So I wanted fullscreen for one of my AppVMs and following
http://wiki.qubes-os.org/trac/wiki/FullScreenMode to the letter, I created the following entry in /etc/qubes/guid.conf:
VM: {
media: {
allow_fullscreen = true;
};
};
Problem is, once I did that, I could not start the AppVM. The GUI was showing me an unhelpful "ERROR: Cannot start qubes_guid!".
A more useful message was offered by running qvm-start media from Dom0:
[...]
--> Starting Qubes GUId...
Critical: error reading config (/etc/qubes/guid.conf:21): duplicate setting name
ERROR: Cannot start qubes_guid!
A-ha! So /etc/qubes/guid.conf cannot have two VM:{} stanzas. This was not obvious to me by the wording "you can do that by creating the following entry in the /etc/qubes/guid.conf file in Dom0" in the documentation. Please consider updating the page to explicitly say that you must only have one VM:{} stanza.