nginx

Place this file in the same directory as your directory of content ("static-html-directory"), then run these commands to build and start your container:

$ docker build -t some-content-nginx .
$ docker run --name some-nginx -d some-content-nginx

Exposing external port

By default, this Nginx image listens on port 8080. To expose this port to the host, use the -p flag on docker run. Assuming you've built the image as shown in the previous example, you can run:

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

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

Customize configuration

You can mount your configuration file, or build a new image with it.

If you wish to adapt the default configuration, you can use cat to output the default configuration file.

$ docker run --rm --entrypoint cat registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag> /etc/nginx/nginx.conf > nginx.conf

Then you can edit the contents in the new local file, and mount it into a new container.

$ docker run --name some-nginx -v $(pwd)/nginx.conf:/etc/nginx/nginx.conf:ro -d -p 8080:8080 registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>

Or, build a new image with your configuration file.

FROM registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>
COPY nginx.conf /etc/nginx/nginx.conf

Using environment variables in Nginx configuration

Note: This feature is only available in the -dev variant of the image.

Out-of-the-box, Nginx doesn't support environment variables inside most configuration blocks. But the -dev variant of this image includes an entrypoint function that will extract environment variables before Nginx starts.

Here is an example using a Compose file.

web:
  image: registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>-dev
  volumes:
   - ./templates:/etc/nginx/templates
  ports:
   - "8080:8080"
  environment:
   - NGINX_HOST=foobar.com
   - NGINX_PORT=8080

By default, this function reads template files in /etc/nginx/templates/*.template and outputs the result of executing envsubst to /etc/nginx/conf.d.

So if you place templates/default.conf.template file, which contains variable references like this:

listen       ${NGINX_PORT};

It outputs to /etc/nginx/conf.d/default.conf like this:

listen       8080;

This behavior can be changed via the following environment variables:

• NGINX_ENVSUBST_TEMPLATE_DIR
  • A directory which contains template files (default: /etc/nginx/templates)
  • When this directory doesn't exist, this function will do nothing about template processing.
• NGINX_ENVSUBST_TEMPLATE_SUFFIX
  • A suffix of template files (default: .template)
  • This function only processes the files whose name ends with this suffix.
• NGINX_ENVSUBST_OUTPUT_DIR
  • A directory where the result of executing envsubst is output (default: /etc/nginx/conf.d)
  • The output filename is the template filename with the suffix removed. For example, /etc/nginx/templates/default.conf.template will be output with the filename /etc/nginx/conf.d/default.conf.
  • This directory must be writable by the user running a container.

Running Nginx in read-only mode

To run Nginx in read-only mode, you will need to mount a Docker volume to every location where Nginx writes information. The default Nginx configuration requires write access to /var/cache/nginx and /var/run. This can be easily accomplished by running Nginx as follows:

$ docker run -d -p 8080:8080 --read-only -v $(pwd)/nginx-cache:/var/cache/nginx -v $(pwd)/nginx-pid:/var/run registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>

If you have a more advanced configuration that requires Nginx to write to other locations, simply add more volume mounts to those locations.

Running Nginx in debug mode

dev variants include the nginx-debug binary that produces verbose output when using higher log levels. It can be used with simple CMD substitution:

$ docker run --name my-nginx -v /host/path/nginx.conf:/etc/nginx/nginx.conf:ro -d registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>-dev nginx-debug -g 'daemon off;'

Similar configuration in compose.yaml may look like this:

web:
  image: registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>-dev
  volumes:
    - ./nginx.conf:/etc/nginx/nginx.conf:ro
  command: [nginx-debug, '-g', 'daemon off;']

Entrypoint quiet logs

Note: This feature is only available in the -dev variant of the image.

A verbose entrypoint was added to the -dev variant. It provides information on what's happening during container startup. You can silence this output by setting environment variable NGINX_ENTRYPOINT_QUIET_LOGS:

$ docker run -d -e NGINX_ENTRYPOINT_QUIET_LOGS=1 registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>-dev

Non-hardened images vs Ghost hardened images

Key differences

Why no shell or package manager?

Ghost hardened images prioritize security through minimalism:

• Reduced attack surface: Fewer binaries mean fewer potential vulnerabilities
• Immutable infrastructure: Runtime containers shouldn't be modified after deployment
• Compliance ready: Meets strict security requirements for regulated environments

The hardened images intended for runtime don't contain a shell unless it's required for the application to run. Runtime images also typically don't include debugging tools. Common debugging methods for applications built with Docker Hardened Images include:

• Docker Debug to attach to containers
• Docker's Image Mount feature to mount debugging tools
• Ecosystem-specific debugging approaches

Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

For example, you can use Docker Debug:

docker debug <image-name>

or mount debugging tools with the Image Mount feature:

docker run --rm -it --pid container:my-container \
  --mount=type=image,source=registry.ghost-prod.alphabravo.io/ghost-base/busybox,destination=/dbg,ro \
  registry.ghost-prod.alphabravo.io/ghost-base/<image-name>:<tag> /dbg/bin/sh

Image variants

Ghost hardened images come in different variants depending on their intended use.

• Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

  • Run as the nonroot user
  • Do not include a shell or package manager unless required for the application to run
  • Contain only the minimal set of libraries needed to run the app

• Build-time variants typically include dev in the variant name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

  • Run as the root user
  • Include a shell and package manager
  • Are used to build or compile applications

Migrate to a Ghost hardened image

Switching to the hardened image does not require any special changes. You can use it as a drop-in replacement for the standard Nginx image in your existing workflows and configurations.

Migration steps

1. Update your image reference. Replace the image reference in your Docker run command or Compose file:
   • From: nginx:<tag>
   • To: registry.ghost-prod.alphabravo.io/ghost-base/nginx:<tag>
2. Update any necessary configuration. If you have custom configurations that rely on features not present in the hardened image (like running as root, exposing port 80, or using a shell), you will need to adjust them.

Troubleshooting migration

The following are common issues that you may encounter during migration.

General debugging

The hardened images intended for runtime don't contain a shell unless it's required for the application to run, and typically don't include debugging tools. The recommended method for debugging applications built with Docker Hardened Images is to use Docker Debug to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Permissions

By default image variants intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the nonroot user can access them.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10. To avoid issues, configure your application to listen on port 1025 or higher inside the container, even if you map it to a lower port on the host. For example, docker run -p 80:8080 my-image will work because the port inside the container is 8080, and docker run -p 80:81 my-image won't work because the port inside the container is 81.

No shell

By default, image variants intended for runtime don't contain a shell unless it's required for the application to run. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

Entry point

Ghost hardened images may have different entry points than images such as Docker Official Images. Use docker inspect to inspect entry points for Ghost hardened images and update your Dockerfile if necessary.