Kubernetes cheatsheet

Some frequent k8s commands with params

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Here is my k8s cheat sheet covering kubenetes most important commands and concepts from installing to running containers and cleaning up:

k8s lights

Installation of Kubernetes

Using Kubeadm

To install Kubernetes using kubeadm, follow these steps:

Prepare the Environment:

Ensure the necessary kernel modules are enabled:

sudo sysctl net/bridge/bridge-nf-call-ip6tables=1
sudo sysctl net/bridge/bridge-nf-call-iptables=1
sudo sysctl net/bridge/bridge-nf-call-arptables=1

Reboot the system to apply the changes.

Install Docker and Other Prerequisites:

Install Docker:

sudo apt-get update
sudo apt-get install -y docker.io

Install ebtables and ethtool:
```
sudo apt-get install ebtables ethtool
```

Install HTTPS support and curl if necessary:

sudo apt-get update
sudo apt-get install -y apt-transport-https curl

Add the Kubernetes repository and install kubeadm, kubelet, and kubectl:

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
sudo cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb http://apt.kubernetes.io/ kubernetes-xenial main
EOF
sudo apt-get update
sudo apt-get install -y kubeadm kubelet kubectl

Initialize the Kubernetes Cluster:
- Initialize the first control plane node:
```
sudo kubeadm init
```
- Join additional control plane and worker nodes:
```
kubeadm join <control-plane-node>:8443 --token <token> --discovery-token-ca-cert-hash <hash>
```

Using Minikube or Kind

For local development, you can use minikube or kind:

Minikube:
```
minikube start
```
Follow the official [Get Started! guide].

Kind:

curl -sfL https://get.k3s.io | sh -
kind create cluster

Follow the [Kind Quick Start page].

Common kubectl Commands

Basic Commands

Get Information About Resources:

kubectl get <resource>  # List resources (e.g., pods, services, deployments)
kubectl get pods --all-namespaces  # List all pods in all namespaces
kubectl get pods -o wide  # List pods with more details
kubectl get pod my-pod -o yaml  # Get a pod's YAML configuration.

Describe Resources:

kubectl describe <resource>  # Detailed description of a resource (e.g., nodes, pods)
kubectl describe nodes my-node
kubectl describe pods my-pod.

Create Resources:

kubectl create -f <manifest-file>  # Create resources from a YAML or JSON file
kubectl create configmap <configmap-name> --from-literal=<key>=<value>  # Create a ConfigMap
kubectl create secret generic <secret-name> --from-literal=<key>=<value>  # Create a Secret.

Delete Resources:

kubectl delete <resource> <name>  # Delete a resource (e.g., pod, deployment)
kubectl delete pod my-pod
kubectl delete deployment my-deployment.

Pod Management

Define a Command and Arguments for a Container:

apiVersion: v1
kind: Pod
metadata:
  name: command-demo
spec:
  containers:
  - name: command-demo-container
    image: debian
    command: ["printenv"]
    args: ["HOSTNAME", "KUBERNETES_PORT"]

kubectl apply -f <manifest-file>
kubectl get pods
kubectl logs command-demo.

Run a Command in a Shell:

apiVersion: v1
kind: Pod
metadata:
  name: shell-demo
spec:
  containers:
  - name: shell-demo-container
    image: debian
    command: ["/bin/sh"]
    args: ["-c", "while true; do echo hello; sleep 10;done"]

kubectl apply -f <manifest-file>
kubectl get pods
kubectl logs shell-demo.

ConfigMap and Secret Management

Create a ConfigMap:

kubectl create configmap <configmap-name> --from-literal=<key>=<value>
kubectl create configmap app-config --from-literal=environment=production --from-literal=log_level=info.

Create a Secret:

kubectl create secret generic <secret-name> --from-literal=<key>=<value>
kubectl create secret generic db-secret --from-literal=username=admin --from-literal=password=supersecret.

Deployment and Service Management

Create a Deployment:

kubectl create deployment <deployment-name> --image=<image-name>
kubectl create deployment my-deployment --image=nginx:latest.

Expose a Deployment as a Service:

kubectl expose deployment <deployment-name> --type=NodePort --port=<port>
kubectl expose deployment my-deployment --type=NodePort --port=80.

Namespace and Node Management

List Namespaces:
```
kubectl get namespaces
```

Create a Namespace:

kubectl create namespace <namespace-name>
kubectl create namespace my-namespace.

List Nodes:

kubectl get nodes
kubectl get nodes --selector='!node-role.kubernetes.io/control-plane'.

Monitoring and Debugging

View Logs:

kubectl logs <pod-name>
kubectl logs -f <pod-name>  # Follow the logs in real-time.

Describe Events:
```
kubectl describe events
```

Check Cluster Information:

kubectl cluster-info
kubectl version  # Check the Kubernetes version.

Advanced Commands

Sort Resources:

kubectl get pods --sort-by='.status.containerStatuses.restartCount'
kubectl get services --sort-by=.metadata.name.

Filter Resources:

kubectl get pods --field-selector=status.phase=Running
kubectl get nodes --selector='!node-role.kubernetes.io/control-plane'.

Retrieve Specific Data:

kubectl get configmap myconfig -o jsonpath='{.data.ca\.crt}'
kubectl get secret my-secret --template='{{index .data "key-name-with-dashes"}}'.