Basic Kubernetes commands

On your orchestrator node (node1), lets run through the following commands to learn about what they do.

Kubernetes commands

Listing

Listing nodes

kubectl get nodes

Listing everything

kubectl get all --all-namespaces

The main program for interacting with Kubernetes is kubectl, which is a CLI tool that talks to the Kubernetes API.

Note

You can also use --kubeconfig to pass a whole config to kubectl

Getting information

Information can be queried with the kubectl get command. Which can query resources like nodes

kubectl get nodes

and auto-complete to the best matching target

kubectl get no
kubectl get node

You can also increase the amount of information with the -o wide argument

kubectl get nodes -o wide

or output in standardized formats like:

• JSON -o json
• YAML -o yaml

Note

Outputting information to JSON is useful since it allows you to query information with jq

kubectl get nodes -o json | jq ".items[] | {name:.metadata.name} + .status.capacity"

Viewing details

The kubectl get command is great for listing resources, but details about each specific item can also be returned with kubectl describe which is used with the format

kubectl describe [type]/[name]
kubectl describe [type] [name]

We can get information about node1 with

kubectl describe node node1

You can also get an explanation about different types of resources with

kubectl explain [type]

# What is a node?
kubectl explain node
# What is a service?
kubectl explain service

Exploring deployments

Services

A service is a pod or deployment exposed to a network. We can see that our cluster already has the API service running with

kubectl get services

A ClusterIP service is internal, meaning that it’s only available from inside the cluster.

Note

The API requires authentication, so it returns a 403 error if you try to connect.

# Assuming this is the IP of your Kubernetes service
curl -k https://10.96.0.1

Running containers

Containers are manipulated through pods, and a pod is a group of containers:

• running together (on the same node)
• sharing resources (RAM, CPU; but also network, volumes)

Running pods can be listed with

kubectl get pods

You’ll quickly find that there are no pods running in the default namespace.

Namespaces

Namespaces are a way to separate resources by named tag. Namespaces can be listed with

kubectl get namespaces

When we looked for pods, we queried the “default” namespace. We list pods running in specific name spaces with the -n argument.

kubectl -n kube-system get pods

Note

Information about these services can be found here. The READY column indicates the number of containers in each pod, and pods with a name ending with -node are the main components (they have been specifically “pinned” to the orchestrator node)