AzathOS

AzathOS (previously called Real Linux From Scratch) is userland for Linux written from scratch. I started this project to get a better understanding of the kernel. My goal is to create a usable UNIX environment with my own init, shell and utilities.

All code is written in Rust and limited to just a few common libraries like libc, chrono, clap and serde.

Building

make
make run

Intramfs

Currently AzathOS works by creating a tiny filesystem in a cpio archive. This is then used as the initramfs for the kernel supplied with -initrd flag in qemu. The kernel will then decompress my filesystem on top of the initramfs already baked into the kernel.

The kernel creates that initramfs during compilation according to default_cpio_list, it creates the /dev/console device and also the /root mountpoint. Because AzathOS does not actually intend to mount a root disk and doesn't use a /root directory you can patch the kernel to not create that directory. See no_root.patch.

Build into the kernel

It is possible to build the initrd into the kernel itself. This is done by specifying the filesystem files, rootfs in CONFIG_INITRAMFS_SOURCE.

You also want to include default_cpio_list which will ensure a console device is created. CONFIG_INITRAMFS_SOURCE="azathos/rootfs azathos/default_cpio_list"

If you also want to have some decent size, I recommend turning off all the debug options I configured and set CONFIG_CC_OPTIMIZE_FOR_SIZE.