# To list all loaded/active units:
systemctl list-units

# To check the status of a service:
systemctl status foo.service

# To start a service:
systemctl start foo.service

# To restart a service:
systemctl restart foo.service

# To stop a service:
systemctl stop foo.service

# To reload a service's configuration:
systemctl reload foo.service

# To enable a service to startup on boot:
systemctl enable foo.service

# To disable a service to startup on boot:
systemctl disable foo.service

# To list the dependencies of a service:
# To When no service name is specified, lists the dependencies of default.target
systemctl list-dependencies foo.service 

# To list currently loaded targets:
systemctl list-units --type=target

# To change current target:
systemctl isolate foo.target

# To change default target:
systemctl enable foo.target
