Guided Exercise: Inspect Kubernetes Resources

Verify the state of an OpenShift cluster by querying its recognized resource types, their schemas, and extracting information from Kubernetes resources that are related to to OpenShift cluster services.

Outcomes

List and explain the supported API resources for a cluster.
Identify resources from specific API groups.
Format command outputs in the YAML and JSON formats.
Use filters to parse command outputs.
Use JSONPath and custom columns to extract information from resources.

As the student user on the workstation machine, use the lab command to prepare your system for this exercise. This command ensures that the cluster is accessible and that all resources are available for this exercise. It also creates a myapp application in the cli-resources project.

[student@workstation ~]$ lab start cli-resources

Procedure 2.2. Instructions

Log in to the OpenShift cluster as the developer user with the developer password. Select the cli-resources project.

 [student@workstation ~]$ oc login -u developer -p developer \
   https://api.ocp4.example.com:6443
 Login successful.
 ...output omitted...

Set the cli-resources project as the active project.

 [student@workstation ~]$ oc project cli-resources
 ...output omitted...

List the available cluster resource types with the api-resources command. Then, use filters to list namespaced and non-namespaced resources.

List the available resource types with the api-resources command.

 [student@workstation ~]$ oc api-resources
 NAME                    SHORTNAMES   APIVERSION   NAMESPACED   KIND
 bindings                             v1           true         Binding
 componentstatuses       cs           v1           false        ComponentStatus
 configmaps              cm           v1           true         ConfigMap
 endpoints               ep           v1           true         Endpoints
 events                  ev           v1           true         Event
 limitranges             limits       v1           true         LimitRange
 namespaces              ns           v1           false        Namespace
 nodes                   no           v1           false        Node
 persistentvolumeclaims  pvc          v1           true         PersistentVolumeClaim
 persistentvolumes       pv           v1           false        PersistentVolume
 pods                    po           v1           true         Pod
 ...output omitted...

The api-resources command prints the supported API resources, including resource names, available shortnames, and the API versions.

Use the --namespaced option to limit the output of the api-resources command to namespaced resources.

Then, determine the number of available namespaced resources. Use the -o name option to list the resource names, and then pipe the output to the wc -l command.

 [student@workstation ~]$ oc api-resources --namespaced
 NAME                    SHORTNAMES   APIVERSION   NAMESPACED   KIND
 bindings                             v1           true         Binding
 configmaps              cm           v1           true         ConfigMap
 endpoints               ep           v1           true         Endpoints
 events                  ev           v1           true         Event
 limitranges             limits       v1           true         LimitRange
 persistentvolumeclaims  pvc          v1           true         PersistentVolumeClaim
 pods                    po           v1           true         Pod
 podtemplates                         v1           true         PodTemplate
 replicationcontrollers  rc           v1           true         ReplicationController
 resourcequotas          quota        v1           true         ResourceQuota
 secrets                              v1           true         Secret
 ...output omitted...
 [student@workstation ~]$ oc api-resources --namespaced -o name | wc -l
 108

The cluster has 108 namespaced cluster resource types, such as the pods, deployments, and services resources.

Limit the output of the api-resources command to non-namespaced resources.

Then, determine the number of available non-namespaced resources. To list the resource names, use the -o name option and then pipe the output to the wc -l command.

 [student@workstation ~]$ oc api-resources --namespaced=false
 NAME                             SHORTNAMES   APIVERSION                       ...
 componentstatuses                cs           v1                               ...
 namespaces                       ns           v1                               ...
 nodes                            no           v1                               ...
 persistentvolumes                pv           v1                               ...
 mutatingwebhookconfigurations                 admissionregistration.k8s.io/v1  ...
 validatingwebhookconfigurations               admissionregistration.k8s.io/v1  ...
 customresourcedefinitions        crd,crds     apiextensions.k8s.io/v1          ...
 ...output omitted...
 [student@workstation ~]$ oc api-resources --namespaced=false -o name | wc -l
 114

The cluster has 114 non-namespaced cluster resource types, such as the nodes, images, and project resources.

Identify and explain the available cluster resource types that the core API group provides. Then, describe a resource from the core API group in the cli-resources project.

List the available resource types with the api-resources command.

