k8s创建pod - 启动pod的流程

deployment 控制器：专门负责在k8s里安装部署pod

kubectl create deployment ：创建部署控制器

k8s-nginx ：是控制器的名字

--image=nginx ：指定控制器去启动pod使用的镜像

-r 3 ：启动3个nginx的pod

副本控制器replicaSET（rs）：作用就是监控pod副本的数量，如果某个node节点挂了，这个节点上的pod也会挂，副本控制器就会在其他的node节点上启动新的pod，数量总数达到副本控制器当时设置的数量 -- 》高可用的体现


[root@k8s-master ~]# kubectl create deployment k8s-nginx --image=nginx -r 3
deployment.apps/k8s-nginx created
[root@k8s-master ~]# kubectl get pod
NAME                         READY   STATUS    RESTARTS   AGE
k8s-nginx-6d779d947c-58j42   1/1     Running   0          114s
k8s-nginx-6d779d947c-mphkp   1/1     Running   0          114s
k8s-nginx-6d779d947c-zwplb   1/1     Running   0          114s
[root@k8s-master ~]# kubectl get deploy
NAME        READY   UP-TO-DATE   AVAILABLE   AGE
k8s-nginx   3/3     3            3           3m10s
[root@k8s-master ~]# kubectl get pod -o wide
NAME                         READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
k8s-nginx-6d779d947c-58j42   1/1     Running   0          13m   10.244.1.2   k8s-node1              
k8s-nginx-6d779d947c-mphkp   1/1     Running   0          13m   10.244.2.2   k8s-node2              
k8s-nginx-6d779d947c-zwplb   1/1     Running   0          13m   10.244.3.4   k8s-node3

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1.1、访问刚才创建的pod的nginx服务

目前只能在内部访问pod的nginx服务，因为还没有将它发布出去，10.244网段是k8s内部的网段


[root@k8s-master ~]# curl 10.244.1.2
<head>
Welcome to nginx!
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.
 
For online documentation and support please refer to
"http://nginx.org/">nginx.org.
Commercial support is available at
"http://nginx.com/">nginx.com.
 
Thank you for using nginx.

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1.2、删除deployment


[root@k8s-master ~]# kubectl get deploy
NAME        READY   UP-TO-DATE   AVAILABLE   AGE
k8s-nginx   3/3     3            3           18h
[root@k8s-master ~]# kubectl get pod
NAME                         READY   STATUS    RESTARTS   AGE
k8s-nginx-6d779d947c-58j42   1/1     Running   0          18h
k8s-nginx-6d779d947c-mphkp   1/1     Running   0          18h
k8s-nginx-6d779d947c-zwplb   1/1     Running   0          18h
[root@k8s-master ~]# kubectl delete deployment  k8s-nginx
deployment.apps "k8s-nginx" deleted
[root@k8s-master ~]# kubectl get deploy
No resources found in default namespace.
[root@k8s-master ~]# kubectl get pod
No resources found in default namespace.

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2、将pod里的服务发布出去

首先创建根据yaml文件创建pod

yaml文件：


[root@k8s-master pod]# cat my_nginx.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
spec:
  selector:
    matchLabels:
      run: my-nginx
  replicas: 3
  template:
    metadata:
      labels:
        run: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 80


[root@k8s-master pod]# kubectl apply -f my_nginx.yaml 
deployment.apps/my-nginx created
[root@k8s-master pod]# kubectl get deploy
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
my-nginx   3/3     3            3           12s
[root@k8s-master pod]# kubectl get pod -o wide
NAME                       READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
my-nginx-cf54cdbf7-5tnfx   1/1     Running   0          24s   10.244.1.5   k8s-node1              
my-nginx-cf54cdbf7-c8wbq   1/1     Running   0          24s   10.244.2.6   k8s-node2              
my-nginx-cf54cdbf7-rhqcv   1/1     Running   0          24s   10.244.3.7   k8s-node3

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2.1、创建Service

my_service.yaml内容：


apiVersion: v1
kind: Service
metadata:
  name: my-nginx
  labels:
    run: my-nginx
spec:
  type: NodePort
  ports:
  - port: 8080
    targetPort: 80
    protocol: TCP
    name: http
  selector:
    run: my-nginx

