kubectl command interface¶

kubectl is the command-line interface (CLI) tool for Kubernetes (often abbreviated as k8s).^[400-devops-06-kubernetes-k8s.md]

Syntax and Resource Management¶

The general syntax for interacting with Kubernetes resources follows the pattern kubectl get <resource>, <resource> can be replaced with specific object types such as pods, deployments, services, configmaps, secrets, or ingress.¹^[400-devops-06-kubernetes-k8s.md]

• Listing Resources: kubectl get pods lists all pods.²^[400-devops-06-kubernetes-k8s.md]
• Describing Resources: kubectl describe <resource> <name> provides detailed status and information about a specific resource.³^[400-devops-06-kubernetes-k8s.md]
• Version: kubectl version displays the version information of the client and server.⁴^[400-devops-06-kubernetes-k8s.md]

Resource Creation and Updates¶

Resources can be created or updated using configuration files.

• Declarative Management: kubectl apply -f <filename>.yaml applies a configuration. This command is idempotent and is preferred for managing existing resources, as it detects configuration changes and updates the resource accordingly.⁵^[400-devops-06-kubernetes-k8s-ithelp-day6-readme.md]
• Imperative Creation: kubectl create -f <filename>.yaml creates a resource. Unlike apply, it is typically used only for resources that do not yet exist.⁶^[400-devops-06-kubernetes-k8s-ithelp-day6-readme.md]

Cluster Configuration¶

kubectl uses a configuration file (typically located at ${HOME}/.kube/config or specified via the KUBECONFIG environment variable) to manage cluster connection details, known as contexts.⁷^[400-devops-06-kubernetes-k8s.md]

• View Context: kubectl config current-context displays the currently active cluster context.⁸^[400-devops-06-kubernetes-k8s.md]
• List Contexts: kubectl config get-contexts lists all available contexts.⁹^[400-devops-06-kubernetes-k8s.md]
• Switch Context: kubectl config use-context <name> switches the active context to a different cluster or namespace.¹⁰^[400-devops-06-kubernetes-k8s.md]

Port Forwarding¶

The kubectl port-forward command allows users to map a local port to a port on a Kubernetes resource, enabling direct access to an application running inside the cluster via localhost.¹¹^[400-devops-06-kubernetes-k8s-ithelp-day6-readme.md]

• Syntax: kubectl port-forward TYPE/NAME [LOCAL_PORT:]REMOTE_PORT.¹²^[400-devops-06-kubernetes-k8s-ithelp-day6-readme.md]
• Example: kubectl port-forward mysql-dp-8dfb795cf-2hkgm 3306:3306 --address 0.0.0.0 forwards port 3306 from a specific Pod to the local machine on all interfaces.¹³^[400-devops-06-kubernetes-k8s.md]

Namespaces¶

Namespaces provide a mechanism to isolate resources within a cluster.

• List Namespaces: kubectl get namespaces.¹⁴^[400-devops-06-kubernetes-k8s.md]
• Create Namespace: kubectl create namespace <name>.¹⁵^[400-devops-06-kubernetes-k8s.md]
• Filter by Namespace: The -n flag filters commands by a specific namespace, such as kubectl get pods -n test.¹⁶^[400-devops-06-kubernetes-k8s.md]

Sources¶

• 400-devops-06-kubernetes-k8s-ithelp-day6-readme.md
• 400-devops-06-kubernetes-k8s.md