hostnamectl(1) man page — Describes hostnamectl including the commands and command options.
hostname(1) man page — Contains an explanation of the hostname and domainname commands.
hostname(5) man page — Contains an explanation of the host name file, its contents, and use.
hostname(7) man page — Contains an explanation of host name resolution.
machine-info(5) man page — Describes the local machine information file and the environment variables it contains.
machine-id(5) man page — Describes the local machine ID configuration file.
systemd-hostnamed.service(8) man page — Describes the systemd-hostnamed system service used by hostnamectl.