How to Manage Systemd Services with Systemctl on Linux
How to control System and Services on Linux
Manage Sockets with Systemctl
You can also manage sockets using the Systemctl command.
To list all available system sockets, run the following command:
$ systemctl list-unit-files --type=socket
UNIT FILE STATE VENDOR PRESET
acpid.socket enabled enabled
avahi-daemon.socket enabled enabled
ssh.socket disabled enabled
cups.socket enabled enabled
dbus.socket static enabled
dm-event.socket enabled enabled
lvm2-lvmpolld.socket enabled enabled
saned.socket disabled enabled
snapd.socket enabled enabled
syslog.socket static disabled
systemd-coredump.socket static enabled
systemd-fsckd.socket static enabled
systemd-initctl.socket static enabled
To start the SSH socket, run the following command:
$ systemctl start ssh.socket
To stop the SSH socket, run the following command:
$ systemctl stop ssh.socket
To restart the SSH socket, run the following command:
$ systemctl restart ssh.socket
To check the status of the SSH socket, run the following command:
$ systemctl status ssh.socket
To enable and disable the SSH socket at boot time, run the following command:
$ systemctl enable ssh.socket $ systemctl disable ssh.socket
Control System Runlevels
How to start a system rescue mode.
# systemctl rescue
Broadcast message from root@tecmint on pts/0 (Wed 2015-04-29 11:31:18 IST):
The system is going down to rescue mode NOW!
How to enter into emergency mode.
$ systemctl emergency
Welcome to emergency mode! After logging in, type "journalctl -xb" to view
system logs, "systemctl reboot" to reboot, "systemctl default" to try again
to boot into default mode.
List current run levels in use.
$ systemctl get-default
multi-user.target
How to start Runlevel 5 aka graphical mode.
$ systemctl isolate runlevel5.target OR $ systemctl isolate graphical.target
How to start Runlevel 3 aka multiuser mode (command line).
$ systemctl isolate runlevel3.target OR $ systemctl isolate multiuser.target
How to set multiuser mode or graphical mode as default run level.
$ systemctl set-default runlevel3.target OR $ systemctl set-default runlevel5.target
How to reboot, halt, suspend, hibernate, or put a system in hybrid-sleep.
$ systemctl reboot $ systemctl halt $ systemctl suspend $ systemctl hibernate $ systemctl hybrid-sleep
For those who may not be aware of run levels and what it does.
Runlevel 0 : Shut down and Power off the system.
Runlevel 1 : Rescue?Maintainance Mode.
Runlevel 3 : multiuser, no-graphic system.
Runlevel 4 : multiuser, no-graphic system.
Runlevel 5 : multiuser, graphical system.
Runlevel 6 : Shutdown and Reboot the machine.
Conclusion
In the above guide, you learned how to manage and control systemd service on Linux. I hope this will helps you to interact with and control your systemd instance. Feel free to ask me if you have any questions.
See also: How to Kill a Process in Linux