PepperOS is a 64-bit freely-licensed monolithic kernel for x86 processors, with round-robin preemptive scheduling and 4-level paging. See the manual for more.

Trying the kernel in QEMU

Debian-based distributions

First, install the dependencies: sudo apt install nasm python3 xorriso make qemu-system

Then, you can get an x86_64 toolchain for compilation. The easiest way to do that on most systems is to install it from Homebrew:

brew install x86_64-elf-gcc

If you're already on a 64-bit machine (which you probably are), and don't want to install a cross-compiler, you can just override CC and LD variables in the Makefile, like so:

CC := gcc
LD := ld

Then, to compile the kernel and make an ISO image file, run: make.
To build the user programs and the initial filesystem, do make user.
To run it with QEMU, do: make run.

Trying the kernel on real hardware

Compile the kernel and generate an ISO image like described above, then burn the image to a USB stick, /dev/sdX being the device name (you can get it using lsblk):

sudo dd if=pepper.iso of=/dev/sdX

Compilation options

By default, PepperOS is compiled without the following features:

UBSAN - undefined behavior sanitization

These features can be activated by setting them to "true" at the end of the make command, for example:

make UBSAN=true

Writing software for PepperOS

If you want to write software for PepperOS, take a look at the Software Developer's guide.

Thanks

PepperOS wouldn't be possible without the following freely-licensed software:

the Limine portable bootloader
Charles Nicholson's nanoprintf
Mintuski's Flanterm terminal emulator

...and without these amazing resources:

the OSDev wiki & forums
Intel 64 and IA-32 Architectures Software Developer's Manual
Documentation for the GNU Compiler Collection
dreamos82's OSDev Notes
the Sortix UBsan hook implementations
the CSC 395 Kernel Development course from Grinnell College

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