 [student@workstation ~]$ oc api-resources
 NAME                    SHORTNAMES   APIVERSION   NAMESPACED   KIND
 bindings                             v1           true         Binding
 componentstatuses       cs           v1           false        ComponentStatus
 configmaps              cm           v1           true         ConfigMap
 endpoints               ep           v1           true         Endpoints
 events                  ev           v1           true         Event
 limitranges             limits       v1           true         LimitRange
 namespaces              ns           v1           false        Namespace
 nodes                   no           v1           false        Node
 persistentvolumeclaims  pvc          v1           true         PersistentVolumeClaim
 persistentvolumes       pv           v1           false        PersistentVolume
 pods                    po           v1           true         Pod
 ...output omitted...
 controllerrevisions                  apps/v1      true         ControllerRevision
 daemonsets              ds           apps/v1      true         DaemonSet
 ...output omitted...
 cronjobs                cj           batch/v1     true         CronJob
 jobs                                 batch/v1     true         Job
 ...output omitted...

You can use the APIVERSIONS field to determine which API group provides the resource. The field lists the group followed by the API version of the resource. For example, the jobs resource type is provided by the batch API group, and v1 is the API version of the resource.

Filter the output of the api-resources command to only show resources from the core API group. Use the --api-group option and set '' as the value.

 [student@workstation ~]$ oc api-resources --api-group ''
 NAME                     SHORTNAMES   APIVERSION   NAMESPACED   KIND
 bindings                              v1           true         Binding
 componentstatuses        cs           v1           false        ComponentStatus
 configmaps               cm           v1           true         ConfigMap
 endpoints                ep           v1           true         Endpoints
 events                   ev           v1           true         Event
 limitranges              limits       v1           true         LimitRange
 namespaces               ns           v1           false        Namespace
 nodes                    no           v1           false        Node
 persistentvolumeclaims   pvc          v1           true         PersistentVolumeClaim
 persistentvolumes        pv           v1           false        PersistentVolume
 pods                     po           v1           true         Pod
 podtemplates                          v1           true         PodTemplate
 replicationcontrollers   rc           v1           true         ReplicationController
 resourcequotas           quota        v1           true         ResourceQuota
 secrets                               v1           true         Secret
 serviceaccounts          sa           v1           true         ServiceAccount
 services                 svc          v1           true         Service

The core API group provides many resource types, such as nodes, events, and pods.

Use the explain command to list a description and the available fields for the pods resource type.

 [student@workstation ~]$ oc explain pods
 KIND:     Pod
 VERSION:  v1

 DESCRIPTION:
      Pod is a collection of containers that can run on a host. This resource is
      created by clients and scheduled onto hosts.

 FIELDS:
    apiVersion    <string>
      APIVersion defines the versioned schema of this representation of an
      object. Servers should convert recognized schemas to the latest internal
      value, and may reject unrecognized values
 ...output omitted...

List all pods in the cli-resources project.

 [student@workstation ~]$ oc get pods
 NAME                     READY   STATUS    RESTARTS   AGE
 myapp-54fcdcd9d7-2h5vx   1/1     Running   0          4m25s

A single pod exists in the cli-resources project. The pod name might differ in your output.

Use the describe command to view the configuration and events for the pod. Specify the pod name from the previous step.

 [student@workstation ~]$ oc describe pod myapp-54fcdcd9d7-2h5vx
 Name:             myapp-54fcdcd9d7-2h5vx
 Namespace:        cli-resources
 ...output omitted...
 Status:           Running
 IP:               10.8.0.127
 IPs:
   IP:           10.8.0.127
 Controlled By:  ReplicaSet/myapp-54fcdcd9d7
 Containers:
   myapp:
     Container ID:   cri-o://e0da...669d
     Image:          registry.ocp4.example.com:8443/ubi8/httpd-24:1-215
     Image ID:       registry.ocp4.example.com:8443/ubi8/httpd-24@sha256:91ad...fd83
 ...output omitted...
     Limits:
       cpu:     500m
       memory:  128Mi
     Requests:
       cpu:        500m
       memory:     128Mi
     Environment:  <none>
 ...output omitted...
 Events:
   Type    Reason          Age    From               Message
   ----    ------          ----   ----               -------
   Normal  Scheduled       10m    default-scheduler  Successfully assigned cli-resources/myapp-54fcdcd9d7-2h5vx to master01
 ....output omitted...

Retrieve the details of the pod in a structured format. Use the get command and specify the output as the YAML format. Compare the results of the describe command versus the get command.

