Options¶

Everything below is under gewis.servicePc, defined in nix/modules/service-pc/.

Session¶

Option	Default	Meaning
`enable`	`false`	Turn the whole thing on
`user`	`"gewis"`	Unprivileged user the session and its applications run as. The module creates it
`uid`	`null`	Fixed uid, also used as the primary group's gid. Pin it where state outlives reinstalls
`workspaces`	`1`	Number of static workspaces
`multiMonitor`	`false`	This host has more than one screen; enables per-monitor placement
`justPerfection`	`false`	Load the Just Perfection extension
`shutdownAt`	`"23:00"`	Daily power-off time, as a systemd calendar expression; `null` keeps the host running

Touch¶

Option	Default	Meaning
`touch.enable`	`false`	This host is a touchscreen with no keyboard or mouse; enables the on-screen keyboard
`touch.vendorId`	`"0eef"`	USB vendor ID of the panel, from `lsusb`
`touch.productId`	`"0001"`	USB product ID of the panel, from `lsusb`

See Touchscreens and workspaces.

Browsers¶

browsers is an attribute set; the name is the attribute key. The browser is always Firefox. The policy file below is Firefox's and the launcher sets MOZ_ENABLE_WAYLAND. Firefox force-installs uBlock Origin in every instance through the ExtensionSettings policy, so ad blocking is on even though the browsers are started straight onto a URL and never opened interactively.

Option	Default	Meaning
`browsers.<name>.url`	`null`	URL to open. Exactly one of this or `urlFile`
`browsers.<name>.urlFile`	`null`	File read at launch, for when the URL is itself a secret
`browsers.<name>.kiosk`	`false`	Fullscreen once the window appears, by sending F11 until it takes
`browsers.<name>.waitForUrl`	`true`	Poll the URL before starting, so a fast-booting PC does not land on an error page
`browsers.<name>.waitTimeout`	`120`	Seconds to poll before starting anyway; `0` waits forever

Each browser is a separate Firefox instance with its own profile at ~/.mozilla/firefox/service-pc-<name>, created on first start, and runs with --new-instance so it never hands its URL to another one and exits. Its window reports firefox-<name> as its class, which is how the placement helper tells the instances apart. A host that wants two pages on two screens names two browsers and gives each a monitor:

multiMonitor = true;
browsers = {
  pos = {
    url = "https://sudosos.gewis.nl/pos";
    monitor = 1;
    kiosk = true;
  };
  dashboard = {
    url = "https://grafana.gewis.nl/d/bar";
    monitor = 2;
  };
};

A browser is restarted whenever it exits, whatever the reason, so closing it over RDP just brings it back.

kiosk waits for the browser's window, raises it, and sends F11 through ydotool, repeating the press until GNOME reports the window as fullscreen. Firefox keeps only a fullscreen state it entered itself, and F11 is a toggle, so each press is checked. Once fullscreen, it keeps sending a bare Shift every couple of seconds for about a minute: Firefox leaves its toolbar showing when F11 arrives while the address bar still has focus, which it does until the page first paints, and only hides it on the next key press. A host with no keyboard or mouse would otherwise show the toolbar until someone connects over RDP. The window is long because $HOME does not survive a reboot, so every boot is Firefox's first run on a new profile and the first paint is slow.

When it does not go fullscreen¶

kiosk runs as an ExecStartPost of the service-pc-browser-<name> user unit, so everything it says is in that unit's journal. It is a user unit, so ask for it by that name rather than with --user, which would look at root's own manager:

$ sudo journalctl -b _SYSTEMD_USER_UNIT=service-pc-browser-<name>.service -o cat

The helper always logs why it gave up, and the four messages mean different things:

org.gnome.Shell.Extensions.Windows never answered — the window-calls extension is not running, so nothing here can work. It is pulled in automatically by kiosk and by workspace/monitor, but GNOME disables an extension that does not declare support for the running shell version. Check with gnome-extensions list --enabled in the session, and look for JS ERROR in the shell's own log: sudo journalctl -b _COMM=gnome-shell.
no window with wm_class 'firefox-<name>' … saw: … — the extension answered, but nothing it listed matched. The saw: list is the set of classes Mutter actually reports; if Firefox is in there under another name, that name is what the helper should be matching on.
ydotool failed: … — the keystroke never left the tool, and the message is ydotool's own. Almost always ydotoold not running or its socket not readable; see the NFC page, which uses the same daemon.
… is still not fullscreen after N F11 presses — the keystrokes went out and the window still is not fullscreen. The line after it dumps what GNOME reports for that window, so compare its width/height against the monitor.

Applications¶

apps is an attribute set; the name is the attribute key. The session exports NIXOS_OZONE_WL=1, so Chromium and Electron apps run natively on Wayland instead of Xwayland, whether started by the module or from the app grid.

Option	Default	Meaning
`apps.<name>.package`	required	Package providing the application
`apps.<name>.exec`	`null`	Command to run; defaults to the package's `meta.mainProgram`
`apps.<name>.wmClass`	`<name>`	Window class the placement helper matches on

Placement¶

Each browser and each app takes these:

Option	Default	Meaning
`workspace`	`null`	One-based workspace to move the window to
`monitor`	`null`	One-based logical monitor to move it to, and maximise it there

A window is placed on one or the other, never both, and monitor requires multiMonitor. Leaving both null lets GNOME put the window wherever it likes. A window that is placed is also maximised, so it fills the screen it landed on.

NFC reader¶

Option	Default	Meaning
`nfcReader.enable`	`false`	Run the background NFC reader
`nfcReader.vendorId`	`"072f"`	USB vendor ID, from `lsusb`
`nfcReader.productId`	`"2200"`	USB product ID, from `lsusb`

See NFC reader.

Remote access¶

Option	Default	Meaning
`remote.enable`	`false`	Remote control of the live session over RDP
`remote.port`	`3389`	Port the RDP server listens on
`remote.username`	`null`	Username clients authenticate with; defaults to `user`
`remote.passwordFile`	required when enabled	File holding the password, readable by `user`
`remote.openFirewall`	`false`	Open the port on every interface
`remote.firewallInterfaces`	`[ ]`	Interfaces to open the port on

See Remote access.