How to use systemctl

The latest version of Linux uses systemd(PID 1) rather than the init process. The command to control this systemd is systemctl.

Usasge	Description
systemctl list-units	Print units with the active state.
systemctl list-units --type service	Print service units with the active state.
systemctl list-units --type service -a	Print service units with the active, inactive and not-found state.
systemctl list-unit-files	Print whether the unit is enabled, disabled or static.
systemctl status sshd	Print the status of sshd service.
systemctl stop sshd	Stop the sshd service.
systemctl start sshd	Start the sshd service
systemctl restart sshd	Restart the sshd service
systemctl disable sshd	Disable the sshd service.
systemctl enable sshd	Enable the sshd service.   * Enable : When the system boots, It is executed automatically.
systemctl mask sshd	Set the mask for the sshd service.   * mask : A configuration that prevents the unit from execute.
systemctl unmask sshd	Remove the mask for the sshd service.
systemctl reload sshd	Reload the mask for the sshd service.
systemctl list-dependencies sshd	Print dependency of sshd service.
systemctl get-default	Print default-target.   * Previous Linux's runlevel has been changed to target.   * See /etc/inittab for details.
systemctl set-default [Target]	Change the default-target.   * Target : multi-user.target(CLI) graphical.target(GUI)
systemctl isolate [Target]	Change current target.