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Pods

pods yaml

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apiVersion: apps/v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
    type: front-end
spec:
   containers:
   - name: nginx-container
     image: nginx

kubectl create -f pod.yml

show pods kubectl get pods

show detail info

create simple yml file

kubectl run redis --image=redis123 --dry-run=client -o yaml > redis-definition.yaml

apply changes

kubectl apply -f redis-definition.yaml

add tolerration to pods

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apiVersion: apps/v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
    type: front-end
spec:
   containers:
   - name: nginx-container
     image: nginx

   tolerration:
   -key:app 
   operator: "equal"
   value: blue
   effect: Noschedle | PreferNoSchedule|NoExecute

limit resource

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apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp-color
  labels:
    name: simple-webapp-color
spec:
 containers:
 - name: simple-webapp-color
   image: simple-webapp-color
   ports:
    - containerPort:  8080
   resources:
     requests:
      memory: "1Gi"
      cpu: "1"

default pods VCPU value is 1 and 512 Mi memory

pods can use more memory that needed but it is permanently it will be terminated

Static pods

if we have only kubelet on server ,but kubelet can create pods. we can provide kubelet to read pod definition files.

we can add yml files /etc/kubernetes/manifests/ folder and kubelet automaticly create this pods. if we delete that file. pod will be removed. it works only with Pods. we can add service parameter to change path --pod-manifest-path=/home/davit/kubemanifest

or kubeconfig.yaml if it is not service.

use docker ps to see pods

use custom sheduler

under spec: schedulerName: custom-scheduler

view events

kubectl get events

get all pods

kubectl get pods --all-namespaces

pod sample

kubectl run redis --image=redis:alpine --dry-run=client -o yaml > redis.yaml

exmpose pod directly NodePort

kubect run custom-nginx --image=ngin --port=8080

expose pod ClusterIp

kubectl run httpd --image=httpd:alpine --port=80 --expose

get system cluster pods

kubectl get pods --namespace kube-system

filter pods by selector

kubectl get pods --selector env=dev

get all objects using selector

kubectl get all --selector env=prod

multiple selectors

kubectl get pods --selector env=prod,bu=finance,tier=frontend

create yaml from running pod

kubectl get pod elephant -o yaml > elep.yaml

replace pod by force

kubectl replace -f elephant.yaml --force

detect static pods

controlplane at the end of pods name

get wide info with pods

kubectl get pods -o wide

add arguments to pods

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apiVersion: v1
kind: Pod
metadata:
  name: ubuntu-sleeper-pod
spec:
 containers:
 - name: ubuntu-sleeper
   image: ubuntu-sleeper
   command: ["sleep2.0"]
   args: ["10"]

add env variables in yml

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apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp-color
spec:
 containers:
 - name: simple-webapp-color
   image: simple-webapp-color
   ports:
   - containerPort: 8080
   env:
   - name: APP_COLOR
     value: pink

add env with configmaps

kubectl create configmap app-config --from-literal=APP_COLOR=blue --from-literal=APP_MODE=prod kubectl create configmap app-config --from-file=app_config.properties (Another way)

or

yaml apiVersion: v1 kind: ConfigMap metadata: name: app-config data: APP_COLOR: blue APP_MODE: prod

kubectl get configmaps

map configmap

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apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp-color
spec:
 containers:
 - name: simple-webapp-color
   image: simple-webapp-color
   ports:
   - containerPort: 8080
   envFrom:
   - configMapRef:
       name: app-config

we can inject using volumes too

use Secrets for passwords

kubectl create secret generic app-secret --from-literal=DB_Host=mysql --from-literal=DB_User=root --from-literal=DB_Password=paswrd kubectl create secret generic app-secret --from-file=app_secret.properties

echo -n "mysql" | base64

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apiVersion: v1
kind: Secret
metadata:
 name: app-secret
data:
  DB_Host: bX1zcWw=
  DB_User: cm9vdA==
  DB_Password: cGFzd3Jk
kubectl create -f secret-data.yaml

kubectl get secrets

get data

kubectl get secret app-secret -o yaml

if it is mounted as Volume

each password will we as file like /opt/passwords

multiple container pods

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apiVersion: v1
kind: Pod
metadata:
  name: simple-webapp
  labels:
    name: simple-webapp
spec:
  containers:
  - name: simple-webapp
    image: simple-webapp
    ports:
    - ContainerPort: 8080
  - name: log-agent
    image: log-agent