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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(wǎng)絡(luò)命令空間
Pod是短暫的
1.infrastructure container 基礎(chǔ)容器(維護整個Pod網(wǎng)絡(luò)空間)
#查看容器的網(wǎng)絡(luò)
cat /opt/kubernetes/cfg/kubelet
#每次創(chuàng)建Pod時候就會創(chuàng)建,與Pod對應(yīng)的,對于用戶是透明的,網(wǎng)絡(luò)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(chuàng)建時一定會被執(zhí)行當中的初始化initcontainers,
在老版本中執(zhí)行時不會區(qū)分前后順序(在系統(tǒng)進行加載時PID號數(shù)字越小,優(yōu)先級別越高,越先被啟動),
隨著云平臺的改進,啟動模式改為主機形式,分隔出的初始化容器會被優(yōu)先加載,
在初始化容器加載完成之后后面的業(yè)務(wù)容器才能正常接著運行
3.container 業(yè)務(wù)容器,并行啟動
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;']
IfNotPresent:默認值,鏡像在宿主機上不存在時才拉取
Always:每次創(chuàng)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
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(xiàn)CrashLoopBackOff創(chuàng)建之后又關(guān)閉的狀態(tài)提示
#失敗的狀態(tài)的原因是因為命令啟動沖突
#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(jié)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(jié)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
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