Introduction to K8s actual combat (3)

3. Getting Started

This chapter will introduce how to deploy an nginx service in a kubernetes cluster and be able to access it.

3.1 Namespace

Namespace is a very important resource in the kubernetes system. Its main function is to realize resource isolation of multiple environments or resource isolation of multi-tenants .

By default, all Pods in a kubernetes cluster are mutually accessible. But in practice, you may not want to allow two Pods to access each other, then you can divide the two Pods into different namespaces. Kubernetes can form logical "groups" by allocating resources within the cluster to different Namespaces, so as to facilitate the isolated use and management of resources in different groups.

Through the kubernetes authorization mechanism, different namespaces can be handed over to different tenants for management, thus realizing multi-tenant resource isolation. At this time, the resource quota mechanism of kubernetes can also be combined to limit the resources that different tenants can occupy, such as CPU usage, memory usage, etc., to realize the management of tenants' available resources.

---

3.1.1 Test Pod connectivity between two different namespaces

[root@k8s-master ~]# mkdir manifest
[root@k8s-master ~]# cd manifest
[root@k8s-master manifest]# pwd
/root/manifest
[root@k8s-master manifest]# cat nginx-pod.yaml 
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  namespace: dev
spec:
  containers:
  - name: nginx-containers
    image: busybox:latest
    command: ["/bin/sleep","6000"]

---

apiVersion: v1
kind: Pod
metadata:
  name: apache  # 不指定名称空间就是跑在默认的
spec:
  containers:
  - name: httpd
    image: busybox:latest
    command: ["/bin/sleep","6000"]
    
[root@k8s-master manifest]# kubectl  get -n default pod
NAME     READY   STATUS    RESTARTS   AGE
apache   1/1     Running   0          19s
[root@k8s-master manifest]# kubectl  get -n dev  pod
NAME        READY   STATUS    RESTARTS   AGE
nginx-pod   1/1     Running   0          25s    

[root@k8s-master ~]# kubectl exec --help  // 查看帮助命令
# kubectl exec pod-name -c container-name -it -n namespace-name -- /bin/sh
exec       在容器中执行命令
pod-name   指定那个Pod
-c         指定容器名字
-it        交互模式
-n         指定名称空间
--         固定写法
/bin/sh    进入容器后执行的命令

# 进入 Pod 的 apache
[root@k8s-master manifest]# kubectl exec apache -it -- sh
/ # ls
bin    dev    etc    home   lib    lib64  proc   root   sys    tmp    usr    var
/ # ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0@if7: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue 
    link/ether 5e:19:37:e6:3e:5a brd ff:ff:ff:ff:ff:ff
    inet 10.244.2.12/24 brd 10.244.2.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::5c19:37ff:fee6:3e5a/64 scope link 
       valid_lft forever preferred_lft forever
/ #

# 进入 Pod 的nginx-pod
[root@k8s-master manifest]# kubectl exec nginx-pod -i -t -n dev -- sh
/ # 
/ # ls
bin    dev    etc    home   lib    lib64  proc   root   sys    tmp    usr    var
/ # ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0@if7: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue 
    link/ether 66:d3:72:81:17:00 brd ff:ff:ff:ff:ff:ff
    inet 10.244.1.16/24 brd 10.244.1.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::64d3:72ff:fe81:1700/64 scope link 
       valid_lft forever preferred_lft forever
/ # ping 10.244.2.12
PING 10.244.2.12 (10.244.2.12): 56 data bytes
64 bytes from 10.244.2.12: seq=0 ttl=62 time=1.170 ms
64 bytes from 10.244.2.12: seq=1 ttl=62 time=0.397 ms
64 bytes from 10.244.2.12: seq=2 ttl=62 time=0.743 ms

---

After the cluster is started, kubernetes will create several namespaces by default

[root@k8s-master ~]#  kubectl  get namespace
NAME              STATUS   AGE
default           Active   45h     #  所有未指定Namespace的对象都会被分配在default命名空间
kube-node-lease   Active   45h     #  集群节点之间的心跳维护，v1.13开始引入
kube-public       Active   45h     #  此命名空间下的资源可以被所有人访问（包括未认证用户）
kube-system       Active   45h     #  所有由Kubernetes系统创建的资源都处于这个命名空间

Let's look at the specific operations of namespace resources:

**Check**

# 1 查看所有的ns  命令：kubectl get ns
[root@k8s-master ~]#  kubectl get ns
NAME              STATUS   AGE
default           Active   45h
kube-node-lease   Active   45h
kube-public       Active   45h     
kube-system       Active   45h     

# 2 查看指定的ns   命令：kubectl get ns ns名称
[root@k8s-master ~]#  kubectl get ns default
NAME      STATUS   AGE
default   Active   45h

