As David Zeuthen suggested in http://lists.freedesktop.org/archives/consolekit/2009-September/000044.html, it's good for ConsoleKit to support retrieving available operating systems and rebooting into one of them.

He suggested the following 2 D-Bus methods should be added.

 GetAvailableOperatingSystems(out array<OperatingSystem>);

with something like

 struct OperatingSystem
 {
   string os_id;
   string os_vendor;
   string os_version;
   string os_name;
   boolean default;
 };

where os_vendor ('fedora', 'ubuntu', 'kubuntu', 'suse', 'sun',
'microsoft'), os_version ('11', '6.06', 'Vista', '7', ...) and os_name
('Fedora 11', 'Ubunty Dapper', 'Microsoft XP', ...) being defined in
the CK docs. And 'id' would be an opaque identifier (with few
guarantees - might change after a reboot / reconfiguration) that is
supposed to be used with

 RebootIntoOperatingSystem(in string os_id, boolean make_default);

or something.

Because it's hard to pass multi parameters by using check_polkit_permissions/check_rbac_permissions because AuthorizedCallback does not take any argument. So I modified
    RebootIntoOperatingSystem(in string os_id, boolean make_default)
a little. The new interface I use in my code is
    RebootWithParameters(in string parameter)
The parameter is something like "id:0 default:1" which is OS specific.