@b0rk@dngrs I can’t vouch for current editions but if they’re as good as the 30 year old version I learned from, I highly recommend checking out the Evi Nemeth system administration books. If you want to go deeper, the old O’Reilly Unix Systems Programming for SVR4 book bridges nicely from the simple, common CLI commands into syscalls down toward OS internals in a relatively abstracted way. The right kernel internals reference below that will vary with OS.
@josh I vaguely recall experimenting with something like this on a certain Android demo platform ten years or so ago. Did some fun (slightly unnatural?) things with reflinks, btrfs, and tmpfs. Sadly I doubt anything beyond vague and fond memories remain, but I periodically think of retrying something related for container layer management. Fascinated to hear if you make something!