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Creating Single-Container Pods

• Creating a pod
• Viewing a pod
• Deleting a pod

A pod is a group of containers that are scheduled onto the same host. Pods serve as units of scheduling, deployment, and horizontal scaling/replication. Pods share fate, and share some resources, such as storage volumes and IP addresses.

Creating a pod

Single-container pods can be created with the run command. The pod’s properties are specified with flags on the command line.

The run command creates a Deployment to monitor the pod(s). The Deployment watches for failed pods and will start up new pods as required to maintain the specified number.

Note: If you don’t want a Deployment to monitor your pod (e.g. your pod is writing non-persistent data which won’t survive a restart, or your pod is intended to be very short-lived), you can create a pod directly with the create command.

To create a pod using the run command:

$ kubectl run NAME
    --image=image
    [--port=port]
    [--replicas=replicas]
    [--labels=key=value,key=value,...]

Where:

• kubectl run creates a Deployment named “nginx” on Kubernetes cluster >= v1.2. If you are running older versions, it creates replication controllers instead. If you want to obtain the old behavior, use --generator=run/v1 to create replication controllers. See kubectl run for more details.

• NAME (required) is the name of the container to create. This value is also applied as the name of the Deployment, and as the prefix of the pod name. For example:

  $ kubectl run example --image=nginx
  deployment "example" created
  
  $ kubectl get pods -l run=example
  NAME                       READY     STATUS    RESTARTS   AGE
  example-1934187764-scau1   1/1       Running   0          13s
  

• --image=IMAGE (required) is the Docker container image to use for this container.
• --port=PORT is the port to expose on the container.
• --replicas=NUM is the number of replicated pods to create. If not specified, one pod will be created.
• --labels=key=value specifies one or more labels to attach to the pod. In addition to any labels specified here, run attaches a label of the format run=NAME. This is used by the Deployment to target the pods created by the command.

There are additional flags that can be specified. For a complete list, run:

$ kubectl run --help

Viewing a pod

To view a specific pod, use the kubectl get command:

$ kubectl get pod NAME
NAME      READY   STATUS    RESTARTS   AGE
example   1/1     Running   0          2d

To return the name of the node on which the pod is scheduled, use the -o wide option:

$ kubectl get pod NAME -o wide
NAME      READY   STATUS    RESTARTS   AGE   NODE
example   1/1     Running   0          2d    gke-example-c6a38-node-xij3

For more details about a pod, including events, use describe in place of get:

$ kubectl describe pod NAME
Name:        example
Namespace:   default
Image(s):    kubernetes/example-php-redis:v2
Node:        gke-example-c6a38461-node-xij3/10.240.34.183
Labels:      name=frontend
Status:      Running
Reason:
Message:
IP:          10.188.2.10
Replication Controllers:  example (5/5 replicas created)
Containers:
  php-redis:
    Image:   kubernetes/example-php-redis:v2
    Limits:
      cpu:   100m
    State:   Running
      Started:   Tue, 04 Aug 2015 09:02:46 -0700
    Ready:   True
    Restart Count: 0
Conditions:
  Type    Status
  Ready   True
Events:
  FirstSeen                       LastSeen                        Coun From                                     SubobjectPath            Reason  Message
  Thu, 06 Aug 2015 11:49:44 -0700 Thu, 06 Aug 2015 11:49:44 -0700 1    {kubelet gke-example-c6a38461-node-xij3} spec.containers{example} started Started with docker id 5705bffa65e2

To list all pods running on a cluster:

$ kubectl get pods

NAME                 READY     STATUS    RESTARTS   AGE
example-xypvc        1/1       Running   0          1m
frontend-7kdod       1/1       Running   0          1d

Deleting a pod

If your pod was created using the run command, kubernetes creates a Deployment to manage the pod. Pods managed by a Deployment are rescheduled if they go away, including being deleted by kubectl delete pod. To permanently delete the pod, delete its Deployment.

First, find the Deployment’s name:

$ kubectl get deployment 
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
example   1         1         1            1           1m

Then, delete the Deployment:

$ kubectl delete deployment DEPLOYMENT_NAME