'Renews DHCP lease via udhcpc client.'

def _renew_lease_udhcpc(self, fixed_ip=None):

    file_path = '/var/run/udhcpc.'
    nic_name = self.get_nic_name_by_ip(fixed_ip)
    pid = self.exec_command('cat    {path}{nic}.pid'.format(path=file_path, nic=nic_name))
    pid = pid.strip()
    cmd = 'sudo    /bin/kill    -{sig}    {pid}'.format(pid=pid, sig='USR1')
    self.exec_command(cmd)