# 3 指定输出格式  命令：kubectl get ns ns名称  -o 格式参数
# kubernetes支持的格式有很多，比较常见的是wide、json、yaml
[root@k8s-master ~]# kubectl get ns default -o yaml
apiVersion: v1
kind: Namespace
metadata:
  creationTimestamp: "2023-01-08T02:04:00Z"
  labels:
    kubernetes.io/metadata.name: default
  name: default
  resourceVersion: "191"
  uid: ed84973a-29b4-4286-ae46-d8df5c113334
spec:
  finalizers:
  - kubernetes
status:
  phase: Active
[root@k8s-master ~]# 
  
# 4 查看ns详情  命令：kubectl describe ns ns名称
[root@k8s-master ~]# kubectl describe ns default 或  kubectl describe pod apache
Name:         default
Labels:       kubernetes.io/metadata.name=default
Annotations:  <none>
Status:       Active  # Active 命名空间正在使用中  Terminating 正在删除命名空间
                       
No resource quota. # Resource Quota 针对namespace做的资源限制

No LimitRange resource.  # LimitRange针对namespace中的每个组件做的资源限制 


[root@k8s-master inventory]# pwd
/root/inventory
[root@k8s-master inventory]# 
[root@k8s-master inventory]# kubectl describe pod apache
Name:             apache  // Pod 名字
Namespace:        default  // 在那个名称空间运行
Priority:         0
Service Account:  default
Node:             k8s-node1/192.168.192.4  // 在那台node节点上运行
Start Time:       Fri, 28 Jul 2023 13:23:17 +0800  // 启动时间
Labels:           <none>
Annotations:      <none>
Status:           Running  //  现在的状态是Runing
IP:               10.244.1.15  // IP 地址
IPs:
  IP:  10.244.1.15
Containers:
  httpd:
    Container ID:   containerd://b7eeb63f0cb390657ad84dd42aa42acd74d56088e17a48b04b1633e1e12ab57a
    Image:          httpd  // 运行那个镜像名
    Image ID:  // 镜像ID     docker.io/library/httpd@sha256:33a91a69517f0642b3e8be5cc8d12f8c1ae245728a83947bfc098376be63c15e
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Fri, 28 Jul 2023 13:25:14 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-xmsjx (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-xmsjx:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:                      <none>
[root@k8s-master inventory]# 

create

# 创建namespace(创建名称空间)
[root@k8s-master ~]#  kubectl create ns dev
namespace/dev created

delete

# 删除namespace(创建名称空间)
[root@k8s-master ~]#  kubectl delete ns dev
namespace "dev" deleted

configuration method

First prepare a yaml file: ns-dev.yaml

# 创建一个最简单的名称空间
apiVersion: v1
kind: Namespace
metadata:
  name: dev

Then you can execute the corresponding create and delete commands:

Create: kubectl create -f ns-dev.yaml

Delete: kubectl delete -f ns-dev.yaml

3.2 Pod

Pod is the smallest unit of kubernetes cluster management. To run a program, it must be deployed in a container, and the container must exist in the Pod.

Pod can be regarded as the package of containers, and one or more containers can exist in a Pod.

---

Test a Pod running multiple containers

[root@k8s-master manifest]# cat testpodrun.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx-containers
    image: httpd:latest
  - name: nginx
    image: nginx:latest
    
[root@k8s-master inventory]# kubectl apply -f test_pod_run.yaml 
pod/nginx-pod created

[root@k8s-master ~]# kubectl get pod nginx-pod
NAME        READY   STATUS             RESTARTS        AGE
nginx-pod   1/2     CrashLoopBackOff   6 (3m49s ago)   10m
# 使用describe 命令查看nginx-pod 在做些什么事
[root@k8s-master manifest]# kubectl describe pod nginx-pod

---

After the kubernetes cluster is started, each component in the cluster also runs as a Pod. You can view it with the following command:

[root@k8s-master ~]#  kubectl get pod -n kube-system
NAMESPACE     NAME                             READY   STATUS    RESTARTS   AGE
kube-system   coredns-6955765f44-68g6v         1/1     Running   0          2d1h
kube-system   coredns-6955765f44-cs5r8         1/1     Running   0          2d1h
kube-system   etcd-master                      1/1     Running   0          2d1h
kube-system   kube-apiserver-master            1/1     Running   0          2d1h
kube-system   kube-controller-manager-master   1/1     Running   0          2d1h
kube-system   kube-flannel-ds-amd64-47r25      1/1     Running   0          2d1h
kube-system   kube-flannel-ds-amd64-ls5lh      1/1     Running   0          2d1h
kube-system   kube-proxy-685tk                 1/1     Running   0          2d1h
kube-system   kube-proxy-87spt                 1/1     Running   0          2d1h
kube-system   kube-scheduler-master            1/1     Running   0          2d1h

build and run

kubernetes does not provide commands to run Pods individually, they are all implemented through Pod controllers

