# dockcross

Cross compiling toolchains in Docker images.

[![image](https://github.com/dockcross/dockcross/workflows/Dockcross%20CI/badge.svg)](https://github.com/dockcross/dockcross/actions?query=branch%3Amaster) [![Shellcheck CI](https://github.com/dockcross/dockcross/actions/workflows/shellcheck.yml/badge.svg)](https://github.com/dockcross/dockcross/actions/workflows/shellcheck.yml)

![GitHub](https://img.shields.io/github/license/dockcross/dockcross) ![GitHub commit activity](https://img.shields.io/github/commit-activity/y/dockcross/dockcross)

## Features

-   Pre-built and configured toolchains for cross compiling.
-   Most images also contain an emulator for the target system.
-   Clean separation of build tools, source code, and build artifacts.
-   Commands in the container are run as the calling user, so that any created files have the expected ownership, (i.e. not root).
-   Make variables **CC**, **CXX**, **LD**, **AS** etc) are set to point to the appropriate tools in the container.
-   Recent [CMake](https://cmake.org) and ninja are precompiled.
-   [Conan.io](https://www.conan.io) can be used as a package manager.
-   Toolchain files configured for CMake.
-   Current directory is mounted as the container\'s workdir, `/work`.
-   Works with the [Docker for Mac](https://docs.docker.com/docker-for-mac/) and [Docker for Windows](https://docs.docker.com/docker-for-windows/).
-   Support using alternative container executor by setting **OCI_EXE** environment variable. By default, it searches for [docker](https://www.docker.com) and [podman](https://podman.io) executable.
-   [crosstool-ng](https://github.com/crosstool-ng/crosstool-ng) and [buildroot](https://github.com/buildroot/buildroot) configuration files.

## Examples

1.  `dockcross make`: Build the *Makefile* in the current directory.
2.  `dockcross cmake -Bbuild -H. -GNinja`: Run CMake with a build directory `./build` for a *CMakeLists.txt* file in the current directory and generate `ninja` build configuration files.
3.  `dockcross ninja -Cbuild`: Run ninja in the `./build` directory.
4.  `dockcross bash -c '$CC test/C/hello.c -o hello'`: Build the *hello.c* file with the compiler identified with the `CC` environmental variable in the build environment.
5.  `dockcross bash`: Run an interactive shell in the build environment.

Note that commands are executed verbatim. If any shell processing for environment variable expansion or redirection is required, please use
```bash
bash -c "<command args>"
```

## Installation

This image does not need to be run manually. Instead, there is a helper script to execute build commands on source code existing on the local host filesystem. This script is bundled with the image.

To install the helper script, run one of the images with no arguments, and redirect the output to a file:

```bash
docker run --rm CROSS_COMPILER_IMAGE_NAME > ./dockcross
chmod +x ./dockcross
mv ./dockcross ~/bin/
```

Where **CROSS_COMPILER_IMAGE_NAME** is the name of the cross-compiler toolchain Docker instance, e.g: **dockcross/linux-armv7**.

Only 64-bit x86_64 images are provided, a 64-bit x86_64 host system is required.

## Usage

For the impatient, here\'s how to compile a hello world for armv7:

```bash
cd ~/src/dockcross
docker run --rm dockcross/linux-armv7 > ./dockcross-linux-armv7
chmod +x ./dockcross-linux-armv7
./dockcross-linux-armv7 bash -c '$CC test/C/hello.c -o hello_arm'
```

Note how invoking any toolchain command (make, gcc, etc.) is just a matter of prepending the **dockcross** script on the commandline:

```bash
./dockcross-linux-armv7 [command] [args...]
```

The dockcross script will execute the given command-line inside the container, along with all arguments passed after the command. Commands that evaluate environmental variables in the image, like **$CC** or **$CXX** above, should be executed in [bash -c]. The present working directory is mounted within the image, which can be used to make source code available in the Docker container.

## Summary cross compilers

| Image name | Target arch | Compiler | Target OS |
|:-------:|:--------:|:------:|:-----:|
| dockcross/base | - | - | - |
| dockcross/android-arm | ARMv7 | Clang | Android |
| dockcross/android-arm64 | ARMv8 | Clang | Android |
| dockcross/android-x86 | x86 | Clang | Android |
| dockcross/android-x86_64 | x86_64 | Clang | Android |
| dockcross/linux-arm64 | ARMv8 | GCC | Linux |
| dockcross/linux-arm64-full | ARMv8 | GCC + libs | Linux |
| dockcross/linux-arm64-musl | ARMv8 | GCC + musl | Linux |
| dockcross/linux-armv5 | ARMv5 | GCC | Linux |
| dockcross/linux-armv5-musl | ARMv5 | GCC + musl | Linux |
| dockcross/linux-armv6 | ARMv6 | GCC | Linux |
| dockcross/linux-armv6-lts | ARMv6 | GCC + Glibc 2.28 | Linux |
| dockcross/linux-armv6-musl | ARMv6 | GCC + musl | Linux |
| dockcross/linux-armv7 | ARMv7 | GCC | Linux |
| dockcross/linux-armv7a | ARMv7a | GCC | Linux |
| dockcross/linux-armv7l-musl | ARMv7l | GCC + musl | Linux |
| dockcross/linux-mips | mips | GCC | Linux |
| dockcross/linux-s390x | s390x | GCC | Linux |
| dockcross/linux-ppc64le | ppc64le | GCC | Linux |
| dockcross/linux-riscv32 | riscv32 | GCC | Linux |
| dockcross/linux-riscv64 | riscv64 | GCC | Linux |
| dockcross/linux-m68k-uclibc | m68k | GCC + uclibc | Linux |
| dockcross/linux-xtensa-uclibc | xtensa | GCC + uclibc | Linux |
| dockcross/manylinux2014-x86 | x86 | GCC | Linux |
| dockcross/manylinux2014-x64 | x86_64 | GCC | Linux |
| dockcross/linux-x86 | x86 | GCC | Linux |
| dockcross/linux-x64 | x86_64 | GCC | Linux |
| dockcross/linux-x86_64-full | x86_64 | GCC + libs | Linux |
| dockcross/linux-x64-clang | x86_64 | Clang | Linux |
| dockcross/linux-x64-tinycc | x86_64 | tinycc + GCC | Linux |
| dockcross/web-wasm | JS | LLVM | Web (JS) |
| dockcross/windows-shared-x86 | x86 | GCC | Windows |
| dockcross/windows-shared-x64 | x86_64 | GCC | Windows |
| dockcross/windows-shared-x64-posix | x86_64 | GCC | Windows |
| dockcross/windows-static-x86 | x86 | GCC | Windows |
| dockcross/windows-static-x64 | x86_64 | GCC | Windows |
| dockcross/windows-static-x64-posix | x86_64 | GCC | Windows |
| dockcross/windows-armv7 | ARMv7 | Clang | Windows |
| dockcross/windows-arm64 | ARMv8 | Clang | Windows |

## Cross compilers

### dockcross/base

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/base/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/base) ![Docker Stars](https://img.shields.io/docker/stars/dockcross/base)

Base image for other toolchain images. From Debian Jessie with GCC, make, autotools, CMake, Ninja, Git, and Python.

### dockcross/android-arm

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/android-arm/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/android-arm)

The Android NDK standalone toolchain for the arm architecture.

### dockcross/android-arm64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/android-arm64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/android-arm64)

The Android NDK standalone toolchain for the arm64 architecture.

### dockcross/android-x86

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/android-x86/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/android-x86)

The Android NDK standalone toolchain for the x86 architecture.

### dockcross/android-x86_64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/android-x86_64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/android-x86_64)

The Android NDK standalone toolchain for the x86_64 architecture.

### dockcross/linux-arm64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-arm64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-arm64)

Cross compiler for the 64-bit ARM platform on Linux, also known as AArch64.

### dockcross/linux-arm64-full

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-arm64-full/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-arm64-full)

Cross compiler for the 64-bit ARM platform on Linux, with cross-libs: SDL2, OpenSSL, Boost, OpenCV and Qt5 (minimal).

### dockcross/linux-arm64-musl

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-arm64-musl/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-arm64-musl)

Cross compiler for the 64-bit ARM platform on Linux (also known as
AArch64), using [musl](https://www.musl-libc.org/) as base \"libc\".

### dockcross/linux-armv5

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv5/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv5)

Linux armv5 cross compiler toolchain for legacy devices like the
Parrot AR Drone.

### dockcross/linux-armv5-musl

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv5-musl/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv5-musl)

Linux armv5 cross compiler toolchain using
[musl](https://www.musl-libc.org/) as base \"libc\".

### dockcross/linux-armv6

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv6/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv6)

Linux ARMv6 cross compiler toolchain for the Raspberry Pi

### dockcross/linux-armv6-lts

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv6-lts/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv6-lts)

Linux ARMv6 cross compiler toolchain for the Raspberry Pi (Debian buster...)

### dockcross/linux-armv6-musl

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv6-musl/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv6-musl)

Linux ARMv6 cross compiler toolchain for the Raspberry Pi, etc,
using [musl](https://www.musl-libc.org/) as base \"libc\".

### dockcross/linux-armv7

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv7/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv7)

Generic Linux armv7 cross compiler toolchain.

### dockcross/linux-armv7a

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv7a/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv7a)

Toolchain configured for ARMv7-A used in Beaglebone Black single
board PC with TI SoC AM3358 on board, Cortex-A8.

### dockcross/linux-armv7l-musl

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-armv7l-musl/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-armv7l-musl)

Toolchain configured for ARMv7-L, using
[musl](https://www.musl-libc.org/) as base \"libc\".

### dockcross/linux-mips

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-mips/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-mips)

Linux mips cross compiler toolchain for big endian 32-bit hard float
MIPS GNU systems.

### dockcross/linux-s390x

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-s390x/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-s390x)

Linux s390x cross compiler toolchain for S390X GNU systems.

### dockcross/linux-riscv64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-riscv64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-riscv64)

Linux risc-v 64bit cross compiler toolchain for risc-v 64bit GNU systems.

### dockcross/linux-riscv32

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-riscv32/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-riscv32)

Linux risc-v 32bit cross compiler toolchain for risc-v 32bit GNU systems.

### dockcross/linux-m68k-uclibc

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-m68k-uclibc/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-m68k-uclibc)

Linux m68k cross compiler toolchain for m68k GNU systems (http://www.mac.linux-m68k.org/ and http://www.linux-m68k.org/).

### dockcross/linux-ppc64le

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-ppc64le/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-ppc64le)

Linux PowerPC 64 little endian cross compiler toolchain for the POWER8, etc. Important: Due to Issue #430, automatic build of newer images has been disabled.

### dockcross/linux-x64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-x64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-x64)

Linux x86_64/amd64 compiler. Since the Docker image is natively x86_64, this is not actually a cross compiler.

### dockcross/linux-x86_64-full

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-x86_64-full/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-x86_64-full)

Linux x86_64/amd64 compiler with libs: SDL2, OpenSSL, Boost, OpenCV and Qt5 (minimal).

### dockcross/linux-x64-clang

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-x64-clang/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-x64-clang)

Linux clang x86_64/amd64 compiler. Since the Docker image is natively x86_64, this is not actually a cross compiler.

### dockcross/linux-x86

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-x86/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-x86)

Linux i686 cross compiler.

### dockcross/linux-x64-tinycc

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/linux-x64-tinycc/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/linux-x64-tinycc)

Linux tcc compiler for C compiler, and GCC for C++ compiler, for linux x86_64/amd64 arch.

### dockcross/manylinux2014-x64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/manylinux2014-x64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/manylinux2014-x64)

Docker [manylinux2014](https://github.com/pypa/manylinux) image for building Linux x86_64 / amd64 [Python wheel packages](http://pythonwheels.com/). It includes Python 3.5, 3.6, 3.7, 3.8, and 3.9. Also has support for the dockcross script, and it has installations of CMake, Ninja, and [scikit-build](http://scikit-build.org). For CMake, it sets **MANYLINUX2014** to \"TRUE\" in the toolchain.

### dockcross/manylinux2014-x86

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/manylinux2014-x86/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/manylinux2014-x86)

Docker [manylinux2014](https://github.com/pypa/manylinux) image for building Linux i686 [Python wheel packages](http://pythonwheels.com/). It includes Python 3.5, 3.6, 3.7, 3.8, and 3.9. Also has support for the dockcross script, and it has installations of CMake, Ninja, and [scikit-build](http://scikit-build.org). For CMake, it sets **MANYLINUX2014** to \"TRUE\" in the toolchain.

### dockcross/manylinux2014-aarch64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/manylinux2014-aarch64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/manylinux2014-aarch64)

Docker [manylinux2014](https://github.com/pypa/manylinux) image for building Linux aarch64 / arm64 [Python wheel packages](http://pythonwheels.com/). It includes Python 3.5, 3.6, 3.7, 3.8, and 3.9. Also has support for the dockcross script, and it has installations of CMake, Ninja, and [scikit-build](http://scikit-build.org). For CMake, it sets **MANYLINUX2014** to \"TRUE\" in the toolchain.

### dockcross/web-wasm

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/web-wasm/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/web-wasm)

The Emscripten WebAssembly/asm.js/JavaScript cross compiler.

### dockcross/windows-static-x64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-static-x64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-static-x64)

64-bit Windows cross-compiler based on [MXE/MinGW-w64](https://mxe.cc/) with win32 threads and static
linking.

### dockcross/windows-static-x64-posix

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-static-x64-posix/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-static-x64-posix)

64-bit Windows cross-compiler based on [MXE/MinGW-w64](https://mxe.cc/) with posix threads and static
linking.

### dockcross/windows-static-x86

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-static-x86/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-static-x86)

32-bit Windows cross-compiler based on [MXE/MinGW-w64](https://mxe.cc/) with win32 threads and static linking.

### dockcross/windows-shared-x64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-shared-x64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-shared-x64)

64-bit Windows cross-compiler based on [MXE/MinGW-w64](https://mxe.cc/) with win32 threads and dynamic linking.

### dockcross/windows-shared-x64-posix

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-shared-x64-posix/latest)  ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-shared-x64-posix)

64-bit Windows cross-compiler based on [MXE/MinGW-w64](https://mxe.cc/) with posix threads and dynamic linking.

### dockcross/windows-shared-x86

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-shared-x86/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-shared-x86)

32-bit Windows cross-compiler based on [MXE/MinGW-w64](https://mxe.cc/) with win32 threads and dynamic linking.

### dockcross/windows-armv7

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-armv7/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-armv7)

ARMv7 32-bit Windows cross-compiler based on [LLVM/MinGW-w64](https://github.com/mstorsjo/llvm-mingw)

### dockcross/windows-arm64

![Docker Image Size (tag)](https://img.shields.io/docker/image-size/dockcross/windows-arm64/latest) ![Docker Pulls](https://img.shields.io/docker/pulls/dockcross/windows-arm64)

ARMv8 64-bit Windows cross-compiler based on [llvm-mingw](https://github.com/mstorsjo/llvm-mingw)

## Summary legacy cross compilers

The list of docker images that are no longer supported or broken

| Image name | Target arch | Compiler | Target OS |
|:-------:|:--------:|:------:|:-----:|
| dockcross/manylinux1-x86 | x86 | GCC | manylinux |
| dockcross/manylinux1-x64 | x86_64 | GCC| manylinux |
| dockcross/manylinux2010-x86 | x86 | GCC | manylinux |
| dockcross/manylinux2010-x64 | x86_64 | GCC | manylinux |

## Articles

-   [dockcross: C++ Write Once, Run
    Anywhere](https://nbviewer.jupyter.org/format/slides/github/dockcross/cxx-write-once-run-anywhere/blob/master/dockcross_CXX_Write_Once_Run_Anywhere.ipynb#/)
-   [Cross-compiling binaries for multiple architectures with
    Docker](https://web.archive.org/web/20170912153531/http://blogs.nopcode.org/brainstorm/2016/07/26/cross-compiling-with-docker)

## Built-in update commands

A special update command can be executed that will update the source
cross-compiler Docker image or the dockcross script itself.

-   `dockcross [--] command [args...]`: Forces a command to run inside
    the container (in case of a name clash with a built-in command), use
    `--` before the command.
-   `dockcross update-image`: Fetch the latest version of the docker
    image.
-   `dockcross update-script`: Update the installed dockcross script
    with the one bundled in the image.
-   `dockcross update`: Update both the docker image, and the dockcross
    script.

