k8s init初始化容器应用

1. k8s-init初始化容器应用

  • Init Container:顾名思义,用于初始化工作,执行完就结束,可以理解为一次性任务。

    • 支持大部分应用容器配置,但不支持健康检查
    • 优先应用容器执行
  • 应用场景:

    • 环境检查:例如确保应用容器依赖的服务启动后再启动应用容器
    • 初始化配置:例如给应用容器准备配置文件
  • 示例:部署一个web网站,网站程序没有打到镜像中,而是希望从代码仓库中动态拉取放到应用容器中

  • 示例代码:

    apiVersion: v1
    kind: Pod
    metadata:
      name: init-demo
    spec:
      initContainers:
      - name: download
        image: busybox
        command:
        - wget
        - "-O"
        - "/opt/index.html"
        - http://www.baidu.com
        volumeMounts:
        - name: wwwroot
          mountPath: "/opt"
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: wwwroot
          mountPath: /usr/share/nginx/html
      volumes:
      - name: wwwroot
        emptyDir: {}
    
    

2. 案例

  • 编写配置文件

    [root@k8s-master yaml]# vim pod-init.yaml
    [root@k8s-master yaml]# cat pod-init.yaml 
    apiVersion: v1
    kind: Pod
    metadata:
      name: init-demo
    spec:
      initContainers:
      - name: download
        image: busybox
        command:
        - wget
        - "-O"
        - "/opt/index.html"
        - http://www.baidu.com
        volumeMounts:
        - name: wwwroot
          mountPath: "/opt"
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: wwwroot
          mountPath: /usr/share/nginx/html
      volumes:
      - name: wwwroot
        emptyDir: {}
    
    
  • 启动服务

    [root@k8s-master yaml]# kubectl apply -f pod-init.yaml 
    pod/init-demo created
    
  • 查看和验证服务

    [root@k8s-master yaml]# kubectl get pods
    NAME         READY   STATUS    RESTARTS   AGE
    init-demo    1/1     Running   0          36s
    pod-envars   1/1     Running   0          38m
    probe-demo   1/1     Running   0          169m
    
  • 进入容器查看共享卷是否有数据了

    [root@k8s-master yaml]# kubectl exec -it init-demo -- /bin/bash       
    root@init-demo:/# ls /usr/share/nginx/html/
    index.html
    root@init-demo:/# cat /usr/share/nginx/html/index.html 
    <!DOCTYPE html>
    <!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer><link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css><title>百度一下,你就知道</title></head> <body link=#0000cc> <div id=wrapper> <div id=head> <div class=head_wrapper> <div class=s_form> <div class=s_form_wrapper> <div id=lg> <img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129> </div> <form id=form name=f action=//www.baidu.com/s class=fm> <input type=hidden name=bdorz_come value=1> <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden name=rsv_bp value=1> <input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span class="bg s_ipt_wr"><input id=kw name=wd class=s_ipt value maxlength=255 autocomplete=off autofocus></span><span class="bg s_btn_wr"><input type=submit id=su value=百度一下 class="bg s_btn"></span> </form> </div> </div> <div id=u1> <a href=http://news.baidu.com name=tj_trnews class=mnav>新闻</a> <a href=http://www.hao123.com name=tj_trhao123 class=mnav>hao123</a> <a href=http://map.baidu.com name=tj_trmap class=mnav>地图</a> <a href=http://v.baidu.com name=tj_trvideo class=mnav>视频</a> <a href=http://tieba.baidu.com name=tj_trtieba class=mnav>贴吧</a> <noscript> <a href=http://www.baidu.com/bdorz/login.gif?login&amp;tpl=mn&amp;u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1 name=tj_login class=lb>登录</a> </noscript> <script>document.write('<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u='+ encodeURIComponent(window.location.href+ (window.location.search === "" ? "?" : "&")+ "bdorz_come=1")+ '" name="tj_login" class="lb">登录</a>');</script> <a href=//www.baidu.com/more/ name=tj_briicon class=bri style="display: block;">更多产品</a> </div> </div> </div> <div id=ftCon> <div id=ftConw> <p id=lh> <a href=http://home.baidu.com>关于百度</a> <a href=http://ir.baidu.com>About Baidu</a> </p> <p id=cp>&copy;2017&nbsp;Baidu&nbsp;<a href=http://www.baidu.com/duty/>使用百度前必读</a>&nbsp; <a href=http://jianyi.baidu.com/ class=cp-feedback>意见反馈</a>&nbsp;京ICP证030173号&nbsp; <img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html>
    
    
  • 小结:

    1. 注意,在编写yaml配置文件的时候,init服务,只能启动一次,如果有修改配置文件,需要删除容器,再次启动容器
posted @   七月流星雨  阅读(711)  评论(0编辑  收藏  举报
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