创建service


[root@k8s-master pod]# kubectl apply -f my_service.yaml 
service/my-nginx created
[root@k8s-master pod]# kubectl get service
NAME         TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)          AGE
kubernetes   ClusterIP   10.1.0.1              443/TCP          24h
my-nginx     NodePort    10.1.20.144           8080:32697/TCP   5s

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2.2、访问发布的pod

我们只要随便访问k8s几区任何一台node节点服务器，包括master

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3、利用yaml文件创建pod

以下是nginx-pod.yaml文件内容


apiVersion: v1   # k8s的api版本 --》用来给k8s传递参数
kind: Pod        # k8s的资源对象类型：pod，deployment，replicaSET，daemonSET
metadata:        # 定义的元数据，描述数据
  name: sc-nginx    # pod的名字
spec:            # 详细信息，指定的信息
  containers:    # 容器
  - name: nginx  # 容器名字
    image: nginx:1.14.2     #容器镜像版本
    ports:       # 端口
    - containerPort: 80

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3.1、根据yaml文件启动pod


[root@k8s-master ~]# vim nginx-pod.yaml 
[root@k8s-master ~]# kubectl apply -f nginx-pod.yaml 
pod/sc-nginx created
[root@k8s-master ~]# kubectl get pod -o wide
NAME       READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
sc-nginx   1/1     Running   0          80s   10.244.2.3   k8s-node2

3.2、删除pod


[root@k8s-master ~]# kubectl delete pod sc-nginx
pod "sc-nginx" deleted
[root@k8s-master ~]# kubectl get pod
No resources found in default namespace.

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4、pod的几种状态

Pending（悬决） pod已经被kubernetes系统接受，但有一个或者多个容器尚未创建，亦未运行，可以通过kubectl describe 查看处于 Pending 状态的原因

Running （运行中） Pod已经绑定到了某个节点，Pod中所有容器都已被创建，至少有一个容器任在运行

Successed （成功） Pod中的所有容器都已经执行成功并终止，并且不会再重启

Failed （失败） Pod中所有容器都终止，并且至少有一个容器是因为失败终止

Unknown （未知）因为某些原因无法取得Pod的状态，通常是因为与Pod所在主机通信失败


[root@k8s-master ~]# kubectl get  pod -n kube-system
NAME                                 READY   STATUS             RESTARTS         AGE
coredns-6d8c4cb4d-92g7b              0/1     CrashLoopBackOff   32 (3m44s ago)   2d23h
coredns-6d8c4cb4d-kl4q5              0/1     CrashLoopBackOff   32 (3m44s ago)   2d23h
etcd-k8s-master                      1/1     Running            0                2d23h
kube-apiserver-k8s-master            1/1     Running            0                2d23h
kube-controller-manager-k8s-master   1/1     Running            0                2d23h
kube-proxy-422b5                     1/1     Running            0                2d23h
kube-proxy-6qpcz                     1/1     Running            0                2d23h
kube-proxy-ggnnt                     1/1     Running            0                2d23h
kube-proxy-vjcnc                     1/1     Running            0                2d23h
kube-scheduler-k8s-master            1/1     Running            0                2d23h

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知识点二：启动pod的流程

用户通过kubectl提交pod创建指令，这个指令可以是命令也可以是yaml文件，yaml文件里面指定了很多关于pod的参数，例如名字，镜像，版本等

pod创建指令信息传给API Server，API Server将Pod信息存入etcd

Controller Manager控制器通过API Server接口发现pod信息的更新，做编排工作，创建应用锁需要的pod，并将创建信息返回给API Server，API Server再将pod信息更新到etcd

Scheduler通过API Server中新pod信息的变化，就会为pod分配一个节点Node，并将分配结果反馈给API Server，API Server再将Pod信息存到etcd

