一、使用命令kubectl run创建应用
语法:
kubectl run NAME --image=image [--env="key=value"] [--port=port] [--replicas=replicas] [--dry-run=bool]
[--overrides=inline-json] [--command] -- [COMMAND] [args...] [options]
实用举例：
[root@k8s-master ~]# kubectl run nginx-deploy --image=nginx:1.14-alpine --port=80 --replicas=1 #创建一个nginx的应用，副本数为1
deployment.apps/nginx-deploy created
[root@k8s-master ~]# kubectl get deployment #获取应用信息，查看应用是否符合预期状态
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx-deploy 1 1 1 1 40s
[root@k8s-master ~]# kubectl get pods #获取pod信息
NAME READY STATUS RESTARTS AGE
nginx-deploy-5b595999-44zwq 1/1 Running 0 1m
[root@k8s-master ~]# kubectl get pods -o wide #查看pod运行在哪个节点上
NAME READY STATUS RESTARTS AGE IP NODE
nginx-deploy-5b595999-44zwq 1/1 Running 0 1m 10.244.2.2 k8s-node02
从上面创建的应用可以得知，nginx-deploy应用的pod的ip为10.244.2.2，这是一个pod ip，仅仅可以在集群内部访问，如下：
[root@k8s-master ~]# curl 10.244.2.2 -I
HTTP/1.1 200 OK
Server: nginx/1.14.0
Date: Thu, 28 Feb 2019 06:13:03 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Fri, 06 Jul 2018 16:53:43 GMT
Connection: keep-alive
ETag: "5b3f9e97-264"
Accept-Ranges: bytes
[root@k8s-node01 ~]# curl 10.244.2.2 -I
HTTP/1.1 200 OK
Server: nginx/1.14.0
Date: Thu, 28 Feb 2019 06:12:04 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Fri, 06 Jul 2018 16:53:43 GMT
Connection: keep-alive
ETag: "5b3f9e97-264"
Accept-Ranges: bytes
[root@k8s-node02 ~]# curl 10.244.2.2 -I
HTTP/1.1 200 OK
Server: nginx/1.14.0
Date: Thu, 23 Aug 2018 09:22:18 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Fri, 06 Jul 2018 16:53:43 GMT
Connection: keep-alive
ETag: "5b3f9e97-264"
Accept-Ranges: bytes
这里要注意的是pod的客户端有2类，1类是其他pod，1类是集群外部客户端，那么集群外部的客户端如何访问到pod呢？pod的地址是随时变化的，假设先删除创建的pod：
[root@k8s-master ~]# kubectl delete pods nginx-deploy-5b595999-44zwq
pod "nginx-deploy-5b595999-44zwq" deleted
要明白pod是通过控制器进行管理的，当控制器发现pod的状态不满足预期的状态时，将会重新创建一个pod
[root@k8s-master ~]# kubectl get pods -o wide #由于在node01节点上没有镜像，需要重新下载
NAME READY STATUS RESTARTS AGE IP NODE
nginx-deploy-5b595999-872c7 0/1 ContainerCreating 0 24s <none> k8s-node01
[root@k8s-master ~]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE
nginx-deploy-5b595999-872c7 1/1 Running 0 56s 10.244.1.2 k8s-node01
此时可以看到新建的pod的ip地址已经更改了，并且本次创建的pod是在node01节点上，这样就需要提供一个固定端点，给集群外部客户端进行访问。这个固定端点就是service：
语法如下:
kubectl expose (-f FILENAME | TYPE NAME) [--port=port] [--protocol=TCP|UDP] [--target-port=number-or-name]
[--name=name] [--external-ip=external-ip-of-service] [--type=type] [options]
[root@k8s-master ~]# kubectl expose deployment nginx-deploy --name=nginx --port=80 --target-port=80 --protocol=TCP #创建一个nginx的service
service/nginx exposed
[root@k8s-master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 1d
nginx ClusterIP 10.106.162.254 <none> 80/TCP 19s
[root@k8s-master ~]# curl 10.106.162.254 -I #通过ClusterIP进行访问nginx pod
HTTP/1.1 200 OK
Server: nginx/1.14.0
Date: Thu, 23 Aug 2018 09:38:09 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Fri, 06 Jul 2018 16:53:43 GMT
Connection: keep-alive
ETag: "5b3f9e97-264"
Accept-Ranges: bytes
10.106.162.254这网段依然是集群内部的网段，只能被集群内部所能访问，外部是无法通过service的ip进行访问的。那么针对pod的客户端除了通过service ip访问还可以通过service的名称进行访问，但是前提是需要对service的名称能够进行解析。而解析时是依赖coredns服务的，而我们本地的dns指向并非coredns，如下：
[root@k8s-master ~]# curl nginx
curl: (6) Could not resolve host: nginx; Unknown error
[root@k8s-master ~]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 8.8.8.8
