tests/virtualbox: Start systemwide DBus in guests.

We want to check whether DBus functionality is working, so let's make
sure it is running in our mini-initrd.

DBus unfortunately requires to have users properly set up and another
configuration file other than in ${dbus.daemon}/etc/dbus-1/system.conf,
so we do provide that as well.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/tests/virtualbox.nix

@@ -8,6 +8,19 @@ import ./make-test.nix ({ pkgs, ... }: with pkgs.lib; let
         #!${pkgs.stdenv.shell} -xe
         export PATH="${pkgs.coreutils}/bin:${pkgs.utillinux}/bin"
 
+        mkdir -p /etc/dbus-1 /var/run/dbus
+        cat > /etc/passwd <<EOF
+        root:x:0:0::/root:/bin/false
+        messagebus:x:1:1::/var/run/dbus:/bin/false
+        EOF
+        cat > /etc/group <<EOF
+        root:x:0:
+        messagebus:x:1:
+        EOF
+        cp -v "${pkgs.dbus.daemon}/etc/dbus-1/system.conf" \
+          /etc/dbus-1/system.conf
+        "${pkgs.dbus.daemon}/bin/dbus-daemon" --fork --system
+
         ${pkgs.linuxPackages.virtualboxGuestAdditions}/bin/VBoxService
         ${(attrs.vmScript or (const "")) pkgs}