# 命令格式： kubectl run (pod控制器名称) [参数] 
# --image  指定Pod的镜像
# --port   指定端口
# --namespace  指定namespace
[root@k8s-master ~]# kubectl create namespace dev
namespace/dev created
[root@k8s-master ~]# kubectl get namespace
NAME              STATUS   AGE
default           Active   204d
dev               Active   7s
kube-flannel      Active   204d
kube-node-lease   Active   204d
kube-public       Active   204d
kube-system       Active   204d
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl run nginx --image=nginx:latest --port=80 --namespace dev
pod/nginx created

View pod information

# 查看Pod基本信息
[root@k8s-master ~]# kubectl get pods -n dev
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          29s


# 查看Pod的详细信息
[root@k8s-master ~]# kubectl describe pod nginx -n dev
Name:             nginx  // Pod 名字
Namespace:        dev  // 名称空间名字
Priority:         0
Service Account:  default
Node:             k8s-node1/192.168.192.4
Start Time:       Mon, 31 Jul 2023 15:21:53 +0800
Labels:           run=nginx
Annotations:      <none>
Status:           Running  // 表示在运行
IP:               10.244.1.18
IPs:
  IP:  10.244.1.18
Containers:
  nginx:
    Container ID:   containerd://a9607020f2f7170b104af0f35ec36f3b0f740a1abe9b5c543b114f145b6e0494
    Image:          nginx:latest
    Image ID:       docker.io/library/nginx@sha256:67f9a4f10d147a6e04629340e6493c9703300ca23a2f7f3aa56fe615d75d31ca
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Mon, 31 Jul 2023 15:21:56 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-726tm (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-726tm:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
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  2m    default-scheduler  Successfully assigned dev/nginx to k8s-node1
  Normal  Pulling    119s  kubelet            Pulling image "nginx:latest"
  Normal  Pulled     117s  kubelet            Successfully pulled image "nginx:latest" in 2.32545784s (2.325463331s including waiting)
  Normal  Created    117s  kubelet            Created container nginx
  Normal  Started    117s  kubelet            Started container nginx
[root@k8s-master ~]# 

Access Pods

# 获取podIP
[root@k8s-master ~]# kubectl get pods -n dev -o wide
NAME    READY   STATUS    RESTARTS   AGE     IP            NODE        NOMINATED NODE   READINESS GATES
nginx   1/1     Running   0          3m38s   10.244.1.18   k8s-node1   <none>           <none>
[root@k8s-master ~]#
#访问POD
[root@k8s-master ~]# curl 10.244.1.18
<!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>
[root@k8s-master ~]# 

Delete the specified Pod

[root@k8s-master ~]# kubectl delete pod nginx -n dev  // 删除Pod 
pod "nginx" deleted
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get pods -n dev 
No resources found in dev namespace.
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get ns
NAME              STATUS   AGE
default           Active   204d
dev               Active   6m12s
kube-flannel      Active   204d
kube-node-lease   Active   204d
kube-public       Active   204d
kube-system       Active   204d
[root@k8s-master ~]# 

[root@k8s-master ~]# kubectl delete namespace dev  // 删除名称空间
namespace "dev" deleted
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get ns
NAME              STATUS   AGE
default           Active   204d
kube-flannel      Active   204d
kube-node-lease   Active   204d
kube-public       Active   204d
kube-system       Active   204d
[root@k8s-master ~]# 

configuration operation

Create a pod-nginx.yaml with the following content:

[root@k8s-master inventory]# pwd
/root/inventory
[root@k8s-master inventory]# cat pod-nginx.yaml 
apiVersion: v1
kind: Namespace
metadata:
  name: dev
---
apiVersion: v1
kind: Pod
metadata:
  name: nginx
  namespace: dev
spec:
  containers:
  - image: nginx:latest
    name: pod
    ports:
    - name: nginx-port
      containerPort: 80
      protocol: TCP
[root@k8s-master inventory]# 

[root@k8s-master inventory]# kubectl apply -f pod-nginx.yaml 
namespace/dev created
pod/nginx created
[root@k8s-master inventory]# 
[root@k8s-master inventory]# kubectl get pod -n dev
NAME    READY   STATUS    RESTARTS   AGE
nginx   1/1     Running   0          14s
[root@k8s-master inventory]# 

[root@k8s-master inventory]# kubectl get -f pod-nginx.yaml 
NAME            STATUS   AGE
namespace/dev   Active   6m47s

NAME        READY   STATUS    RESTARTS   AGE
pod/nginx   1/1     Running   0          6m47s
[root@k8s-master inventory]# 

Then you can execute the corresponding create and delete commands:

Create: kubectl create -f pod-nginx.yaml

Delete: kubectl delete -f pod-nginx.yaml

3.3 Label

Label is an important concept in the kubernetes system. Its role is to add identification to resources to distinguish and select them.