nameserver 114.114.114.114
下面查看一下coredns的ip地址：
[root@k8s-master ~]# kubectl get pods -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE
coredns-78fcdf6894-nmcmz 1/1 Running 0 1d 10.244.0.3 k8s-master
coredns-78fcdf6894-p5pfm 1/1 Running 0 1d 10.244.0.2 k8s-master
etcd-k8s-master 1/1 Running 1 1d 192.168.56.11 k8s-master
kube-apiserver-k8s-master 1/1 Running 8 1d 192.168.56.11 k8s-master
kube-controller-manager-k8s-master 1/1 Running 4 1d 192.168.56.11 k8s-master
kube-flannel-ds-n5c86 1/1 Running 0 1d 192.168.56.11 k8s-master
kube-flannel-ds-nrcw2 1/1 Running 0 5h 192.168.56.13 k8s-node02
kube-flannel-ds-pgpr7 1/1 Running 1 1d 192.168.56.12 k8s-node01
kube-proxy-glzth 1/1 Running 0 5h 192.168.56.13 k8s-node02
kube-proxy-rxlt7 1/1 Running 1 1d 192.168.56.11 k8s-master
kube-proxy-vxckf 1/1 Running 0 1d 192.168.56.12 k8s-node01
kube-scheduler-k8s-master 1/1 Running 2 1d 192.168.56.11 k8s-master
而一般，也不会直接通过coredns的这个pod ip地址进行访问，而是通过service进行访问，查看一下coredns的service：
[root@k8s-master ~]# kubectl get svc -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP 1d
那么就可以通过这个service ip：10.96.0.10进行解析上面的nginx服务，如下：
[root@k8s-master ~]# yum install -y bind-utils
[root@k8s-master ~]# dig -t A nginx.default.svc.cluster.local @10.96.0.10 #这里需要使用完整的服务名称，否则会因为dns搜索域的问题而导致无法解析成功
; <<>> DiG 9.9.4-RedHat-9.9.4-61.el7 <<>> -t A nginx.default.svc.cluster.local @10.96.0.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 78
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;nginx.default.svc.cluster.local. IN A
;; ANSWER SECTION:
nginx.default.svc.cluster.local. 5 IN A 10.106.162.254 #这样就可以正常解析出nginx的service ip了
;; Query time: 155 msec
;; SERVER: 10.96.0.10#53(10.96.0.10)
;; WHEN: Thu Aug 23 05:40:22 EDT 2018
;; MSG SIZE rcvd: 107
那么再演示通过pod 客户端进行访问：
[root@k8s-master ~]# kubectl run client --image=busybox --replicas=1 -it --restart=Never #创建pod
[root@k8s-master ~]# kubectl exec -it client /bin/sh #首次创建如果没进入到容器，可以使用这命令进入
/ # cat /etc/resolv.conf #查看dns，这里就是自动指向coredns
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5
/ # wget -O - -q http://nginx:80 #请求解析nginx
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
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>
这就是service提供给pod的固定访问端点的使用，而pod的增删改查，并不会影响通过service进行访问，可以通过以下命令来查看service的详细信息：
[root@k8s-master ~]# kubectl describe svc nginx
Name: nginx
Namespace: default
Labels: run=nginx-deploy
Annotations: <none>
Selector: run=nginx-deploy
Type: ClusterIP
IP: 10.106.162.254
Port: <unset> 80/TCP
TargetPort: 80/TCP
Endpoints: 10.244.1.5:80 #pod 的ip，会根据资源变化改变，但是实际访问的service 依旧有效
Session Affinity: None
Events: <none>
那么pod的增删改，service又是如何确定对pod的访问呢？这就需要通过标签选择器进行选定，无论pod的ip如何变化，但是标签不会变化，从而达到固定端点的访问效果，查看一下pod的标签：
[root@k8s-master ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
client 1/1 Running 0 21h run=client
nginx-deploy-5b595999-872c7 1/1 Running 2 22h pod-template-hash=16151555,run=nginx-deploy
run=nginx-deploy就是这个应用的标签，所以当pod的改变，并不会影响service的访问。
二、应用副本的动态伸缩
语法如下:
kubectl scale [--resource-version=version] [--current-replicas=count] --replicas=COUNT (-f FILENAME | TYPE NAME)
（1）创建应用myapp
[root@k8s-master ~]# kubectl run myapp --image=ikubernetes/myapp:v1 --replicas=2
deployment.apps/myapp created
[root@k8s-master ~]# kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
myapp 2 2 2 1 15s
nginx-deploy 1 1 1 1 22h
（2）查看pod详细信息
[root@k8s-master ~]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE
