[root@kde-vm user]# systemctl status spice-vdagentd
○ spice-vdagentd.service - Agent daemon for Spice guests
     Loaded: loaded (/usr/lib/systemd/system/spice-vdagentd.service; indirect; vendor pre>
     Active: inactive (dead)
TriggeredBy: ● spice-vdagentd.socket
[root@kde-vm user]# systemctl enable --now spice-vdagentd
The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled using systemctl.
 
Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit's
  .wants/ or .requires/ directory.
• A unit's purpose may be to act as a helper for some other unit which has
  a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
  D-Bus, udev, scripted systemctl call, ...).
• In case of template units, the unit is meant to be enabled with some
  instance name specified.
[root@kde-vm user]# systemctl status spice-vdagentd.s
spice-vdagentd.service  spice-vdagentd.socket   
[root@kde-vm user]# systemctl status spice-vdagentd.s
spice-vdagentd.service  spice-vdagentd.socket   
[root@kde-vm user]# systemctl status spice-vdagentd.socket 
● spice-vdagentd.socket - Activation socket for spice guest agent daemon
     Loaded: loaded (/usr/lib/systemd/system/spice-vdagentd.socket; static)
     Active: active (running) since Tue 2021-04-20 15:03:31 CEST; 1min 11s ago
   Triggers: ● spice-vdagentd.service
     Listen: /run/spice-vdagentd/spice-vdagent-sock (Stream)
      Tasks: 0 (limit: 11617)
     Memory: 0B
        CPU: 0
     CGroup: /system.slice/spice-vdagentd.socket

apr 20 15:03:31 kde-vm systemd[1]: Listening on Activation socket for spice guest agent daemon.