Who is sending my Guix System to sleep?

[Konrad Hinsen]

Hi Guix,

In an attempt to make more use of Guix in my daily life on a
MacBook, I have set up a virtual machine (using VirtualBox)
that contains a desktop installation of Guix. I have then set
up ssh with X11 forwarding, and thus run software such as Emacs
from my macOS terminal. Since I don't need the virtual machine's
display, I usually run the machine in headless mode.

The only problem is that after 20 minutes, the virtual machine
seems to freeze. I found the cause in /var/log/messages:

    Sep 26 08:54:40 localhost NetworkManager[282]: <info>  [1569480880.2246] 
manager: sleep: sleep requested (sleeping: no  enabled: yes)
    Sep 26 08:54:40 localhost NetworkManager[282]: <info>  [1569480880.2247] 
manager: NetworkManager state is now ASLEEP
    Sep 26 08:54:40 localhost NetworkManager[282]: <info>  [1569480880.2248] 
device (enp0s3): state change: activated -> deactivating (reason 'sleeping', 
sys-iface-state: 'managed')
    Sep 26 08:54:40 localhost NetworkManager[282]: <info>
    [1569480880.2293] device (enp0s3): state change: deactivating ->
    disconnected (reason 'sleeping', sys-iface-state: 'managed')

Something requests NetworkManager to go to sleep, which is obviously not
good for my ssh connection. But what?

First I went to the XFCE settings and switched off all automatic suspend
and hibernate actions. No success. Then I replaced %desktop-services in
my config.scm by %base-services plus the explicit list of what
%desktop-services adds to it. And then I removed suspect and/or unneeded
services one by one. Now I have nothing left that I can remove without
losing some functionality or getting en error message at "guix system
reconfigure". But my system still goes to sleep after 20 minutes.

These are the services I still have, in addition to %base-services:

      (list (service xfce-desktop-service-type)
            (service openssh-service-type
                     (openssh-configuration
                      (x11-forwarding? #t)))
            (set-xorg-configuration
              (xorg-configuration
               (keyboard-layout keyboard-layout)))

            (service gdm-service-type)
            (service network-manager-service-type)
            (service wpa-supplicant-service-type)
            (service avahi-service-type)
            (accountsservice-service)
            (elogind-service)
            (dbus-service)

            (service ntp-service-type)

            x11-socket-directory-service)

Does anyone have an idea what could cause the automatic sleep?

BTW, I also tried using a basic non-desktop system, but then I cannot
run X11 applications for whatever reason.

Thanks in advance,
  Konrad