# Configuring & Building MOS

This guide will walk you through the process of configuring and building MOS from source.

If it's your first time building MOS, you will need to initialise the build system by running:

mkdir build && cd build
cmake .. -DMOS_ARCH=x86_64 -GNinja # remove -GNinja if you want to use Make

MOS uses Kconfig, a configuration system that is also used by the Linux kernel, to manage its configuration options. You can change the configuration options by running:

ninja menuconfig

This will open a menu where you can change the configuration options, the menu is similar to the Linux kernel's menuconfig and it's even easier to use.

You can also set the configuration options via CMake, see Kconfig Configuration System for more information.

You can then examine which targets are available to build by running:

ninja mos_print_summary

A bootable target is a target that produces either a bootable binary or an image that can be started by a bootloader, or virtual machine. The list of bootable targets can be found in the output of mos_print_summary above.

Use ninja <target> to build a specific target, e.g. ninja mos_limine.

There are several utility targets that you can use to build specific parts of MOS:

• mos_kernel: Only build the kernel sources into object files, not a single binary or archive would be produced.
• mos_initrd: Build the initrd image, which is a CPIO1 archive that contains the userspace binaries and libraries.
• mos_cleanup_initrd: Remove the initrd image, and remove all contents of the initrd/ directory.
• mos_print_summary: Print a summary of the available build targets.