Prerequisite

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/ztunnel:<tag>
• Mirrored image: <your-namespace>/dhi-ztunnel:<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 ztunnel image

This Docker Hardened Image includes:

• ztunnel binary — Rust-based per-node L4 proxy for Istio ambient mesh
• Standard TLS certificates for secure communication
• Prometheus metrics endpoint on port 15020 (/metrics and /stats/prometheus)
• Health check endpoint on port 15021 (/healthz/ready)
• CIS benchmark compliance (runtime), FIPS 140 + STIG + CIS compliance (FIPS variant, requires DHI Enterprise subscription)

Start a ztunnel instance

Ztunnel is a per-node DaemonSet proxy for Istio ambient mesh. It is not designed to run as a standalone container. It requires the Istio control plane (Istiod) and Istio CNI to function. You must install these components before installing ztunnel.

First follow the authentication instructions for DHI in Kubernetes⁠.

Log in to the DHI Helm registry:

$ helm registry login dhi.io

Create a Kubernetes namespace and secret for pulling DHI images:

$ kubectl create namespace istio-system
$ kubectl create secret docker-registry dhi-pull-secret \
    --docker-server=dhi.io \
    --docker-username=<Docker username> \
    --docker-password=<Docker token> \
    --docker-email=<Docker email> \
    -n istio-system

Install the Istio control plane prerequisites:

$ helm install istio-base oci://dhi.io/istio-base-chart --version <version> \
    -n istio-system --wait
$ helm install istiod oci://dhi.io/istio-discovery-chart --version <version> \
    -n istio-system \
    --set "global.imagePullSecrets[0]=dhi-pull-secret" \
    --set profile=ambient --wait

Install the Istio CNI using the upstream Helm chart with the DHI image override:

$ helm repo add istio https://istio-release.storage.googleapis.com/charts
$ helm install istio-cni istio/cni --version <version> \
    -n istio-system \
    --set hub=dhi.io \
    --set image=istio-install-cni \
    --set tag=<tag> \
    --set "global.imagePullSecrets[0]=dhi-pull-secret" \
    --set ambient.enabled=true --wait

Install ztunnel using the DHI Helm chart. Replace <version> with the chart version:

$ helm install ztunnel oci://dhi.io/ztunnel-chart --version <version> \
    --namespace istio-system \
    --set "imagePullSecrets[0]=dhi-pull-secret" \
    --wait

Verify the ztunnel DaemonSet is running:

$ kubectl get pods -n istio-system -l app=ztunnel

Common ztunnel use cases

Ambient mesh L4 proxy for zero-trust service-to-service communication

Ztunnel is the foundational data plane component of Istio's ambient mesh mode. It runs as a DaemonSet on every node and automatically intercepts all traffic for enrolled workloads, encrypting it with mutual TLS (mTLS) without requiring sidecar injection or application code changes.

After completing the installation steps in Start a ztunnel instance⁠, enroll a namespace in the ambient mesh:

$ kubectl label namespace default istio.io/dataplane-mode=ambient

Deploy sample workloads to verify traffic flows through ztunnel:

$ kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.29/samples/bookinfo/platform/kube/bookinfo.yaml
$ kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.29/samples/sleep/sleep.yaml

Test encrypted service-to-service communication:

$ kubectl exec deploy/sleep -- curl -s -o /dev/null -w "%{http_code}" http://productpage:9080/

Expected output: 200

Verify mTLS is active by checking ztunnel logs for HBONE tunnel connections:

$ kubectl logs -n istio-system -l app=ztunnel --tail=20

FIPS-compliant service mesh deployments

For organizations that require Federal Information Processing Standards (FIPS) compliance, the DHI ztunnel FIPS variant ensures all cryptographic operations use a FIPS 140-2 validated OpenSSL module. In FIPS mode, ztunnel is compiled with --no-default-features --features tls-openssl instead of the default Rustls TLS backend.

Install ztunnel with the FIPS variant using the DHI Helm chart. Use a FIPS-tagged image by setting the appropriate tag value:

$ helm install ztunnel oci://dhi.io/ztunnel-chart --version <version> \
    -n istio-system \
    --set "imagePullSecrets[0]=dhi-pull-secret" \
    --set tag=<tag>-fips \
    --wait

Verify FIPS mode is active by checking the container environment variables (the runtime image does not include a shell or env command):

$ kubectl get pod -n istio-system \
    $(kubectl get pods -n istio-system -l app=ztunnel -o jsonpath='{.items[0].metadata.name}') \
    -o jsonpath='{.spec.containers[0].env}' | grep -i fips

Alternatively, use Docker Debug⁠ to inspect the running container directly.

Deploy ztunnel in Kubernetes

Ztunnel is designed exclusively for Kubernetes and deploys as a DaemonSet via Helm. Follow the steps in Start a ztunnel instance⁠ to install the full stack.

Verify the DaemonSet is running on all nodes:

$ kubectl get pods -n istio-system -l app=ztunnel -o wide

Enroll a namespace in ambient mesh:

$ kubectl label namespace default istio.io/dataplane-mode=ambient

Remove a namespace from the mesh (no pod restarts required):

$ kubectl label namespace default istio.io/dataplane-mode-

Official Docker image (DOI) vs Docker Hardened Image (DHI)

Image variants

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

Runtime variants

Runtime variants are the default production images. They run as the nonroot user, do not include a shell or package manager, and are CIS benchmark compliant. These are the recommended variants for production ambient mesh deployments.

Dev variants

Dev variants include -dev in the tag name. They run as root and include a shell and package manager. Use dev variants for debugging, troubleshooting, and development environments. Dev variants are CIS compliant.

FIPS variants

FIPS variants include -fips in the tag name. They are built with FIPS 140-2 validated OpenSSL instead of the default Rustls TLS backend. All TLS operations use the OpenSSL FIPS module (Certificate #4282⁠). FIPS variants run as the nonroot user and are CIS, FIPS, and STIG compliant. FIPS configuration is automatically applied at runtime.

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. Inspect the image variants to identify which packages are already installed.

   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.

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.