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 Adminer image

This Docker Hardened Adminer image provides a complete PHP-FPM environment for running Adminer:

• Adminer: compiled from source at the latest release, including the design theme collection and bundled community plugins
• PHP-FPM: FastCGI Process Manager on port 9000 for high-performance PHP processing (PHP CLI is also present, used by the entrypoint to load ADMINER_PLUGINS)
• Database drivers: mysqli and pdo_pgsql, pdo_sqlite, pdo_odbc, pdo_dblib covering MySQL/MariaDB, PostgreSQL, SQLite, generic ODBC, and MS SQL/Sybase
• Security hardening: runs as nonroot user (uid/gid 65532), minimal attack surface
• Tuned PHP configuration: raised upload size, memory, and execution time limits so SQL dump import/export work at realistic file sizes

Unlike some database tools, Adminer does not read database connection details from environment variables. You connect to a database directly from Adminer's login form (driver, server, username, password) after the container starts.

Note: PHP-FPM runs on port 9000 and requires a web server (nginx, Apache, Caddy) to handle HTTP requests and proxy to PHP-FPM.

Start an Adminer instance

docker run -d \
  --name adminer \
  -p 9000:9000 \
  dhi.io/adminer:<tag>

This starts PHP-FPM on port 9000. You'll need a web server in front of it to serve HTTP requests (see the complete stack example below). Once running, open Adminer in a browser and log in with the driver, host, and credentials of the database you want to manage — no connection configuration is required in the container itself.

Selecting a design or loading plugins

The official environment-variable contract is preserved:

• ADMINER_DESIGN: selects one of the bundled UI themes (for example flat, nette) by symlinking its stylesheet on container start
• ADMINER_PLUGINS: a space-separated list of bundled plugin names (for example slugify tables-filter) to load automatically on container start
• ADMINER_DEFAULT_SERVER: prefills the "Server" field on the login form

docker run -d \
  --name adminer \
  -p 9000:9000 \
  -e ADMINER_DESIGN=flat \
  -e ADMINER_DEFAULT_SERVER=db \
  dhi.io/adminer:<tag>

Common Adminer use cases

Complete stack with nginx and MySQL

services:
  db:
    image: dhi.io/mysql:8.4
    command: mysqld
    environment:
      MYSQL_ROOT_PASSWORD: rootsecret
    volumes:
      - db_data:/var/lib/mysql
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "127.0.0.1", "-uroot", "-prootsecret"]
      interval: 2s
      timeout: 3s
      retries: 30

  adminer:
    image: dhi.io/adminer:<tag>
    environment:
      ADMINER_DEFAULT_SERVER: db
    depends_on:
      db:
        condition: service_healthy

  nginx:
    image: dhi.io/nginx:1
    ports:
      - "8080:8080"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
    depends_on:
      - adminer

volumes:
  db_data:

ADMINER_DEFAULT_SERVER only prefills the login form's Server field — you still log in with real credentials at the login page, Adminer never auto-authenticates from environment variables.

Example nginx configuration (nginx.conf):

Important: The DHI nginx image runs as nonroot and requires the PID file directive to use a writable location.

pid /tmp/nginx.pid;

events {
    worker_connections 1024;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    server {
        listen 8080;

        # Adminer is a single front controller; nginx has no access to the
        # adminer container's filesystem, so every request (including
        # adminer.css) is dispatched to index.php with the original URI
        # preserved in DOCUMENT_URI.
        location / {
            fastcgi_pass adminer:9000;
            fastcgi_index index.php;
            include fastcgi_params;
            fastcgi_param SCRIPT_FILENAME /var/www/html/index.php;
            fastcgi_param DOCUMENT_URI $uri;
        }
    }
}

Adding custom PHP extensions

If you need additional extensions beyond the bundled database drivers (for example redis, mongodb), use a multi-stage build with dhi.io/php as the builder base.

# Stage 1: Compile extension using dev variant
FROM dhi.io/php:8.5-dev as builder

RUN set -eux; \
    apt-get update && \
    apt-get install -y --no-install-recommends \
        git \
        libpcre2-dev && \
    cd /tmp && \
    git clone https://github.com/krakjoe/apcu.git && \
    cd apcu && \
    phpize && \
    ./configure --enable-apcu && \
    make && \
    make install && \
    mkdir -p /extensions && \
    cp $(php-config --extension-dir)/apcu.so /extensions/ && \
    mkdir -p /ext-config && \
    echo "extension=apcu.so" > /ext-config/docker-php-ext-apcu.ini

# Stage 2: Runtime image with extension
FROM dhi.io/adminer:<tag>

ARG PHP_EXT_DIR=/usr/lib/php/extensions/no-debug-non-zts-20250925
ARG PHP_CONF_DIR=/etc/php-8.5/conf.d

COPY --from=builder /extensions/apcu.so "${PHP_EXT_DIR}/"
COPY --from=builder /ext-config/docker-php-ext-apcu.ini "${PHP_CONF_DIR}/"

Docker Official 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

Most hardened images intended for runtime don't contain a shell nor any tools for debugging. This image is an exception: its entrypoint requires bash to set up ADMINER_DESIGN/ADMINER_PLUGINS, so a minimal shell is present. 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

For example, you can use Docker Debug:

docker debug adminer

or mount debugging tools with the Image Mount feature:

docker run --rm -it --pid container:adminer \
  --mount=type=image,source=dhi.io/busybox,destination=/dbg,ro \
  dhi.io/adminer:<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 Adminer

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 install additional PHP extensions or customize the environment

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.

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.

Troubleshooting migration

The following are common issues that you may encounter during migration.

General debugging

Most hardened images intended for runtime don't contain a shell nor any tools for debugging; this image ships a minimal bash for its entrypoint (see No shell⁠ below). The recommended method for debugging applications built with Docker Hardened Images is to use Docker Debug⁠ to attach to these containers.

# View PHP-FPM logs
docker logs adminer

# Use Docker Debug for interactive troubleshooting
docker debug adminer

Permissions

By default image variants intended for runtime run as the nonroot user (uid/gid 65532). If you set ADMINER_DESIGN or ADMINER_PLUGINS, the entrypoint writes a symlink and generated plugin files directly under /var/www/html, which is already writable by the nonroot user in this image.

Privileged ports

Non-dev hardened images run as a nonroot user by default. PHP-FPM's default port 9000 is not affected by this limitation and works without any special configuration. Your web server (nginx, Apache) will bind to ports 80/443, not the Adminer container.

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.

The Adminer image uses /entrypoint.sh as its entry point, with php-fpm as the default command. The entrypoint sets up ADMINER_DESIGN/ADMINER_PLUGINS before starting PHP-FPM; if you customize the entry point, ensure it still performs that setup (or does it yourself) and that PHP-FPM continues to run in the foreground.

No shell

Most image variants intended for runtime don't contain a shell. This image is an exception: it ships a minimal bash, required by /entrypoint.sh to set up ADMINER_DESIGN/ADMINER_PLUGINS on container start. Use dev images in build stages to run other shell commands and then copy any necessary artifacts into the runtime stage.