Connecting to the Server

Detailed Guide for MobaXterm Commands

In this section, you will execute commands to connect from your local machine to the Bastion Host, and then from the Bastion Host to the Backend server to install and run the application.

Note: The commands should be executed sequentially. Ensure you have successfully connected in the previous step before proceeding to the next one.

1. Connect to the Bastion Host

This is the first step, connecting from your computer to the Bastion Host in the Public Subnet.

  • Open MobaXterm and create a new SSH session.
  • Remote host: Enter the Public IPv4 address of project-bastion-host-ec2.
  • Specify username: ec2-user.
  • Use private key: Select the project-keypair.pem file you downloaded when creating the EC2 instance.

Setting up an SSH session in MobaXterm

2. Jump to the Backend Instance

Now that you are inside the Bastion Host, we need to prepare to connect to the Backend server.

  • Step 1: Recreate the key pair file on the Bastion Host. Open a text editor like nano and paste the content of the .pem file from your local machine.

    nano project-keypair.pem

    Pasting the key content into nano

  • Step 2: Set the correct permissions for the key file. SSH requires the key file to be protected; otherwise, it will refuse the connection.

    chmod 400 project-keypair.pem

    Setting permissions for the key file

  • Step 3: SSH into the Backend. Use the Private IPv4 address of project-backend-ec2.

    ssh -i project-keypair.pem ec2-user@<Private_IP_of_Backend_EC2>

    Successfully connected to the Backend server

3. Set up the Environment and Application on the Backend

Once inside the Backend server, install the necessary tools.

  • Update the system:

    sudo yum update -y

    Updating system packages

  • Install Git:

    sudo yum install -y git

    Installing Git

  • Clone the project source code from GitHub:

    git clone https://github.com/tuilatri/weather-application.git

    Cloning the project

  • Navigate into the backend directory:

    cd weather-application/backend

    Changing to the backend directory

  • Install Node.js:

    sudo dnf install -y nodejs

    Installing Node.js

  • Install project dependencies:

    npm install

    Installing npm packages

  • Configure environment variables:

    nano .env

    Configuring the .env file

4. Start and Test the Backend

  • Start the application:

    npm run start

    Backend application is running

  • Test the application directly on the server: Open another terminal window in MobaXterm, connect again, and then use the curl command to test.

    curl http://localhost:3000/

    Testing the backend with curl

5. Update the Frontend with the Backend’s CloudFront Address

After the Backend is operational, you need to get the Backend’s CloudFront URL and update it in the Frontend’s configuration file on S3.

  • Step 1: Get the Backend’s CloudFront Distribution Domain Name. Go to the CloudFront service in the AWS Console, find and copy the Domain Name of the distribution pointing to the backend.

  • Step 2: Access the S3 bucket containing the Frontend source code. Go to the S3 service and select the bucket that holds the frontend source code.

  • Step 3: Open and edit the api.js file. Find the api.js file (usually in a js folder or similar), select the file, and click Edit.

  • Step 4: Update the API address. In the file’s content, find the line declaring the API variable and paste the Backend’s CloudFront URL. Then click Save changes.

    // Change the value of this variable
const API_URL = 'https://your-cloudfront-backend-domain.cloudfront.net';

    Pasting the CloudFront URL and saving

  • Step 5: Wait for the Frontend’s CloudFront to update. After you save the api.js file, the CloudFront serving the Frontend will need a few minutes to clear the old cache and update to the new version of the file. Please wait about 5-10 minutes before checking the website again.

    Waiting for CloudFront to update

6. Troubleshooting Guide

If you update the code on GitHub but the changes do not appear on the web, follow these steps on the Backend server:

  • Pull the latest code:

    git pull origin main

  • Find the running Node.js process:

    ps aux | grep node

  • Stop the old process using its PID:

    kill -9 <PID>

    Real-world example:

    [ec2-user@ip-10-0-144-101 backend]$ ps aux | grep node
ec2-user    3117  0.0  6.6 1127836 64896 pts/1   Sl+   10:15   0:00 node server.js

[ec2-user@ip-10-0-144-101 backend]$ kill -9 3117

  • Restart the application:

    npm run start