 [student@workstation ~]$ oc get pod myapp-54fcdcd9d7-2h5vx -o yaml
 apiVersion: v1
 kind: Pod
 metadata:
   annotations:
 ...output omitted...
   labels:
     app: myapp
     pod-template-hash: 54fcdcd9d7
   name: myapp-54fcdcd9d7-2h5vx
   namespace: cli-resources
 ...output omitted...
 spec:
   containers:
   - image: registry.ocp4.example.com:8443/ubi8/httpd-24:1-215
     imagePullPolicy: Always
     name: myapp
     resources:
       limits:
         cpu: 500m
         memory: 128Mi
       requests:
         cpu: 500m
         memory: 128Mi
 ...output omitted...

Using a structured format with the get command provides more details about a resource than the describe command.

Identify and explain the available cluster resource types that the Kubernetes apps API group provides. Then, describe a resource from the apps API group in the cli-resources project.

List the resource types that the apps API group provides.

 [student@workstation ~]$ oc api-resources --api-group apps
 NAME                  SHORTNAMES   APIVERSION   NAMESPACED   KIND
 controllerrevisions                apps/v1      true         ControllerRevision
 daemonsets            ds           apps/v1      true         DaemonSet
 deployments           deploy       apps/v1      true         Deployment
 replicasets           rs           apps/v1      true         ReplicaSet
 statefulsets          sts          apps/v1      true         StatefulSet

Use the explain command to list a description and fields for the deployments resource type.

 [student@workstation ~]$ oc explain deployments
 KIND:     Deployment
 VERSION:  apps/v1

 DESCRIPTION:
      Deployment enables declarative updates for Pods and ReplicaSets.

 FIELDS:
    apiVersion    <string>
      APIVersion defines the versioned schema of this representation of an
      object. Servers should convert recognized schemas to the latest internal
      value, and may reject unrecognized values.
 ...output omitted...

Use the get command to identify any deployment resources in the cli-resources project.

 [student@workstation ~]$ oc get deploy
 NAME    READY   UP-TO-DATE   AVAILABLE   AGE
 myapp   1/1     1            1           25m

The myapp deployment exists in the cli-resources project. Use the get command and the -o wide option to identify the container name and the container image in the deployment.
```
 [student@workstation ~]$ oc get deploy myapp -o wide
 NAME  ... CONTAINERS IMAGES                                              SELECTOR
 myapp ... myapp      registry.ocp4.example.com:8443/ubi8/httpd-24:1-215  app=myapp
```
The myapp deployment uses the registry.ocp4.example.com:8443/ubi8/httpd-24:1-215 container image for the myapp container.

Describe the myapp deployment to view more details about the resource.

 [student@workstation ~]$ oc describe deployment myapp
 Name:                   myapp
 Namespace:              cli-resources
 CreationTimestamp:      Wed, 01 Mar 2023 18:41:39 -0500
 Labels:                 my-app
 Annotations:            deployment.kubernetes.io/revision: 1
 Selector:               app=myapp
 Replicas:               1 desired | 1 updated | 1 total | 1 available | 0 unavailable
 StrategyType:           RollingUpdate
 MinReadySeconds:        0
 RollingUpdateStrategy:  25% max unavailable, 25% max surge
 Pod Template:
   Labels:  app=myapp
   Containers:
    myapp:
     Image:      registry.ocp4.example.com:8443/ubi8/httpd-24:1-215
     Port:       8080
     Host Port:  8080
     Limits:
       cpu:        500m
       memory:     128Mi
     Environment:  <none>
     Mounts:       <none>
   Volumes:        <none>
 Conditions:
   Type           Status  Reason
   ----           ------  ------
   Available      True    MinimumReplicasAvailable
   Progressing    True    NewReplicaSetAvailable
 OldReplicaSets:  <none>
 NewReplicaSet:   myapp-54fcdcd9d7 (1/1 replicas created)
 Events:
   Type    Reason             Age   From                   Message
   ----    ------             ----  ----                   -------
   Normal  ScalingReplicaSet  30m   deployment-controller  Scaled up replica set myapp-54fcdcd9d7 to 1

Identify and explain the available cluster resource types that the OpenShift configuration API group provides. Then, describe a resource from the OpenShift configuration API group.

List the resource types that the OpenShift configuration API group provides.

