A small Unix-like operating system for x86_64, written in mach: the kernel, the boot loader and the userland.

What it has

• Kernel: every CPU core (SMP), preemptive multitasking, processes and threads (futexes), signals, pipes, mmap, readiness queues, /proc, /dev/events
• Boot: machboot, its own UEFI boot loader (also written in mach), dual boot with Windows, a live ISO that runs from memory and can install itself, and an updater
• Storage: AHCI and NVMe disks, GPT, ext2 (the root), FAT32 and exFAT (USB sticks, the EFI partition), fsck
• Devices: xHCI USB with hubs and hotplug, PS/2 and USB keyboards, framebuffer and serial consoles, RTC with time zones
• Userland: over eighty programs, most of them on mach's std: a shell with job control and line editing, nano, less, tar, gzip, grep, sort, top, and so on. ls /bin lists them

Try it

tools/run.sh        # build a disk image and boot it in QEMU

Log in as root (no password).

Building

You need the mach compiler (6.10) and, on Arch:

sudo pacman -S lld gptfdisk e2fsprogs mtools xorriso qemu-system-x86 edk2-ovmf python

tools/run.sh              # build a disk image and boot it in QEMU
tools/run.sh release      # the same, optimized
tools/run.sh --fresh      # start from a new disk
tools/iso.sh              # build the live ISO (out/machos.iso)
tools/test.py             # run all the tests
tools/test.py wget tcp    # run only the named tests

The ISO is UEFI: it boots from a CD, from a USB stick (dd it there) or from Ventoy. Inside, install puts MachOS on a disk.

Tests

tools/test.py boots MachOS in QEMU and drives it over the serial console: boot, shell, USB, boot loader menus, dual boot, install, update, filesystems, fsck and rescue, the network (a host-side UDP echo and web server stand in for the internet), and std's own test suite. Tests that need the internet, such as dns, say so in the test table.

Debugging

tools/gdb.sh                    # boot paused, with a gdb stub on :1234
tools/mount.sh                  # mount the dev disk on the host, without sudo
tools/put.sh FILE               # copy a file onto the disk image
tools/boot.sh IMAGE|/dev/sdX    # boot an existing install as it is

Layout

Directory	What is in it
kernel/	the kernel: arch, mm, kern (processes, system calls), fs, dev, net, boot
machboot/	the UEFI boot loader
sdk/	MachOS's own system-call layer and runtime, for the programs that need it
userland/	the programs (src/bin) and their shared code (src/lib); mach.toml is generated by tools/programs.sh
root/	files copied onto the root filesystem: /etc, the motd
examples/	hello, posixtest and stdtest, which run std's tests on MachOS
tools/	build, run, test and image scripts

Status

MachOS is a hobby system. It runs on QEMU and boots from USB sticks and disks, but expect rough edges.

License

MachOS is licensed under GNU General Public License, version 3 only. Third-party components retain their respective licences.