To manage a Kubernetes cluster, you need to know some basic commands to be able to manage the cluster. Below are basic command lines to manage pods, nodes, services, etc.

Pods

kubectl get pods is a command-line tool used in Kubernetes, a popular container orchestration platform, to retrieve information about pods that are running within a cluster. Pods are the smallest deployable units in Kubernetes and can contain one or more containers.

When you run the kubectl get pods command, it queries the Kubernetes API server for information about the pods within the current context or specified namespace. The output of this command will typically display a table containing various columns that provide information about each pod. The columns might include:

NAME: The name of the pod.
READY: This column shows the number of containers in the pod that are ready out of the total number of containers.
STATUS: The current status of the pod, which can be “Running,” “Pending,” “Succeeded,” “Failed,” or “Unknown.”
RESTARTS: The number of times the containers in the pod have been restarted.
AGE: The amount of time that the pod has been running since its creation.
IP: The IP address assigned to the pod within the cluster network.
NODE: The name of the node where the pod is scheduled to run.

Here’s an example output of the kubectl get pods command:

kubectl get pods

Output:

[rahil@k8s-master-node ~]$ kubectl get pods
NAME                     READY     STATUS    RESTARTS   AGE
nginx-7587c6fdb6-dz7tj   1/1       Running   0          29m

The below command will watch for events and provide you status on console.

kubectl get pods -w

Output:

[rahil@k8s-master-node ~]$ kubectl get pods -w
NAME                     READY     STATUS              RESTARTS   AGE
nginx-7587c6fdb6-dz7tj   0/1       ContainerCreating   0          20s
nginx-7587c6fdb6-dz7tj   1/1       Running   0         58s

If you like to see more details on individual pods, you can use kubectl describe.

kubectl describe pods <pod_name>

Output:

[rahil@k8s-master-node ~]$ kubectl describe pods nginx
Name:           nginx-7587c6fdb6-dz7tj
Namespace:      default
Node:           k8s-worker-node-1/192.168.0.226
Start Time:     Sun, 25 Feb 2018 17:06:46 -0500
Labels:         pod-template-hash=3143729862
                run=nginx
Annotations:    <none>
Status:         Running
IP:             10.244.1.2
Controlled By:  ReplicaSet/nginx-7587c6fdb6
Containers:
  nginx:
    Container ID:   docker://22a5e181b9c7b56351ccdc9ed41c1f6dfd776e56d45e464399d9a92479657a18
    Image:          nginx
    Image ID:       docker-pullable://docker.io/nginx@sha256:4771d09578c7c6a65299e110b3ee1c0a2592f5ea2618d23e4ffe7a4cab1ce5de
    Port:           80/TCP
    State:          Running
      Started:      Sun, 25 Feb 2018 17:07:42 -0500
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-jpflm (ro)
Conditions:
  Type           Status
  Initialized    True
  Ready          True
  PodScheduled   True
Volumes:
  default-token-jpflm:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-jpflm
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason                 Age   From                        Message
  ----    ------                 ----  ----                        -------
  Normal  Scheduled              6m    default-scheduler           Successfully assigned nginx-7587c6fdb6-dz7tj to k8s-worker-node-1
  Normal  SuccessfulMountVolume  6m    kubelet, k8s-worker-node-1  MountVolume.SetUp succeeded for volume "default-token-jpflm"
  Normal  Pulling                6m    kubelet, k8s-worker-node-1  pulling image "nginx"
  Normal  Pulled                 6m    kubelet, k8s-worker-node-1  Successfully pulled image "nginx"
  Normal  Created                6m    kubelet, k8s-worker-node-1  Created container
  Normal  Started                5m    kubelet, k8s-worker-node-1  Started container

Nodes

The below command will get all the nodes.

kubectl get nodes

Output:

[rahil@k8s-master-node ~]$ kubectl get nodes
NAME                STATUS    ROLES     AGE       VERSION
k8s-master-node     Ready     master    3h        v1.9.3
k8s-worker-node-1   Ready     <none>    2h        v1.9.3

The below command will provide you with all the information about nodes in table view mode.

kubectl get nodes -o wide

Output:

[rahil@k8s-master-node ~]$ kubectl get nodes -o wide
NAME                STATUS    ROLES     AGE       VERSION   EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION               CONTAINER-RUNTIME
k8s-master-node     Ready     master    3h        v1.9.3    <none>        CentOS Linux 7 (Core)   3.10.0-693.17.1.el7.x86_64   docker://1.12.6
k8s-worker-node-1   Ready     <none>    2h        v1.9.3    <none>        CentOS Linux 7 (Core)   3.10.0-693.17.1.el7.x86_64   docker://1.12.6

