPLATE_NAME TEMPLATE_REVISION

Using Kubernetes Templates

While starting the CSE server, a default Kubernetes template and revision must be specified in the config file, for CSE server to successfully start up. Tenants can always override the default templates via specifying their choice of revision of a template during cluster operations like vcd cse cluster create, vcd cse cluster resize, and vcd cse node create.

Updating Kubernetes Templates

Service Providers can expect newer templates as updates to OS versions, Kubernetes major or minor versions, or Weave major or minor versions are made available. They can also expect revised templates (through a change to the revision of existing templates) with updated Kubernetes patch versions. Service Providers can refresh their existing templates with revised versions or install new templates by using below command. Please note that a graceful shut down of CSE Server is advised before attempting to update the templates.

cse template list --display diff
cse template install TEMPLATE_NAME TEMPLATE_REVISION

The refreshed templates do not impact existing Kubernetes clusters in the environment.

Restricting Kubernetes Templates for Tenants

Out of the box, Kubernetes templates are not restricted for use. All tenants have access to all the Kubernetes templates to deploy Kubernetes clusters, as long as they have sufficient permissions to interact with CSE. However, starting from CSE 2.5, service providers have the option to selectively restrict Kubernetes templates from being used by tenants in order to prohibit them from deploying Kubernetes Clusters.

This is accomplished with the use of VDC Compute Policies feature of VCD 10.0. CSE 2.5 offers the capability to service providers to tag selected templates and organization VDCs with compute policy which restricts Kubernetes cluster deployments from tagged templates to only tagged organization VDCs.

Enable Restriction on Kubernetes Templates

Restriction on Kubernetes templates is enabled by leveraging the template_rules section in CSE config file. Service Providers can mark Kubernetes templates as protected by tagging them with a VdcComputePolicy. To do so, Service Providers need to define a template rule in the template_rules section, whose target is the template to protect, and as action a value must be specified for the key compute_policy.

template_rules:
- name: Photon Template Rule
  target:
    name: photon-v2_k8-1.12_weave-2.3.0
    revision: 1
  action:
    compute_policy: "Photon Template Policy"

Service providers select the name of the compute policy per their choice, and CSE creates that compute policy in VCD, if it’s not already present. During CSE server startup, the template rule “Photon Template Rule” is processed and the defined Kubernetes template is tagged with the compute policy. At this point, the Kubernetes template is restricted from further use, until tenant organization VDCs are enabled with matching compute policy to permit Kubernetes cluster deployments.

Grant Tenants access to Kubernetes Templates

Service providers select tenants to whom they want to grant access of certain Kubernetes Templates based cluster deployments. Then, they enable selected tenants’ organization VDCs with the same compute policy as present on the Kubernetes Template. To do so, the following command should be used

vcd cse ovdc compute-policy add ORG_NAME OVDC_NAME POLICY_NAME

Revoke Permission to use Kubernetes Templates from Tenants

Permission to use a protected template can be revoked at any time from the tenant, via the following command.

vcd cse ovdc compute-policy remove ORG_NAME OVDC_NAME POLICY_NAME

If there are Kubernetes clusters in that organization VDC, use -f/--force flag to force the operation. The clusters will remain deployed, and will switch to System Default compute policy.

Remove restriction from Kubernetes Templates

In order to remove the restriction from Kubernetes templates, Service providers can delete the template rule from the config file and restart the CSE server. Alternatively, the same outcome can be achieved by specifying an empty policy name in the concerned rule.

template_rules:
- name: Rule1
  target:
    name: out_of_box_protected_tempalte
    revision: 1
  action:
    compute_policy: ""

Source .ova Files for Kubernetes Templates

The following table lists URLs of the OVA files that are used as the base for the Kubernetes templates.

OS	OVA Name	URL	SHA256
Photon OS 2.0 GA	photon-custom-hw11-2.0-304b817.ova	http://dl.bintray.com/vmware/photon/2.0/GA/ova/photon-custom-hw11-2.0-304b817.ova	cb51e4b6d899c3588f961e73282709a0d054bb421787e140a1d80c24d4fd89e1
Ubuntu 16.04.4 LTS	ubuntu-16.04-server-cloudimg-amd64.ova	https://cloud-images.ubuntu.com/releases/xenial/release-20180418/ubuntu-16.04-server-cloudimg-amd64.ova	3c1bec8e2770af5b9b0462e20b7b24633666feedff43c099a6fb1330fcc869a9