How to use this image

All examples in this guide use the public image. If you’ve mirrored the repository for your own use (for example, to your Docker Hub namespace), update your commands to reference the mirrored image instead of the public one.

For example:

• Public image: dhi.io/<repository>:<tag>
• Mirrored image: <your-namespace>/dhi-<repository>:<tag>

For the examples, you must first use docker login dhi.io to authenticate to the registry to pull the images.

Using the OpenSCAP Docker Hardened Image (General Use)

This Docker Hardened Image is a drop-in replacement for the oscap CLI tool. It can evaluate both XCCDF benchmarks and OVAL definitions and generate the appropriate results.

OpenSCAP can also be used to validate the STIG posture for all Docker Hardened Images.

Running OpenSCAP

To test this image, you can run oscap and point it to the DHI GPOS SRG file that is embedded in the image itself:

docker run --rm -it dhi.io/openscap:<tag> info /opt/docker/gpos/xml/scap/ssg/content/ssg-dhi-gpos-ds.xml

Document type: Source Data Stream
Imported: 2025-11-16T18:03:16

Stream: scap_org.open-scap_datastream_from_xccdf_all-resolved-xccdf-v3r2.xml
...

Use the --profile option to obtain info about a given profile:

docker run --rm -it dhi.io/openscap:<tag> info --profile <profile> <SCAP file>

To evaluate content against a set of OVAL rules, use the oscap validate command and examine the exit code, for example:

docker run --rm -it -v $(pwd)/extra-content:/extra-content dhi.io/openscap:<tag> oval validate <SCAP file> && echo "ok" || echo "exit code = $? validation failure"

To customize evaluation even further you could mount the extra content to be evaluated, and customize the dictionary and STIG profile along with the output directories.

docker run --rm -it \
  -v $(pwd)/out:/out \
  -v $(pwd)/extra-content:/extra-content \
  -v $(pwd)/stigs:/stigs \
  --entrypoint oscap dhi.io/openscap:<tag> \
  xccdf eval --profile <profile> \
  --results /out/results.xml \
  --report /out/results.html \
  --cpe /stigs/<dictionary> \
  /stigs/<SCAP file>

Using the OpenSCAP Docker Hardened Image with DHI images

Following are several sets of instructions that will help you scanning DHI images for compliance with all frameworks supporting oval rules, like for example STIG.

Obtaining the DHI GPOS STIG Profile

The DHI GPOS STIG Profile can be obtained from the OpenSCAP DHI⁠ image at GitHub.

Running OpenSCAP on a DHI image from registry

Note: You need to use the dev variant for this functionality to work as it requires root access.

You can use the oscap tool to evaluate the STIG posture on any of the DHI images. The OpenSCAP DHI image includes oscap-docker a Python utility that can be used to evaluate any Docker container or image. You can point this tool to a registry image and use an experimental Docker feature that allows to mount a shell on top of an existing image. This happens automatically if you invoke oscap-docker pointing to the image.

# The image must be pulled first
docker pull dhi.io/airflow:3-fips

# Scan the image directly
docker run --rm -it --pid=host -v "$HOME/.docker/run/docker.sock:/var/run/docker.sock" -v $(pwd)/out:/out --entrypoint oscap-docker dhi/openscap:<tag>-dev image dhi.io/airflow:3-fips xccdf eval --profile xccdf_dhi-gpos_profile_.check --results /out/oval-results.xml --report /out/compliance-report.html /opt/docker/gpos/xml/scap/ssg/content/ssg-dhi-gpos-ds.xml

The above command scans the image against the DHI GPOS. You'll get an output like this:

Creating a temporary container for the image...
...
Title   The operating system must prohibit user installation of
system software without explicit privileged status.
Rule    xccdf_mil.disa.stig_rule_SV-203716r982210_rule
Ident   CCI-003980
Result  pass

Title   The operating system must include only approved
trust anchors in trust stores or certificate stores managed by the
organization.
Rule    xccdf_mil.disa.stig_rule_SV-263659r982563_rule
Ident   CCI-004909
Result  pass

Temporary container 61ac917501f0ed65f2c17abbb09bf8918db63764d7d78e0004852a335d2197ac cleaned
Cleaning temporary extracted container...