Label features:

• A Label will be attached to various objects in the form of key/value key-value pairs, such as Node, Pod, Service, etc.
• A resource object can define any number of Labels, and the same Label can also be added to any number of resource objects
• Label is usually determined when the resource object is defined, of course, it can also be dynamically added or deleted after the object is created

Multi-dimensional grouping of resources can be realized through Label, so that resource allocation, scheduling, configuration, deployment and other management work can be performed flexibly and conveniently.

Some commonly used Label examples are as follows:

• Version tags: "version": "release", "version": "stable"…
• Environment tags: "environment": "dev", "environment": "test", "environment": "prod"
• Schema tags: "tier": "frontend", "tier": "backend"

After the label is defined, the selection of the label must also be considered, which requires the use of the Label Selector, namely:

Label is used to define an identifier for a resource object

Label Selector is used to query and filter resource objects with certain labels

There are currently two Label Selectors:

• Equation-based Label Selector

  name = slave: Select all objects containing key="name" and value="slave" in Label

  env != production: select all objects including key="env" in Label and value not equal to "production"

• Set-based Label Selector

  name in (master, slave): Select all objects containing key="name" and value="master" or "slave" in Label

  name not in (frontend): Select all objects that contain the key="name" in the Label and the value is not equal to "frontend"

Multiple label selection criteria can be used. In this case, multiple Label Selectors can be combined and separated by commas ",". For example:

name=slave，env!=production

name not in (frontend)，env!=production

command mode

[root@k8s-master ~]# kubectl get pods -n dev  // 查看名称空间dev中有哪些Pod
NAME    READY   STATUS    RESTARTS      AGE
nginx   1/1     Running   1 (39m ago)   4d17h
[root@k8s-master ~]# 

# 1.查看是否已有标签
[root@k8s-master ~]# kubectl describe -n dev pods nginx | grep -i labels
Labels:           <none>
[root@k8s-master ~]# 
# 2.查看是否已有标签
[root@k8s-master ~]# kubectl get pods nginx -n dev --show-labels
NAME    READY   STATUS    RESTARTS      AGE     LABELS
nginx   1/1     Running   1 (42m ago)   4d17h   <none>  // 标签
[root@k8s-master ~]# 


# 为pod资源打标签
[root@k8s-master ~]# kubectl label pod nginx app=test -n dev
pod/nginx labeled

[root@k8s-master ~]# kubectl describe -n dev pod nginx | grep -i labels
Labels:           app=test
[root@k8s-master ~]# 

[root@k8s-master ~]# kubectl label -n dev pod nginx app=test1
error: 'app' already has a value (test), and --overwrite is false
//  需要带 [--overwrite] 不然会报错

# 为pod资源更新标签
[root@k8s-master ~]# kubectl label pod nginx app=test1 -n dev --overwrite
pod/nginx labeled


# 查看标签
[root@k8s-master ~]# kubectl get -n dev pod nginx --show-labels
NAME    READY   STATUS    RESTARTS      AGE     LABELS
nginx   1/1     Running   1 (49m ago)   4d17h   app=test1
[root@k8s-master ~]# 


# 筛选标签
[root@k8s-master ~]# kubectl get -n dev pod  -l app=test1 --show-labels
NAME    READY   STATUS    RESTARTS      AGE     LABELS
nginx   1/1     Running   1 (52m ago)   4d17h   app=test1
[root@k8s-master ~]# 


# 取反
[root@k8s-master ~]# kubectl get pod -n dev -l app!=test1 --show-labels
No resources found in dev namespace.

#删除标签
[root@k8s-master ~]# kubectl label pod nginx -n dev app-
pod/nginx unlabeled
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get pod nginx -n dev --show-labels
NAME    READY   STATUS    RESTARTS      AGE     LABELS
nginx   1/1     Running   1 (54m ago)   4d17h   <none>
[root@k8s-master ~]# 

configuration method

[root@k8s-master manifest]# cat test.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    version: web
  name: httpd
  namespace: default
spec:
  containers:
  - image: httpd:latest
    imagePullPolicy: IfNotPresent
    name: httpd
    ports:
    - containerPort: 80
      name: httpd-port
      hostPort: 8080
      protocol: TCP

[root@k8s-master manifest]# kubectl apply -f test.yaml 
pod/httpd created
[root@k8s-master manifest]# kubectl get pod httpd --show-labels
NAME    READY   STATUS    RESTARTS   AGE    LABELS
httpd   1/1     Running   0          101s   version=web

Then you can execute the corresponding update command: kubectl apply -f pod-nginx.yaml

3.4 Deployment

In kubernetes, pod is the smallest control unit, but kubernetes seldom directly controls pods, usually through the pod controller. The pod controller is used for pod management to ensure that the pod resources meet the expected state. When the pod resources fail, it will try to restart or rebuild the pod.

