How to use environment variables in nginx configuration file

Preface

Nginx is an HTTP server designed for performance. Compared with Apache and lighttpd, it has the advantages of less memory usage and higher stability.

Since we need to deploy nginx docker now, we hope that the server_name in the nginx configuration file can be dynamically modified before starting the container.
However, the nginx configuration file does not support the use of environment variables. I found many solutions online and finally chose to use envsubst to rewrite the nginx configuration file.

How it works

Nginx consists of a kernel and modules. The kernel is very small and concise, and its work is also very simple. It only maps client requests to a location block (location is a directive in the Nginx configuration for URL matching) by looking up the configuration file. Each directive configured in this location will start different modules to complete the corresponding work.

Nginx modules are structurally divided into core modules, basic modules and third-party modules:

Core modules: HTTP module, EVENT module and MAIL module Basic modules: HTTP Access module, HTTP FastCGI module, HTTP Proxy module and HTTP Rewrite module,
Third-party modules: HTTP Upstream Request Hash module, Notice module, and HTTP Access Key module.

Learn envsubst

envsubst replaces the environment variables with the values ​​of the specified tags in the file.
For example, there is a file env.conf with the following content:

[test]
ip = ${ip}
port = ${port}
url = http://${ip}:${port}/index.html
phone = ${phone}

When executing export ip=192.168.1.5 , export port=8081 , export phone=13522223334 , the environment variables are written.
Then execute envsubst < env.conf > env.new.conf to generate the following env.new.conf

[test]
ip = 192.168.1.5
port = 8081
url = http://192.168.1.5:8081/index.html
phone = 13522223334

You can also specify to replace only some environment variables, source env.env && envsubst '$ip;$phone' < env.conf , which will only replace the two variables ip and phone.
The above only replaces part of the environment variables. In Linux testing, only single quotes can be used. Double quotes are invalid. I have tried delimiters , . ; | and these four are all OK. I guess there are more delimiters.

Apply nginx configuration file

docker-compose.yml file is as follows

version: "3"
 
services:
  nginx:
    image: nginx:1.20.1-alpine
    container_name: nginx
    ports:
      - 80:80
      -443:443
    environment:
      - NGINX_HOST=www.janbar.com
      - NGINX_PORT=80
    volumes:
      - /root/janbar.temp:/etc/nginx/conf.d/janbar.temp
    command: /bin/sh -c "envsubst < /etc/nginx/conf.d/janbar.temp > /etc/nginx/conf.d/default.conf && exec nginx -g 'daemon off;'"
    network_mode: bridge
    restart: always

The contents of the /root/janbar.temp file are as follows

server {
    listen ${NGINX_PORT};
    listen [::]:${NGINX_PORT};
    server_name ${NGINX_HOST};

    location / {
        root /usr/share/nginx/html;
        index index.html index.htm;
    }

    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
        root /usr/share/nginx/html;
    }
}

According to the above docker-compose.yml configuration file, the configuration file in the docker container is finally generated as follows cat /etc/nginx/conf.d/default.conf

server {
    listen 80;
    listen [::]:80;
    server_name www.janbar.com;

    location / {
        root /usr/share/nginx/html;
        index index.html index.htm;
    }

    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
        root /usr/share/nginx/html;
    }
}

Summarize

After the above operations, you can finally update the internal configuration file of the nginx docker container through environment variables. Mission accomplished!

The above is the details of using environment variables in the nginx configuration file. For more information about nginx environment variables, please pay attention to other related articles on 123WORDPRESS.COM!