 [student@workstation ~]$ oc api-resources --api-group config.openshift.io
 NAME                 SHORTNAMES  APIVERSION              NAMESPACED KIND
 apiservers                       config.openshift.io/v1  false      APIServer
 authentications                  config.openshift.io/v1  false      Authentication
 builds                           config.openshift.io/v1  false      Build
 clusteroperators     co          config.openshift.io/v1  false      ClusterOperator
 clusterversions                  config.openshift.io/v1  false      ClusterVersion
 consoles                         config.openshift.io/v1  false      Console
 dnses                            config.openshift.io/v1  false      DNS
 featuregates                     config.openshift.io/v1  false      FeatureGate
 imagecontentpolicies             config.openshift.io/v1  false      ImageContentPolicy
 images                           config.openshift.io/v1  false      Image
 infrastructures                  config.openshift.io/v1  false      Infrastructure
 ingresses                        config.openshift.io/v1  false      Ingress
 networks                         config.openshift.io/v1  false      Network
 nodes                            config.openshift.io/v1  false      Node
 oauths                           config.openshift.io/v1  false      OAuth
 operatorhubs                     config.openshift.io/v1  false      OperatorHub
 projects                         config.openshift.io/v1  false      Project
 proxies                          config.openshift.io/v1  false      Proxy
 schedulers                       config.openshift.io/v1  false      Scheduler

The config.openshift.io API group provides multiple, non-namespaced resource types.

Use the explain command to list a description and fields for the projects resource type.

 [student@workstation ~]$ oc explain projects
 KIND:     Project
 VERSION:  project.openshift.io/v1

 DESCRIPTION:
      Projects are the unit of isolation and collaboration in OpenShift. A
      project has one or more members, a quota on the resources that the project
      may consume, and the security controls on the resources in the project.
      Within a project, members may have different roles - project administrators
      can set membership, editors can create and manage the resources, and
      viewers can see but not access running containers. In a normal cluster
      project administrators are not able to alter their quotas - that is
      restricted to cluster administrators.

      Listing or watching projects will return only projects the user has the
      reader role on.
 ...output omitted...

Describe the cli-resources project.

 [student@workstation ~]$ oc describe project cli-resources
 Name:            cli-resources
 Created:        10 minutes ago
 Labels:            kubernetes.io/metadata.name=cli-resources
             pod-security.kubernetes.io/audit=restricted
             pod-security.kubernetes.io/audit-version=v1.24
             pod-security.kubernetes.io/warn=restricted
             pod-security.kubernetes.io/warn-version=v1.24
 Annotations:        openshift.io/description=
             openshift.io/display-name=
             openshift.io/requester=system:admin
             openshift.io/sa.scc.mcs=s0:c27,c4
             openshift.io/sa.scc.supplemental-groups=1000710000/10000
             openshift.io/sa.scc.uid-range=1000710000/10000
 Display Name:        <none>
 Description:        <none>
 Status:            Active
 Node Selector:        <none>
 Quota:            <none>
 Resource limits:    <none>

Retrieve more details of the cli-resources project. Use the get command, and format the output to use JSON.

 [student@workstation ~]$ oc get project cli-resources -o json
 {
     "apiVersion": "project.openshift.io/v1",
     "kind": "Project",
     "metadata": {
 ...output omitted....
         "labels": {
             "kubernetes.io/metadata.name": "cli-resources",
             "pod-security.kubernetes.io/audit": "restricted",
             "pod-security.kubernetes.io/audit-version": "v1.24",
             "pod-security.kubernetes.io/warn": "restricted",
             "pod-security.kubernetes.io/warn-version": "v1.24"
         },
         "name": "cli-resources",
         "resourceVersion": "705313",
         "uid": "53cbbe45-31ea-4b41-93a9-4ba5c2c4c1f3"
     },
 ...output omitted...
     "status": {
         "phase": "Active"
     }
 }

The get command provides additional details, such as the kind and apiVersion attributes, of the project resource.

Verify the cluster status by inspecting cluster services. Format command outputs by using filters.

Retrieve the list of pods for the Etcd operator. The Etcd operator is available in the openshift-etcd namespace. Specify the namespace with the --namespace or -n option.

 [student@workstation ~]$ oc get pods -n openshift-etcd
 Error from server (Forbidden): pods is forbidden: User "developer" cannot list resource "pods" in API group "" in the namespace "openshift-etcd"

The developer user cannot access resources in the openshift-etcd namespace. Regular cluster users, such as the developer user, cannot query resources in the openshift- namespaces.

Log in as the admin user with the redhatocp password. Then, retrieve the list of pods in the openshift-etcd namespace.

