Jonathan Lalou's Blog

In the rapidly evolving landscape of containerization technology, Docker remains a cornerstone for developers and system administrators. However, specific use cases—such as legacy application compatibility, testing, or reproducing historical environments—may necessitate installing an older version of Docker on a modern operating system. This guide provides a detailed walkthrough for installing Docker Engine 20.10.9, a release from September 2021, on Debian 13 (codename “Trixie”), the testing branch of Debian as of September 2025. While the steps can be adapted for other versions or Debian releases, this case study addresses the unique challenges of downgrading Docker on a contemporary distribution.

Introduction: The Challenges and Rationale for Installing an Older Docker Version

Installing an outdated Docker version like 20.10.9 on a recent Debian release such as Trixie is fraught with challenges due to Docker’s evolution and Debian’s forward-looking package management. Docker transitioned from Calendar Versioning (CalVer, e.g., 20.10) to Semantic Versioning (SemVer, starting with 23.0 in May 2023), introducing significant updates in security, features, and dependencies. This creates several obstacles:

• Package Availability and Compatibility: Docker’s official APT repository prioritizes current versions (e.g., 28.x in 2025) for supported Debian releases. Older versions like 20.10.9 are often archived and unavailable via apt for newer codenames like Trixie, requiring manual downloads of .deb packages from a compatible release (e.g., bullseye for Debian 11). This can lead to dependency mismatches or installation failures.
• Security and Support Risks: Version 20.10.9 is end-of-life (EOL) since mid-2023, lacking official security patches for known vulnerabilities (e.g., CVEs in networking or containerd). This poses risks for production environments. Additionally, compatibility issues may arise with modern WSL2 networking in Windows Subsystem for Linux (WSL) environments.
• Dependency Conflicts: Older Docker versions rely on specific versions of components like containerd.io, which may conflict with newer libraries on Debian 13, potentially causing installation or runtime errors.
• Docker Compose Compatibility: Modern Docker integrates Compose as a plugin (docker compose), but older setups require the standalone docker-compose (v1, with hyphen), necessitating a separate binary installation.

Why pursue this downgrade? Legacy applications, specific toolchains, or compatibility with older Dockerfiles may require it—such as maintaining a telemetry stack with Elasticsearch, Kibana, and APM Server in a controlled environment. However, for production or security-sensitive deployments, upgrading to the latest Docker version (e.g., 28.3.3) is strongly recommended. This guide assumes a WSL/Debian Trixie setup but is applicable to native Debian installations, with precautions for data loss and system stability.

Prerequisites

Before proceeding, ensure the following:

• A running Debian 13 (Trixie) system (verify with lsb_release -cs).
• Administrative access (sudo privileges).
• Backup of critical Docker data (e.g., export volumes using docker volume ls).
• Internet access for downloading packages.
• Awareness of risks: Manual package installation bypasses APT’s dependency resolution, and EOL versions lack security updates.

Step 1: Prune All Local Docker Resources

Why This Step is Needed

Before uninstalling the current Docker version (e.g., 28.3.3), pruning all local resources—images, containers, volumes, and networks—ensures a clean slate. This prevents conflicts from residual data, reclaims disk space, and prepares the system for the downgrade. Since pruning is irreversible, backing up critical data (e.g., telemetry stack volumes) is essential.

What It Does

The docker system prune command removes all unused Docker artifacts, including stopped containers, unused images, volumes, and networks, ensuring no remnants interfere with the new installation.

Commands

# Stop all running containers (if any)
docker stop $(docker ps -q) 2>/dev/null || true

# Prune everything: images, containers, volumes, networks, and build cache
docker system prune -a --volumes -f
    

Verification

Run these commands to confirm cleanup:

docker images -a  # Should list no images
docker volume ls  # Should be empty
docker network ls # Should show only defaults (bridge, host, none)
docker ps -a      # Should show no containers
    

If permission errors occur, verify your user is in the docker group (sudo usermod -aG docker $USER and log out/in) or use sudo.

Step 2: Remove the Current Docker Installation

Why This Step is Needed

Removing the existing Docker version (e.g., 28.3.3) eliminates potential conflicts in packages, configurations, or runtime components. Residual files or newer dependencies could cause the older 20.10.9 installation to fail or behave unpredictably.

What It Does

This step stops Docker services, purges installed packages, deletes data directories and configurations, and removes the Docker APT repository to prevent accidental upgrades to newer versions.

Commands

# Stop Docker services
sudo systemctl stop docker
sudo systemctl stop docker.socket

# Uninstall Docker packages
sudo apt-get purge -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin docker-ce-rootless-extras
sudo apt-get autoremove -y --purge

# Remove Docker data and configs
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd
sudo rm -rf /etc/docker
sudo rm -f /etc/apparmor.d/docker
sudo rm -f /var/run/docker.sock
sudo groupdel docker 2>/dev/null || true

# Remove Docker repository
sudo rm -f /etc/apt/sources.list.d/docker.list
sudo rm -f /etc/apt/keyrings/docker.gpg
sudo apt-get update

# Verify removal
docker --version  # Should show "command not found"
    

Reboot WSL if needed (in Windows PowerShell: wsl --shutdown).

