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.

Prerequisites

Codecov Frontend is the web application of a self-hosted Codecov deployment. It serves static files only; every page it renders calls the Codecov API, so a working deployment also needs the Codecov API, worker and gateway services and their data stores. The Codecov self-hosted repository⁠ carries the reference compose file this image follows, and the Codecov configuration reference⁠ documents the deployment.

Start a Codecov Frontend instance

The built application points at the hosted Codecov service. At container start the image rewrites the API and web hosts in the JavaScript bundles from CODECOV_API_HOST, CODECOV_BASE_HOST and CODECOV_SCHEME, renders the nginx configuration and starts nginx on port 8080. Set the hosts to the address your users reach the Codecov gateway at:

$ docker run -d --name codecov-frontend -p 127.0.0.1:8080:8080 \
    -e CODECOV_BASE_HOST=codecov.example.com \
    -e CODECOV_API_HOST=codecov.example.com \
    dhi.io/codecov-frontend:<tag>

Replace <tag> with the tag of the variant you want to run. The port is bound to the loopback interface above because the frontend is meant to sit behind the Codecov gateway; expose it directly only on a trusted network. GET http://localhost:8080/frontend_health answers HTTP 200 with the packaged release as its body once nginx is serving, and GET / serves the application.

The frontend service of the upstream compose file runs unchanged with the image reference swapped (its CODECOV_IA_HOST line is not read by the frontend and is left out here):

services:
  frontend:
    image: dhi.io/codecov-frontend:<tag>
    environment:
      - CODECOV_BASE_HOST=localhost:8080
      - CODECOV_API_HOST=localhost:8080
      - CODECOV_SCHEME=http
    ports:
      - "8080"

Environment variables

The start script reads these variables. Every substitution is applied to the JavaScript bundles at container start, so a change needs a container restart.

Common Codecov Frontend use cases

Connect a self-managed git provider

Codecov supports GitHub Enterprise Server, GitLab self-managed and Bitbucket Server next to the hosted providers. Set the matching host so the login and repository links in the application point at your server:

$ docker run -d --name codecov-frontend -p 127.0.0.1:8080:8080 \
    -e CODECOV_BASE_HOST=codecov.example.com \
    -e CODECOV_API_HOST=codecov.example.com \
    -e CODECOV_GHE_HOST=github.example.com \
    dhi.io/codecov-frontend:<tag>

The container logs Replacing GHE https://github.example.com before nginx starts. The API service needs the matching provider configuration from the Codecov configuration reference.

Run on IPv4-only hosts

On a host or cluster without IPv6, nginx fails to bind its [::]:8080 listener. Disable it:

$ docker run -d --name codecov-frontend -p 127.0.0.1:8080:8080 \
    -e CODECOV_BASE_HOST=codecov.example.com \
    -e CODECOV_API_HOST=codecov.example.com \
    -e CODECOV_FRONTEND_IPV6_DISABLED=1 \
    dhi.io/codecov-frontend:<tag>

The container logs Codecov frontend ipv6 disabled and serves on IPv4 only.

Health checks

/frontend_health returns HTTP 200 with the release as its body. Runtime images carry no curl, so probe from the orchestrator:

readinessProbe:
  httpGet:
    path: /frontend_health
    port: 8080
  periodSeconds: 5

Run a command in the image

Passing a command to the image runs it instead of starting nginx, the same as the upstream image:

$ docker run --rm dhi.io/codecov-frontend:<tag> nginx -v

Non-hardened images vs. Docker Hardened Images

• The application is installed from the dhi/pkg-codecov-frontend package at /usr/share/codecov-frontend/gazebo, and the upstream start script as /usr/bin/codecov-frontend. Upstream serves /var/www/app/gazebo and starts through /usr/bin/start-nginx; both paths are kept as symlinks, the image's entrypoint is /usr/local/bin/codecov-frontend and the work directory is the upstream path /var/www/app.
• The image runs as uid 65532; upstream runs as the codecov user (uid 1000). The assets directory of the application is the only path the runtime user owns, because the start script rewrites the bundles in place.
• The nginx templates the start script renders live at /etc/codecov-frontend/nginx.conf.template and /etc/codecov-frontend/nginx-no-ipv6.conf.template instead of /etc/nginx, and the rendered configuration and the pid file are written to /tmp. Extra nginx configuration is included from /etc/codecov-frontend/conf.d/*.conf instead of /etc/nginx/conf.d, which the Debian nginx package populates with its own default server.
• The prebuilt Codecov uploader binaries the upstream image serves under /uploader are not shipped; those paths answer HTTP 404. The uploader is deprecated upstream in favour of the Codecov CLI, and prebuilt binaries cannot be built from source or covered by the SBOM.
• Upstream publishes the channel tags latest-stable, latest-calver and rolling next to the release tag; this image publishes release tags only (26.7.6, 26.7, 26 and their distro-suffixed forms), so a compose file that pins latest-calver moves to a release tag.
• The runtime image ships bash, sed and envsubst on Debian and BusyBox and envsubst on Alpine because the upstream start script needs them; it ships no other shell tooling, no curl and no package manager.

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 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 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. 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.

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 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. 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.