2, systemd process
when systemd process is maintained throughout all processes running Linux system "brain" ,, systemd process is therefore not allowed to be easily terminated, the system needs to switch to a different operating states can be sent to the systemd process the correct command systemd itself to complete the related operations.
Second, the use systemd management system
1, systemd unit
in systemd systemd different types of objects are collectively referred to as unit, is to let the system know how to operate and manage the main target resources, so there are many systemd unit type.
Common types of systemd unit