/lib/systemd/system-generators/systemd-getty-generator
systemd-getty-generator is a generator that automatically instantiates serial-getty@.service on the kernel console /dev/console if that is not directed to the virtual console subsystem. It will also instantiate serial-getty@.service instances for virtualizer consoles, if execution in a virtualized environment is detected. Finally, it will instantiate container-getty@.service instances for additional container pseudo TTYs as requested by the container manager (see m[blue]Container Interfacem[][1]). This should ensure that the user is shown a login prompt at the right place, regardless of which environment the system is started in. For example, it is sufficient to redirect the kernel console with a kernel command line argument such as console= to get both kernel messages and a getty prompt on a serial TTY. See m[blue]kernel-parameters.txtm[][2] for more information on the console= kernel parameter.
systemd-getty-generator implements the m[blue]generator specificationm[][3].
Further information about configuration of gettys you may find in m[blue]systemd for Administrators, Part XVI: Gettys on Serial Consoles (and Elsewhere)m[][4].