There are many types of Pod controllers in kubernetes, and this chapter only introduces one: Deployment.

command operation

# 命令格式: kubectl create deployment 名称  [参数] 
# --image  指定pod的镜像
# --port   指定端口
# --replicas  指定创建pod数量
# --namespace  指定namespace
[root@k8s-master ~]# kubectl get namespace
NAME              STATUS   AGE
default           Active   209d
dev               Active   4d21h
kube-flannel      Active   209d
kube-node-lease   Active   209d
kube-public       Active   209d
kube-system       Active   209d
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl create namespace test  // 创建一个名称空间
namespace/test created
[root@k8s-master ~]# kubectl get ns test  // 指定查看名称空间
NAME   STATUS   AGE
test   Active   18s
[root@k8s-master ~]# 

# 查看[名称空间test] namespace，以yaml格式展示结果
[root@k8s-master ~]# kubectl get ns test -o yaml
apiVersion: v1
kind: Namespace
metadata:
  creationTimestamp: "2023-08-05T05:34:26Z"
  labels:
    kubernetes.io/metadata.name: test
  name: test
  resourceVersion: "1093635"
  uid: f9ddabdc-d52f-4952-ae39-4fa93cc2751c
spec:
  finalizers:
  - kubernetes
status:
  phase: Active
[root@k8s-master ~]# kubectl get ns test --show-labels
NAME   STATUS   AGE   LABELS
test   Active   23m   kubernetes.io/metadata.name=test
[root@k8s-master ~]# 


[root@k8s-master ~]# kubectl create deployment nginx --image=nginx:latest --port=80 --replicas=4 -n test
deployment.apps/nginx created


# 查看创建的Pod
[root@k8s-master ~]# kubectl get -n test pods
NAME                         READY   STATUS    RESTARTS   AGE
my-deploy-6648745bcc-7ttcf   1/1     Running   0          3m3s
my-deploy-6648745bcc-vm4vg   1/1     Running   0          3m3s
my-deploy-6648745bcc-x87ng   1/1     Running   0          3m3s
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get -n test pods -o wide
NAME                         READY   STATUS    RESTARTS   AGE     IP            NODE        NOMINATED NODE   READINESS GATES
my-deploy-6648745bcc-7ttcf   1/1     Running   0          3m38s   10.244.1.22   k8s-node1   <none>           <none>
my-deploy-6648745bcc-vm4vg   1/1     Running   0          3m38s   10.244.2.16   k8s-node2   <none>           <none>
my-deploy-6648745bcc-x87ng   1/1     Running   0          3m38s   10.244.2.15   k8s-node2   <none>           <none>
[root@k8s-master ~]#


# 查看deployment的信息
[root@k8s-master ~]# kubectl get deploy -n test -o wide
NAME        READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS   IMAGES         SELECTOR
my-deploy   3/3     3            3           4m38s   nginx        nginx:latest   app=my-deploy
[root@k8s-master ~]# 

# UP-TO-DATE：成功升级的副本数量
# AVAILABLE：可用副本的数量

# 加参数 --show-labels 查看标签
[root@k8s-master ~]# kubectl get deploy -n test --show-labels
NAME        READY   UP-TO-DATE   AVAILABLE   AGE     LABELS
my-deploy   3/3     3            3           5m53s   app=my-deploy

[root@k8s-master ~]# kubectl get pods -n test --show-labels
NAME                         READY   STATUS    RESTARTS   AGE     LABELS
my-deploy-6648745bcc-7ttcf   1/1     Running   0          6m33s   app=my-deploy,pod-template-hash=6648745bcc
my-deploy-6648745bcc-vm4vg   1/1     Running   0          6m33s   app=my-deploy,pod-template-hash=6648745bcc
my-deploy-6648745bcc-x87ng   1/1     Running   0          6m33s   app=my-deploy,pod-template-hash=6648745bcc
[root@k8s-master ~]# 


# 查看deployment的详细信息
[root@k8s-master ~]# kubectl describe deployment my-deploy -n test
Name:                   my-deploy
Namespace:              test
CreationTimestamp:      Sat, 05 Aug 2023 13:42:53 +0800
Labels:                 app=my-deploy
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=my-deploy
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=my-deploy
  Containers:
   nginx:
    Image:        nginx:latest
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   my-deploy-6648745bcc (3/3 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  8m58s  deployment-controller  Scaled up replica set my-deploy-6648745bcc to 3
[root@k8s-master ~]# 

