systemd-notify

Notify the service manager about start-up completion and other daemon status changes. This command is useless outside systemd service scripts. More information: https://www.freedesktop.org/software/systemd/man/systemd-notify.html.

• Notify systemd that the service has completed its initialization and is fully started. It should be invoked when the service is ready to accept incoming requests:
  systemd-notify --booted
• Signal to systemd that the service is ready to handle incoming connections or perform its tasks:
  systemd-notify --ready
• Provide a custom status message to systemd (this information is shown by systemctl status):
  systemd-notify --status="{{Add custom status message here...}}"