Stop Cloning Stale Hostnames: Practical `systemd-firstboot` for Linux Images

If you build Linux images for VMs, lab machines, edge devices, or golden templates, you have probably hit the same mess at least once. You clone an image, boot it, and realize it still carries a stale hostname, the wrong timezone, or a machine identity you never meant to duplicate. systemd-firstboot is a small tool that solves exactly that class of problem. It writes first-boot configuration directly into an offline root filesystem or disk image, before the system ever starts. That makes it usef