systemctl list-unit-files <===> vypíše UPLNE vsechny všechny služby (pouze na SystemD) i ty co jsou disabled // The status is [ + ] for running services, [ - ] for stopped services and [ ? ] for services without a status command.
systemctl list-units <===> vypíše všechny služby (services / socket / device / target / timer / mount )
systemctl list-units -t service <===> vypíše POUZE sluzby typu service

systemctl start {sluzba}
systemctl stop {sluzba}
systemctl restart {sluzba}
systemctl status {sluzba}
systemctl enable {sluzba} <===> sluzba se spusti automaticky i po restartu???overit
systemctl disable {sluzba}
systemctl is-active {sluzba} <===> zjisti zda je sluzba aktivni
systemctl is-enabled {sluzba} <===> zjisti zda je sluzba zapnuta

napr

systemctl status sshd.service
sudo systemctl status sshd


It instigated one of the great flame wars of our time. In light of the perceived shortcomings of init (which are highlighted here), systemd (or the system daemon) was developed.
This uses a completely new system with the goal of starting a service "when all its conditions are met." Like Upstart however, it can still support the init-style scripts provided by many packages, with a few notable exceptions.

Note in the image above how directories have names like "this.thing.wants." This demonstrates systemd's "on-demand" behavior -- when something "wants" bluetooth access and the
conditions are met, systemd will start the service for it.