What is Docker? How to package Nodejs program?

Have you ever heard such a conversation?

This kind of conversation is very common. This is generally caused by different work environment settings or configurations. This is the main purpose of using docker.

In this article, I will teach you what docker is, why it is used and how to use it to package nodejs programs.

[Related recommendations: Docker video tutorial, node js tutorial]

What is Docker?

Docker is defined as:

Docker is a containerization platform used to package applications and their dependencies together to ensure that applications can run easily regardless of the work environment .

Well, these words just tell us:

Docker is a tool for easily creating, deploying and running applications using containers.

Why use Docker?

Docker will provide your machine environment to others along with your code, so that when your team members get your code, they can also get your machine configuration. Since the code runs on the computer with these configurations, it will certainly run on other computers because they have the same configuration as yours.

The time spent configuring the new computer can now be invested in more important tasks.

How to use Docker?

Installation

• Please visit the Docker official website
• View how to install it under the Docker Desktop tab in the menu Install docker on your machine

Windows users please note

1. You need to enable virtualization in your computer. To check if virtualization is enabled, follow these steps:

• On your keyboard press ctrl alt del
• In the menu that follows Select "Task Manager"
• Click the "Performance" tab in the pop-up Windows dialog box. Here is my

2. For those using Windows 8 or earlier, please use docker toolbox

Use Docker to package Nodejs programs

Make sure docker is started and set to running so that you can see the changes or docker effects.

• First clone the project from github
• Follow the instructions in the readme fileto set up the project.
• If you have the project set up and the server is running, you should get the following response in your browser

• Next, Create a file in the root directory of your project and name it Dockerfile without an extension.

Configure Dockerfile

• Enter the following code in the file to specify the docker node we are using

# use docker node 10
FROM node:10

• Enter the following code to create a directory for the Docker application

# create a directory to run docker
WORKDIR /app

• The following code copies the package.json file to the /app directory

# copy package.json into the new directory
COPY package.json /app

• The following code is applied in Docker Install the dependencies of the project in

# install the dependencies
RUN npm install

• Now copy all the files and folders in the project to the /app directory of docker . The following is the code:

# copy all other files and folder into the app directory
COPY . /app

• The following code specifies the port on which the docker application is running

# open port 5000
EXPOSE 5000

• Run the docker application using the following code

# run the server
CMD node index.js

Now our Dockerfile looks like this:

# use docker node 10
FROM node:10

# create a directory to run docker
WORKDIR /app

# copy package.json into the new directory
COPY package.json /app

# install the dependencies
RUN npm install

# copy all other files into the app directory
COPY . /app

# open port 5000
EXPOSE 5000


# run the server
CMD node index.js

Build the Docker application

• To build the docker application, type the following command in the terminal and press Enter

docker build -t docker-node-app .

Your terminal should output something like the following information:

在上面的命令中，docker-node-app 是我们正在创建的 docker 应用的名称。你的可能会有所不同。另外，请不要忘记结尾处的句点（.）

运行 Docker App

• 最后在终端中用以下命令运行 docker 应用：

docker run -it -p 5000:3000 docker-node-app

它会输出与普通应用完全相同的消息，但是这次，它加载在端口5000上

在上面的命令中，我们告诉 docker 运行在端口 5000 上构建的程序，即使我们的程序运行在端口 3000 上。

结果

现在，我们的 Docker 运行在 5000 端口上，而原始应用程序运行在 3000 端口上。检查你的浏览器

要查看所有正在运行的 docker 程序，请在终端中使用以下命令

docker ps

如果检查 Docker 仪表板，则会看到你的 Docker 程序：

你已经用 docker 创建了你的第一个部署。

总结

在快速迭代的系统中， docker 是很重要。因此我们需要学习它。

我们使用的大多数代码都在 docker hub 上找到。像 Microsoft、mongoDB、PHP 等许多公司已经为这些事情制作了代码（或镜像），因此你需要做的就是制作自己的副本。

这些配置称为镜像。例如可以在这里找到我们所使用的 node 镜像。

谢谢你的阅读。

原文：https://dev.to/ebereplenty/docker-an-introduction-with-nodejs-4o2j?utm_source=dormosheio&utm_campaign=dormosheio

作者：NJOKU SAMSON EBERE

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