Troubleshooting Services With 'systemctl`

To view a description of all the active, loaded units, execute the systemctl command without any options or arguments:

systemctl

To see all the loaded, active, and inactive units and their description, run this command:

systemctl --all

To see all the unit files and their current status but no description, run this command:

systemctl list-unit-files

The grep command filters the services by a search term, a helpful tactic to recall the exact name of a unit file without looking through a long list of names. Example:

systemctl list-unit-files | grep network
org.freedesktop.network1.busname           static
dbus-org.freedesktop.network1.service      enabled
systemd-networkd-wait-online.service       enabled
systemd-networkd.service                   enabled
systemd-networkd.socket                    enabled
network-online.target                      static
network-pre.target                         static
network.target  

For example, to list all the services that you can manage on Photon OS, you run the following command instead of ls /etc/rc.d/init.d/:

systemctl list-unit-files --type=service

Similarly, to check whether the sshd service is enabled, on Photon OS you run the following command instead of chkconfig sshd:

systemctl is-enabled sshd

The chkconfig --list command that shows which services are enabled for which runlevel on a SysVinit computer becomes substantially different on Photon OS because there are no runlevels, only targets:

ls /etc/systemd/system/*.wants

You can also display similar information with the following command:

systemctl list-unit-files --type=service

The following is list of some of the systemd commands that take the place of SysVinit commands on Photon OS:

USE THIS SYSTEMD COMMAND     INSTEAD OF THIS SYSVINIT COMMAND
systemctl start sshd         service sshd start
systemctl stop sshd         service sshd stop
systemctl restart sshd         service sshd restart
systemctl reload sshd         service sshd reload
systemctl condrestart sshd     service sshd condrestart
systemctl status sshd         service sshd status
systemctl enable sshd         chkconfig sshd on
systemctl disable sshd         chkconfig sshd off
systemctl daemon-reload        chkconfig sshd --add