Voir :

• https://serverfault.com/questions/936985/cannot-use-systemctl-user-due-to-failed-to-get-d-bus-connection-permission
• https://stackoverflow.com/questions/59860849/is-there-a-way-to-reliably-check-that-systemd-supports-user
• https://blogs.igalia.com/dpino/2016/04/10/network-namespaces/
• https://github.com/AsamK/signal-cli/issues/394
• https://wiki.openbsd.fr.eu.org/doku.php/system/x11/dbus
• https://superuser.com/questions/1561076/systemctl-use-failed-to-connect-to-bus-no-such-file-or-directory-debian-9

dbus-send --session           \
  --dest=org.freedesktop.DBus \
  --type=method_call          \
  --print-reply               \
  /org/freedesktop/DBus       \
  org.freedesktop.DBus.ListNames
 
dbus-send --system            \
  --dest=org.freedesktop.DBus \
  --type=method_call          \
  --print-reply               \
  /org/freedesktop/DBus       \
  org.freedesktop.DBus.ListNames
 
dbus-send --system             \
  --dest=org.freedesktop.DBus  \
  --type=method_call           \
  --print-reply                \
  /org/freedesktop/DBus/UPower \
  org.freedesktop.DBus.ListNames  
 
 
dbus-send --print-reply --system --dest=org.freedesktop.UPower /org/freedesktop/UPower org.freedesktop.UPower.Suspend
 
dbus-send \
  --system \
  --print-reply \
  --dest=org.freedesktop.login1 \
  /org/freedesktop/login1 \
  org.freedesktop.login1.Manager.Suspend \
  boolean:true