API Server通知对应节点的kubelet，kubelet发现Pod调度到本节点，通过容器（例如docker）创建并运行Pod的容器

Kube-proxy给pod分配网络资源，包括服务的发布以及负载均衡的配置

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知识点三：pod有哪些调度算法

根据pod调度策略和方法

1、deployment：全自动调度，根据node的算力（cpu，内存，带宽，已经运行的pod等）

2、node selector：定向调度

3、nodeaffinity：尽量把不同的pod放到一台node上

4、podaffinity：尽量把相同的pod放到一起

5、taints和tolerations：污点和容忍

1、 kubectl describe node k8s-master 输出一个node的详细信息


[root@k8s-master ~]# kubectl describe node k8s-master
Name:               k8s-master
Roles:              control-plane,master
Labels:             beta.kubernetes.io/arch=amd64
                    beta.kubernetes.io/os=linux
                    kubernetes.io/arch=amd64
                    kubernetes.io/hostname=k8s-master
                    kubernetes.io/os=linux
                    node-role.kubernetes.io/control-plane=
                    node-role.kubernetes.io/master=
                    node.kubernetes.io/exclude-from-external-load-balancers=
Annotations:        flannel.alpha.coreos.com/backend-data: {"VNI":1,"VtepMAC":"fe:ca:d8:cc:01:2e"}
                    flannel.alpha.coreos.com/backend-type: vxlan
                    flannel.alpha.coreos.com/kube-subnet-manager: true
                    flannel.alpha.coreos.com/public-ip: 192.168.44.210
                    kubeadm.alpha.kubernetes.io/cri-socket: /var/run/dockershim.sock
                    node.alpha.kubernetes.io/ttl: 0
                    volumes.kubernetes.io/controller-managed-attach-detach: true
CreationTimestamp:  Sun, 25 Sep 2022 18:20:27 +0800
Taints:             node-role.kubernetes.io/master:NoSchedule
Unschedulable:      false
Lease:
  HolderIdentity:  k8s-master
  AcquireTime:     <unset>
  RenewTime:       Wed, 28 Sep 2022 17:36:36 +0800
Conditions:
  Type                 Status  LastHeartbeatTime                 LastTransitionTime                Reason                       Message
  ----                 ------  -----------------                 ------------------                ------                       -------
  NetworkUnavailable   False   Sun, 25 Sep 2022 18:33:20 +0800   Sun, 25 Sep 2022 18:33:20 +0800   FlannelIsUp                  Flannel is running on this node
  MemoryPressure       False   Wed, 28 Sep 2022 17:33:08 +0800   Sun, 25 Sep 2022 18:20:26 +0800   KubeletHasSufficientMemory   kubelet has sufficient memory available
  DiskPressure         False   Wed, 28 Sep 2022 17:33:08 +0800   Sun, 25 Sep 2022 18:20:26 +0800   KubeletHasNoDiskPressure     kubelet has no disk pressure
  PIDPressure          False   Wed, 28 Sep 2022 17:33:08 +0800   Sun, 25 Sep 2022 18:20:26 +0800   KubeletHasSufficientPID      kubelet has sufficient PID available
  Ready                True    Wed, 28 Sep 2022 17:33:08 +0800   Sun, 25 Sep 2022 18:33:28 +0800   KubeletReady                 kubelet is posting ready status
Addresses:
  InternalIP:  192.168.44.210
  Hostname:    k8s-master
Capacity:
  cpu:                4
  ephemeral-storage:  17394Mi
  hugepages-1Gi:      0
  hugepages-2Mi:      0
  memory:             1863028Ki
  pods:               110
Allocatable:
  cpu:                4
  ephemeral-storage:  16415037823
  hugepages-1Gi:      0
  hugepages-2Mi:      0
  memory:             1760628Ki
  pods:               110
System Info:
  Machine ID:                 6d6ca2c7ec0f478097733b00d2892ca0
  System UUID:                0A004D56-3924-4215-F717-9E4DAD9C840B
  Boot ID:                    dd78d95d-a6e7-460e-892b-8d4cf8191823
  Kernel Version:             3.10.0-1160.el7.x86_64
  OS Image:                   CentOS Linux 7 (Core)
  Operating System:           linux
  Architecture:               amd64
  Container Runtime Version:  docker://20.10.18
  Kubelet Version:            v1.23.6
  Kube-Proxy Version:         v1.23.6
PodCIDR:                      10.244.0.0/24
PodCIDRs:                     10.244.0.0/24
Non-terminated Pods:          (6 in total)
  Namespace                   Name                                  CPU Requests  CPU Limits  Memory Requests  Memory Limits  Age
  ---------                   ----                                  ------------  ----------  ---------------  -------------  ---
  kube-flannel                kube-flannel-ds-rphnc                 100m (2%)     100m (2%)   50Mi (2%)        50Mi (2%)      2d23h
  kube-system                 etcd-k8s-master                       100m (2%)     0 (0%)      100Mi (5%)       0 (0%)         2d23h
  kube-system                 kube-apiserver-k8s-master             250m (6%)     0 (0%)      0 (0%)           0 (0%)         2d23h
  kube-system                 kube-controller-manager-k8s-master    200m (5%)     0 (0%)      0 (0%)           0 (0%)         2d23h
  kube-system                 kube-proxy-ggnnt                      0 (0%)        0 (0%)      0 (0%)           0 (0%)         2d23h
  kube-system                 kube-scheduler-k8s-master             100m (2%)     0 (0%)      0 (0%)           0 (0%)         2d23h
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  Resource           Requests    Limits
  --------           --------    ------
  cpu                750m (18%)  100m (2%)
  memory             150Mi (8%)  50Mi (2%)
  ephemeral-storage  0 (0%)      0 (0%)
  hugepages-1Gi      0 (0%)      0 (0%)
  hugepages-2Mi      0 (0%)      0 (0%)
Events:

