02 容器化一个应用

容器化一个应用

For the rest of this guide, you will be working with a simple todo list manager

Get the app

运行运用之前，你需要下载源码到你的主机上。

1. 克隆仓库：git clone https://github.com/docker/getting-started.git

2. 进入getting-started/app下, 可以看到spec文件夹、src文件夹、和package.json

   [root@localhost getting-started]# tree
   .
   ├── app
   │   ├── package.json
   │   ├── spec
   |       └──//...
   │   ├── src
   │       └──//... 
   │   └── yarn.lock
   //...

Build the app’s image

In order to build hte container image, you’ll need to use a Dockerfile. A Dockerfile is simply a text-based file with no file extension. A Dockerfile contains a script of instructions that Docker uses to create a container image.

1. In the app directory, the same location as the package.json file, create a file named Dockerfile. You can use the following commands below to create a Dockerfile based on your operating system.

   for linux:

   [root@localhost getting-started]# pwd
   /root/docker/getting-started
   [root@localhost getting-started]# cd app
   [root@localhost getting-started]# touch Dockerfile
   [root@localhost getting-started]# vim Dockerfile

   编辑内容，内容如下

   # syntax=docker/dockerfile:1
   
   FROM node:18-alpine
   WORKDIR /app
   COPY . .
   RUN yarn install --production
   CMD ["node", "src/index.js"]
   EXPOSE 3000

2. Build the container image using the following commands

   先进入app目录（Dockerfile所在目录)

   [root@localhost app]# cd /root/docker/getting-started/app

   然后执行如下命令构建镜像

   docker build -t getting-started .

   The docker build command uses the Dockerfile to build a new container image. You might have noticed that Docker downloaded a lot of “layers”. The is because you instructed the builder that you wanted to start from node:18-alpine image. But, since you didn’t have that on your machine, Docker needed to download the image.

   After Docker downloaded the image, the instructions from the Dockerfile copied in your application and use yarn to install your application’s dependencies. The CMD directive specifies the default command to run when starting a container from this image.

   finally, the -t flag tags your image. Think of this simply as a hunman-readable name from the final image. Since you named the image getting-started, you can refer to that image when you run a container.

   The . at the end of the docker build command tell the docker that it should look for the Dockerfile in the current directory.

Start an app container

Now that you have an image, you can run the application in a container. To do so, you will use the docker run command.

1. Start your container using the docker run command and specify the name of the image you just created:

   docker run -d -p 3000:3000 getting-started

   You use the -d flag to run the new container in “detached” mode(in the background). You also use the -p flag to create a mapping between the host’s port 3000 to the container’s port 3000. Without the port mapping, you wouldn’t be able to access the application.

2. After a few seconds, open your web browser to http://<your_machine_ip>:3000, you should see you app.