Q) Kubernetes Components:
The control
plane is the system that maintains a record of all Kubernetes objects.
1. Master
Components:
Ø kube-apiserver: It acts as front-end for Kubernetes
control plane. It exposes the Kubernetes API. CLItools (like kubectl), Users
and even Master components (scheduler, control manager, etcd) and worker node
components (like kubelet) everything talks with API server.
Øetcd: Consistent and highly available
key-value store used as Kubernetes backing store for all cluster data. It
stores all master and worker node information.
Økube-scheduler: Scheduler is responsible for
distributing containers across multiple nodes. It watches for the newly created pod
with no assigned node and select a node for them to run on.
Økube-control-manager: Controllers are responsible for
noticing and responding when nodes, containers, or endpoints go down. They make decisions to bring up new
containers in such cases.
Node
controller:
Responsible for noticing and responding when nodes go down.
Replication
controller:
Responsible for maintaining the correct number of pods for every replication
controller object in the system.
Endpoints
controller: Populates
the Endpoints object (that is, joins Services & Pods).
Service
Account & Token controllers:
Create default accounts and API access tokens for new namespaces.
2. Worker
Components:
Ø
kubete: It is the Agent that runs on each
node in the cluster. This agent is responsible for making sure that containers
are running in a pod on a node.
Ø
kube-proxy: It is a network proxy that runs on
each node in your cluster. It maintains network rules on nodes. Handles network communication between
nodes by adding firewall routing rules.
Container Runtime: The container runtime is the software
that is responsible for running containers. Kubernetes supports several
container runtimes: Docker, containerd, CRI-O
Q) Kubernetes Node Type:
Kube Cluster
is made up of two types of nodes:
Kube Masters: These servers are responsible for
managing the Kube cluster as a whole. It has all the master components
installed on it. They are also referred to as the controller node.
Kube Workers: These servers are responsible for
running the actual pods, that the Kube Master instructs them to run. They have
all the worker components installed on
them.
Q)
Kubernetes Service and its Type?
A Service
enables network access to a set of Pods in Kubernetes.
The type property
in the Service's spec determines how the service is exposed to the network. The
possibles types are ClusterIP, NodePort, LoadBalancer, and ExternalName
Ø
ClusterIp:
The default value. The service is only accessible from within the Kubernetes
cluster
Ø
NodePort:
This makes the service accessible on a static port on each Node in the cluster.
Ø
LoadBalancer:
The service becomes accessible externally through a cloud provider's load
balancer functionality. GCP, AWS, Azure, and OpenStack offer this
functionality.
Ø
ExternalName:
Exposes the Service using an arbitrary name by returning a CNAME record with
the name.
