Serving Multiple Applications with Nginx

Imagine this scenario, you just got your dream DevOps job. You are very excited. In no time, you get your first task to host a javascript, python and PHP application on a single Linux centos server. At first, you are confused about how you'll serve multiple applications from a single server. You do a little digging and then you strike gold. Nginx!

"NGINX is open-source software for web serving, reverse proxying, caching, load balancing, media streaming, and more. It started out as a web server designed for maximum performance and stability. In addition to its HTTP server capabilities, NGINX can also function as a proxy server for email (IMAP, POP3, and SMTP) and a reverse proxy and load balancer for HTTP, TCP, and UDP servers."

Prerequisite:

• Linux centos server

STEP 1

Log in to your server using ssh

ssh root@server_ip_address

You'll be asked to input your password.

Installing Nginx on Centos
Nginx packages can be gotten from EPEL repositories:

sudo yum install epel-release

Install Nginx:

sudo yum install nginx

Output should look like:

Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Importing GPG key 0x352C64E5:
Userid     : "Fedora EPEL (7) <[e-mail]>"
Fingerprint: 91e9 7d7c 4a5e 96f1 7f3e 888f 6a2f aea2 352c 64e5
Package    : epel-release-7-9.noarch (@extras)
From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Is this ok [y/N]:

Press y and enter

Upon completion, start Nginx and check it's status using:

sudo systemctl enable nginx
sudo systemctl start nginx
sudo systemctl status nginx

If all goes well, you should see this:

● nginx.service - The nginx HTTP and reverse proxy server
  Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled)
  Active: active (running) since Mon 2018-03-12 16:12:48 UTC; 2s ago
  Process: 1677 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS)
  Process: 1675 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS)
  Process: 1673 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS)
Main PID: 1680 (nginx)
  CGroup: /system.slice/nginx.service
          ├─1680 nginx: master process /usr/sbin/nginx
          └─1681 nginx: worker process

Open HTTP(80) and HTTPS(433) if you are behind a firewall with these commands:

sudo firewall-cmd --permanent --zone=public --add-service=http
sudo firewall-cmd --permanent --zone=public --add-service=https
sudo firewall-cmd --reload

Open http://YOUR_IP in your browser of choice, you should see an Nginx homepage displayed. Congratulation!!!

Step 2

Create a New User Account with sudo Privileges
For security reasons, it is advisable not to use the root user to run commands but to create a new user with sudo privileges:

useradd username

• Replace username with your username with Sudo privileges.

Set the User Password

passwd username

You should get the output:

output
Changing password for user username.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.

Add User to the sudo Group

usermod -aG wheel username

Switch to Newly Created User

su - username

Then list \root directory content:

sudo ls -l /root

You'll see a banner message the first time you sudo from this account:

output
We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

[sudo] password for username:

Serve Multiple Applications

Log in to the Server Using Your username with Root Privileges

Our directory structure would look like this:

/var/www/
├── javascriptapp.com
│   └── public_html
├── pythonapp.com
│__ └── public_html

Let's create a directory where your javascript and python application would reside:

sudo mkdir -p /var/www/javascriptapp.com/public_html
sudo mkdir -p /var/www/pythonapp.com/public_html

Important!
To avoid any permission issues, let us change ownership to our username with sudo privileges:

sudo chown -R username: /var/www/javascriptapp.com
sudo chown -R username: /var/www/pythonapp.com

sudo vi /var/www/javascriptapp.com/public_html/index.html

Copy and paste the following lines:

\<!DOCTYPE html>
\<html lang="en" dir="ltr">
  \<head>
    \<meta charset="utf-8">
    \<title>Welcome to javascriptapp.com</title>
  \</head>
  \<body>
    \<h1>Success! javascriptapp.com home page!</h1>
  \</body>
\</html>

Create a Server Block
Server blocks are stored in the /etc/nginx/conf.d directory and must end with .conf

sudo vi /etc/nginx/conf.d/javascriptapp.com.conf

Copy and paste the following lines into the file, remember to replace the server name with your value:

server {
    listen 80;
    listen [::]:80;
    root /var/www/javascriptapp.com/public_html;
    index index.html;
    server_name example.com www.javascriptapp.com;
    access_log /var/log/nginx/javascriptapp.com.access.log;
    error_log /var/log/nginx/javascriptapp.com.error.log;
    location / {
        try_files $uri $uri/ =404;
    }
}

Save the file and check that configuration is right:

sudo nginx -t

Restart Nginx:

sudo systemctl restart nginx

Then visit your server name:
http://javascriptapp.com

NB: This must be a configured DNS to your server else just use the server IP address.

Final Step

Configure Nginx for Node JS Application

Upload node project to /var/www/javascriptapp.com/public_html, build the application and start node application on a designated port.

Edit the application .conf file to look like this:
sudo vi /etc/nginx/conf.d/javascriptapp.com.conf

server {
    listen 80;
    listen [::]:80;
    root /var/www/javascriptapp.com/public_html;
    server_name example.com www.javascriptapp.com;
    access_log /var/log/nginx/javascriptapp.com.access.log;
    error_log /var/log/nginx/javascriptapp.com.error.log;
    location / {
        proxy_pass http://internal_server_ip:node_app_PORT;
        try_files $uri $uri/ =404;
    }
}

NB: You can get the internal_server_ip by running hostname -I on the terminal. See https://www.linuxtrainingacademy.com/determine-public-ip-address-command-line-curl/ for more.

Restart Nginx:

sudo systemctl restart nginx

And visit your server name or IP to verify that your application is served.

Congratulation! Your javascript app is successfully served!
You can follow a similar process to serve your python application in the created directory.

This post is inspired by https://www.linuxtrainingacademy.com/determine-public-ip-address-command-line-curl/