Customizing Installation

Instead of forking the Linkerd install and upgrade process,Kustomize can be used to patch the output of linkerdinstall in a consistent way. This allows customization of the install to addfunctionality specific to installations.

To get started, save the output of install to a YAML file. This will be thebase resource that Kustomize uses to patch and generate what is added to yourcluster.

  1. linkerd install > linkerd.yaml

NoteWhen upgrading, make sure you populate this file with the content from linkerdupgrade. Using the latest kustomize releases, it would be possible toautomate this with an execplugin.

Next, create a kustomization.yaml file. This file will contain theinstructions for Kustomze listing the base resources and the transformations todo on those resources. Right now, this looks pretty empty:

  1. resources:
  2. - linkerd.yaml

Now, let’s look at how to do some example customizations.

NoteKustomize allows as many patches, transforms and generators as you’d like. Theseexamples show modifications one at a time but it is possible to do as many asrequired in a single kustomization.yaml file.

Add PriorityClass

There are a couple components in the control plane that can benefit from beingassociated with a critical PriorityClass. While this configuration isn’tcurrently supported as a flag to linkerd install, it is not hard to add byusing Kustomize.

First, create a file named priority-class.yaml that will contain the overlay.This overlay will explain what needs to be modified.

  1. apiVersion: apps/v1
  2. kind: Deployment
  3. metadata:
  4.   name: linkerd-identity
  5. spec:
  6.   template:
  7.     spec:
  8.       priorityClassName: system-cluster-critical
  9. ---
  10. apiVersion: apps/v1
  11. kind: Deployment
  12. metadata:
  13.   name: linkerd-controller
  14. spec:
  15.   template:
  16.     spec:
  17.       priorityClassName: system-cluster-critical

Then, add this as a strategic merge option to kustomization.yaml:

  1. resources:
  2. - linkerd.yaml
  3. patchesStrategicMerge:
  4. - priority-class.yaml

Applying this to your cluster requires taking the output of kustomize buildand piping it to kubectl apply. For example you can run:

  1. kubectl kustomize build . | kubectl apply -f -

Modify Grafana Configuration

Interested in enabling authentication for Grafana? It is possible tomodify the ConfigMap as a one off to do this. Unfortunately, the changes willend up being reverted every time linkerd upgrade happens. Instead, create afile named grafana.yaml and add your modifications:

  1. kind: ConfigMap
  2. apiVersion: v1
  3. metadata:
  4.   name: linkerd-grafana-config
  5. data:
  6.   grafana.ini: |-
  7.     instance_name = linkerd-grafana
  9.     [server]
  10.     root_url = %(protocol)s://%(domain)s:/grafana/
  12.     [analytics]
  13.     check_for_updates = false

Then, add this as a strategic merge option to kustomization.yaml:

  1. resources:
  2. - linkerd.yaml
  3. patchesStrategicMerge:
  4. - grafana.yaml

Finally, apply this to your cluster by generating YAML with kustomize buildand piping the output to kubectl apply.

  1. kubectl kustomize build . | kubectl apply -f -