Kubectl

Introduction to Kubectl

TL;DR

Kubectl is the Kubernetes cli
Kubectl provides a swiss army knife of functionality for working with Kubernetes clusters
Kubectl may be used to deploy and manage applications on Kubernetes
Kubectl may be used for scripting and building higher-level frameworks

Kubectl is the Kubernetes cli version of a swiss army knife, and can do many things.

While this Book is focused on using Kubectl to declaratively manage Applications in Kubernetes, it also covers other Kubectl functions.

Command Families

Most Kubectl commands typically fall into one of a few categories:

Type	Used For	Description
Declarative Resource Management	Deployment and Operations (e.g. GitOps)	Declaratively manage Kubernetes Workloads using Resource Config
Imperative Resource Management	Development Only	Run commands to manage Kubernetes Workloads using Command Line arguments and flags
Printing Workload State	Debugging	Print information about Workloads
Interacting with Containers	Debugging	Exec, Attach, Cp, Logs
Cluster Management	Cluster Ops	Drain and Cordon Nodes

Declarative Application Management

The preferred approach for managing Resources is through declarative files called Resource Config used with the Kubectl Apply command. This command reads a local (or remote) file structure and modifies cluster state to reflect the declared intent.

Apply

Apply is the preferred mechanism for managing Resources in a Kubernetes cluster.

Printing state about Workloads

Users will need to view Workload state.

Printing summarize state and information about Resources
Printing complete state and information about Resources
Printing specific fields from Resources
Query Resources matching labels

Debugging Workloads

Kubectl supports debugging by providing commands for:

Printing Container logs
Printing cluster events
Exec or attaching to a Container
Copying files from Containers in the cluster to a user’s filesystem

Cluster Management

On occasion, users may need to perform operations to the Nodes of cluster. Kubectl supports commands to drain Workloads from a Node so that it can be decommission or debugged.

Porcelain

Users may find using Resource Config overly verbose for Development and prefer to work with the cluster imperatively with a shell-like workflow. Kubectl offers porcelain commands for generating and modifying Resources.

Generating + creating Resources such as Deployments, StatefulSets, Services, ConfigMaps, etc
Setting fields on Resources
Editing (live) Resources in a text editor

Porcelain For Dev Only

Porcelain commands are time saving for experimenting with workloads in a dev cluster, but shouldn’t be used for production.