Adding page for advance agent configuration with k8s (#802)

* adding page for adavnce agent with k8s

* adding kubernetes provider example

* fxing typos and indentation

* fxing typos and indentation

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: David Kilfoyle <[email protected]>

* udpating code yaml box and adding parameter of manifest

* updating number in list

* updating number in list and iamge for kibana UI

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

* Update docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

Co-authored-by: Tetiana Kravchenko <[email protected]>

* adding comment for state

* fixing list

---------

Co-authored-by: David Kilfoyle <[email protected]>
Co-authored-by: Tetiana Kravchenko <[email protected]>

docs/en/ingest-management/elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc

@@ -0,0 +1,110 @@
+[[advanced-kubernetes-managed-by-fleet]]
+= Advanced {agent} configuration managed by {fleet}
+
+For basic {agent} managed by {fleet} scenarios follow the steps in <<running-on-kubernetes-managed-by-fleet>>.
+
+On managed {agent} installations it can be useful to provide the ability to configure more advanced options, such as the configuration of providers during the startup. Refer to <<providers>> for more details.
+
+Following steps demonstrate above scenario:
+
+[discrete]
+== Step 1: Download the {agent} manifest
+
+It is advisable to follow the steps of <<install-fleet-managed-elastic-agent>> with Kubernetes Integration installed in your policy and download the {agent} manifest from Kibana UI
+
+image::images/k8skibanaUI.png[{agent} with K8s Package manifest]
+
+Notes:: 
+Sample manifests can also be found https://github.com/elastic/elastic-agent/blob/main/deploy/kubernetes/elastic-agent-managed-kubernetes.yaml[here]
+
+[discrete]
+== Step 2: Create a new configmap
+
+[source,yaml]
+.Create a new configmap
+------------------------------------------------
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: agent-node-datastreams
+  namespace: kube-system
+  labels:
+    k8s-app: elastic-agent
+data:
+  agent.yml: |-
+    providers.kubernetes_leaderelection.enabled: false
+    fleet.enabled: true
+    fleet.access_token: "<FLEET_ENROLLMENT_TOKEN>"
+---
+------------------------------------------------
+
+Notes:: 
+1. In the above example the disablement of `kubernetes_leaderelection` provider is demonstrated. Same procedure can be followed for alternative scenarios.
+[source,yaml]
+.Example of configmap to configure kubernetes metadata enrichment
+------------------------------------------------
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: agent-node-datastreams
+  namespace: kube-system
+  labels:
+    k8s-app: elastic-agent
+data:
+  agent.yml: |-
+    providers.kubernetes: 
+      add_resource_metadata:
+        deployment: true
+        cronjob: true
+    fleet.enabled: true
+    fleet.access_token: "<FLEET_ENROLLMENT_TOKEN>"
+---
+------------------------------------------------
+
+1. Find more information about https://www.elastic.co/guide/en/fleet/current/fleet-enrollment-tokens.html[Enrollment Tokens].
+
+[discrete]
+== Step 3: Configure Daemonset
+
+Inside the downloaded manifest, update the Daemonset resource:
+
+[source,yaml]
+.Update entrypoint 
+------------------------------------------------
+containers:
+  - name: elastic-agent
+    image: docker.elastic.co/beats/elastic-agent: <ImageVersion>     
+    args: ["-c", "/etc/elastic-agent/agent.yml", "-e"]
+------------------------------------------------
+
+Notes:: 
+The <ImageVersion> is just a placeholder for the elastic-agent image version that you will download in your manifest: eg. `image: docker.elastic.co/beats/elastic-agent: 8.11.0`
+Important thing is to update your manifest with args details 
+
+[source,yaml]
+.Add extra Volume Mount 
+------------------------------------------------
+volumeMounts:
+  - name: datastreams
+    mountPath: /etc/elastic-agent/agent.yml
+    readOnly: true
+    subPath: agent.yml
+------------------------------------------------
+
+[source,yaml]
+.Add new Volume 
+------------------------------------------------
+volumes:
+  - name: datastreams
+    configMap:
+      defaultMode: 0640
+      name: agent-node-datastreams
+------------------------------------------------
+
+[discrete]
+== Important Notes
+
+1. By default the manifests for {agent} managed by {fleet} have `hostNetwork:true`. In order to support multiple installations of {agent}s in the same node you should set `hostNetwork:false`. See this relevant https://github.com/elastic/elastic-agent/tree/main/docs/manifests/hostnetwork[example] as described in https://github.com/elastic/elastic-agent/blob/main/docs/elastic-agent-ksm-sharding.md[{agent} Manifests in order to support Kube-State-Metrics Sharding].  
+
+2. The volume `/usr/share/elastic-agent/state` must remain mounted in https://github.com/elastic/elastic-agent/blob/main/deploy/kubernetes/elastic-agent-managed-kubernetes.yaml[elastic-agent-managed-kubernetes.yaml], otherwise custom config map provided above will be overwritten.
+

docs/en/ingest-management/elastic-agent/install-elastic-agent-in-container.asciidoc

@@ -12,6 +12,8 @@ To learn how to run {agent}s in a containerized environment, see:
 
 * <<running-on-kubernetes-managed-by-fleet>>
 
+** <<advanced-kubernetes-managed-by-fleet>>
+
 ** <<running-on-gke-managed-by-fleet>>
 
 ** <<running-on-eks-managed-by-fleet>>

docs/en/ingest-management/elastic-agent/install-elastic-agent.asciidoc

@@ -46,6 +46,7 @@ Refer to:
 --
 * <<elastic-agent-container>>
 * <<running-on-kubernetes-managed-by-fleet>>
+** <<advanced-kubernetes-managed-by-fleet>>
 ** <<running-on-gke-managed-by-fleet>>
 ** <<running-on-eks-managed-by-fleet>>
 ** <<running-on-aks-managed-by-fleet>>

docs/en/ingest-management/index.asciidoc

@@ -67,6 +67,8 @@ include::elastic-agent/elastic-agent-container.asciidoc[leveloffset=+3]
 
 include::elastic-agent/running-on-kubernetes-managed-by-fleet.asciidoc[leveloffset=+3]
 
+include::elastic-agent/advanced-kubernetes-managed-by-fleet.asciidoc[leveloffset=+3]
+
 include::elastic-agent/running-on-gke-managed-by-fleet.asciidoc[leveloffset=+3]
 
 include::elastic-agent/running-on-eks-managed-by-fleet.asciidoc[leveloffset=+3]