lables,selector,replicaset,deploymentset 

 Labels:-
Labels are the mechanism to organize Kubernetes objects such as Pods 
 A label is a key-value pair.
Labels can be attached to objects at creation time or added and modified at any time.  
"metadata": {
  "labels": {
    "key1" : "value1",
    "key2" : "value2"
  }
}
To create lables imperative we can use
kubectl label pods delhipod myname=ajay  // delhipod is pod name 

to check the lables 
kubectl get pods --show-labels // to show the lables of pods 
To get the pods where env is not equal to development 
kubectl get pods -l env!=development   // We need to use ! sign before key (env is key hear)
We can also delete the pods using lables
kubectl delete pod -l env!=development  

Labels Selector
Once the lables are attached to an object, we would need filters to narrow down and these are called as labels selector

The API currently supports two types of selector - 
1 equality based  ( =, !=)  equal to or not equal to. 
example name=ajay 
2 Set based : ( in, notin or exists)
env in (production, dev)
env notin (team1 , team2) 
Kuberntes also supports setbased slectors ie match multiple values. 

Replication controller :- 

Replication Controller is one of the key features of Kubernetes, which is responsible for managing the pod lifecycle. It is responsible for making sure that the specified number of pod replicas are running at any point of time. It is used in time when one wants to make sure that the specified number of pod or at least one pod is running. It has the capability to bring up or down the specified no of pod.
It is a best practice to use the replication controller to manage the pod life cycle rather than creating a pod again and again.


apiVersion: v1
kind: ReplicationController
metadata:
  name: nginx
spec:
  replicas: 3
  selector:
    app: nginx
  template:
    metadata:
      name: nginx
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80


Replication Set :- 

Replica Set ensures how many replica of pod should be running. It can be considered as a replacement of replication controller. The key difference between the replica set and the replication controller is, the replication controller only supports equality-based selector whereas the replica set supports set-based selector.
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: frontend
  labels:
    app: guestbook
    tier: frontend
spec:
  # modify replicas according to your case
  replicas: 3
  selector:
    matchLabels:
      tier: frontend
  template:
    metadata:
      labels:
        tier: frontend
    spec:
      containers:
      - name: php-redis
        image: gcr.io/google_samples/gb-frontend:v3


Difference between rc and rs 

Replication Controller 
 Replica Set  
The Replication Controller is the original form of replication in Kubernetes
ReplicaSets are a higher-level API that gives the ability to easily run multiple instances of a given pod
The Replication Controller uses equality-based selectors to manage the pods.
ReplicaSets Controller uses set-based selectors to manage the pods.
The rolling-update command works with Replication Controllers
The rolling-update command won’t work with ReplicaSets.
Replica Controller is deprecated and replaced by ReplicaSets.
Deployments are recommended over ReplicaSets.

Deployment



Comments

Post a Comment

Popular posts from this blog

Advanced Pods

  Scheduling  :- The process of assigning Pods to Nodes so kubelets can run them.  Scheduler :-  Control plane component that handles scheduling  Scheduling Process The kubernets scheduler selects a suitable Node for each pod. It takes into account thins like Resource requests vs. avaiable node resource Various configurations that affect scheduling using node labels NodeSelector :- We can configure a node Selector for our pods to limit which nodes the pod can be scheduled on. Node selectos use node labels to filter suitable nodes.  Create labeles to node :- kubectl label nodes k8s-worker1 special=true NodeName :- We can bypass scheduling and assign a pod to specific node by name using nodeName.  What is DaemonSet  DaemonSet Automatically runs a copy of a Pod on each node.  DaemonSets will run a copy of the Pod on new nodes as they are added to the cluster.  DaemonSets and Scheduling DaemonSets respect normal scheduling rules around node ...
Read more

Docker

  hostnamectl set-hostname docker-host     // Change the hostname to docker-host Docker  There is not password for run pull request for docker   yum update -y      yum install docker* systemctl status docker systemctl start docker systemctl enable docker systemctl enable docker.service   // auto enable service for docker  systemctl status docker pull the images for docker hub https://dlcdn.apache.org/tomcat/tomcat-9/v9.0.82/bin/apache-tomcat-9.0.82.tar.gz docker pull centos // if we do not put tags it will download the latest images docker pull centos: 7 // It has verion 7 tags Note we can pull docker images without login to dockerhub    docker images        docker info | grep -i dir     // Docker info for storing docker images        ls -l /var/lib/docker/    //Location where docker images are stored    ls -l /var/lib/docker/overlay2/6a61...
Read more

RBAC

Image
 RBAC in K8s Role-based access control (RBAC) in k8s allows us to control what users are allowed to do and access within your cluster. For example, we can use RBAC to allow developers to read metadata and logs from Kubernetes pods but not make changes to them.  Roles and ClusterRoles are kubernetes object that define a set of permissions. These permissions determine what users can do in the cluster.  A role defines permissions within a particular namespace, and a cluster role defines cluster-wide permissions not specific to a single namespace.  RoleBininding and cluserRoleBinding are objects that connect Roles and ClusterRoles to users.  Service accounts What is service accounts ? Service account is an account used by container processes within Pods to authenticate with the k8s API.  If your Pods need to communicate with the k8s, we can use service accounts to control their access.  Creating Service accounts A service account object can be created wit...
Read more