A generated report will be available at out/report.html for you to browse. This report contains the evaluation results against the Docker Hardened Image - Alpine 3.22/Debian 12/13 GPOS STIG Profile.

Running OpenSCAP on a DHI running container

You can do the same technique on any running container. Below we start the postgres FIPS image and mount busybox on top to run a sleep command immediately after. This allows us to have a latent container that we can scan:

docker pull busybox:uclibc
docker run --rm --name dhi_postgres_16-alpine3.22-fips -u 0:0 --mount type=image,source=busybox:uclibc,target=/busybox --entrypoint /busybox/bin/sleep dhi/postgres:16-alpine3.22-fips "infinite" &

With the above command we have now the DHI image running sleep. We can now point DHI OpenSCAP to that container.

docker run --rm --pid=host -v "$HOME/.docker/run/docker.sock:/var/run/docker.sock" -v $(pwd)/out:/out dhi.io/openscap:<dev-tag> dhi_postgres_16-alpine3.22-fips

Container dhi_postgres_16-alpine3.22-fips is running, using its existing mount...
Docker container dhi_postgres_16-alpine3.22-fips ready to be scanned.
--- Starting Evaluation ---
....
.... many more checks...
....
Title   The operating system must prohibit user installation of
system software without explicit privileged status.
Rule    xccdf_._rule_V_203716
Result  pass

Title   The operating system must include only approved
trust anchors in trust stores or certificate stores managed by the
organization.
Rule    xccdf_._rule_V_263659
Result  pass

Scanning a custom application built on top of a DHI image

Following with the above examples, we can download the DHI Stig profile and apply it to a custom application built on top of DHI. To make the example complete, first we will build an application on top of DHI's Python FIPS.

Create a new directory and use the following Dockerfile to get started.

# syntax=docker/dockerfile:1

## -----------------------------------------------------
## Build stage (use tag with -dev suffix: e.g. 3.9.23-debian13-fips-dev)
FROM dhi.io/python:<tag> AS build-stage

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PATH="/app/venv/bin:$PATH"

WORKDIR /app

RUN python -m venv /app/venv
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

## -----------------------------------------------------
## Final stage (use the same tag as above but without the -dev suffix e.g. 3.9.23-debian13-fips)
FROM dhi.io/python:<tag> AS runtime-stage

ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PATH="/app/venv/bin:$PATH"

WORKDIR /app

COPY --from=build-stage /app/venv /app/venv
COPY app.py .

CMD ["python", "/app/app.py"]

Next, create app.py and requirements.txt files in the same directory.

# app.py

import openai
import numpy as np
import pandas as pd

def main():
    print("Package versions:")
    print(f"openai: {openai.__version__}")
    print(f"numpy: {np.__version__}")
    print(f"pandas: {pd.__version__}")

    print("Waiting 10 minutes for OpenSCAP scan...")

if __name__ == "__main__":
    main()

openai
numpy
pandas

Run the following commands to build and run the sample app mounting busybox on it.

docker build -t my-python-app .

docker run --rm --name my-running-app -u 0:0 --mount type=image,source=busybox:uclibc,target=/busybox --entrypoint /busybox/bin/sleep my-python-app "infinite" &

Finally, run the following to execute the STIG profile that we downloaded earlier on this new DHI FIPS Python application that was just created.

