Ask HN: What Linux components one must learn towards Mastery?

Just the title, in order to master Linux, what components you think would be necessary to master?

I think of:

- iptables/netfilter

- systemd

- LVM?

- seccomp?

Also, more fundamental question is - how linux get configured at its very core? Does it read files from specific locations? I highly doubt that, rather i would assume all the configuration happens via either syscalls or writing to the virtual /proc or similar file system via bash scripts and then there are just file location and naming conventions that might vary from distribution to distribution?