This article explains how to configure NTP on Windows Server 2012. If you're looking for Windows Server 2008 R2, see my article here. Remember, that in a domain environment, time synchronization is taken care of but you should configure the PDC Emulator of a domain to sync externally since that is the server which decides what time it is!
This is all you need if you want to keep it simple. Run using PowerShell as admin:
w32tm /config /manualpeerlist:pool.ntp.org /syncfromflags:MANUAL
If the machine is a VM inside Hyper-V, you have to disable time sync. Open VM settings -> Management -> Integration Services and uncheck Time Synchronization.
That should be it! Want to know more? Doesn't work? Have you screwed up the config and want to start from the beginning? Keep on reading...
W32tm is the command to use. Sure, there are articles out there mentioning "net time", but you should not use that. Some other also mentions editing the registry directly, but as Microsoft mentions in the article: It is recommended that you do not directly edit the registry unless there is no other alternative. But if you really want to check the registry, it's here: HKLM\System\CurrentControlSet\Services\W32Time.
Which NTP-server to use? Or several?
The pool.ntp.org is a round-robin of random selected NTP servers. As they say "This is usually good enough for end-users". But you might want to add several NTP-servers yourself for redundancy?
w32tm /config /manualpeerlist:"0.pool.ntp.org 1.pool.ntp.org" /syncfromflags:MANUAL
Just keep adding them with a space in between them. Yes, I know some sites say you should separate them using comma but that doesn't work. Also, I've experienced issues that it configures correctly, but still after restarting the service, it doesn't work. I just needed to do the configuration again, and try once more. Also, remember that cut'n'paste from the web can sometimes screw up the " character so write it manually instead of cut'n'paste to be sure.
Don't forget your firewall
If you got a firewall between your host and the Internet, it might drop udp/123 which is the NTP protocol. This is how it looked in my Cisco ASA FW:
So I created a rule to allow it and after that it worked.
More info and debug logging
The following commands are quite useful which lists the current source, when it last sync'ed etc.
w32tm /query /status
Eventually, when the server can't get time from the NTP server it will add an event to the event log:
Log Name: System
Event ID: 47
Description: Time Provider NtpClient: No valid response has been received from manually configured peer pool.ntp.org after 8 attempts to contact it. This peer will be discarded as a time source and NtpClient will attempt to discover a new peer with this DNS name. The error was: The peer is unreachable.
Otherwise, when it's working, you will get:
Log Name: System
Event ID: 35
Description: The time service is now synchronizing the system time with the time source pool.ntp.org (ntp.m|0x0|0.0.0.0:123->220.127.116.11:123).
You still getting problems? You can easily turn on debugging to a logfile which in this case is limited t0 10 MB and include ALL debug entries.
w32tm /debug /enable /file:C:\Temp\w32tmdebug.log /size:10485760 /entries:0-300
Turn it off again with:
w32tm /debug /disable
Expect a lot of info in this debug log. For me, when it worked, the following entries showed it was working:
- Reachability: peer pool.ntp.org (ntp.m|0x0|0.0.0.0:123->18.104.22.168:123) is reachable.
- Logging information: NtpClient is currently receiving valid time data from pool.ntp.org (ntp.m|0x0|0.0.0.0:123->22.214.171.124:123).
But when I had my firewall blocking the packets, I would get the following. Don't trust this too much though, since I did get this when I allowed it in the firewall also, but when it was blocked, I did not get the entries above.
- Logging error: NtpClient has been configured to acquire time from one or more time sources, however none of the sources are currently accessible and no attempt to contact a source will be made for 1 minutes. NTPCLIENT HAS NO SOURCE OF ACCURATE TIME.
Force a resync
If you want to force the client to resync, run:
Sending resync command to local computer
The command completed successfully.
If you get the following error, the computer can't reach the NTP-server(s).
The computer did not resync because no time data was available.
Start from scratch
If you completely screwed up the config, you can always do the following command and it will completely erase and add a default W32time configuration:
When doing the unregister I got the following error for some reason, but it seems like it worked anyway.
The following error occurred: Access is denied. (0x80070005)
Sometimes when doing the /register, I would get the following. This usually solved by waiting for a while. I would suggest you stop the service before doing /unregister. Otherwise, a reboot would probably solve most problems.
The following error occurred: The specified service has been marked for deletion. (0x80070430)
If you miss any important information, let me know and I'll add it.