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2、pod的重启策略

always ：当容器失败时，由kubelet自动重启该容器

OnFailure ：当容器终止运行且退出码为0时，由kubelet自动重启该容器

Never ：不论容器运行状态如何，kubelet都不会重启该容器

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知识点四：pod的通信方式

kubernetes 的网络模型假定了所有Pod都在一个可以直接连通的扁平的网络空间中，kubernetes假定这个网络已经存在，

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知识点五：k8s的各种控制器

1、k8s里面有哪些控制器？

deployment

replicaSET

daemonSET

1.1、ReplicaSET 副本控制器

ReplicaSET 副本控制器，用来确保容器应用的副本数始终保持在用户定义的副本数，即如果有容器异常退出，会自动创建新的pod来替代，而如果异常出来的容器也会自动回收

1.2、DaemonSet

Daemon确保全部node（或者一些）上运行一个pod的副本，当有node加入集群时，也会为他们新增一个pod，当有node从集群移除时，这些pod也会被回收，删除DaemonSet会删除它创建的所有pod

1.3、Job

Job负责批处理任务，即仅执行一次的任务，它保证批处理任务的一个或多个Pod成功结束

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2、deployment，replicaSET，pod的关系

首先部署一个deployment k8s-nginx，启动三个pod，pod里面运行nginx


[root@k8s-master ~]# kubectl create deployment k8s-nginx --image=nginx -r 3
deployment.apps/k8s-nginx created
[root@k8s-master ~]# kubectl get pod -o wide
NAME                         READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
k8s-nginx-6d779d947c-hd64b   1/1     Running   0          21s   10.244.1.3   k8s-node1              
k8s-nginx-6d779d947c-j9pkd   1/1     Running   0          21s   10.244.3.5   k8s-node3              
k8s-nginx-6d779d947c-rf7tm   1/1     Running   0          21s   10.244.2.4   k8s-node2              
[root@k8s-master ~]# kubectl get deploy
NAME        READY   UP-TO-DATE   AVAILABLE   AGE
k8s-nginx   3/3     3            3           27s
[root@k8s-master ~]# kubectl get replicaset
NAME                   DESIRED   CURRENT   READY   AGE
k8s-nginx-6d779d947c   3         3         3       41s

2.1、既然pod是replicaSET启动的，那么删除replicaSET会发生什么？


[root@k8s-master ~]# kubectl delete replicaset k8s-nginx-6d779d947c
replicaset.apps "k8s-nginx-6d779d947c" deleted
[root@k8s-master ~]# kubectl get pod
NAME                         READY   STATUS    RESTARTS   AGE
k8s-nginx-6d779d947c-2xp8r   1/1     Running   0          7s
k8s-nginx-6d779d947c-gw5x8   1/1     Running   0          7s
k8s-nginx-6d779d947c-rmx9x   1/1     Running   0          7s
[root@k8s-master ~]# kubectl get rs
NAME                   DESIRED   CURRENT   READY   AGE
k8s-nginx-6d779d947c   3         3         3       12s

可以看到，删除replicaSET以后，又会重新生成一个replicaSET副本控制器，因为replicaSET是由deployment部署的，所以replicaSET挂了以后又会重新生成

但是如果删除了deployment，无论是replicaSET，pod，都会被删除

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原文地址：https://blog.csdn.net/qq_48391148/article/details/127042156