Pod特點
k8s的最小管理單元
一組容器的集合
一個Pod中的容器共享網絡命令空間
Pod是短暫的
Pod容器分類
1.infrastructure container 基礎容器(維護整個Pod網絡空間)
- node節點操作
#查看容器的網絡
cat /opt/kubernetes/cfg/kubelet
#每次創建Pod時候就會創建,與Pod對應的,對於用戶是透明的,網絡組件會被自動加載成一個組件提供出去
docker ps
2.initcontainers 初始化容器
pod在進行創建時一定會被執行當中的初始化initcontainers,
在老版本中執行時不會區分前後順序(在系統進行加載時PID號數字越小,優先級別越高,越先被啓動),
隨着雲平臺的改進,啓動模式改爲主機形式,分隔出的初始化容器會被優先加載,
在初始化容器加載完成之後後面的業務容器才能正常接着運行
3.container 業務容器,並行啓動
示例:
Init containers in use
This example defines a simple Pod that has two init containers.
The first waits for myservice, and the second waits for mydb.
Once both init containers complete, the Pod runs the app container from its spec section.
apiVersion: v1
kind: Pod
metadata:
name: myapp-pod
labels:
app: myapp
spec:
containers:
- name: myapp-container
image: busybox:1.28
command: ['sh', '-c', 'echo The app is running! && sleep 3600']
initContainers:
- name: init-myservice
image: busybox:1.28
command: ['sh', '-c', 'until nslookup myservice; do echo waiting for myservice; sleep 2; done;']
- name: init-mydb
image: busybox:1.28
command: ['sh', '-c', 'until nslookup mydb; do echo waiting for mydb; sleep 2; done;']
鏡像拉取策略(image PullPolicy)
IfNotPresent:默認值,鏡像在宿主機上不存在時才拉取
Always:每次創建Pod都會重新拉取一次鏡像
Never:Pod永遠不會主動拉取這個鏡像
示例:
Verify by creating a pod that uses a private image, e.g.:
kubectl apply -f - <<EOF
apiVersion: v1
kind: Pod
metadata:
name: private-image-test-1
spec:
containers:
- name: uses-private-image
image: $PRIVATE_IMAGE_NAME
imagePullPolicy: Always
command: [ "echo", "SUCCESS" ]
EOF
在master1端操作
kubectl get pods
kubectl edit deployment/nginx
cd demo/
vim pod1.yaml
apiVersion: v1
kind: Pod
metadata:
name: mypod
spec:
containers:
- name: nginx
image: nginx
imagePullPolicy: Always
command: [ "echo", "SUCCESS" ]
kubectl create -f pod1.yaml
kubectl get pods
#此時會出現CrashLoopBackOff創建之後又關閉的狀態提示
#失敗的狀態的原因是因爲命令啓動衝突
#刪除 command: [ "echo", "SUCCESS" ]
#同時更改一下版本
image: nginx:1.14
#刪除原有的資源
kubectl delete -f pod1.yaml
#更新資源
kubectl apply -f pod1.yaml
#查看分配節點
kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
mypod 1/1 Running 0 1m42s 172.17.56.3 192.168.142.130 <none>
#在任意node節點使用curl查看頭部信息
curl -I 172.17.56.3
HTTP/1.1 200 OK
Server: nginx/1.14.2
Date: Sat, 18 Feb 2020 19:32:55 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 04 Dec 2018 14:44:49 GMT
Connection: keep-alive
ETag: "5c0692e1-264"
Accept-Ranges: bytes