Logging in Kubernetes illustrated:
Kubernetes is a container orchestration framework that hosts applications. The logs from the applications are saved local to the container. Hosts are nodes of a cluster and can be scaled out to as many as required for the application workload. A forwarding agent forwards the logs from the container to a sink. A sink is a destination where all the logs forwarded can be redirected to a log service that can better handle the storage and analysis of the logs. The sink is usually external to the cluster so it can scale independently and may be configured to receive via a well known protocol called syslog. A continuously running process forwards the logs from the container to the node before drains to the sink via the forwarding agent. This process is specified with a syntax referred to as a Daemonset which enables the same process to be started on a set of nodes which is usually all the nodes in the cluster.

 The log destination may be internal to the Kubernetes if the application providing log service hosted within the cluster.
The following are the configurations to setup the above logging mechanism:
1. Registering a sink controller:
apiVersion: apps.pivotal.io/v1beta1
kind: Sink
metadata:
  name: YOUR-SINK
  namespace: YOUR-NAMESPACE
spec:
  type: syslog
  host: YOUR-LOG-DESTINATION
  port: YOUR-LOG-DESTINATION-PORT
  enable_tls: true

2. Deploying a forwarding agent
apiVersion: v1
kind: ServiceAccount
metadata:
  name: fluentd
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: fluentd
  namespace: kube-system
rules:
- apiGroups:
  - ""
  resources:
  - pods
  - namespaces
  verbs:
  - get
  - list
  - watch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: fluentd
roleRef:
  kind: ClusterRole
  name: fluentd
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: fluentd
  namespace: kube-system
3. Deploying the Daemonset
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: fluentd
  namespace: kube-system
  labels:
    k8s-app: fluentd-logging
    version: v1
    kubernetes.io/cluster-service: "true"
spec:
  template:
    metadata:
      labels:
        k8s-app: fluentd-logging
        version: v1
        kubernetes.io/cluster-service: "true"
    spec:
      serviceAccount: fluentd
      serviceAccountName: fluentd
      tolerations:
      - key: node-role.kubernetes.io/master
        effect: NoSchedule
      containers:
      - name: fluentd
        image: fluent/fluentd-kubernetes-daemonset:elasticsearch
        env:
          - name:  FLUENT_ELASTICSEARCH_HOST
            value:  “sample.elasticsearch.com”
          - name:  FLUENT_ELASTICSEARCH_PORT
            value: "30216"
          - name: FLUENT_ELASTICSEARCH_SCHEME
            value: "https"
          - name: FLUENT_UID
            value: "0"
          # X-Pack Authentication
          # =====================
          - name: FLUENT_ELASTICSEARCH_USER
            value: "someusername"
          - name: FLUENT_ELASTICSEARCH_PASSWORD
            value: "somepassword"
        resources:
          limits:
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 200Mi
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
      terminationGracePeriodSeconds: 30
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers