You must be running a 64-bit x86 Linux distribution. Darling cannot be used on a 32-bit x86 system, not even to run 32-bit applications.

It is recommended that you use at least Clang 3.8. You can force a specific version of Clang (if it is installed on your system) by editing Toolchain.cmake.

Linux 4.9 and higher is required.

sudo apt install cmake clang bison flex xz-utils libfuse-dev libudev-dev pkg-config libc6-dev-i386 linux-headers-amd64 libcap2-bin git libgcc-5-dev:i386 libcairo2-dev libgl1-mesa-dev libtiff5-dev libfreetype6-dev libfreetype6-dev:i386 libxml2-dev libegl1-mesa-dev libfontconfig1-dev libbsd-dev

sudo apt install cmake clang-4.0 bison flex xz-utils libfuse-dev libudev-dev pkg-config libc6-dev-i386 linux-headers-amd64 libcap2-bin git libcairo2-dev libgl1-mesa-dev libtiff5-dev libfreetype6-dev libxml2-dev libegl1-mesa-dev libfontconfig1-dev libbsd-dev

sudo apt install cmake clang-6.0 bison flex xz-utils libfuse-dev libudev-dev pkg-config libc6-dev-i386 linux-headers-amd64 libcap2-bin git libcairo2-dev libgl1-mesa-dev libtiff5-dev libfreetype6-dev libxml2-dev libegl1-mesa-dev libfontconfig1-dev libbsd-dev

sudo apt install cmake clang-7 bison flex xz-utils libfuse-dev libudev-dev pkg-config libc6-dev-i386 linux-headers-amd64 libcap2-bin git libcairo2-dev libgl1-mesa-dev libtiff5-dev libfreetype6-dev libxml2-dev libegl1-mesa-dev libfontconfig1-dev libbsd-dev

sudo apt install cmake clang bison flex xz-utils libfuse-dev libudev-dev pkg-config libc6-dev-i386 linux-headers-generic gcc-multilib libcap2-bin libcairo2-dev libgl1-mesa-dev libtiff5-dev libfreetype6-dev git libelf-dev libxml2-dev libegl1-mesa-dev libfontconfig1-dev libbsd-dev

sudo pacman -S --needed make cmake clang flex bison icu fuse linux-headers gcc-multilib lib32-gcc-libs pkg-config fontconfig cairo libtiff python2 mesa llvm

sudo dnf install make cmake clang bison flex python2 glibc-devel.i686 fuse-devel systemd-devel kernel-devel elfutils-libelf-devel cairo-devel freetype-devel.{x86_64,i686} libjpeg-turbo-devel.{x86_64,i686} libtiff-devel.{x86_64,i686} fontconfig-devel.{x86_64,i686} libglvnd-devel.{x86_64,i686} mesa-libGL-devel.{x86_64,i686} mesa-libEGL-devel.{x86_64,i686} libxml2-devel libbsd-devel

Darling makes extensive use of Git submodules, therefore you cannot use a plain git clone. Make a clone like this:

git clone --recursive https://github.com/darlinghq/darling.git

The build system of Darling is CMake. Makefiles are generated by CMake by default.

Now let's build Darling:

# Move into the cloned sources
cd darling

# Make a build directory
mkdir build && cd build

# Configure the build
cmake ..

# Build and install Darling
make
sudo make install

Darling also requires a kernel module named darling-mach:

make lkm
sudo make lkm_install

If module installation produces warnings such as SSL error:02001002:system library:fopen:No such file or directory: bss_file.c:175, then these can be usually ignored, unless you configured your system to enforce secure boot.

The kernel module is an experimental piece of code; it's likely to have many bugs and vulnerabilities. Be prepared for kernel hangups and crashes, and run Darling on a virtual machine if possible.

You will notice that it takes a long time to build Darling. Darling contains the software layer equivalent to an entire operating system, which means a large amount of code. You can optionally disable some large and less vital parts of the build in order to get faster builds.

To do this, use the -DFULL_BUILD=OFF option when configuring Darling through CMake.

You may encounter some things to be missing, such as JavaScriptCore. Before creating an issue about a certain library or framework missing from Darling, verify that you are doing a full build by not using this option or setting it to ON.

Another way to speed up the build is to run make with multiple jobs. For this, run make -j8 instead, where 8 is a number of current jobs to run of your choosing. In general, avoid running more jobs than twice the amount CPU cores of your machine.

If you run lldb and encounter messages indicating a lack of debug symbols, make sure you are doing a debug build. To do this, use the -DCMAKE_BUILD_TYPE=Debug.

If your distribution is Backbox and you run into build issues try the following commands:

sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-4.0 400
sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-4.0 400

On SELinux you may see the following error when starting darling:

Cannot open mnt namespace file: No such file or directory

To work around this try this command: setsebool -P mmap_low_allowed 1.