# 查看deployment，以yaml 格式展示结果  查看某个pod,以yaml格式展示结果
[root@k8s-master ~]# kubectl get deployment my-deploy -o yaml -n test
apiVersion: apps/v1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "1"
  creationTimestamp: "2023-08-05T05:42:53Z"
  generation: 1
  labels:
    app: my-deploy
  name: my-deploy
  namespace: test
  resourceVersion: "1094451"
  uid: cf361c04-0c57-46f1-be24-4fc93680c493
spec:
  progressDeadlineSeconds: 600
  replicas: 3
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: my-deploy
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: my-deploy
    spec:
      containers:
      - image: nginx:latest
        imagePullPolicy: Always
        name: nginx
        ports:
        - containerPort: 80
          protocol: TCP
        resources: {
    
    }
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {
    
    }
      terminationGracePeriodSeconds: 30
status:
  availableReplicas: 3
  conditions:
  - lastTransitionTime: "2023-08-05T05:43:00Z"
    lastUpdateTime: "2023-08-05T05:43:00Z"
    message: Deployment has minimum availability.
    reason: MinimumReplicasAvailable
    status: "True"
    type: Available
  - lastTransitionTime: "2023-08-05T05:42:53Z"
    lastUpdateTime: "2023-08-05T05:43:00Z"
    message: ReplicaSet "my-deploy-6648745bcc" has successfully progressed.
    reason: NewReplicaSetAvailable
    status: "True"
    type: Progressing
  observedGeneration: 1
  readyReplicas: 3
  replicas: 3
  updatedReplicas: 3
[root@k8s-master ~]# 
//  如果要写yaml格式的创建名称空间[namespace]或者是deployment、pod的都是可以手动先创建出来然后执行[kubectl get pod pod_name -o yaml]展示出来后，可以照着展示出来的内容写。

# 删除 
[root@k8s-master ~]# kubectl delete -n test deployment my-deploy
deployment.apps "my-deploy" deleted
[root@k8s-master ~]# 

configuration operation

Create a deploy-nginx.yaml with the following content:

[root@k8s-master ~]# cd inventory/
[root@k8s-master inventory]# 
[root@k8s-master inventory]# cat deploy-nginx.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: my-deploy-nginx
  name: my-deploy-nginx  // Pod 名字叫做：my-deploy-nginx
  namespace: test
spec:
  replicas: 4  // 在这个Pod下运行4个容器
  selector:
    matchLabels:
      app: my-deploy
  template:
    metadata:
      labels:
        app: my-deploy
    spec:
      containers:
      - image: nginx:latest
        imagePullPolicy: IfNotPresent  // 如果镜像存在本地，不拉取，如果没有存在本地着拉取
        name: nginx-containers  // Pod 中容器的名称
        ports:
        - containerPort: 80
          protocol: TCP
[root@k8s-master inventory]#
[root@k8s-master inventory]# kubectl apply -f deploy-nginx.yaml 
deployment.apps/my-deploy-nginx created
[root@k8s-master inventory]# 
[root@k8s-master inventory]# kubectl get -f deploy-nginx.yaml 
NAME              READY   UP-TO-DATE   AVAILABLE   AGE
my-deploy-nginx   4/4     4            4           17m
[root@k8s-master inventory]# kubectl get -f deploy-nginx.yaml -o wide
NAME              READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS         IMAGES         SELECTOR
my-deploy-nginx   4/4     4            4           17m   nginx-containers   nginx:latest   app=my-deploy
[root@k8s-master inventory]# 
[root@k8s-master inventory]# kubectl get pods -n test
NAME                               READY   STATUS    RESTARTS   AGE
my-deploy-nginx-6bdd87fd6d-c5sxz   1/1     Running   0          18m
my-deploy-nginx-6bdd87fd6d-cnjrd   1/1     Running   0          18m
my-deploy-nginx-6bdd87fd6d-v8b8z   1/1     Running   0          18m
my-deploy-nginx-6bdd87fd6d-wd25q   1/1     Running   0          18m
[root@k8s-master inventory]# 


# 查看deployment的标签[--show-labels]
[root@k8s-master inventory]# kubectl get deploy -n test --show-labels
NAME              READY   UP-TO-DATE   AVAILABLE   AGE   LABELS
my-deploy-nginx   4/4     4            4           19m   app=my-deploy-nginx
[root@k8s-master inventory]# 

# 查看Pod的标签[--show-labels]
[root@k8s-master inventory]# kubectl get pods -n test --show-labels
NAME                               READY   STATUS    RESTARTS   AGE   LABELS
my-deploy-nginx-6bdd87fd6d-c5sxz   1/1     Running   0          20m   app=my-deploy,pod-template-hash=6bdd87fd6d
my-deploy-nginx-6bdd87fd6d-cnjrd   1/1     Running   0          20m   app=my-deploy,pod-template-hash=6bdd87fd6d
my-deploy-nginx-6bdd87fd6d-v8b8z   1/1     Running   0          20m   app=my-deploy,pod-template-hash=6bdd87fd6d
my-deploy-nginx-6bdd87fd6d-wd25q   1/1     Running   0          20m   app=my-deploy,pod-template-hash=6bdd87fd6d
[root@k8s-master inventory]# 