The below command will provide you with detail about a node.

kubectl describe nodes <node_name>

Output:

[rahil@k8s-master-node ~]$ kubectl describe nodes k8s-worker-node-1
Name:               k8s-worker-node-1
Roles:              <none>
Labels:             beta.kubernetes.io/arch=amd64
                    beta.kubernetes.io/os=linux
                    kubernetes.io/hostname=k8s-worker-node-1
Annotations:        flannel.alpha.coreos.com/backend-data={"VtepMAC":"d2:bd:02:7a:cb:65"}
                    flannel.alpha.coreos.com/backend-type=vxlan
                    flannel.alpha.coreos.com/kube-subnet-manager=true
                    flannel.alpha.coreos.com/public-ip=192.168.0.226
                    node.alpha.kubernetes.io/ttl=0
                    volumes.kubernetes.io/controller-managed-attach-detach=true
Taints:             <none>
CreationTimestamp:  Sun, 25 Feb 2018 14:42:46 -0500
Conditions:
  Type             Status  LastHeartbeatTime                 LastTransitionTime                Reason                       Message
  ----             ------  -----------------                 ------------------                ------                       -------
  OutOfDisk        False   Sun, 25 Feb 2018 17:22:32 -0500   Sun, 25 Feb 2018 14:42:46 -0500   KubeletHasSufficientDisk     kubelet has sufficient disk space available
  MemoryPressure   False   Sun, 25 Feb 2018 17:22:32 -0500   Sun, 25 Feb 2018 14:42:46 -0500   KubeletHasSufficientMemory   kubelet has sufficient memory available
  DiskPressure     False   Sun, 25 Feb 2018 17:22:32 -0500   Sun, 25 Feb 2018 14:42:46 -0500   KubeletHasNoDiskPressure     kubelet has no disk pressure
  Ready            True    Sun, 25 Feb 2018 17:22:32 -0500   Sun, 25 Feb 2018 14:44:06 -0500   KubeletReady                 kubelet is posting ready status
Addresses:
  InternalIP:  192.168.0.226
  Hostname:    k8s-worker-node-1
Capacity:
 cpu:     2
 memory:  916556Ki
 pods:    110
Allocatable:
 cpu:     2
 memory:  814156Ki
 pods:    110
System Info:
 Machine ID:                 46a73b56be064f2fb8d81ac54f2e0349
 System UUID:                8601D8C9-C1D9-2C4B-B6C9-2A3D2A598E4A
 Boot ID:                    963f0791-c81c-4bb1-aecd-6bd079abea67
 Kernel Version:             3.10.0-693.17.1.el7.x86_64
 OS Image:                   CentOS Linux 7 (Core)
 Operating System:           linux
 Architecture:               amd64
 Container Runtime Version:  docker://1.12.6
 Kubelet Version:            v1.9.3
 Kube-Proxy Version:         v1.9.3
PodCIDR:                     10.244.1.0/24
ExternalID:                  k8s-worker-node-1
Non-terminated Pods:         (3 in total)
  Namespace                  Name                      CPU Requests  CPU Limits  Memory Requests  Memory Limits
  ---------                  ----                      ------------  ----------  ---------------  -------------
  default                    nginx-7587c6fdb6-dz7tj    0 (0%)        0 (0%)      0 (0%)           0 (0%)
  kube-system                kube-flannel-ds-wtdz4     100m (5%)     100m (5%)   50Mi (6%)        50Mi (6%)
  kube-system                kube-proxy-m2hfm          0 (0%)        0 (0%)      0 (0%)           0 (0%)
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  CPU Requests  CPU Limits  Memory Requests  Memory Limits
  ------------  ----------  ---------------  -------------
  100m (5%)     100m (5%)   50Mi (6%)        50Mi (6%)
Events:         <none>

Services

The below command will give you all the available services in default namespace.

kubectl get services

Output:

[rahil@k8s-master-node ~]$ kubectl get services
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   3h

The below command will give you all the services in all namespaces.

kubectl get services --all-namespaces

Output:

[rahil@k8s-master-node ~]$ kubectl get services --all-namespaces
NAMESPACE     NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)         AGE
default       kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP         3h
kube-system   kube-dns     ClusterIP   10.96.0.10   <none>        53/UDP,53/TCP   3h

Kubernetes Command line

Pods

Nodes

Services

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Pods

Nodes

Services

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