Kubernetes - Revision history

Kenneth: /* Create Pod from Yaml */

2023-12-22T22:09:42Z

Create Pod from Yaml

Kenneth: /* Create simple bash pods in background */

2023-12-22T17:36:55Z

Create simple bash pods in background

Kenneth: /* Pod Template */

2023-12-22T17:36:06Z

Pod Template

Kenneth: /* = Create simple bash pods in background */

2023-12-20T14:24:58Z

= Create simple bash pods in background

Kenneth: /* Create Simple Bash Pod */

2023-12-20T14:24:49Z

Create Simple Bash Pod

Kenneth: /* kubectl install */

2023-12-19T19:16:17Z

kubectl install

Kenneth: /* Basic Commands */

2023-10-02T18:03:57Z

Basic Commands

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<br/>

== Kubernetes ==

Kubernetes, also known as K8s.

Kubernetes is a container or microservice platform that orchestrates computing, networking, and storage infrastructure workloads.

The Kubernetes Project was open-sourced by Google in 2014 after using it to run production workloads at scale for more than a decade. Kubernetes provides the ability to run dynamically scaling, containerised applications, and utilising an API for management. Kubernetes is a vendor-agnostic container management tool, minifying cloud computing costs whilst simplifying the running of resilient and scalable applications.

== k8s ==

"By the way, if you’re wondering where the name “Kubernetes” came from, it is a Greek word, meaning helmsman or pilot. The abbreviation K8s is derived by replacing the eight letters of “ubernete” with the digit 8." [https://www.bmc.com/blogs/what-is-kubernetes/]

== kubectl install ==

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"

curl -LO "https://dl.k8s.io/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
echo "$(cat kubectl.sha256) kubectl" | sha256sum --check

sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl

kubectl version --client

Bash completion:
echo 'source <(kubectl completion bash)' >>~/.bashrc

Alias:
echo 'alias k=kubectl' >>~/.bashrc
echo 'alias k8s=kubectl' >>~/.bashrc
echo 'complete -o default -F __start_kubectl k' >>~/.bashrc
echo 'complete -o default -F __start_kubectl k8s' >>~/.bashrc

ref: [https://kubernetes.io/docs/tasks/tools/]

== Kubectl config ==

.kube/config

== Definitions ==

Basic objects include:

Pod. A group of one or more containers.

Service. An abstraction that defines a logical set of pods as well as the policy for accessing them.

Volume. An abstraction that lets us persist data. (This is necessary because containers are ephemeral—meaning data is deleted when the container is deleted.)

Namespace. A segment of the cluster dedicated to a certain purpose, for example a certain project or team of devs.

== Create Simple Bash Pod ==

kubectl run my-shell --rm -i --tty --image ubuntu -- bash

* my-shell: This ends up being the name of the Deployment that is created. Your pod name will typically be this plus a unique hash or ID at the end.
* --rm: Delete any resources we've created once we detach. When you exit out of your session, this cleans up the Deployment and Pod.
* -i/--tty: The combination of these two are what allows us to attach to an interactive session.
* --: Delimits the end of the kubectl run options from the positional arg (bash).
* bash: Overrides the container's CMD. In this case, we want to launch bash as our container's command

ref [https://gc-taylor.com/blog/2016/10/31/fire-up-an-interactive-bash-pod-within-a-kubernetes-cluster]

== Basic Commands ==

=== NODE MANAGEMENT ===

=== Get Nodes ===

Get Nodes:
kubectl get nodes

# Example:
# kubectl get nodes
NAME STATUS ROLES AGE VERSION
ci-2210 Ready <none> 509d v1.22.2
ci-2211 Ready <none> 509d v1.22.2
ci-2212 Ready <none> 509d v1.22.2
ci-4010 NotReady <none> 157d
ci-0 Ready control-plane,master 299d v1.22.2

=== Evict Pods from Node ===

kubectl drain <nodename>

=== Make Node Unschedulable ===

kubectl cordon <nodename>

=== Make Node Scheduable ===

kubectl uncordon <nodename>

=== Delete Node ===

kubectl delete node <nodename>

=== POD MANAGEMENT ===

=== Get Pods ===

Get Pods (in the default name space)
kubectl get pods

# Example:
# kubectl get pods
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kshell 1/1 Running 0 3d20h 50.0.40.7 uls-ep-essdci45 <none> <none>

Get Pods (more details):
kubectl get pods -o wide

# Example
# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
kshell 1/1 Running 0 3d20h 50.0.40.7 uls-ep-essdci45 <none> <none>

