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In this article, we explore how to use the kubectl get command to inspect your Kubernetes cluster resources. For convenience, an alias (k) for kubectl is used in the examples below. If you haven’t already, enable shell autocompletion for a smoother workflow. Below you’ll find a detailed walkthrough of various commands and options to inspect your cluster effectively. ──────────────────────────────────────────────

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Listing Cluster Resources

If your Kubernetes cluster has multiple resources deployed, simply running: 
kubectl get
will list the available resources. Using the alias, you can list all resources with: 
controlplane ~ ➜ alias k=kubectl
controlplane ~ ➜ k get all
NAME                      READY   STATUS      RESTARTS   AGE
pod/logs-generator       1/1     Running     4          40m

NAME                     TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
service/kubernetes       ClusterIP   10.96.0.1      <none>        443/TCP        136m
controlplane ~ ➜
To list resources across all namespaces, add the -A flag. This command displays pods, services, daemon sets, deployments, replica sets, jobs, and more: 
controlplane ~ ➜ k get all -A
kube-system   pod/metrics-server-7ccf778fc5-m52nw                 1/1     Running   0          40m
kube-system   pod/weave-net-fblw4                                  2/2     Running   0          136m
uat           pod/notes-app-deployment-6c564d459fb-rjsk2            1/1     Running   0          40m
uat           pod/notes-app-deployment-6c564d459fb-s57sn            1/1     Running   0          40m

NAMESPACE      NAME                                                      TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)                   AGE
default        service/kubernetes                                         ClusterIP      10.96.0.1      <none>          443/TCP                   136m
dev            service/nginx-service                                      NodePort       10.108.97.113  <none>          80:31000/TCP              40m
ingress-nginx  service/ingress-nginx-controller                           NodePort       10.104.104.166 <none>          80:31669/TCP,443:31498/TCP   40m
kube-system    service/kube-dns                                           ClusterIP      10.96.0.10     <none>          53/UDP,53/TCP,9153/TCP     136m
kube-system    service/metrics-server                                     ClusterIP      10.97.234.143  <none>          443/TCP                   40m
uat           service/notes-app-deployment                               ClusterIP      10.111.226.142 <none>          80/TCP                    40m

NAMESPACE      NAME                                                         DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR              AGE
kube-system    daemonset.apps/kube-proxy                                    2         2         2       2            2           kubernetes.io/os-linux     136m
kube-system    daemonset.apps/weave-net                                     2         2         2       2            2           <none>                   136m

NAMESPACE      NAME                                                       READY   UP-TO-DATE   AVAILABLE   AGE
ingress-nginx  deployment.apps/ingress-nginx-controller                    1/1     1            1           40m
kube-system    deployment.apps/coredns                                     2/2     2            2           136m
kube-system    deployment.apps/metrics-server                              1/1     1            1           40m
kube-system    deployment.apps/notes-app-deployment                        2/2     2            2           40m

NAMESPACE      NAME                                                         DESIRED   CURRENT   READY   AGE
ingress-nginx  replicaset.apps/ingress-nginx-controller-55dbd56cfb         1         1         1       40m
kube-system    replicaset.apps/coredns-77d6f4654                            2         2         2       136m
kube-system    replicaset.apps/metrics-server-7ccf778fc5                   2         2         2       40m
kube-system    replicaset.apps/notes-app-deployment-6c564d459fb            2         2         2       40m

NAMESPACE      NAME                                                     STATUS      COMPLETIONS   DURATION   AGE
ingress-nginx  job.batch/ingress-nginx-admission-create                   Complete    1/1         17s       40m
ingress-nginx  job.batch/ingress-nginx-admission-patch                    Complete    1/1         20s       40m

controlplane ~ ➜
──────────────────────────────────────────────

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Exploring Namespaces and Deployments

First, list all namespaces in your cluster with: 
controlplane ~ ➜ k get ns
NAME              STATUS   AGE
default           Active   137m
dev               Active   40m
ingress-nginx     Active   40m
kube-node-lease   Active   137m
kube-public       Active   137m
kube-system       Active   137m
monitoring        Active   40m
qa                Active   40m
staging           Active   40m
test              Active   40m
uat               Active   40m
To inspect the deployments in the User Acceptance Testing (uat) namespace, run: 
controlplane ~ ➜ k get -n uat deployments.apps
NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
notes-app-deployment    2/2     2            2           41m
──────────────────────────────────────────────

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Inspecting a Deployment Manifest

To review a detailed deployment configuration (for example, “notes-app-deployment”), output the full manifest in YAML format. This manifest mirrors the original configuration file that created the Deployment: 
creationTimestamp: "2024-10-20T18:46:54Z"
generation: 1
labels:
  app: notes-app
name: notes-app-deployment
namespace: uat
resourceVersion: "8757"
uid: 7e486af6-f24e-4136-b259-f5e1513dac5f
spec:
  progressDeadlineSeconds: 600
  replicas: 2
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: notes-app
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: notes-app
    spec:
      containers:
        - image: pavnasa/notes-app
          imagePullPolicy: IfNotPresent
          name: notes-app-deployment
          ports:
            - containerPort: 3000
              protocol: TCP
          resources:
            requests:
              cpu: 100m
This YAML output includes all key details such as metadata, specifications, and container configurations.
The manifest output closely resembles the original file used for deployment creation, making it an excellent reference for understanding the resource structure.
──────────────────────────────────────────────

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Filtering Specific Information

Sometimes you only need to extract specific information from the manifest, such as the number of replicas. You have two options:
  1. Using grep:
    This method filters the YAML output for occurrences of the replicas field.     
    controlplane ~ ➜ k get -n uat deployments.apps notes-app-deployment -o yaml | grep replicas
  replicas: 2
  replicas: 2
  2. Using JSONPath:
    For a cleaner output, use the JSONPath flag to extract just the value of replicas.     
    controlplane ~ ➜ k get -n uat deployments.apps notes-app-deployment -o jsonpath="{.spec.replicas}"
2
──────────────────────────────────────────────

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Extracting Container Specifications

To delve deeper into a deployment’s container specifications (such as image, ports, and resource requests), use JSONPath. Since the container configurations are nested under spec.template.spec.containers, running the command below will provide the necessary details: 
controlplane ~ ➜ k get -n uat deployments.apps notes-app-deployment -o jsonpath="{.spec.template.spec.containers}"
[{"image": "pavnasa/notes-app", "imagePullPolicy": "IfNotPresent", "name": "notes-app-deployment", "ports": [{"containerPort":3000, "protocol": "TCP"}], "resources": {"requests": {"cpu": "100m"}}}]
This output displays all container configuration details defined in the Deployment. ──────────────────────────────────────────────

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Summary

In summary, this article covered:
  • How to list cluster resources using kubectl get with or without namespaces.
  • Exploring namespaces and specific deployments in the cluster.
  • Inspecting detailed deployment manifests in YAML format.
  • Extracting specific information (like the number of replicas) using grep or JSONPath.
  • Retrieving container specifications directly from the deployment definition.
For more detailed information and advanced use cases, make sure to visit the official Kubernetes documentation.

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