A Docker containerized cross-compile toolchain for building bootable images and operating system services. This uses the method described on the OSDev wiki to make an i686-elf cross compiler. Then I also borrowed some ideas from the dockcross tools to make it a bit easier to run the tools from the container using a wrapper script.
Assuming you have Docker installed and setup already you should be able to use the toolchain by just installing the ktool wrapper script from this repo. I do most of my work on OS X and some on Linux, so I've somewhat tested out those two. I can't really help with running on Windows. But it appears the dockcross tools do work under Windows, so if you need to make this work on Windows maybe check to see what dockcross does. I'll give some examples for OS X, but they should be pretty close for Ubuntu as well.
I have a public image up on Docker Hub so all you should have to do is grab the ktool script from this repo, make it executable, and put it somewhere in your PATH. The first time you try to run the script it will pull down the Docker image with the toolchain. Try running a version check on the gcc compiler in the container for example:
ktool i686-elf-gcc --version
You should get back something like this:
i686-elf-gcc (GCC) 10.2.0 Copyright (C) 2020 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
I use the tools in the container to experiment with some of the examples from the OSDev wiki. You should be able to compile anything from the Bare Bones examples if you need a place to start. Assuming you have boot.s, kernel.c and linker.ld in your current directory you should be able to:
ktool i686-elf-as boot.s -o boot.o ktool i686-elf-gcc -c kernel.c -o kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra ktool i686-elf-gcc -T linker.ld -o myos.bin -ffreestanding -O2 -nostdlib boot.o kernel.o -lgcc
The ktool script mounts the current working directory inside the container by default, so you don't have to worry about copying files into or back out of the container. You should have a myos.bin file in the current directory after you run those three commands. And you should be able to run it on your host system to make sure everything worked correctly:
qemu-system-i386 -kernel myos.bin