## Download all images

To easily download all images, the convenience target `display_images`
could be used:
```bash
curl https://raw.githubusercontent.com/dockcross/dockcross/master/Makefile -o dockcross-Makefile
for image in $(make -f dockcross-Makefile display_images); do
  echo "Pulling dockcross/$image"
  docker pull dockcross/$image
done
```

## Install all dockcross scripts

To automatically install in `~/bin` the dockcross scripts for each
images already downloaded, the convenience target `display_images` could
be used:

```bash
curl https://raw.githubusercontent.com/dockcross/dockcross/master/Makefile -o dockcross-Makefile
for image in $(make -f dockcross-Makefile display_images); do
  if [[ $(docker images -q dockcross/$image) == "" ]]; then
    echo "~/bin/dockcross-$image skipping: image not found locally"
    continue
  fi
  echo "~/bin/dockcross-$image ok"
  docker run dockcross/$image > ~/bin/dockcross-$image && \
  chmod u+x  ~/bin/dockcross-$image
done
```

## Dockcross configuration

The following environmental variables and command-line options are used.
In all cases, the command-line option overrides the environment
variable.

### DOCKCROSS_CONFIG / \--config\|-c \<path-to-config-file>

This file is sourced, if it exists, before executing the rest of the
dockcross script.

Default: `~/.dockcross`

### DOCKCROSS_IMAGE / \--image\|-i \<docker-image-name>

The Docker cross-compiler image to run.

Default: Image with which the script was created.

### DOCKCROSS_ARGS / \--args\|-a \<docker-run-args>

Extra arguments to pass to the `docker run` command. Quote the entire set of args if they contain spaces.

## Per-project dockcross configuration

If a shell script named `.dockcross` is found in the current directory where the dockcross script is started, it is executed before the dockcross script `command` argument. The shell script is expected to have a shebang like `#!/usr/bin/env bash`.

For example, commands like
`git config --global advice.detachedHead false` can be added to this
script.

## How to extend Dockcross images

In order to extend Dockcross images with your own commands, one must:

1.  Use `FROM dockcross/<name_of_image>`.
2.  Set `DEFAULT_DOCKCROSS_IMAGE` to a name of the tag you\'re planning
    to use for the image. This tag must then be used during the build
    phase, unless you mean to pass the resulting helper script the
    `DOCKCROSS_IMAGE` argument.

An example Dockerfile would be:

```
FROM dockcross/linux-armv7

ENV DEFAULT_DOCKCROSS_IMAGE my_cool_image
RUN apt-get install nano
```

And then in the shell:

```
docker build -t my_cool_image .                   ## Builds the dockcross image.
docker run my_cool_image > linux-armv7                ## Creates a helper script named linux-armv7.
chmod +x linux-armv7                          ## Gives the script execution permission.
./linux-armv7 bash                            ## Runs the helper script with the argument "bash", which starts an interactive container using your extended image.
```

## What is the difference between **dockcross** and **dockbuild** ?

The key difference is that [dockbuild](https://github.com/dockbuild/dockbuild#readme) images do **NOT** provide a [toolchain file](https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html) but they use the same method to conveniently isolate the build environment as [dockcross](https://github.com/dockcross/dockcross#readme).

**dockbuild** is used to build binaries for Linux x86_64/amd64 that will work across most Linux distributions.
**dockbuild** performs a native Linux build where the host build system is a Linux x86_64 / amd64 Docker image (so that it can be used for building binaries on any system which can run Docker images) and the target runtime system is Linux x86_x64/ amd64.

**dockcross** is used to build binaries for many different platforms. **dockcross** performs a cross compilation where the host build system is a Linux x86_64 / amd64 Docker image (so that it can be used for building binaries on any system which can run Docker images) and the target runtime system varies.

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Credits:
- [sdt/docker-raspberry-pi-cross-compiler](https://github.com/sdt/docker-raspberry-pi-cross-compiler), who invented the base of the **dockcross** script.
- [https://github.com/steeve/cross-compiler](https://github.com/steeve/cross-compiler),