k8s创建pod - 启动pod的流程
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
目录
1、 kubectl describe node k8s-master 输出一个node的详细信息
2、deployment，replicaSET，pod的关系
2.1、既然pod是replicaSET启动的，那么删除replicaSET会发生什么？
知识点一：启动一个pod
1、使用命令启动一个nginx pod
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 <none> <none>
k8s-nginx-6d779d947c-mphkp 1/1 Running 0 13m 10.244.2.2 k8s-node2 <none> <none>
k8s-nginx-6d779d947c-zwplb 1/1 Running 0 13m 10.244.3.4 k8s-node3 <none> <none>
##########################################################################################
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
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>
<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>
##########################################################################################
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.
##########################################################################################
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 <none> <none>
my-nginx-cf54cdbf7-c8wbq 1/1 Running 0 24s 10.244.2.6 k8s-node2 <none> <none>
my-nginx-cf54cdbf7-rhqcv 1/1 Running 0 24s 10.244.3.7 k8s-node3 <none> <none>
##########################################################################################
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 <none> 443/TCP 24h
my-nginx NodePort 10.1.20.144 <none> 8080:32697/TCP 5s
##########################################################################################
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
##########################################################################################
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##########################################################################################
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 <none> <none>
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.
##########################################################################################
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
##########################################################################################
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
##########################################################################################
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: <none>
##########################################################################################
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
##########################################################################################
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，
##########################################################################################
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 <none> <none>
k8s-nginx-6d779d947c-j9pkd 1/1 Running 0 21s 10.244.3.5 k8s-node3 <none> <none>
k8s-nginx-6d779d947c-rf7tm 1/1 Running 0 21s 10.244.2.4 k8s-node2 <none> <none>
[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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