client 1/1 Running 0 21h 10.244.2.3 k8s-node02
client2 1/1 Running 0 48m 10.244.1.6 k8s-node01
client3 1/1 Running 0 27m 10.244.2.4 k8s-node02
myapp-848b5b879b-bdp7t 1/1 Running 0 26s 10.244.1.7 k8s-node01
myapp-848b5b879b-swt2c 0/1 ErrImagePull 0 26s 10.244.2.5 k8s-node02
nginx-deploy-5b595999-872c7 1/1 Running 2 22h 10.244.1.5 k8s-node01
（3）配置service端点
[root@k8s-master ~]# kubectl expose deployment myapp --name=myapp --port=80
service/myapp exposed
（4）查看服务信息
[root@k8s-master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d
myapp ClusterIP 10.106.67.242 <none> 80/TCP 14s
nginx ClusterIP 10.106.162.254 <none> 80/TCP 21h
（5）Pod客户端访问
/ # wget -O - -q http://myapp:80
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
（6）副本增加到5
[root@k8s-master ~]# kubectl scale --replicas=5 deployment myapp
deployment.extensions/myapp scaled
[root@k8s-master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client 1/1 Running 0 21h
client2 1/1 Running 0 51m
client3 1/1 Running 0 30m
myapp-848b5b879b-6p6ml 1/1 Running 0 1m
myapp-848b5b879b-7xmnj 0/1 ImagePullBackOff 0 1m
myapp-848b5b879b-bdp7t 1/1 Running 0 3m
myapp-848b5b879b-swt2c 0/1 ImagePullBackOff 0 3m
myapp-848b5b879b-zlvl2 1/1 Running 0 1m
nginx-deploy-5b595999-872c7 1/1 Running 2 22h
（7）副本收缩到3
[root@k8s-master ~]# kubectl scale --replicas=3 deployment myapp
deployment.extensions/myapp scaled
三、应用的版本升级
语法如下:
kubectl set image (-f FILENAME | TYPE NAME) CONTAINER_NAME_1=CONTAINER_IMAGE_1 ... CONTAINER_NAME_N=CONTAINER_IMAGE_N
（1）版本升级为v2
[root@k8s-master ~]# kubectl set image deployment myapp myapp=ikubernetes/myapp:v2
deployment.extensions/myapp image updated
（2）查看升级过程
[root@k8s-master ~]# kubectl rollout status deployment myapp #查看更新过程
Waiting for deployment "myapp" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "myapp" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "myapp" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "myapp" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "myapp" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "myapp" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "myapp" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "myapp" rollout to finish: 1 old replicas are pending termination...
deployment "myapp" successfully rolled out
（3）获取pod信息
[root@k8s-master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
client 1/1 Running 0 21h
client2 1/1 Running 0 53m
client3 1/1 Running 0 33m
myapp-74c94dcb8c-2djgg 1/1 Running 0 1m
myapp-74c94dcb8c-92d9p 1/1 Running 0 28s
myapp-74c94dcb8c-nq7zt 1/1 Running 0 25s
nginx-deploy-5b595999-872c7 1/1 Running 2 22h
[root@k8s-master ~]# kubectl describe pods myapp-74c94dcb8c-2djgg
（4）pod客户端测试访问，可以看到是v2版本
/ # wget -O - -q http://myapp:80
Hello MyApp | Version: v2 | <a href="hostname.html">Pod Name</a>
四、应用的版本回滚
语法如下:
kubectl rollout undo (TYPE NAME | TYPE/NAME) [flags] [options]
[root@k8s-master ~]# kubectl rollout undo deployment myapp #不指定版本直接回滚到上一个版本
deployment.extensions/myapp
/ # wget -O - -q http://myapp:80
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
五、实现外部访问service
[root@k8s-master ~]# kubectl edit svc myapp
TYPE:CLUSTER-IP改为
TYPE:NodePort
[root@k8s-master ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d
myapp NodePort 10.106.67.242 <none> 80:32432/TCP 18m
nginx ClusterIP 10.106.162.254 <none> 80/TCP 22h
这里再查看service信息，可以看到myapp进行了端口映射，将myapp的80端口映射到本地32432端口，则可以使用http://192.168.56.11:32432进行访问。如图：
