The main pain point jbundle solves is that jpackage generates installers (.deb, .rpm, .dmg, .msi), not plain executables. jbundle produces a single self-contained binary — just a shell stub concatenated with a compressed payload. You chmod +x it, distribute it, and the user runs ./app. No installation step, no system-level changes.
It also automates the full pipeline (detect build system → build uberjar → download JDK → jdeps → jlink → pack) so you don't need a JDK installed on the build machine — it fetches the exact version from Adoptium. Plus it includes startup optimizations like AppCDS (auto-created on first run, JDK 19+), CRaC checkpoints, and profile-tuned JVM flags for CLI vs server workloads.
Cross-compilation:
Yes — jbundle build --target linux-x64 (or linux-aarch64, macos-x64, macos-aarch64). Since the JAR is platform-independent, it just downloads the appropriate JDK runtime for the target OS/arch from Adoptium and bundles it. You can build a Linux binary from macOS and vice-versa.
Plain executable (not an installer):
That's exactly what jbundle produces. The output is a single file you can scp to a server or hand to someone. On first run it extracts the runtime and jar to ~/.jbundle/cache/ (keyed by content hash), so subsequent runs are instant. No .deb, no .dmg, no "install this first" — just a binary.
For the macOS testing concern: since it's a CLI binary (not a .app bundle), it doesn't require signing/notarization to run. And with --target macos-aarch64 you can build it from a Linux CI without needing a Mac.
I built a tool to solve a problem I kept hitting: deploying Clojure apps without requiring Java on the target machine.23:20:00 [3/101]
The usual answer is GraalVM native-image, but in practice it means dealing with reflection configs, library incompatibilities, long build times, and a complex toolchain. For many projects it's more friction than it's worth.
clj-pack takes a different approach: it bundles a minimal JVM runtime (via jlink) with your uberjar into a single executable. The result is a binary that runs anywhere with zero external dependencies and full JVM compatibility — no reflection configs, no unsupported libraries, your app runs exactly as it does in development.
clj-pack build --input ./my-project --output ./dist/my-app
./dist/my-app # no Java needed
How it works:
Detects your build system (deps.edn or project.clj)
Compiles the uberjar
Downloads a JDK from Adoptium (cached locally)
Uses jdeps + jlink to create a minimal runtime (~30-50 MB)
Packs everything into a single binary
The binary extracts on first run (cached by content hash), subsequent runs are instant.
Trade-off is honest: binaries are slightly larger than GraalVM output (~30-50 MB vs ~20-40 MB), and first execution has extraction overhead. But you get full compatibility and a simple build process in return.
Written in Rust, supports Linux and macOS (x64/aarch64).