k8s基礎命令：https://kubernetes.io/zh/docs/reference/kubectl/kubectl-cmds/
k8s基礎知識：https://kubernetes.io/zh/docs/tutorials/kubernetes-basics/
一，部署應用
kubectl create deployment my-test-ngx --image=nginx
deployment.apps/my-test-ngx created
二，瞭解應用
查看deployment
kubectl get deployment
NAME READY UP-TO-DATE AVAILABLE AGE
my-test-ngx 1/1 1 1 103s
get deployment -o wide
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
my-test-ngx 1/1 1 1 2m17s nginx nginx app=my-test-ngx
查看pod
kubectl get pod
NAME READY STATUS RESTARTS AGE
my-test-ngx-77d994d88-srhzm 1/1 Running 0 39s
kubectl get pod -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
my-test-ngx-77d994d88-srhzm 1/1 Running 0 2m54s 10.244.0.7 master.oopxiajun.com <none> <none>
利用這個IP我們訪問下
curl 10.244.0.7
<!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>
本機瀏覽器也是可以訪問
三，公佈應用
kubectl create service clusterip my-test-ngx --tcp=8001:80
service/my-test-ngx created
這裏注意：
1：my-test-ngx 這個名字需要與svc 的名字一樣。
2：--tcp=8001:80 這裏8001是公佈對外的端口，80是容器內部端口
我看看svc詳細信息
kubectl describe svc/my-test-ngx
Name: my-test-ngx
Namespace: default
Labels: app=my-test-ngx
Annotations: <none>
Selector: app=my-test-ngx
Type: ClusterIP
IP: 10.105.139.80
Port: 8001-80 8001/TCP
TargetPort: 80/TCP
Endpoints: 10.244.0.7:80
Session Affinity: None
Events: <none>
可以看到IP: 10.105.139.80
curl 10.105.139.80:8001
<!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>
可以訪問到這個IP:port對應的容器信息
刪掉pod，看看有什麼不一樣。
#看看pod名
kubectl get pod
NAME READY STATUS RESTARTS AGE
my-test-ngx-77d994d88-srhzm 1/1 Running 0 28m
#刪掉pod
[root@master xiajun]# kubectl delete pod my-test-ngx-77d994d88-srhzm
pod "my-test-ngx-77d994d88-srhzm" deleted
#再次看看pod
[root@master xiajun]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-test-ngx-77d994d88-vsrwf 0/1 ContainerCreating 0 14s
#發現pod名字變了
pod刪掉後，又建了一個，pod名字變了，不僅僅是pod名字變了，容器的ip也有變化
kubectl describe svc/my-test-ngx
Name: my-test-ngx
Namespace: default
Labels: app=my-test-ngx
Annotations: <none>
Selector: app=my-test-ngx
Type: ClusterIP
IP: 10.105.139.80
Port: 8001-80 8001/TCP
TargetPort: 80/TCP
Endpoints: 10.244.0.8:80
Session Affinity: None
Events: <none>
前面我們看到：Endpoints: 10.244.0.7:80
這是我們看到：Endpoints: 10.244.0.8:80
Name: my-test-ngx
Namespace: default
Labels: app=my-test-ngx
Annotations: <none>
Selector: app=my-test-ngx
Type: ClusterIP
IP: 10.105.139.80
Port: 8001-80 8001/TCP
TargetPort: 80/TCP
Endpoints: 10.244.0.14:80
Session Affinity: None
Events: <none>
但是IP：10.105.139.80 是沒變的。所以pod即使是被幹掉了，或者某個node的掛掉了，甚至是關機、重啓宿主機，我們也一樣是可以通過這個ip:port訪問的。
curl 10.105.139.80:8001
<!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>
很遺憾：這個地址也只能本機訪問，用域名也是無法訪問的。
curl my-test-ngx
curl: (6) Could not resolve host: my-test-ngx
用k8s本地的域名也是不行的。
curl my-test-ngx.default.svc.cluster.local.
curl: (7) Failed to connect to my-test-ngx.default.svc.cluster.local port 80: Connection refused
那我們怎麼才能讓應用公佈到外網呢？
這裏有一個叫kube-dns的svc，
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,9153/TCP 30h
說明k8s有個dns服務器，其ip地址爲10.96.0.10
那麼我們是否可以將作爲我們宿主機的dns服務器呢？我們來試試。
cat /etc/resolv.conf
# Generated by NetworkManager
search localdomain oopxiajun.com
nameserver 192.168.134.2
這兒我們看到了我們nameserver是192.168.134.2
我們改下這個nameserver
vim /etc/resolv.conf
# Generated by NetworkManager
search localdomain oopxiajun.com
nameserver 10.96.0.10
然後訪問
curl my-test-ngx.default.svc.cluster.local.
<!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>
瀏覽器中也可以了
這樣還是不夠的哦。
觀察下這個域名 my-test-ngx.default.svc.cluster.local
my-test-ngx：是service的名稱，
default:是命名空間
svc.cluster.local：是k8s固定的dns-domain格式
我們要將這個域名改爲我們自己定義的就需要在 kubeadm init 是 加入我們的參數 --service-dns-domain
如果不加這個 --service-dns-domain ，那麼默認的dns-domain就是svc.cluster.local.
這個點我們後面再來詳細研究。
四，伸縮引用
我們這兒舉例 就用 k8s 提供的一個鏡像 ikubernetes/myapp
#部署
kubectl create deployment myapp-test --image=ikubernetes/myapp:v1
deployment.apps/myapp-test created
#公佈節點
kubectl create service clusterip myapp-test --tcp=80:80
service/myapp-test created
#訪問
[root@master xiajun]# curl myapp-test.default.svc.cluster.local.
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
#hostname.html 中就是 pod的名稱
curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
kubectl get pod
NAME READY STATUS RESTARTS AGE
my-test-ngx-77d994d88-f99lf 1/1 Running 0 36m
myapp-test-cc8865788-6s9xh 1/1 Running 0 2m16s
擴容
kubectl scale --replicas=3 deployment myapp-test
deployment.apps/myapp-test scaled
訪問
kubectl get pod
NAME READY STATUS RESTARTS AGE
my-test-ngx-77d994d88-f99lf 1/1 Running 0 43m
myapp-test-cc8865788-6s9xh 1/1 Running 0 9m2s
myapp-test-cc8865788-dw6nc 1/1 Running 0 33s
myapp-test-cc8865788-xw2mw 1/1 Running 0 33s
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-xw2mw
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-dw6nc
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-dw6nc
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-xw2mw
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-6s9xh
[root@master xiajun]# curl myapp-test.default.svc.cluster.local./hostname.html
myapp-test-cc8865788-dw6nc
可以看到是隨機訪問了pod