[root@k8s-master ~]# kubectl get -n test pods -o wide
NAME                               READY   STATUS    RESTARTS   AGE   IP            NODE        NOMINATED NODE   READINESS GATES
my-deploy-nginx-6bdd87fd6d-c5sxz   1/1     Running   0          29m   10.244.1.24   k8s-node1   <none>           <none>
my-deploy-nginx-6bdd87fd6d-cnjrd   1/1     Running   0          29m   10.244.2.18   k8s-node2   <none>           <none>
my-deploy-nginx-6bdd87fd6d-v8b8z   1/1     Running   0          29m   10.244.2.17   k8s-node2   <none>           <none>
my-deploy-nginx-6bdd87fd6d-wd25q   1/1     Running   0          29m   10.244.1.23   k8s-node1   <none>           <none>
[root@k8s-master ~]# 
[root@k8s-master ~]# curl 10.244.2.17  // 只能在内部访问
<!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>
[root@k8s-master ~]# 

You can execute the corresponding create and delete commands:

Create: kubectl create -f deploy-nginx.yaml

Delete: kubectl delete -f deploy-nginx.yaml

3.5 Service

Through the study of the previous chapter, you have been able to use Deployment to create a set of Pods to provide services with high availability.

Although each Pod will be assigned a separate Pod IP, there are two problems as follows:

• Pod IP will change as the Pod is rebuilt
• Pod IP is only a virtual IP visible in the cluster and cannot be accessed externally

This makes it difficult to access the service. Therefore, kubernetes designed Service to solve this problem.

Service can be regarded as an external access interface for a group of Pods of the same type . With Service, applications can easily implement service discovery and load balancing.

Operation 1: Create a Service accessible within the cluster

# 在上面已经使用yaml格式创建了4个容器，使用deployment
[root@k8s-master ~]# kubectl get pods -n test
NAME                               READY   STATUS    RESTARTS   AGE
my-deploy-nginx-6bdd87fd6d-c5sxz   1/1     Running   0          87m
my-deploy-nginx-6bdd87fd6d-cnjrd   1/1     Running   0          87m
my-deploy-nginx-6bdd87fd6d-v8b8z   1/1     Running   0          87m
my-deploy-nginx-6bdd87fd6d-wd25q   1/1     Running   0          87m
[root@k8s-master ~]#
[root@k8s-master ~]# kubectl get deployment -n test  // deployment名为：my-deploy-nginx
NAME              READY   UP-TO-DATE   AVAILABLE   AGE
my-deploy-nginx   4/4     4            4           90m
[root@k8s-master ~]# 

# 默认的名称空间[default]
[root@k8s-master ~]# kubectl get service  // 查看当前有那些service服务
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   209d // 系统自带的
[root@k8s-master ~]#

# 查看指定的名称空间[-n 指定查看那个的名称空间]
[root@k8s-master ~]# kubectl get -n test service
No resources found in dev namespace.
[root@k8s-master ~]# 


# 暴露Service
[root@k8s-master ~]# kubectl expose deployment my-deploy-nginx --name=svc-my-deploy-nginx --port=80 --target-port=80 --type=ClusterIP -n test
service/svc-my-deploy-nginx exposed
[root@k8s-master ~]#

# 查看service
[root@k8s-master ~]# kubectl get -n test service
NAME                  TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
svc-my-deploy-nginx   ClusterIP   10.103.51.241   <none>        80/TCP    3m24s
[root@k8s-master ~]# 

# 这里产生了一个CLUSTER-IP，这就是service的IP，在Service的生命周期中，这个地址是不会变动的
# 可以通过这个IP访问当前service对应的POD
[root@k8s-master ~]# curl 10.103.51.241:80
<!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>  # 欢迎使用nginx!
<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>
[root@k8s-master ~]#

Operation 2: Create a Service that can also be accessed outside the cluster

# 上面创建的Service的type类型为ClusterIP，这个ip地址只用集群内部可访问
# 如果需要创建外部也可以访问的Service，需要修改type为NodePort
[root@k8s-master ~]# kubectl expose deployment my-deploy-nginx --name=svc-nginx --port=80 --target-port=80 --type=NodePort -n test
service/svc-nginx exposed
[root@k8s-master ~]# 

# 此时查看，会发现出现了NodePort类型的Service，而且有一对Port（80:30044/TC）
[root@k8s-master ~]# kubectl get -n test service
NAME                  TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
svc-my-deploy-nginx   ClusterIP   10.103.51.241    <none>        80/TCP         14m
svc-nginx             NodePort    10.103.113.161   <none>        80:30044/TCP   9s
[root@k8s-master ~]# 

