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 phpmyadmin image

This Docker Hardened phpMyAdmin image ships the phpMyAdmin⁠ web application as a PHP-FPM service.

• the phpMyAdmin application at /var/www/html, installed from the dhi-phpmyadmin Debian package built from the GPG-verified upstream release
• the Docker Hardened PHP runtime with FPM and the extensions phpMyAdmin uses: mysqli, gd, zip, bz2, bcmath, opcache, and uploadprogress
• the configuration directory at /etc/phpmyadmin with the standard environment-driven config.inc.php

The image serves FastCGI on port 9000/tcp and requires a web server in front of it. There is no Apache variant: the catalog's hardened PHP stack ships PHP-FPM and CLI packages with no Apache mod_php, so deployments using the upstream image's default Apache variant must move to a web server plus FastCGI layout.

Run phpMyAdmin with nginx and MySQL

PHP-FPM serves FastCGI, not HTTP, so phpMyAdmin runs behind a web server that shares its document root. The example below publishes the phpMyAdmin files to the web server through a shared volume:

services:
  mysql:
    image: dhi.io/mysql:8.4
    command: [mysqld]
    environment:
      MYSQL_ROOT_PASSWORD: <root-password>

  phpmyadmin:
    image: dhi.io/phpmyadmin:<tag>
    environment:
      PMA_HOST: mysql
    volumes:
      - document-root:/var/www/html

  nginx:
    image: dhi.io/nginx:1
    ports:
      - "8080:8080"
    volumes:
      - document-root:/var/www/html:ro
      - ./nginx.conf:/etc/nginx/conf.d/default.conf:ro

volumes:
  document-root:

The nginx configuration listens on an unprivileged port and forwards PHP requests to the FPM service:

server {
    listen 8080;
    root /var/www/html;
    index index.php;

    location ~ /\. {
        deny all;
    }

    location ~* ^/(composer\.(json|lock)|ChangeLog|LICENSE|README(\.md)?)$ {
        deny all;
    }

    location ^~ /vendor/ {
        deny all;
    }

    location ^~ /libraries/ {
        deny all;
    }

    location / {
        try_files $uri $uri/ =404;
    }

    location ~ \.php$ {
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_pass phpmyadmin:9000;
        fastcgi_index index.php;
    }
}

Open http://localhost:8080⁠ and sign in with your MySQL credentials.

The named document-root volume is populated from the image once, on first start, and shadows the packaged application directory. After pulling a newer image tag, remove the volume (docker compose down --volumes); otherwise the container keeps serving the old files while its package database and SBOM report the new version. docker run --rm <image> dpkg -V dhi-phpmyadmin verifies the served payload matches the package.

Configuration

phpMyAdmin reads its configuration from environment variables through /etc/phpmyadmin/config.inc.php, matching the upstream image's contract. The most common variables:

This table is a getting-started subset; the full list of supported variables is documented in the upstream image's README⁠.

Variables holding credentials, plus PMA_HOST, PMA_HOSTS, and PMA_CONTROLHOST, also accept the _FILE suffix to read the value from a mounted secrets file. MYSQL_ROOT_PASSWORD and MYSQL_PASSWORD are resolved the same way.

The session encryption secret (blowfish_secret) is generated at first start and stored at /etc/phpmyadmin/config.secret.inc.php. Sign-in sessions survive container restarts only if /etc/phpmyadmin is a persistent volume or the secret is provided through PMA_CONFIG_BASE64. When running more than one replica behind a load balancer, provide the same secret to every replica through PMA_CONFIG_BASE64 or a shared /etc/phpmyadmin volume; otherwise each replica generates its own secret and cookie sign-in breaks across replicas. When PMA_CONFIG_BASE64 is set, the entrypoint skips secret generation and the provided configuration must define $cfg['blowfish_secret'] itself.

To run with a read-only root filesystem, mount tmpfs filesystems owned by the nonroot user (uid 65532) over the writable paths, and provide the session secret yourself through a read-only mount:

docker run --read-only \
  --tmpfs /sessions:uid=65532,gid=65532,mode=0700 \
  --tmpfs /var/lib/phpmyadmin/tmp:uid=65532,gid=65532,mode=0700 \
  -v ./config.secret.inc.php:/etc/phpmyadmin/config.secret.inc.php:ro \
  -e PMA_HOST=mysql dhi.io/phpmyadmin:<tag>

Alternatively, mount a tmpfs with the same ownership options at /etc/phpmyadmin and supply the full configuration through PMA_CONFIG_BASE64. The explicit uid/gid options matter: plain docker run and Kubernetes emptyDir volumes mount tmpfs root-owned by default (use fsGroup in Kubernetes), while Docker Compose applies the image's directory ownership automatically.

Ports

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.

In this image, the validated OpenSSL provider covers PHP's openssl extension paths, such as TLS connections to the database. phpMyAdmin encrypts its authentication cookies with libsodium (sodium_crypto_secretbox), which is not part of the FIPS module.

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.