Yocto Project

Yocto is not a distribution but a factory for making them. The Linux Foundation launched it in 2010 on top of OpenEmbedded, which itself grew out of hobbyist distributions for the Sharp Zaurus. The BitBake build tool reads recipes that describe how each package is fetched, patched and cross-compiled, and recipes are grouped into layers (meta-*) that board vendors and companies stack on top of each other. The reference distribution is called Poky.

The output is reproducible and traceable down to the licence of every file, which is why carmakers and industrial firms pick it. The cost is the learning curve and the build time: a first run takes hours and wants a hundred-odd gigabytes of disk. The lighter-weight rival is Buildroot.