Static and Mostly Static Images

With GraalVM Native Image you can create static or mostly static images, depending on the purposes.

Static native images are statically linked binaries which can be used without any additional library dependencies. This makes them easier to distribute and to deploy on slim or distroless container images. They are created by statically linking against musl-libc, a lightweight, fast and simple libc implementation.

Mostly static native images statically link against all libraries except libc. This approach is ideal for deploying such native images on distroless container images. Note that it currently only works when linking against glibc.

Prerequisites #

Linux AMD64 operating system
GraalVM distribution for Java 11 with Native Image support
A 64-bit musl toolchain, make, and configure
The latest zlib library

Preparation #

You should get the musl toolchain first, and then compile and install zlib into the toolchain.

Download the musl toolchain from musl.cc. This one is recommended. Extract the toolchain to a directory of your choice. This directory will be referred as $TOOLCHAIN_DIR.
Download the latest zlib library sources from here and extract them. This guide uses zlib-1.2.11.
Set the following environment variable:
```
 CC=$TOOLCHAIN_DIR/bin/gcc
```
Change into the zlib directory, and then run the following commands to compile and install zlib into the toolchain:
```
 ./configure --prefix=$TOOLCHAIN_DIR --static
 make
 make install
```

Build Static Native Image #

First, ensure $TOOLCHAIN_DIR/bin is present on your PATH variable. To verify this, run:
```
 x86_64-linux-musl-gcc
```
You should get a similar output printed:
```
 x86_64-linux-musl-gcc: fatal error: no input files
 compilation terminated.
```

Build a static native image by using this command:

 native-image --static --libc=musl [other arguments] Class

Build Mostly Static Native Image #

As of GraalVM version 20.2, you can build a “mostly static” native image which statically links everything except libc. Statically linking all your libraries except glibc ensures your application has all the libraries it needs to run on any Linux glibc-based distribution.

To build a mostly-static native image native image, use this command:

native-image -H:+StaticExecutableWithDynamicLibC [other arguments] Class

Note: This currently only works for glibc.

Frequently Asked Questions #

What is the recommended base Docker image for deploying a static or mostly static native image? #

A fully static native image gives you the most flexibility to choose a base image - it can run on anything including a FROM scratch image. A mostly static native image requires a container image that provides glibc, but has no additional requirements. In both cases, choosing the base image mostly depends on what your particular native image needs without having to worry about run-time library dependencies.