 [student@workstation ~]$ oc login -u admin -p redhatocp
 Login successful
 ...output omitted...
 [student@workstation ~]$ oc get pods -n openshift-etcd
 NAME                   READY   STATUS      RESTARTS   AGE
 etcd-master01          4/4     Running     36         25d
 installer-2-master01   0/1     Completed   0          25d
 installer-3-master01   0/1     Completed   0          25d

Retrieve the conditions status of the etcd-master01 pod in the openshift-etcd namespace. Use filters to limit the output to the .status.conditions attribute of the pod. Compare the outputs of the JSONPath and jq filters.

 [student@workstation ~]$ oc get pods etcd-master01 -n openshift-etcd \
   -o=jsonpath='{.status.conditions}{"\n"}'
 [{"lastProbeTime":null,"lastTransitionTime":"2023-03-07T18:05:13Z",
 "status":"True","type":"Initialized"},{"lastProbeTime":null,
 "lastTransitionTime":"2023-03-07T18:05:28Z","status":"True","type":"Ready"},
 {"lastProbeTime":null,"lastTransitionTime":"2023-03-07T18:05:28Z",
 "status":"True","type":"ContainersReady"},
 {"lastProbeTime":null,"lastTransitionTime":"2023-03-07T18:05:06Z",
 "status":"True","type":"PodScheduled"}]

 [student@workstation ~]$ oc get pods -n openshift-etcd etcd-master01 \
   -o json | jq .status.conditions
 [
   {
     "lastProbeTime": null,
     "lastTransitionTime": "2023-03-07T18:05:13Z",
     "status": "True",
     "type": "Initialized"
   },
   {
     "lastProbeTime": null,
     "lastTransitionTime": "2023-03-07T18:05:28Z",
     "status": "True",
     "type": "Ready"
   },
   {
     "lastProbeTime": null,
     "lastTransitionTime": "2023-03-07T18:05:28Z",
     "status": "True",
     "type": "ContainersReady"
   },
   {
     "lastProbeTime": null,
     "lastTransitionTime": "2023-03-07T18:05:06Z",
     "status": "True",
     "type": "PodScheduled"
   }
 ]

Using the JSON format and the jq filter provides a structured output for the .status.conditions attribute.

Retrieve the condition status of the prometheus-k8s-0 pod in the openshift-monitoring namespace. Configure the output to use the YAML format, and then filter the output with the yq filter.

 [student@workstation ~]$ oc get pods -n openshift-monitoring prometheus-k8s-0 \
   -o yaml |  yq r - 'status.conditions'
 - lastProbeTime: null
   lastTransitionTime: "2023-03-07T18:07:17Z"
   status: "True"
   type: Initialized
 - lastProbeTime: null
   lastTransitionTime: "2023-03-07T18:07:45Z"
   status: "True"
   type: Ready
 - lastProbeTime: null
   lastTransitionTime: "2023-03-07T18:07:45Z"
   status: "True"
   type: ContainersReady
 - lastProbeTime: null
   lastTransitionTime: "2023-02-09T22:39:52Z"
   status: "True"
   type: PodScheduled

The r - option tells the yq command to read the standard input (STDIN) for the YAML output of the get command.

Use the get command to retrieve detailed information for the pods in the openshift-storage namespace. Use the YAML format and custom columns to filter the output according to the following table:

| Column title | Object | | --- | --- | | Pod | metadata.name | | API | apiVersion | | Container | spec.containers[].name | | Phase | status.phase | | IP | status.podIP | | Ports | spec.containers[].ports[].containerPort |

 [student@workstation ~]$ oc get pods -n openshift-storage -o yaml \
   -o custom-columns=PodName:".metadata.name",\
 ContainerName:"spec.containers[].name",\
 Phase:"status.phase",\
 IP:"status.podIP",\
 Ports:"spec.containers[].ports[].containerPort"
 PodName                      ContainerName       Phase    IP          Ports
 lvm-operator-controller-...  kube-rbac-proxy     Running  10.8.0.97   8443
 topolvm-controller-....      topolvm-controller  Running  10.8.0.98   9808
 topolvm-node-9spzf           lvmd                Running  10.8.0.100  <none>
 vg-manager-z8g5k             vg-manager          Running  10.8.0.101  <none>

Finish

On the workstation machine, use the lab command to complete this exercise. This step is important to ensure that resources from previous exercises do not impact upcoming exercises.

[student@workstation ~]$ lab finish cli-resources

Guided Exercise: Inspect Kubernetes Resources

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