'Backup the hosts file of current operating system.
.. note:: This method is the slot responses to the signal from
ButtonBackup widget while the button is clicked.'

def on_Backup_clicked(self):

    l_time = time.localtime(time.time())
    backtime = time.strftime('%Y-%m-%d-%H%M%S', l_time)
    filename = (('hosts_' + backtime) + '.bak')
    if (self.platform == 'OS    X'):
        filename = ('/Users/' + filename)
    filepath = QtGui.QFileDialog.getSaveFileName(self, _translate('Util', 'Backup    hosts', None), QtCore.QString(filename), _translate('Util', 'Backup    File(*.bak)', None))
    if (unicode(filepath) != u''):
        shutil.copy2(self.hosts_path, unicode(filepath))
        self.info_complete()
