systemctl: add global status example (#6849)

pages/linux/systemctl.md

@@ -3,6 +3,10 @@
 > Control the systemd system and service manager.
 > More information: <https://www.freedesktop.org/software/systemd/man/systemctl.html>.
 
+- Show all running services:
+
+`systemctl status`
+
 - List failed units:
 
 `systemctl --failed`
@@ -27,10 +31,6 @@
 
 `systemctl daemon-reload`
 
-- Check if a unit is active:
-
-`systemctl is-active {{unit}}`
-
 - Check if a unit is enabled:
 
 `systemctl is-enabled {{unit}}`