Step 3: Install Docker Engine 20.10.9 via Manual .deb Packages

Why This Step is Needed

Debian Trixie’s Docker repository does not include 20.10.9, as it is an EOL version from 2021, unsupported since mid-2023. The standard apt installation fails due to version mismatches, so we manually download and install .deb packages from Docker’s archive for Debian 11 (bullseye), which is compatible with Trixie. This approach bypasses repository limitations but requires careful dependency management.

What It Does

The commands download specific .deb files for Docker CE, CLI, and containerd.io, install them using dpkg, resolve dependencies with apt, and lock the version to prevent upgrades. The process also ensures Docker starts correctly and is accessible without root privileges.

Commands

# Install prerequisites
sudo apt-get update
sudo apt-get install -y ca-certificates curl gnupg lsb-release

# Create directory for downloads
mkdir -p ~/docker-install
cd ~/docker-install

# Download .deb packages for 20.10.9 (bullseye, amd64)
curl -O https://download.docker.com/linux/debian/dists/bullseye/pool/stable/amd64/containerd.io_1.4.13-1_amd64.deb
curl -O https://download.docker.com/linux/debian/dists/bullseye/pool/stable/amd64/docker-ce-cli_20.10.9~3-0~debian-bullseye_amd64.deb
curl -O https://download.docker.com/linux/debian/dists/bullseye/pool/stable/amd64/docker-ce_20.10.9~3-0~debian-bullseye_amd64.deb

# Verify file sizes (should be MBs, not bytes)
ls -lh *.deb

# Install .deb packages
sudo dpkg -i containerd.io_1.4.13-1_amd64.deb
sudo dpkg -i docker-ce-cli_20.10.9~3-0~debian-bullseye_amd64.deb
sudo dpkg -i docker-ce_20.10.9~3-0~debian-bullseye_amd64.deb

# Fix any dependency issues
sudo apt-get install -f

# Hold versions to prevent upgrades
sudo apt-mark hold docker-ce docker-ce-cli containerd.io

# Start and enable Docker
sudo systemctl start docker
sudo systemctl enable docker

# Add user to docker group (log out/in after)
sudo usermod -aG docker $USER

# Verify installation
docker --version  # Should show "Docker version 20.10.9, build ..."
docker run --rm hello-world  # Test pull and run

# Clean up downloaded files
cd /mnt/c/workarea/development-tools/telemetry-poc/etc/docker/telemetry
rm -rf ~/docker-install
    

Note: If the curl URLs return 404 errors, browse Docker’s bullseye pool to find the exact filenames (e.g., try docker-ce_20.10.10~3-0~debian-bullseye_amd64.deb if 20.10.9 is unavailable). Use containerd.io_1.4.11-1_amd64.deb if 1.4.13 fails.

Step 4: Install Standalone docker-compose (v1.29.2)

Why This Step is Needed

Modern Docker includes Compose as a plugin (docker compose, v2), but legacy setups like 20.10.9 often require the standalone docker-compose (v1, with hyphen) for compatibility with older workflows or scripts. This binary ensures the hyphenated command is available.

What It Does

Downloads the v1.29.2 binary (the last v1 release, compatible with 20.10.9) from GitHub, installs it to /usr/local/bin, and makes it executable.

Commands

sudo curl -L "https://github.com/docker/compose/releases/download/1.29.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose

# Verify
docker-compose --version  # Should show "docker-compose version 1.29.2, build ..."
    

Step 5: Post-Installation and Verification

Why This Step is Needed

Post-installation steps ensure Docker and docker-compose function correctly, especially in a WSL environment where networking can be temperamental. Verifying the setup confirms compatibility with your telemetry stack (e.g., Elasticsearch, Kibana, APM Server).

What It Does

Restarts WSL to apply changes, tests Docker and docker-compose, and rebuilds your telemetry stack. It also checks network accessibility from Windows.

Commands

# Restart WSL (in Windows PowerShell)
wsl --shutdown

# Reopen WSL terminal and verify
docker --version  # Should show "Docker version 20.10.9, build ..."
docker-compose --version  # Should show "docker-compose version 1.29.2, build ..."
docker run --rm hello-world

Troubleshooting

If issues arise, consider these steps:

• Download Failures: Check Docker’s bullseye pool for correct filenames. Use curl -I <URL> to verify HTTP status (200 OK).
• Dependency Errors: Run sudo apt-get install -f to resolve.
• Docker Not Starting: Check sudo systemctl status docker or journalctl -u docker.
• WSL Networking: Update WSL (wsl --update) and restart Docker (sudo service docker restart).
• Share Outputs: Provide ls -lh ~/docker-install/*.deb, dpkg -l | grep docker, or error messages for debugging.

Conclusion

Installing an older version of Docker, such as 20.10.9, on a recent Debian release like Trixie (Debian 13) is a complex but achievable task, requiring careful management of package dependencies and manual installation of archived .deb files. By pruning existing Docker resources, removing the current installation, and installing bullseye-compatible packages, you can successfully downgrade to meet legacy requirements. The addition of the standalone docker-compose ensures compatibility with older workflows..

However, this approach comes with caveats: version 20.10.9 is end-of-life, lacking security updates, and may face compatibility issues with modern tools or WSL2 networking. For production environments, consider using the latest Docker version (e.g., 28.3.3 as of September 2025) to benefit from ongoing support and enhanced features. Always test thoroughly after installation, and maintain backups to mitigate data loss risks. If you encounter issues or need to adapt this process for other versions, consult Docker’s official repository or community forums for additional resources.