Dockerfile

容器container自定義的安裝

由一行行命令語句組成，並且支援以 # 開頭的註解行。

他大致上會擁有四個東西

• 基底映像檔
• 維護者(非必要)
• 操作指令
• 容器啟動時執行指令(不一定每個都有)

建置流程

1. 建立一個目錄

2. 使用 cd 指令進入到該目錄

3. 建立一個檔案名稱為 Dockerfile

4. 編輯該檔案內容如下

   # 使用一個image為基底
   FROM python:2.7-slim
   
   # 維護者
   MAINTAINER william [email protected]
   
   # Set the working directory to /app
   WORKDIR /app
   
   # Copy the current directory contents into the container at /app
   ADD . /app
   
   # Install any needed packages specified in requirements.txt
   RUN pip install -r requirements.txt
   
   # Make port 80 available to the world outside this container
   EXPOSE 80
   
   # Define environment variable
   ENV NAME World
   
   # Run app.py when the container launches
   CMD ["python", "app.py"]
   

5. 依照不同application建立相關部署檔案, 以Python為例
   requirements.txt

   Flask
   Redis
   

   app.py

   from flask import Flask
   from redis import Redis, RedisError
   import os
   import socket
   
   # Connect to Redis
   redis = Redis(host="redis", db=0, socket_connect_timeout=2, socket_timeout=2)
   
   app = Flask(__name__)
   
   @app.route("/")
   def hello():
       try:
           visits = redis.incr("counter")
       except RedisError:
           visits = "<i>cannot connect to Redis, counter disabled</i>"
   
       html = "<h3>Hello {name}!</h3>" \
              "<b>Hostname:</b> {hostname}<br/>" \
              "<b>Visits:</b> {visits}"
       return html.format(name=os.getenv("NAME", "world"), hostname=socket.gethostname(), visits=visits)
   
   if __name__ == "__main__":
       app.run(host='0.0.0.0', port=80)
   

6. 建立App的Docker image, 並命名為 friendlyhello
docker build -t friendlyhello .

7. 查詢在本地端建立好的Docker image

   $ docker images
   
   REPOSITORY            TAG                 IMAGE ID
   friendlyhello         latest              326387cea398
   

8. 運行使用該Docker image 運行 container 並指定將Host主機的 4000 Port 對應到 Container的80 Port
   docker run -p 4000:80 friendlyhello

9. You should see a notice that Python is serving your app at http://0.0.0.0:80. But that message is coming from inside the container, which doesn’t know you mapped port 80 of that container to 4000, making the correct URL http://localhost:4000.

   Go to that URL in a web browser to see the display content served up on a web page, including “Hello World” text, the container ID, and the Redis error message.