El utilitario systemctl permite controlar el gestor de inicio y servicios systemd.

Listar servicios

Para listar los servicios activos, simplemente ejecutar systemctl list-units.

Si se desea filtrar, es posible emplear una expresión regular, por ejemplo:

[email protected]:~# systemctl list-units php*
UNIT                  LOAD   ACTIVE SUB     DESCRIPTION                          
php7.3-fpm.service    loaded active running The PHP 7.3 FastCGI Process Manager  
phpsessionclean.timer loaded active waiting Clean PHP session files every 30 mins

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

2 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.

Si se desean listar todas las unidades, activas e inactivas, agregar la opción -a:

[email protected]:~# systemctl -a list-units php*
UNIT                    LOAD   ACTIVE   SUB     DESCRIPTION                          
php7.3-fpm.service      loaded active   running The PHP 7.3 FastCGI Process Manager  
phpsessionclean.service loaded inactive dead    Clean php session files              
phpsessionclean.timer   loaded active   waiting Clean PHP session files every 30 mins

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

3 loaded units listed.
To show all installed unit files use 'systemctl list-unit-files'.

Si se desean listar todos los servicios instalados (habilitados y deshabilitados), ejecutar:

[email protected]:~# systemctl -a list-unit-files php*
UNIT FILE               STATE   
php7.0-fpm.service      disabled
php7.2-fpm.service      disabled
php7.3-fpm.service      enabled 
phpsessionclean.service static  
phpsessionclean.timer   enabled 

5 unit files listed.

Ahora bien, systemd llama “units” (unidades) a los servicios, pero una unidad puede ser también un socket, un dispositivo, un timer, etc. (consultar la página de manual “systemd” para conocer todos los tipos de unidades).

Si se desea listar absolutamente todas las unidades, ejecutar: systemctl --all.

Para listar sólo las unidades que corresponden con servicios, es necesario filtrar por tipo de unidad empleando la opción -t service:

[email protected]:~# systemctl -a -t service list-units php*
UNIT                    LOAD   ACTIVE   SUB     DESCRIPTION                        
php7.3-fpm.service      loaded active   running The PHP 7.3 FastCGI Process Manager
phpsessionclean.service loaded inactive dead    Clean php session files            

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.

2 loaded units listed.
To show all installed unit files use 'systemctl list-unit-files'.

Consultar el estado de un servicio

Para consultar el estado de un servicio se debe emplear el subcomando status con el nombre de la unidad como parámetro (al revés que el utilitario service):

[email protected]:~# systemctl status php7.3-fpm.service
● php7.3-fpm.service - The PHP 7.3 FastCGI Process Manager
   Loaded: loaded (/lib/systemd/system/php7.3-fpm.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2020-11-19 17:35:26 -03; 4 days ago
     Docs: man:php-fpm7.3(8)
  Process: 24438 ExecStopPost=/usr/lib/php/php-fpm-socket-helper remove /run/php/php-fpm.sock /etc/php/7.3/fpm/pool.d/www.conf 7
  Process: 24483 ExecStartPost=/usr/lib/php/php-fpm-socket-helper install /run/php/php-fpm.sock /etc/php/7.3/fpm/pool.d/www.conf
 Main PID: 24462 (php-fpm7.3)
   Status: "Processes active: 0, idle: 20, Requests: 363350, slow: 0, Traffic: 5.3req/sec"
    Tasks: 21 (limit: 4915)
   CGroup: /system.slice/php7.3-fpm.service
           ├─ 9842 php-fpm: pool www.linuxito.com
           ├─16069 php-fpm: pool blog.linuxito.com
           ├─16267 php-fpm: pool blog.linuxito.com
           ├─16392 php-fpm: pool www.linuxito.com
           ├─17013 php-fpm: pool www.linuxito.com
           ├─18461 php-fpm: pool www.linuxito.com
           ├─18466 php-fpm: pool www.linuxito.com
           ├─18499 php-fpm: pool www.linuxito.com
           ├─18501 php-fpm: pool www.linuxito.com
           ├─19446 php-fpm: pool www.linuxito.com
           ├─19449 php-fpm: pool www.linuxito.com
           ├─24462 php-fpm: master process (/etc/php/7.3/fpm/php-fpm.conf)
           ├─24475 php-fpm: pool blog.linuxito.com
           ├─24476 php-fpm: pool blog.linuxito.com
           ├─24477 php-fpm: pool blog.linuxito.com
           ├─24481 php-fpm: pool www
           ├─24482 php-fpm: pool www
           ├─24531 php-fpm: pool blog.linuxito.com
           ├─24573 php-fpm: pool www.linuxito.com
           ├─24584 php-fpm: pool blog.linuxito.com
           └─25902 php-fpm: pool blog.linuxito.com

Nov 19 17:35:26 www.linuxito.com systemd[1]: Starting The PHP 7.3 FastCGI Process Manager...
Nov 19 17:35:26 www.linuxito.com systemd[1]: Started The PHP 7.3 FastCGI Process Manager.

Referencias

• man systemctl
• man systemd