Statically Linked Dropbear SSH and sftp-server Binaries (built with Zig)

This repo publishes prebuilt musl-linked static ELF binaries of Dropbear, built automatically from upstream mkj/dropbear using Zig for static musl compilation. Similarly for sftp-server.

These binaries should run on virtually any modern Linux distribution with no external dependencies. Builds include X11 forwarding support.

Motivation

I want to provide basic ssh server support for very general Docker containers, with no installation requirements. E.g,. ssh for minimal SUSE or Ubuntu images, without having to run package managers.

Contents

Each release provides these tarballs:

dropbear-x86_64-linux-musl.tar.xz
dropbear-aarch64-linux-musl.tar.xz

Extracting one yields:

dropbear-x86_64-linux-musl/
  dropbear
  dropbearkey
  dropbearconvert
  dbclient
  scp

To install, copy the two files somewhere on your PATH, e.g.:

sudo cp dropbear* /usr/local/bin/

In order to support sftp transparently, e.g., so sshfs works, extract the sftp-server binary and place it in /usr/libexec/:

sudo cp sftp-server /usr/libexec/sftp-server

Basic Dropbear Tutorial

Generate a host key:

mkdir -p ~/dropbear-test
cd ~/dropbear-test
dropbearkey -t ed25519 -f key

Start the server in the foreground on port 2222:

dropbear -F -E -p 2222 -r key

From another terminal, connect:

ssh -p 2222 localhost

Build Reproducibility

Binaries are built by build.sh and GitHub Actions workflows in this repo. You can rerun the same process yourself to verify results.

Notes

• Features: X11 forwarding enabled; PAM and zlib disabled; bundled libtom used.
• These builds are intended for lightweight use in containers or resource-constrained environments.
• Security: As with any SSH server, configure carefully (authorized_keys, permissions, etc.).