# 接下来就可以通过集群外的主机访问 节点IP:30044 访问服务了
# 例如在的电脑主机上通过浏览器访问下面的地址
http://192.168.192.4:30044/  或者 http://192.168.192.5:30044/ 

---

Delete Service

[root@k8s-master ~]# kubectl delete -n test service svc-my-deploy-nginx svc-nginx 
service "svc-my-deploy-nginx" deleted
service "svc-nginx" deleted
[root@k8s-master ~]# kubectl get -n test service
No resources found in test namespace.
[root@k8s-master ~]# 

configuration method

Create a svc-nginx.yaml with the following content:

[root@k8s-master inventory]# kubectl get pods -n test --show-labels
NAME                               READY   STATUS    RESTARTS   AGE    LABELS
my-deploy-nginx-6bdd87fd6d-c5sxz   1/1     Running   0          3h1m   app=my-deploy,pod-template-hash=6bdd87fd6d
my-deploy-nginx-6bdd87fd6d-cnjrd   1/1     Running   0          3h1m   app=my-deploy,pod-template-hash=6bdd87fd6d
my-deploy-nginx-6bdd87fd6d-v8b8z   1/1     Running   0          3h1m   app=my-deploy,pod-template-hash=6bdd87fd6d
my-deploy-nginx-6bdd87fd6d-wd25q   1/1     Running   0          3h1m   app=my-deploy,pod-template-hash=6bdd87fd6d
[root@k8s-master inventory]# 

[root@k8s-master ~]# cd inventory/
[root@k8s-master inventory]# 
[root@k8s-master inventory]# cat svc-nginx.yaml 
apiVersion: v1
kind: Service
metadata:
  name: svc-nginx
  namespace: test
spec:
  clusterIP: 10.109.179.231  # 固定service的内网IP。也可以不写它自动创建一个IP出来
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: my-deploy  # 指定容器标签my-deploy
  type: NodePort
[root@k8s-master inventory]# 
[root@k8s-master inventory]# kubectl apply -f svc-nginx.yaml 
service/svc-nginx created
[root@k8s-master inventory]# 
[root@k8s-master inventory]# kubectl get svc -n test
NAME                  TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
svc-nginx             NodePort    10.109.179.231   <none>        80:30726/TCP   9s
[root@k8s-master inventory]#
[root@k8s-master inventory]# curl 10.109.179.231
<!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>
[root@k8s-master inventory]#
#  查看端口没有发现有30726端口，因为这个端口在iptables规则里
[root@k8s-master inventory]# ss -antl  
State       Recv-Q Send-Q   Local Address:Port                  Peer Address:Port              
LISTEN      0      128          127.0.0.1:10248                            *:*                  
LISTEN      0      128          127.0.0.1:10249                            *:*                  
LISTEN      0      128      192.168.192.3:2379                             *:*                  
LISTEN      0      128          127.0.0.1:2379                             *:*                  
LISTEN      0      128      192.168.192.3:2380                             *:*                  
LISTEN      0      128          127.0.0.1:2381                             *:*                  
LISTEN      0      128          127.0.0.1:10257                            *:*                  
LISTEN      0      128          127.0.0.1:10259                            *:*                  
LISTEN      0      128                  *:22                               *:*                  
LISTEN      0      100          127.0.0.1:25                               *:*                  
LISTEN      0      128          127.0.0.1:43905                            *:*                  
LISTEN      0      128               [::]:10250                         [::]:*                  
LISTEN      0      128               [::]:6443                          [::]:*                  
LISTEN      0      128               [::]:10256                         [::]:*                  
LISTEN      0      128               [::]:22                            [::]:*                  
LISTEN      0      100              [::1]:25                            [::]:*                  
[root@k8s-master inventory]# 
[root@k8s-master ~]# iptables -t nat -nvL | grep 30726  // 查看iptables规则  
    0     0 KUBE-EXT-WUUAWPAQCWK2NLSB  tcp  --  *      *       0.0.0.0/0            0.0.0.0/0            /* test/svc-nginx */ tcp dpt:30726
[root@k8s-master ~]# 

# 接下来就可以通过集群外的主机访问 节点IP:30726 访问服务了
# 例如在的电脑主机上通过浏览器访问下面的地址
http://192.168.192.4:30726

You can execute the corresponding create and delete commands:

Create: kubectl create -f svc-nginx.yaml

Delete: kubectl delete -f svc-nginx.yaml

---

apiVersion: v1
kind: Service
metadata:
  name: svc-nginx
  namespace: test
spec:
  clusterIP: 10.109.179.231
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: my-deploy
  type: ClusterIP   

summary

So far, you have mastered the basic operations of Namespace, Pod, Deployment, and Service resources. With these operations, you can implement simple deployment and access of a service in a kubernetes cluster, but if you want to use kubernetes better, you need Learn the details and rationale of each of these resources in depth.