Filter for specific pod:
kubectl get pods -o wide | grep <nodename>

To specify a different name space add "-n [namespace]"
kubectl get pods -n MyNamespace

ref [https://www.bluematador.com/blog/safely-removing-pods-from-a-kubernetes-node]

=== Get Specific Pod Details ===

kubectl get pod [pod-name]

# Example:
# kube get pod kshell
NAME READY STATUS RESTARTS AGE
kshell 1/1 Running 0 3d20h

=== Connect to Pod and Run Bash ===

kubectl exec -it [single-container-pod] -- bash

# example:
kubectl exec --stdin --tty shell-demo -- /bin/bash

=== Get Logs of Pod ===

kubectl logs [pod-name]

=== Create Simple Pod from Image ===

kubectl run my-shell --rm -i --tty --image ubuntu -- bash

# run in background
kubectl run my-shell -i --tty --image ubuntu -- bash
ctrl+p ctrl+q

Note: "image" is Docker image name

=== Attach to Simple Pod ===

kubectl attach my-shell -c my-shell -i -t

kubectl exec my-shell -it -- /bin/bash

=== Delete Pod ===

kubectl delete pod [pod-name]

=== NAME SPACE MANAGEMENT ===

kubectl create namespace [namespace]

Use name space
kubectl -ns [namespace] ...other_k8_commands...

Set default namespace for commands: [https://kubernetes.io/docs/reference/kubectl/cheatsheet/]
kubectl config set-context --current --namespace=[namespace]

To unset:
kubectl config set-context --current --namespace=""

View current context namespace: [https://stackoverflow.com/questions/55373686/how-to-switch-namespace-in-kubernetes]
kubectl config view | grep namespace:
# or
kubectl config view -o jsonpath={.contexts[].context.namespace}

=== CONTEXT MANAGEMENT ===

ref: https://stackoverflow.com/questions/55373686/how-to-switch-namespace-in-kubernetes

kubectl config set-context gce-dev --user=cluster-admin --namespace=dev
kubectl config use-context gce-dev

With aliases:
$ alias kubens='kubectl config set-context --current --namespace '
$ alias kubectx='kubectl config use-context '

// Usage
$ kubens kube-system // Switch to a different namespace
$ kubectx docker // Switch to separate context

With addons like kubectx & kubens
* https://github.com/ahmetb/kubectx
kubens kube-system

With addon like kubectl-use:
* https://github.com/kvaps/kubectl-use

# kubectl use prod
Switched to context "prod".

# kubectl use default
Switched to namespace "default".

# kubectl use stage kube-system
Switched to context "stage".
Switched to namespace "kube-system".

With kubie alternative to kubectl: [https://stackoverflow.com/questions/55373686/how-to-switch-namespace-in-kubernetes]
* https://github.com/sbstp/kubie
kubie ctx ...

== Create Pod from Yaml ==

Sample Yaml: (php.yml)
<pre>
apiVersion: v1
kind: Pod
metadata:
name: nodejsapp-pod
labels:
app: nodejsapp
type: front-end
spec:
containers:
- name: nodejsapp-erp
image: bharathirajutut/erp:1.0
</pre>

Create pod from Yaml:
kubectl apply -f php.yaml

ref [https://medium.com/codex/create-a-pod-in-kubernetes-cluster-b9e0c33bb904]

---

Sample Yaml: (shell-demo.yaml)
<pre>
apiVersion: v1
kind: Pod
metadata:
name: shell-demo
spec:
volumes:
- name: shared-data
emptyDir: {}
containers:
- name: nginx
image: nginx
volumeMounts:
- name: shared-data
mountPath: /usr/share/nginx/html
hostNetwork: true
dnsPolicy: Default
</pre>

Create pod from Yaml:
kubectl apply -f https://k8s.io/examples/application/shell-demo.yaml

ref [https://kubernetes.io/docs/tasks/debug/debug-application/get-shell-running-container/]

== Sample Pod Configs ==

More Samples:
Pod - Kubernetes examples
https://k8s-examples.container-solutions.com/examples/Pod/Pod.html

=== Nginx ===

<pre>
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80
</pre>

kubectl apply -f https://k8s.io/examples/pods/simple-pod.yaml

ref: [https://kubernetes.io/docs/concepts/workloads/pods/]

=== Pod Template ===

Prints one thing, then exits. Template for something bigger.

