Rails server cannot be started in Cloud9

problem

After installing Rails on AWS Cloud9 for the first time, I got an error in the terminal when I tried to create a new app and launch a server.

Development environment

• AWS Cloud9
• Rails -v 5

Error that occurred

• ** webpacker ** is not installed
• ** yarn ** is not installed

Time series until the error occurs

Install Rails-v5 on Cloud9

$ gem install rails -v 5

Create a new 〇〇 app

$ rails new 〇〇

〇 〇 Move to the application directory

$ cd ~/environment/〇〇

Start the server

$ rails s -b $IP -p $PORT

: warning: ** Error occurred **: warning:
Looking at the error statement in the terminal, the error content was as follows.

Please run rails webpacker:install Error: No such file or directory

The error is that ** webpacker ** is not installed. It is the content.

Solution Install webpacker and yarn

I found out that the cause was that webpacker was not installed, so

$ rails webpacker install

Install ** webpacker **. At this time, ** yarn ** was not installed, so the following error occurred.

Yarn not installed. 
Please download and install Yarn from https://yarnpkg.com/lang/en/docs/install/

The error is that ** yarn ** is not installed. It is the content. ** yarn ** is required to install ** webpacker **, so install ** yarn ** first.

$ npm install -g yarn

Install ** yarn ** with the command. After installing ** yarn **, then install ** webpacker **.

$ rails webpacker install

If you can install ** webpacker **, it's OK.

After installing ** yarn ** and ** webpacker **, start the server again.

$ rails s -b $IP -p $PORT

The server started up successfully: thumbs up:

Supplement

** webpacker: ** A Gem file that enables Rails to use webpack. It is for improving communication speed by combining JavaScript and CSS into one.

** yarn: ** JavaScript package manager. Mechanism for managing JavaScript