Basic Kubectl Commands

Some of the basic kubectl commands apply to all k8s objects

Namespaces

• used to group objects in the cluster
• each namespace acts like a folder holding a set of objects
• kubectl works with the default namespace by default
• —namespace can be passed to specify a different one

Context

• can be used to change the default namespace, manage different clusters or different users for authenticating to them
• To change the namespace to abc, run: $ kubectl config set-context my-context --namespace=abc
• This command just creates a context. To run it, use: $ kubectl config use-context my-context
• This records the change in the kubectl config file while is usually located at $HOME/.kube/config. This file also stores information related to finding and authenticating to the cluster.

Viewing Kubernetes API Objects

• Everything is represented by a RESTful resource, called objects.
• Each object has a unique HTTP endpoint scoped using namespaces.
• kubectl uses these endpoints to fetch the objects
• Viewing resources in the current namespace: kubectl get <resource-name>
• Viewing a specific resource: kubectl get <resource-name> <object-name> Use describe instead of `get`` for more detailed information about the object
• To get more info than normally displayed, use -o wide flag
• To get raw JSON or YAML objects from the API server, use -o json, -o yaml.

Creating, Updating, and Destroying Kubernetes Objects

• k8s objects are represented using YAML or JSON files (each object has its own JSON/YAML file?)
• used to manipulate objects on the server
• To create an object described using obj.yaml: kubectl apply -f obj.yaml K8s automatically infers the type, it doesn’t need to be specified.

Labeling and Annotating Objects

• used to tag objects
• kubectl label/annotate pods bar color=red adds the color=red label to a pod called bar.
• To remove a label: kubectl label pods bar -color

Debugging Commands

To see logs for a container: kubectl logs <pod-name>

• Use -c to choose a particular container
• Use -f to stream logs to terminal
• kubectl exec -it <pod-name> — bash provides an interactive shell within the container.