My ntpd on my Slackware machine doesn't syncronize with a time server.

I set up the /etc/ntp.conf file like so:
And the ntpd starts fine. But when i do "ntpq -p" the string in the "refid" column is always ".RSTR." and the jitter is always 4000.00. I read in the manual that ".RSTR." means "Access denied due to local policy. No further messages will be sent to the server. " but I don't understand one bit what it means. I don't understand what local policy means. I didn't set any firewall...

I have to mention that using ntpdate -u ntp.cesnet.cz works just fine.

ntp.cesnet.cz is a Stratum 1 server. "Access denied due to local policy" means they are blocking you from connecting. If you read on that site it says "Access Policy: open to servers providing synchronization to ten or more hosts, others by arrangement".

Basically, you shouldn't be connecting to a stratum 1 server. Stratum 1 servers are directly connected to a clock.

Stratum 2 servers connect to stratum 1 (usually aranged beforehand).

End users should use an open access server. Put one of these URLs into ntp.conf.

I solved it by removing the line "restrict default noquery notrust nomodify" from ntp.conf. I don't understand why it doesn't work on my machine because on other RedHats which I have in my network it works fine with that line in the configuration file.

Well even if it works you shouldn't be using a stratum 1 server. That server is there to provide other servers with the time, which provide other servers, which you can connect to. If you keep using it your IP will be blocked. There's probably only a difference of a <50 milliseconds anyway.

Change your server to europe.pool.ntp.org

Removing only the "notrust" flag should let you syncronize your clock and keep you (somewhat) secure.

Please have a look at:

http://www.edafe.org/slackware/index.html#ntp

Regards,
Edafe