pod运行应用对应字段

常用字段总结

initContainers
hostAliases
imagePullSecrets
affinity
nodeName
nodeSelector
tolerations
hostNetwork
containers
restartPolicy
dnsPolicy
imagePullPolicy
ports
volumeMounts
volumes
securityContext
startupProbe
livenessProbe
readinessProbe
resources
lifecycle
workingDir
command
args
env
envFrom

容器镜像拉取策略

imagePullPolicy: 容器的镜像拉取策略

IfNotPresent 本地有镜像则使用本地镜像本地不存在则拉取镜像
Always 每次都会尝试拉取策略
Never: 永不拉取如果镜像已经存在本地 kubelet 会尝试启动容器，否则会启动失败

案例

apiVersion: v1
kind: Pod
metadata:
  name: default-pod
  namespace: default
spec:
    containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80

如果你省略了 imagePullPolicy 字段，并且容器镜像的标签是:latest， imagePullPolicy 会⾃动设置为 Always。如果你省略了 imagePullPolicy 字段，并且没有指定容器镜像的标签，imagePullPolicy 会⾃动设置为 Always。如果你省略了imagePullPolicy 字段，并且为容器镜像指定了⾮ :latest 的标签， imagePullPolicy 就会⾃动设置为 IfNotPresent。

获取私有仓库镜像

ImagePullSecrets 拉取私有仓库中的镜像
创建一个仓库认证的secret

kubectl create secret docker-
registry aliyun !"docker-username=123qq.com -
-docker-password=123456 !"docker-server registry.cn-
huhehaote.aliyuncs.com

案例

apiVersion: v1
kind: Pod
metadata:
  name: default-pod
  namespace: default
spec:
  imagePullSecrets:
  - name: aliyun
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - containerPort: 80

env 为容器内部传递变量

基本实例

apiVersion: v1
kind: Pod
metadata:
  name: default-pod
  namespace: default
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    env:
    - name: pod_name
      value: "default-pod"
    ports:
    - containerPort: 80

改变容器的启动命令 command & args

基本示例

apiVersion: v1
kind: Pod
metadata:
  name: default-pod
  namespace: default
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    command:
    - /bin/bash
    args:
    - -c
    - sleep 10 ; echo success > /root/done.txt
    ports:
    - containerPort: 80

指定容器的工作目录 workingDir

案例

apiVersion: v1
kind: Pod
metadata:
  name: default-pod
  namespace: default
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    workingDir: /tmp/
    command:
    - /bin/bash
    args:
    - -c
    - sleep 10 ; echo success > /root/done.txt
    ports:
    - containerPort: 80

服务暴露 ports

ports ⽤于暴露 pod 对外访问的端⼝，如不指定，则⽆法通过PodIP + PodPort 访问该应⽤
containerPort <integer> -required-: 填写Pod对外暴露的端⼝（0~65535）
name <string!' 为端⼝指定⼀个名称，当服务存在多个端⼝，可以通过名称区分；
protocol <string>：指定端⼝对应的协议，有TCP，UDP，SCTP，默认不写为TCP；

应用案例

apiVersion: v1
kind: Deployment
metadata:
  name: default-pod
  namespace: defualt
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
      protocol: TCP

pod重启策略 restartPolicy

Pod 的 spec 中包含⼀个 restartPolicy 字段，⽤来设置 Pod 中所有容器的重启策略，取值有Always、OnFailure、Never。默认值是Always。
Always：当容器出现异常退出时，kubelet 会尝试重启该容器，已恢复正常状态；（默认策略）
Never：当容器退出时，kubelet 永远不会尝试重启该容器（适合Job类⼀次性任务）
OnFailure：当容器异常退出（且退出状态码⾮0时），kubelet会尝试重启容器（适合Job类⼀次性任务）

应用案例

apiVersion: v1
kind: Deployment
metadata:
  name: default-pod
  namespace: defualt
  labels:
    app: nginx
spec:
  restartPolicy: Always
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80

探针配置规范

spec:
  containers:
  - name: ...
    image: ...
    livenessProbe:
      exec <0bject>     #命令式探针
      httpGet <0bject>  #httpGET类型的探针
      tcpSocket <0bject>  #tcp Socket类型的探针 I
      initialDelaySeconds <integer> #发起初次探测请求的延后时长
      periodSeconds <integer>  #请求周期
      timeoutSeconds <integer> #超时时长
      successThreshold <integer>  #成功阈值
      failureThreshold <integer>  #失败阈值

案例

[root@k8s-master Probe]# cat liveness-exec-damo.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: liveness-exec-demo
  namespace: default
spec:
  containers:
  - name: demo
    image: ikubernetes/demoapp:v1.0
    imagePullPolicy: IfNotPresent
    livenessProbe:
      exec:
        command: ['/bin/sh','-c','[ "$(curl -s 127.0.0.1/livez)" == "OK" ]']
      initialDelaySeconds: 5  #初始化等待时间5秒后探测
      timeoutSeconds: 1   #超时时间
      periodSeconds: 5   #每隔5秒探测一次

$ kubectl apply -f liveness-exec-damo.yaml
$ kubectl get pod  -o wide
NAME                                READY   STATUS            RESTARTS   AGE     IP              NODE        NOMINATED NODE   READINESS GATES
...
liveness-exec-demo                  1/1     Running           0          76s     10.244.2.84     k8s-node2   <none>           <none>
...

$ curl 10.244.2.84:/livez
OK

$ curl -X POST -d 'livez=FAIL' 10.244.2.84:/livez      #能过POST修改livez值
$ curl 10.244.2.84:/livez
FAIL
$ kubectl describe pod liveness-exec-demo
...
Events:
  Type     Reason     Age                  From               Message
  ----     ------     ----                 ----               -------
  Normal   Scheduled  7m38s                default-scheduler  Successfully assigned default/liveness-exec-demo to k8s-node2
  Warning  Unhealthy  89s (x3 over 99s)    kubelet            Liveness probe failed:    #存活检测失败 重启容器
  Normal   Killing    89s                  kubelet            Container demo failed liveness probe, will be restarted
  Normal   Pulled     59s (x2 over 7m33s)  kubelet            Container image "ikubernetes/demoapp:v1.0" already present on machine
  Normal   Created    59s (x2 over 7m33s)  kubelet            Created container demo
  Normal   Started    59s (x2 over 7m33s)  kubelet            Started container demo


$ kubectl get pod  -o wide
NAME                                READY   STATUS            RESTARTS   AGE     IP              NODE        NOMINATED NODE   READINESS GATES
...
liveness-exec-demo                  1/1     Running           1          9m15s   10.244.2.84     k8s-node2   <none>           <none>    #显示容器已重启
...

容器内部调试工具

用于记录下k8s集群中用于调试dns及网络连通性的容器工具。此工具提供了基本的网络排查指令，如curl、wget、ping、traceroute、nslookup、dig。

$ cat dns_utils.yaml      # yaml文件如下
apiVersion: v1
kind: Pod
metadata:
  name: dnsutils
  namespace: default
spec:
  containers:
  - name: dnsutils
    image: mydlqclub/dnsutils:1.3
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
  
$ kubectl apply -f dns_utils.yaml     # 执行yaml文件