# What is nginx?

Nginx (pronounced "engine-x") is an open source reverse proxy server for HTTP, HTTPS, SMTP, POP3, and IMAP protocols, as well as a load balancer, HTTP cache, and a web server (origin server). The nginx project started with a strong focus on high concurrency, high performance and low memory usage. It is licensed under the 2-clause BSD-like license and it runs on Linux, BSD variants, Mac OS X, Solaris, AIX, HP-UX, as well as on other *nix flavors. It also has a proof of concept port for Microsoft Windows.

> [wikipedia.org/wiki/Nginx](https://en.wikipedia.org/wiki/Nginx)

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# How to use this image

## Hosting some simple static content

```console
$ docker run --name some-nginx -v /some/content:/usr/share/nginx/html:ro -d nginx
```

Alternatively, a simple `Dockerfile` can be used to generate a new image that includes the necessary content (which is a much cleaner solution than the bind mount above):

```dockerfile
FROM nginx
COPY static-html-directory /usr/share/nginx/html
```

Place this file in the same directory as your directory of content ("static-html-directory"), run `docker build -t some-content-nginx .`, then start your container:

```console
$ docker run --name some-nginx -d some-content-nginx
```

## Exposing external port

```console
$ docker run --name some-nginx -d -p 8080:80 some-content-nginx
```

Then you can hit `http://localhost:8080` or `http://host-ip:8080` in your browser.

## Complex configuration

```console
$ docker run --name my-custom-nginx-container -v /host/path/nginx.conf:/etc/nginx/nginx.conf:ro -d nginx
```

For information on the syntax of the nginx configuration files, see [the official documentation](http://nginx.org/en/docs/) (specifically the [Beginner's Guide](http://nginx.org/en/docs/beginners_guide.html#conf_structure)).

If you wish to adapt the default configuration, use something like the following to copy it from a running nginx container:

```console
$ docker run --name tmp-nginx-container -d nginx
$ docker cp tmp-nginx-container:/etc/nginx/nginx.conf /host/path/nginx.conf
$ docker rm -f tmp-nginx-container
```

This can also be accomplished more cleanly using a simple `Dockerfile` (in `/host/path/`):

```dockerfile
FROM nginx
COPY nginx.conf /etc/nginx/nginx.conf
```

If you add a custom `CMD` in the Dockerfile, be sure to include `-g daemon off;` in the `CMD` in order for nginx to stay in the foreground, so that Docker can track the process properly (otherwise your container will stop immediately after starting)!

Then build the image with `docker build -t custom-nginx .` and run it as follows:

```console
$ docker run --name my-custom-nginx-container -d custom-nginx
```

### Using environment variables in nginx configuration

Out-of-the-box, nginx doesn't support environment variables inside most configuration blocks. But `envsubst` may be used as a workaround if you need to generate your nginx configuration dynamically before nginx starts.

Here is an example using docker-compose.yml:

```yaml
web:
  image: nginx
  volumes:
   - ./mysite.template:/etc/nginx/conf.d/mysite.template
  ports:
   - "8080:80"
  environment:
   - NGINX_HOST=foobar.com
   - NGINX_PORT=80
  command: /bin/bash -c "envsubst < /etc/nginx/conf.d/mysite.template > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'"
```

The `mysite.template` file may then contain variable references like this:

`listen       ${NGINX_PORT};
`

## Running nginx in debug mode

Images since version 1.9.8 come with `nginx-debug` binary that produces verbose output when using higher log levels. It can be used with simple CMD substitution:

```console
$ docker run --name my-nginx -v /host/path/nginx.conf:/etc/nginx/nginx.conf:ro -d nginx nginx-debug -g 'daemon off;'
```

Similar configuration in docker-compose.yml may look like this:

```yaml
web:
  image: nginx
  volumes:
    - ./nginx.conf:/etc/nginx/nginx.conf:ro
  command: [nginx-debug, '-g', 'daemon off;']
```