一、Pod管理

• Pod是可以创建和管理Kubernetes计算的最小可部署单元，一个Pod代表着集群
中运行的一个进程，每个pod都有一个唯一的ip。
• 一个pod类似一个豌豆荚，包含一个或多个容器（通常是docker），多个容器间
共享IPC、Network和UTC namespace。

[root@k8s1 ~]# kubectl run demo --image=nginx
pod/demo created
[root@k8s1 ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
demo   1/1     Running   0          55s
[root@k8s1 ~]# kubectl get pod -o wide
NAME   READY   STATUS    RESTARTS   AGE     IP           NODE   NOMINATED NODE   READINESS GATES
demo   1/1     Running   0          4m46s   10.244.2.2   k8s3   <none>           <none>

kubectl scale deployment demo --replicas=1这是它的一个控制器，可以控制pod的数量，我们可以对其进行扩容和缩容，根据我们的需求

[root@k8s1 ~]# kubectl create deployment demo --image=nginx
deployment.apps/demo created
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS              RESTARTS   AGE
demo-6c54f77c95-tkvfv   0/1     ContainerCreating   0          13s
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS              RESTARTS   AGE
demo-6c54f77c95-tkvfv   0/1     ContainerCreating   0          17s
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS              RESTARTS   AGE
demo-6c54f77c95-tkvfv   0/1     ContainerCreating   0          23s
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS    RESTARTS   AGE
demo-6c54f77c95-tkvfv   1/1     Running   0          28s
[root@k8s1 ~]# kubectl delete pod demo-6c54f77c95-tkvfv 
pod "demo-6c54f77c95-tkvfv" deleted
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS              RESTARTS   AGE
demo-6c54f77c95-h2db7   0/1     ContainerCreating   0          3s
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS    RESTARTS   AGE
demo-6c54f77c95-h2db7   1/1     Running   0          15s
[root@k8s1 ~]# kubectl scale deployment demo --replicas=3
deployment.apps/demo scaled
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS              RESTARTS   AGE
demo-6c54f77c95-2f7gh   0/1     ContainerCreating   0          7s
demo-6c54f77c95-h2db7   1/1     Running             0          49s
demo-6c54f77c95-m2tj6   0/1     ContainerCreating   0          7s
[root@k8s1 ~]# kubectl get pod
NAME                    READY   STATUS    RESTARTS   AGE
demo-6c54f77c95-2f7gh   1/1     Running   0          21s
demo-6c54f77c95-h2db7   1/1     Running   0          63s
demo-6c54f77c95-m2tj6   1/1     Running   0          21s

kubectl expose deployment demo --port=80 --target-port=80可以将其发布出去，并且暴露端口，svc可以起到pod的负载均衡的作用，由于现在我们只有一个pod，所以在这里体现不出来

[root@k8s1 ~]# kubectl expose deployment demo --port=80 --target-port=80
service/demo exposed
[root@k8s1 ~]# kubectl get svc
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
demo         ClusterIP   10.102.98.54   <none>        80/TCP    10s
kubernetes   ClusterIP   10.96.0.1      <none>        443/TCP   9h
[root@k8s1 ~]# kubectl describe svc demo 
Name:              demo
Namespace:         default
Labels:            app=demo
Annotations:       <none>
Selector:          app=demo
Type:              ClusterIP
IP Family Policy:  SingleStack
IP Families:       IPv4
IP:                10.102.98.54
IPs:               10.102.98.54
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.244.2.4:80
Session Affinity:  None
Events:            <none>
[root@k8s1 ~]# kubectl delete svc demo 
service "demo" deleted

二、资源清单

pod.yaml/中的就是标准化的资源定义，

[root@k8s1 ~]# kubectl delete -f pod.yaml 
pod "demo" deleted
[root@k8s1 ~]# cat pod.yaml 
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: demo
  name: demo
spec:
  containers:
  - image: nginx
    name: demo
    resources: {}

我们对其做资源限制，比如限制cpu或者内存，这个点在以后会比较重要

[root@k8s1 ~]# kubectl describe pod demo 
Name:             demo
Namespace:        default
Priority:         0
Service Account:  default
Node:             k8s3/192.168.1.13
Start Time:       Sun, 13 Nov 2022 02:26:50 +0800
Labels:           run=demo
Annotations:      <none>
Status:           Running
IP:               10.244.2.5
IPs:
  IP:  10.244.2.5
Containers:
  demo:
    Container ID:   docker://827337d551044d248111a4729644b11d9f259abe373f4b72ac7df36286012385
    Image:          nginx
    Image ID:       docker-pullable://nginx@sha256:bab399017a659799204147065aab53838ca6f5aeed88cf7d329bc4fda1d2bac7
    Port:           80/TCP
    Host Port:      80/TCP
    State:          Running
      Started:      Sun, 13 Nov 2022 02:27:06 +0800
    Ready:          True
    Restart Count:  0
    Limits:
      cpu:     200m
      memory:  512Mi
    Requests:
      cpu:        100m
      memory:     200Mi
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-xs6lb (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-xs6lb:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   Burstable
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  63s   default-scheduler  Successfully assigned default/demo to k8s3
  Normal  Pulled     48s   kubelet            Container image "nginx" already present on machine
  Normal  Created    48s   kubelet            Created container demo
  Normal  Started    47s   kubelet            Started container demo

资源清单

打标签以及添加资源选择器

我们可以打标签并且在yaml文件中增加标签选择器

[root@k8s1 ~]# kubectl label nodes k8s3 disktype=ssd
spec:
  hostNetwork: true
  nodeSelector:
    disktype: ssd
  containers:
  - image: nginx
    name: demo
    resources:
      limits:
        cpu: 200m
        memory: 512Mi
      requests:
        cpu: 100m
        memory: 200Mi
    imagePullPolicy: IfNotPresent

[root@k8s1 ~]# kubectl get pod
NAME   READY   STATUS    RESTARTS   AGE
demo   1/1     Running   0          6m32s
[root@k8s1 ~]# kubectl get pod -o wide
NAME   READY   STATUS    RESTARTS   AGE     IP             NODE   NOMINATED NODE   READINESS GATES
demo   1/1     Running   0          6m36s   192.168.1.13   k8s3   <none>           <none>