Kubernetes

Kubernetes is a tool used for orchestrating containers.

Namespaces

Set default namespace

kubectl config set-context --current --namespace=<namespace>

Exec into pod

Open bash shell kubectl exec -it myapp-123 -- /bin/bash (//bin//bash on Windows)

Run command and exit kubectl exec myapp-123 -- ls

Cronjobs/Jobs

Create and run a job based on a cronjob

this can be used to manually trigger a cronjob

kubectl create job --from=cronjob/<cronjob name> <job name>

KIND

KIND stands for Kubernetes IN Docker. Kind is a tool that creates a development Kubernetes cluster inside of Docker quickly and easily. KIND also allows local multi-node setups.

choco install kind - Use Chocolatey to install kind on Windows

kind create cluster --name my-kind-cluster - Create a cluster

kubectl config get-contexts - List clusters

kubectl config use-context {name of context} - Switch to the KIND cluster

kind delete cluster --name my-kind-cluster - Delete the KIND cluster

Configuring a KIND cluster

KIND also allows you to customize your cluster when it is created via a yaml config file. (related blog post)

./my-cluster-config.yaml

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
- role: worker
- role: worker
- role: worker

kind create cluster --name my-custom-kind-cluster --config ./my-cluster-config.yaml - Create a KIND cluster based on the config file

JQ

JQ is a CLI tool that can be used to filter/format json. It can be used to select specific values from json output from the kubectl get <resource> command.

See my notes on jq for more info

Get all images for a pod

$ kubectl get pod/mypod -o json | jq '.spec.containers[].image' -r

nginx
image2
image3

Get all resource types, names, and images

$ kubectl get all -o json | jq '.items[] | ("Resource kind: " + .kind),("Resource name: " + .metadata.name),("images: " + spec.containers[]?.image),("")' -r

Resource kind: Pod
Resource name: mypod
images: nginx

Resource kind: Service
Resource name: myservice