Skip to content

Latest commit

 

History

History
343 lines (253 loc) · 7.2 KB

a.core_concepts.md

File metadata and controls

343 lines (253 loc) · 7.2 KB

Core Concepts (13%)

kubernetes.io > Documentation > Reference > kubectl CLI > kubectl Cheat Sheet

kubernetes.io > Documentation > Tasks > Monitoring, Logging, and Debugging > Get a Shell to a Running Container

kubernetes.io > Documentation > Tasks > Access Applications in a Cluster > Configure Access to Multiple Clusters

kubernetes.io > Documentation > Tasks > Access Applications in a Cluster > Accessing Clusters using API

kubernetes.io > Documentation > Tasks > Access Applications in a Cluster > Use Port Forwarding to Access Applications in a Cluster

Create a namespace called 'mynamespace' and a pod with image nginx called nginx on this namespace

show

kubectl create namespace mynamespace
kubectl run nginx --image=nginx --restart=Never -n mynamespace

Create the pod that was just described using YAML

show

Easily generate YAML with:

kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml > pod.yaml
cat pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
kubectl create -f pod.yaml -n mynamespace

Alternatively, you can run in one line

kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml | kubectl create -n mynamespace -f -

Create a busybox pod (using kubectl command) that runs the command "env". Run it and see the output

show

kubectl run busybox --image=busybox --command --restart=Never -it -- env # -it will help in seeing the output
# or, just run it without -it
kubectl run busybox --image=busybox --command --restart=Never -- env
# and then, check its logs
kubectl logs busybox

Create a busybox pod (using YAML) that runs the command "env". Run it and see the output

show

# create a  YAML template with this command
kubectl run busybox --image=busybox --restart=Never --dry-run -o yaml --command -- env > envpod.yaml
# see it
cat envpod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  containers:
  - command:
    - env
    image: busybox
    name: busybox
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}
# apply it and then see the logs
kubectl apply -f envpod.yaml
kubectl logs busybox

Get the YAML for a new namespace called 'myns' without creating it

show

kubectl create namespace myns -o yaml --dry-run

Get the YAML for a new ResourceQuota called 'myrq' with hard limits of 1 CPU, 1G memory and 2 pods without creating it

show

kubectl create quota myrq --hard=cpu=1,memory=1G,pods=2 --dry-run -o yaml

Get pods on all namespaces

show

kubectl get po --all-namespaces

Alternatively

kubectl get po -A

Create a pod with image nginx called nginx and allow traffic on port 80

show

kubectl run nginx --image=nginx --restart=Never --port=80

Change pod's image to nginx:1.7.1. Observe that the pod will be killed and recreated as soon as the image gets pulled

show

# kubectl set image POD/POD_NAME CONTAINER_NAME=IMAGE_NAME:TAG
kubectl set image pod/nginx nginx=nginx:1.7.1
kubectl describe po nginx # you will see an event 'Container will be killed and recreated'
kubectl get po nginx -w # watch it

Note: you can check pod's image by running

kubectl get po nginx -o jsonpath='{.spec.containers[].image}{"\n"}'

Get nginx pod's ip created in previous step, use a temp busybox image to wget its '/'

show

kubectl get po -o wide # get the IP, will be something like '10.1.1.131'
# create a temp busybox pod
kubectl run busybox --image=busybox --rm -it --restart=Never -- wget -O- 10.1.1.131:80

Alternatively you can also try a more advanced option:

# Get IP of the nginx pod
NGINX_IP=$(kubectl get pod nginx -o jsonpath='{.status.podIP}')
# create a temp busybox pod
kubectl run busybox --image=busybox --env="NGINX_IP=$NGINX_IP" --rm -it --restart=Never -- sh -c 'wget -O- $NGINX_IP:80'

Or just in one line:

kubectl run busybox --image=busybox --rm -it --restart=Never -- wget -O- $(kubectl get pod nginx -o jsonpath='{.status.podIP}:{.spec.containers[0].ports[0].containerPort}')

Get pod's YAML

show

kubectl get po nginx -o yaml
# or
kubectl get po nginx -oyaml
# or
kubectl get po nginx --output yaml
# or
kubectl get po nginx --output=yaml

Get information about the pod, including details about potential issues (e.g. pod hasn't started)

show

kubectl describe po nginx

Get pod logs

show

kubectl logs nginx

If pod crashed and restarted, get logs about the previous instance

show

kubectl logs nginx -p

Execute a simple shell on the nginx pod

show

kubectl exec -it nginx -- /bin/sh

Create a busybox pod that echoes 'hello world' and then exits

show

kubectl run busybox --image=busybox -it --restart=Never -- echo 'hello world'
# or
kubectl run busybox --image=busybox -it --restart=Never -- /bin/sh -c 'echo hello world'

Do the same, but have the pod deleted automatically when it's completed

show

kubectl run busybox --image=busybox -it --rm --restart=Never -- /bin/sh -c 'echo hello world'
kubectl get po # nowhere to be found :)

Create an nginx pod and set an env value as 'var1=val1'. Check the env value existence within the pod

show

kubectl run nginx --image=nginx --restart=Never --env=var1=val1
# then
kubectl exec -it nginx -- env
# or
kubectl exec -it nginx -- sh -c 'echo $var1'
# or
kubectl describe po nginx | grep val1
# or
kubectl run nginx --restart=Never --image=nginx --env=var1=val1 -it --rm -- env