mkdir -p out stigs
wget https://raw.githubusercontent.com/docker-hardened-images/catalog/refs/heads/main/image/openscap/config/ssg-dhi-gpos-ds.xml -O stigs/ssg-dhi-gpos-ds.xml
docker run --rm --pid=host \
           -v /var/run/docker.sock:/var/run/docker.sock \
           -v $(pwd)/out:/out \
           -v $(pwd)/stigs:/stigs \
           --entrypoint oscap-docker \
           dhi.io/openscap:<dev-tag> \
           container my-running-app \
           xccdf eval \
           --profile xccdf_dhi-gpos_profile_.check \
           --results /out/oval-results.xml \
           --report /out/compliance-report.html \
           /stigs/ssg-dhi-gpos-ds.xml


Docker container my-running-app ready to be scanned.
--- Starting Evaluation ---

Title   The operating system must prohibit the use or
connection of
unauthorized hardware
components.
...
...
Title   The operating system must prohibit user installation of
system software without explicit privileged status.
Rule    xccdf_._rule_V_203716
Result  pass

Title   The operating system must include only approved
trust anchors in trust stores or certificate stores managed by the
organization.
Rule    xccdf_._rule_V_263659
Result  pass

You can easily determine if the evaluation has passed or failed by looking at the report and find checks that have failed. For automated validation, inspecting the exit code of the docker run command is the most reliable way to find that there has been broken rules.

Scanning a DHI image against other set of security rules

DHI images or derivatives can be scanned against other set of rules following the same process described in the above examples. Simply replace the DHI security guide with your own file:

docker run --rm --pid=host \
           -v /var/run/docker.sock:/var/run/docker.sock \
           -v $(pwd)/out:/out \
           -v $(pwd)/stigs:/stigs \
           --entrypoint oscap-docker \
           dhi.io/openscap:<dev-tag> \
           container my-running-app \
           xccdf eval \
           --profile xccdf_dhi-gpos_profile_.check \
           --results /out/oval-results.xml \
           --report /out/compliance-report.html \
           /stigs/<SCAP File>

Non-hardened images vs Docker Hardened Images

Key differences

Hardened image debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. 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
• Application-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 <container-name>

or mount debugging tools with the Image Mount feature:

docker run --rm -it --pid container:my-container \
  --mount=type=image,source=dhi.io/busybox,destination=/dbg,ro \
  dhi.io/openscap:<tag> /dbg/bin/sh

Image variants

Docker Hardened Images come in different variants depending on their intended use. Image variants are identified by their tag.

• 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 a non-root user (UID 65532)
  • Do not include a shell or a package manager
  • Contain only the minimal set of libraries needed to run the app

• Build-time variants typically include dev in the tag 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

• FIPS variants include fips in the variant name and tag. They come in both runtime and build-time variants. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations. For example, usage of MD5 fails in FIPS variants.

To view the image variants and get more information about them, select the Tags tab for this repository, and then select a tag.

Migrate to a Docker Hardened Image

To migrate your application to a Docker Hardened Image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Docker Hardened Image. This and a few other common changes are listed in the following table of migration notes.

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Docker Hardened Images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. To view if a package manager is available for an image variant, select the Tags tab for this repository. To view what packages are already installed in an image variant, select the Tags tab for this repository, and then select a tag.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

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 nor any tools for debugging. 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 a nonroot user. Ensure that necessary files and directories are accessible to that user. You may need to copy files to different directories or change permissions so your application running as a nonroot user can access them.

To view the user for an image variant, select the Tags tab for this repository.

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. The default ports are:

• Master: 9333 (HTTP), 19333 (gRPC)
• Volume: 8080 (HTTP), 18080 (gRPC)
• Filer: 8888 (HTTP), 18888 (gRPC)
• S3: 8333
• WebDAV: 7333

No configuration changes are needed to run SeaweedFS as a nonroot user.

No shell

By default, image variants intended for runtime don't contain a shell. 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.

To see if a shell is available in an image variant and which one, select the Tags tab for this repository.

Entry point

Docker Hardened Images may have different entry points than images such as Docker Official Images.

To view the Entrypoint or CMD defined for an image variant, select the Tags tab for this repository, select a tag, and then select the Specifications tab.