Linux – How to force locally isolated ntpd update time

Objective

I had locally isolated hosts. I'd like them all have the same time. One takes role of the time server, other syncs with it as clients.

All machines has sporadic uptime. They are powered rarely. So they could gain significant offset. Entire hosts set should become synced within minutes after setting the server local time manually.

To confirm reliability I had tested the ntp hosts connection by setting great manual adjusts (several hours) and measured how fast clients synced.

ntpd – ntpd case

I tried use ntpd for clients as well the server. ntpd take very long time to adjust clock. Moreover it refuses to rewind time by couple of hours.

If it could be fixed, I prefer to use ntpd as client. So I'm looking for configuration options to hint ntpd for being eager at accepting network clock updates.

But if there is no way to employ ntpd, ntpdate alternative is still acceptable.

ntpd – ntpdate case

ntpdate perfectly updates clock without hesitation. I put it in a cron task and got rough but working solution. Unfortunately the first impression was wrong. After several tests I noticed that the ntpdate client started refusing the server. For some reasons server decided to return stratum 16. I explicitly put fudge 127.127.1.0 stratum 8 into the ntp.conf on the sever side to avoid this exact behaviour. But ntpdate -v -d output shows "stratum 16" transmitted from the server.

So I see two ways. Either compel the ntpd server return stratum 9 regardless of local time jumping or force the ntpdate client to accept any server, even if it has stratum 16.

I tried to google either way but found nothing. Could anyone suggest suitable configuration options?