Show HN: Unregistry – "docker push" directly to servers without a registry

▸ Push docker images directly to remote servers without an external registry ◂

Unregistry is a lightweight container image registry that stores and serves images directly from your Docker daemon's storage.

The included docker pussh command (extra 's' for SSH) lets you push images straight to remote Docker servers over SSH. It transfers only the missing layers, making it fast and efficient.

The problem

You've built a Docker image locally. Now you need it on your server. Your options suck:

• Docker Hub / GitHub Container Registry - Your code is now public, or you're paying for private repos
• Self-hosted registry - Another service to maintain, secure, and pay for storage
• Save/Load - docker save | ssh | docker load transfers the entire image, even if 90% already exists on the server
• Rebuild remotely - Wastes time and server resources. Plus now you're debugging why the build fails in production

You just want to move an image from A to B. Why is this so hard?

The solution

docker pussh myapp:latest user@server

That's it. Your image is on the remote server. No registry setup, no subscription, no intermediate storage, no exposed ports. Just a direct transfer of the missing layers over SSH.

Here's what happens under the hood:

1. Establishes SSH tunnel to the remote server
2. Starts a temporary unregistry container
3. Forwards a random localhost port to the unregistry port over the tunnel
4. docker push to unregistry through the forwarded port, transferring only the layers that don't already exist remotely. The transferred image is instantly available on the remote Docker daemon
5. Stops the unregistry container and closes the SSH tunnel

It's like rsync for Docker images — simple and efficient.

Note

Unregistry was created for Uncloud, a lightweight tool for deploying containers across multiple Docker hosts. We needed something simpler than a full registry but more efficient than save/load.

Installation

macOS/Linux via Homebrew

brew install psviderski/tap/docker-pussh

After installation, to use docker-pussh as a Docker CLI plugin (docker pussh command) you need to create a symlink:

mkdir -p ~/.docker/cli-plugins
ln -sf $(brew --prefix)/bin/docker-pussh ~/.docker/cli-plugins/docker-pussh

macOS/Linux via direct download

# Download the latest version
curl -sSL https://raw.githubusercontent.com/psviderski/unregistry/main/docker-pussh \
  -o ~/.docker/cli-plugins/docker-pussh

# Make it executable
chmod +x ~/.docker/cli-plugins/docker-pussh

Windows

Windows is not currently supported, but you can try using WSL 2 with the above Linux instructions.

Verify installation

docker pussh --help

Usage

Push an image to a remote server. Please make sure the SSH user has permissions to run docker commands (user is root or non-root user is in docker group). If sudo is required, ensure the user can run sudo docker without a password prompt.

docker pussh myapp:latest [email protected]

With SSH key authentication if the private key is not added to your SSH agent:

docker pussh myapp:latest [email protected] -i ~/.ssh/id_rsa

Using a custom SSH port:

docker pussh myapp:latest user@server:2222

Push a specific platform for a multi-platform image. The local Docker has to use containerd image store to support multi-platform images.

docker pussh myapp:latest user@server --platform linux/amd64

Use cases

Deploy to production servers

Build locally and push directly to your production servers. No middleman.

docker build --platform linux/amd64 -t myapp:1.2.3 .
docker pussh myapp:1.2.3 deploy@prod-server
ssh deploy@prod-server docker run -d myapp:1.2.3

CI/CD pipelines

Skip the registry complexity in your pipelines. Build and push directly to deployment targets.

- name: Build and deploy
  run: |
    docker build -t myapp:${{ github.sha }} .
    docker pussh myapp:${{ github.sha }} deploy@staging-server

Homelab and air-gapped environments

Distribute images in isolated networks without exposing them to the internet.

docker pussh image:latest [email protected]

Requirements

On local machine

• Docker CLI with plugin support (Docker 19.03+)
• OpenSSH client

On remote server

• Docker is installed and running
• SSH user has permissions to run docker commands (user is root or non-root user is in docker group)
• If sudo is required, ensure the user can run sudo docker without a password prompt

Tip

The remote Docker daemon works best with containerd image store enabled. This allows unregistry to access images more efficiently.

Add the following configuration to /etc/docker/daemon.json on the remote server and restart the docker service:

{
  "features": {
    "containerd-snapshotter": true
  }
}

Advanced usage

Running unregistry standalone

Sometimes you want a local registry without the overhead. Unregistry works great for this:

# Run unregistry locally and expose it on port 5000
docker run -d -p 5000:5000 --name unregistry \
  -v /run/containerd/containerd.sock:/run/containerd/containerd.sock \
  ghcr.io/psviderski/unregistry

# Use it like any registry
docker tag myapp:latest localhost:5000/myapp:latest
docker push localhost:5000/myapp:latest

Custom SSH options

Need custom SSH settings? Use the standard SSH config file:

# ~/.ssh/config
Host prod-server
    HostName server.example.com
    User deploy
    Port 2222
    IdentityFile ~/.ssh/deploy_key

# Now just use
docker pussh myapp:latest prod-server

Contributing

Found a bug or have a feature idea? We'd love your help!

• 🐛 Found a bug? Open an issue
• 💡 Have ideas or need help? Join Uncloud Discord community where we discuss features, roadmap, implementation details, and help each other out.

Inspiration & acknowledgements

• Spegel - P2P container image registry that inspired me to implement a registry that uses containerd image store as a backend.
• Docker Distribution - the bulletproof Docker registry implementation that unregistry uses as a base.