GNU OS Cross-Compiler

About

This project is a GNU operating system cross-compiler, named gnuxc for short, tailored to run on Fedora as the build system. It can create a free, portable, Hurd-based, desktop OS from scratch.

There are two distinct components for building a working operating system:

Sysroot libraries and cross-tools: These are packaged into RPMs for the latest Fedora release. They provide a GNU Hurd cross-compiling environment on the build system, a standard base of software to run and link against when compiling software for the operating system itself. Their build files are located in specs and patches.
Operating system compilation rules: The options and procedures used to build all of the OS software are contained in make.pkg.d and patches. These files are mostly reusable on the GNU system to rebuild or upgrade packages at runtime.

A documentation file BUILD.md is provided to walk-through the entire build procedure and how to test running the OS virtually. All sample commands in the documentation can be pasted directly into a bash prompt. Some of the commands require your account to have sudo access, for example to install system packages or work with loop devices.

The file RUNTIME.md documents how to use and configure the main environments at runtime, especially the aspects that are unique to the gnuxc project.

Requirements

Operating system: Fedora 27 is the current release targeted by this code.

Disk space: At least 20 GiB of total available storage is required when building everything on the same machine, plus however much space is desired for creating a virtual disk image. Using solid-state storage for the working directories will greatly improve build times.

Installing only the packages necessary to build the complete OS requires half a gigabyte. This is the default action of the sysroot builder script.
The sysroot builder script leaves RPMs, SRPMs, and source archives on the disk after it finishes, requiring about 2 GiB of disk space. (This space can be reclaimed by removing the RPM build environment after installation.)
The main working directory will use around 17 GiB after compilation.

Memory: The build is usually tested on systems with at least 8 GiB of RAM.

Processor(s): The build has been tested on various CPUs ranging from 2-cores under 2 GHz to 8-cores around 5 GHz. Bigger is better. The CPU should support hosting a virtual x86 guest with KVM for best results with running the OS.

Install

The gnuxc source directory is self-contained, and it is functional from any file system location. To install it at a certain path, simply move or copy the whole directory into place.

An unprivileged user account can run everything out of its home directory. If a shared install is desired, the gnuxc directory can be placed in a read-only system location such as /usr/share/gnuxc.

Usage

Calling the main GNUmakefile will build the projects in your current working directory, or the path given to GNU Make with its -C option.

All commands in this documentation assume that your current directory is your desired build path, so change to that directory before pasting any commands.

The given commands also assume your working directory is the gnuxc directory, unless you set the SOURCE_DIR variable to its location. (Note that this variable is only a convention for the example commands; it is never used in the actual project code.) For example, run the following if gnuxc was installed into /usr/share.

SOURCE_DIR=/usr/share/gnuxc

See BUILD.md for a detailed walk-through of building the complete OS.

License

Files written specifically for this cross-compilation system (i.e., not patches to other projects) are distributed under GPLv3+ terms. The full text of this license is included in a COPYING file under the patches directory.

The changes in the patch files should be considered under the same license as the files they modify, to ease applying the patches upstream if appropriate. Most patches are too trivial to warrant any copyright or licensing concerns.

Quick Update Guide

The following steps can be run after updating the gnuxc files to rebuild the entire updated OS from scratch. You must run the full build process at least once before this will work. See BUILD.md for complete instructions.

Remove old packages.

rm -fr "$(rpm -E %_rpmdir)" "$(rpm -E %_srcrpmdir)"
sudo dnf -y remove 'gnuxc-*'
gmake clean

Update RPM source files.

ln -fst "$(rpm -E %_sourcedir)" "${SOURCE_DIR:-$PWD}"/patches/*
ln -fst "$(rpm -E %_specdir)" "${SOURCE_DIR:-$PWD}"/specs/*

Rebuild the system. This assumes that you've mounted your target disk over gnu-root beforehand. Don't forget to run the ownership correction step after installation.

time make -f "${SOURCE_DIR:-.}/setup-sysroot.scm" $(rpm -E %_smp_mflags) -k
time ( gmake download && gmake $(rpm -E %_smp_mflags) && gmake install )