[CentOS] NTP server

-----Original Message-----
From: Scott Ehrlich
Sent: Friday, February 01, 2008 11:37 AM
To: [email protected]
Subject: [CentOS] NTP server


I have a Centos 5 64-bit server that has ntp service enabled. Windows XP
with SP2 cannot properly sync to it for time, but can communicate with it
via samba, ssh, and anything else. I also disabled the Windows
Firewall. The C5 system does not have any firewall enabled.

Other C5 workstations can successfully sync to it via ntpdate.

What else could cause the XP machine to not be able to time sync with the
C5 server?
~~~~~~

Try this; create a DNS entry called ntp.yourinternaldomain.com, then plug
that name into XP's internet time. I had a similar problem and changing the
IP address to FQDN fixed it.

Perhaps it will work for you.

Good luck,

~James

Try running these from the command line

net time /setsntp:10.0.0.87 <====your NTP ip here

net time /querysntp

net stop w32time && net start w32time

-Jason

----
I think that you have to have administrative privileges or group policy
permissions to be able to do those commands in Windows.

Craig

XP command line:

net time \\servername returns what?

Perhaps the response will give a clue.


To set it:

net time \\servername /set /yes

Net time is only used to set time from a domain controller, not an ntp server.
They use two completely different protocols.

however,

NET TIME /SETSNTP:ip-of-ntp-server

WILL set the windows 'internet time' server IP.

NET TIME /QUERYSNTP

will show the current 'internet time' server(s).

note that the default Windows NTP client is really braindead, it just
'sets' the system clock once a day, its not a proper NTP
implementation. for most users, this is fine, but realize oddities can
happen like the clock being set back a few seconds such that a given
time happens twice.

Very true.

You can modify the time interval by editing your registry.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time
\TimeProviders\NtpClient]

"SpecialPollInterval"=dword:00001c20

This will set it to update every two hours. The dword can be modified to
set it for 1 hour to whatever.

-jason

I stand partially corrected, as the originally posted command line of
"net time \\servername /set /yes" would not query a ntp server.

The following would stop this:

1) DNS with a fully qualified name.
2) CentOS-5 server does not have port 123 open on its firewall
iptables -nxvL | grep 123

should give you an answer to that
3) CentOS-5 server is not serving NTP to your network

netstat -nalp | grep :123

should have something other than
udp 0 0 127.0.0.1:123 0.0.0.0:*

This is configured in the /etc/ntp.conf file.

I'd double-check the c5 ntpd config. Are the xp machines really in the
same allowed subnet like the c5 workstations?

Personally I don't use Windows' time sync anymore, I use the ntp
implementation for windows from here:

http://www.meinberg.de/english/sw/ntp.htm

Install/config is very easy, you even get the ntpdc command.

Rainer