Kubernetes基础：Pod的详细介绍

apiVersion: v1
kind: Pod
metadata:
  name: first-pod
  labels:
    app: bash
    tir: backend
spec:
  containers:
  - name: bash-container
    image: docker.io/busybox
    command: ['sh', '-c', 'echo Hello Kubernetes! && sleep 3600']

[root@devops-101 ~]# kubectl explain pod
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. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#resources

   kind <string>
     Kind is a string value representing the REST resource this object
     represents. Servers may infer this from the endpoint the client submits
     requests to. Cannot be updated. In CamelCase. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#types-kinds

   metadata <Object>
     Standard object's metadata. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata

   spec <Object>
     Specification of the desired behavior of the pod. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status

   status   <Object>
     Most recently observed status of the pod. This data may not be up to date.
     Populated by the system. Read-only. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status
[root@devops-101 ~]# kubectl explain pod.spec
KIND:     Pod
VERSION:  v1

RESOURCE: spec <Object>

DESCRIPTION:
     Specification of the desired behavior of the pod. More info:
     https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status

     PodSpec is a description of a pod.

FIELDS:
   activeDeadlineSeconds    <integer>
     Optional duration in seconds the pod may be active on the node relative to
     StartTime before the system will actively try to mark it failed and kill
     associated containers. Value must be a positive integer.

   affinity <Object>
     If specified, the pod's scheduling constraints

   automountServiceAccountToken <boolean>
     AutomountServiceAccountToken indicates whether a service account token
     should be automatically mounted.

$ kubectl create -f first-pod.yml 

[root@devops-101 ~]# kubectl get pod first-pod -o yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: 2018-08-08T01:45:16Z
  labels:
    app: bash
  name: first-pod
  namespace: default
  resourceVersion: "184988"
  selfLink: /api/v1/namespaces/default/pods/first-pod
  uid: b2d3d2b7-9aac-11e8-84f4-080027b7c4e9
spec:
  containers:
  - command:
    - sh
    - -c
    - echo Hello Kubernetes! && sleep 3600
    image: docker.io/busybox
    imagePullPolicy: Always
    name: bash-container
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: default-token-trvqv
      readOnly: true
  dnsPolicy: ClusterFirst
  nodeName: devops-102
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - name: default-token-trvqv
    secret:
      defaultMode: 420
      secretName: default-token-trvqv
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: 2018-08-08T01:45:16Z
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: 2018-08-08T01:45:16Z
    message: 'containers with unready status: [bash-container]'
    reason: ContainersNotReady
    status: "False"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: null
    message: 'containers with unready status: [bash-container]'
    reason: ContainersNotReady
    status: "False"
    type: ContainersReady
  - lastProbeTime: null
    lastTransitionTime: 2018-08-08T01:45:16Z
    status: "True"
    type: PodScheduled
  containerStatuses:
  - image: docker.io/busybox
    imageID: ""
    lastState: {}
    name: bash-container
    ready: false
    restartCount: 0
    state:
      waiting:
        reason: ContainerCreating
  hostIP: 192.168.0.102
  phase: Pending
  qosClass: BestEffort
  startTime: 2018-08-08T01:45:16Z

[root@devops-101 ~]# kubectl logs first-pod
Hello Kubernetes!

[root@devops-101 ~]# kubectl get pods --show-labels
NAME        READY     STATUS    RESTARTS   AGE       LABELS
first-pod   1/1       Running   0          15m       app=bash

[root@devops-101 ~]# kubectl create -f first-pod.yml 
pod/second-pod created
[root@devops-101 ~]# kubectl get pods --show-labels
NAME         READY     STATUS              RESTARTS   AGE       LABELS
first-pod    1/1       Running             0          17m       app=bash
second-pod   0/1       ContainerCreating   0          20s       app=bash,tir=backend

[root@devops-101 ~]# kubectl get pods -l tir=backend --show-labels
NAME         READY     STATUS    RESTARTS   AGE       LABELS
second-pod   1/1       Running   0          1m        app=bash,tir=backend

[root@devops-101 ~]# kubectl label pod first-pod tir=frontend
pod/first-pod labeled
[root@devops-101 ~]# kubectl get pods --show-labels
NAME         READY     STATUS    RESTARTS   AGE       LABELS
first-pod    1/1       Running   0          24m       app=bash,tir=frontend
second-pod   1/1       Running   0          7m        app=bash,tir=backend

[root@devops-101 ~]# kubectl label pod first-pod tir=unkonwn --overwrite
pod/first-pod labeled
[root@devops-101 ~]# kubectl get pods --show-labels
NAME         READY     STATUS    RESTARTS   AGE       LABELS
first-pod    1/1       Running   0          25m       app=bash,tir=unkonwn
second-pod   1/1       Running   0          8m        app=bash,tir=backend

[root@devops-101 ~]# kubectl get pods -L app,tir
NAME         READY     STATUS    RESTARTS   AGE       APP       TIR
first-pod    1/1       Running   0          26m       bash      unkonwn
second-pod   1/1       Running   0          9m        bash      backend

[root@devops-101 ~]# kubectl delete pods first-pod
pod "first-pod" deleted

[root@devops-101 ~]# kubectl delete pods -l tir=backend
pod "second-pod" deleted

[root@devops-101 ~]# kubectl explain pod.spec.initContainers
KIND:     Pod
VERSION:  v1

RESOURCE: initContainers <[]Object>

DESCRIPTION:
     List of initialization containers belonging to the pod. Init containers are
     executed in order prior to containers being started. If any init container
     fails, the pod is considered to have failed and is handled according to its
     restartPolicy. The name for an init container or normal container must be
     unique among all containers. Init containers may not have Lifecycle
     actions, Readiness probes, or Liveness probes. The resourceRequirements of
     an init container are taken into account during scheduling by finding the
     highest request/limit for each resource type, and then using the max of of
     that value or the sum of the normal containers. Limits are applied to init
     containers in a similar fashion. Init containers cannot currently be added
     or removed. Cannot be updated. More info:
     https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

     A single application container that you want to run within a pod.

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: docker.io/busybox
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: docker.io/busybox
    command: ['sh', '-c', 'echo init-service && sleep 2']
  - name: init-mydb
    image: docker.io/busybox
    command: ['sh', '-c', 'echo init-mydb && sleep 2']

podpreset.admission.kubernetes.io/exclude: "true"