<pre>
apiVersion: batch/v1
kind: Job
metadata:
name: hello
spec:
template:
# This is the pod template
spec:
containers:
- name: hello
image: busybox:1.28
command: ['sh', '-c', 'echo "Hello, Kubernetes!" && sleep 3600']
restartPolicy: OnFailure
# The pod template ends here
</pre>

=== Busy Box Command ===

<pre>
apiVersion: v1
kind: Pod
metadata:
labels:
run: busybox
name: busybox
spec:
containers:
- command:
- /bin/sh
- -c
- |
echo "running below scripts"
i=0;
while true;
do
echo "$i: $(date)";
i=$((i+1));
sleep 1;
done
name: busybox
image: busybox
</pre>

ref: [https://stackoverflow.com/questions/33887194/how-to-set-multiple-commands-in-one-yaml-file-with-kubernetes]

== Create Kubernetes Cluster ==

See [[Kubernetes/Cluster]]

== keywords ==

← Older revision		Revision as of 22:09, 22 December 2023
Line 298:		Line 298:

	ref [https://kubernetes.io/docs/tasks/debug/debug-application/get-shell-running-container/]		ref [https://kubernetes.io/docs/tasks/debug/debug-application/get-shell-running-container/]
		+
		+	== Get YAML from Object ==
		+
		+	kubectl get deployment,service,pod yourapp -o yaml --export
		+
		+	kubectl get deploy --all-namespaces -o yaml --export
		+
		+	kubectl get deploy deploymentname -o yaml
		+
		+	kubectl get deploy,sts,svc,configmap,secret -n default -o yaml --export > default.yaml
		+
		+	Get YAML for deployed Kubernetes services? - Stack Overflow
		+	https://stackoverflow.com/questions/43941772/get-yaml-for-deployed-kubernetes-services

	== Sample Pod Configs ==		== Sample Pod Configs ==

@@ Line 90: / Line 90: @@
 === Create simple bash pods in background ===
-  kubectl run shell1 --image ubuntu sleep 10000
+  kubectl run shell1 --image ubuntu sleep infinity
-  kubectl run shell2 --image ubuntu sleep 10000
+  kubectl run shell2 --image ubuntu sleep infinity
-  kubectl run shell3 --image ubuntu sleep 10000
+  kubectl run shell3 --image ubuntu sleep infinity
 == Basic Commands ==

@@ Line 88: / Line 88: @@
 ref [https://gc-taylor.com/blog/2016/10/31/fire-up-an-interactive-bash-pod-within-a-kubernetes-cluster]
-=== Create simple bash pods in background ==
+=== Create simple bash pods in background ===
   kubectl run shell1 --image ubuntu sleep 10000

← Older revision		Revision as of 14:24, 20 December 2023
Line 87:		Line 87:

	ref [https://gc-taylor.com/blog/2016/10/31/fire-up-an-interactive-bash-pod-within-a-kubernetes-cluster]		ref [https://gc-taylor.com/blog/2016/10/31/fire-up-an-interactive-bash-pod-within-a-kubernetes-cluster]
		+
		+	=== Create simple bash pods in background ==
		+
		+	kubectl run shell1 --image ubuntu sleep 10000
		+	kubectl run shell2 --image ubuntu sleep 10000
		+	kubectl run shell3 --image ubuntu sleep 10000

	== Basic Commands ==		== Basic Commands ==

@@ Line 340: / Line 340: @@
        - name: hello
          image: busybox:1.28
-         command: ['sh', '-c', 'echo "Hello, Kubernetes!" && sleep 3600']
+         command: ['sh', '-c', 'echo "Hello, Kubernetes!" && sleep infinity']
        restartPolicy: OnFailure
      # The pod template ends here

@@ Line 17: / Line 17: @@
 "By the way, if you’re wondering where the name “Kubernetes” came from, it is a Greek word, meaning helmsman or pilot. The abbreviation K8s is derived by replacing the eight letters of “ubernete” with the digit 8." [https://www.bmc.com/blogs/what-is-kubernetes/]
 == kubectl install ==
   curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
   curl -LO "https://dl.k8s.io/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
   echo "$(cat kubectl.sha256)  kubectl" | sha256sum --check
   sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
   kubectl version --client
 Bash completion:
   echo 'source <(kubectl completion bash)' >>~/.bashrc
-Alias:
+Aliases:
   echo 'alias k=kubectl' >>~/.bashrc
   echo 'alias k8s=kubectl' >>~/.bashrc