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.

What's included in this PgBouncer Exporter Hardened Image

This image contains the following tools:

• pgbouncer_exporter: The PgBouncer Exporter, the main component.

The entry point for the image is pgbouncer_exporter.

Run a PgBouncer Exporter instance

PgBouncer Exporter connects to a PgBouncer instance through its pgbouncer virtual database and exposes the collected statistics as Prometheus metrics on port 9127. Provide the connection string via the --pgBouncer.connectionString flag or the PGBOUNCER_EXPORTER_CONNECTION_STRING environment variable.

$ docker run -d --name pgbouncer-exporter -p 9127:9127 \
  dhi.io/pgbouncer-exporter:<tag> \
  --pgBouncer.connectionString="postgres://pgbouncer:password@pgbouncer-host:6432/pgbouncer?sslmode=disable"

Verify it's running:

$ curl http://localhost:9127/metrics

Common PgBouncer Exporter use cases

Connect using an environment variable

Pass the connection string as an environment variable instead of a flag to avoid exposing credentials in process listings:

$ docker run -d --name pgbouncer-exporter -p 9127:9127 \
  -e PGBOUNCER_EXPORTER_CONNECTION_STRING="postgres://pgbouncer:password@pgbouncer-host:6432/pgbouncer?sslmode=disable" \
  dhi.io/pgbouncer-exporter:<tag>

Use a custom listen address or metrics path

Override the default listen address or metrics path with CLI flags:

$ docker run -d --name pgbouncer-exporter -p 9200:9200 \
  -e PGBOUNCER_EXPORTER_CONNECTION_STRING="postgres://pgbouncer:password@pgbouncer-host:6432/pgbouncer?sslmode=disable" \
  dhi.io/pgbouncer-exporter:<tag> \
  --web.listen-address=0.0.0.0:9200 \
  --web.telemetry-path=/pgbouncer/metrics

Non-hardened images vs Docker Hardened Images

Key differences

Why no shell or package manager?

Docker 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 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
• 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=dhi.io/busybox,destination=/dbg,ro \
  dhi.io/pgbouncer-exporter:<tag> /dbg/bin/sh

Image variants

Docker 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 a package manager
• 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

• 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.

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.

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.

Troubleshoot 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 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.

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.

Entry point

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