Kubernetes Namespace

CozyFex included in kubernetes k8s orchestration

2021-05-08 358 words 2 minutes

Contents

You must know

Kubernetes generate default namespace when it’s installed.
And there are kube-system and kube-pulibc namespaces.

DNS

Connect to a service in the same namespace

If you want to connect to a database that is named db-service in the same namespace that is default.

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mysql.connect("db-service")

Connect to a service in the another namespace

If you want to connect to a database that is named db-service in the another namespace that is dev.

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mysql.connect("db-service.dev.svc.cluster.local")

cluster.local

Default domain name of the kubernetes cluster

svc

Sub domain for the service

dev

Namespace

db-service

Service name

Show PODs of the specific namespace

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# Show PODs of the `default` namespace
kubectl get pods

# Show PODs of the `kube-system` namespace
kubectl get pods --namespace=kube-system

Create a POD to the specific namespace

_{pod-definition.yml}

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# To the `default` namespace
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    type: front-end
spec:
  containers:
    - name: nginx-container
      image: nginx

_{dev-pod-definition.yml}

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# To the `dev` namespace
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  namespace: dev # -> Namespace
  labels:
    type: front-end
spec:
  containers:
    - name: nginx-container
      image: nginx

_{Create a POD}

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# To the `default` namespace
kubectl create -f pod-definition.yml

# To the `dev` namespace
kubectl create -f pod-definition.yml --namespace=dev
kubectl create -f dev-pod-definition.yml

Create namespace

_{namespace-dev.yml}

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apiVersion: v1
kind: Namespace
metadata:
  name: dev

_{Create namespace}

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# With YAML file
kubectl create -f namesapce-dev.yml

# Command
kubectl create namesapce dev

Switch namespace of the terminal

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kubectl config set-context $(kubectl config current-context) --namespace=dev

# Now, you can get PODs of `dev` namespace without `--namespace` option
kubectl pods

Show PODs of all namespaces

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kubectl get pods --all-namespaces

Resource Quota

_{compute-quota.yml}

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apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: dev
spec:
  hard:
    pods: "10"
    requests.cpu: "4"
    requests.memory: 5Gi
    limits.cpu: "10"
    limits.memory: 10Gi

_{Create Quota}

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kubectl create -f compute-quota.yml