It's almost entirely (80%) drivers. Next heaviest is architecture specific code, then filesystems, networking, sound, documentation, and then the actual core of

It's almost entirely (80%) drivers. Next heaviest is architecture specific code, then filesystems, networking, sound, documentation, and then the actual core of the kernel. A minimal build of linux uses about 300k lines of code. https://unix.stackexchange.com/questions/223746/why-is-the-linux-kernel-15-million-lines-of-code https://unix.stackexchange.com/questions/223746/why-is-the-l... So it's still substantially heavier than would be easy to study, but you could probably still fit the core into your head (I've been able to deeply understand systems with similar LOC counts, though there's probably substantial differences in 'density' between codebases)