> i have not stable dhcpd server (over WiFi) and it took some time to get a lease,
> but problem is that after client ifdown/ifup - dhclient tell 'No working leases in persistent database - sleeping.'
> this is strange, cause server configured to give lease for few days.
> i found that on ifdown - dhclient updates leases file,
Check the logs - both client and server. My *guess* is that your system is releasing the lease before shutting down the interface. In that case, it would be correct to also update the leases file to show the lease as expired - otherwise the client could later try and use an address that the server doesn't have listed as currently leased out (it could even have been re-allocated to another client).