SUMMARY: How to synchronize clocks on multiple systems?

From: J M Thompson (
Date: Fri Aug 20 1993 - 07:33:35 CDT

Many thanks to the people you took the time to respond to my question.
I found the responses were very helpful. Listed below is my original
question and following it is a summary of the responses.

> I need to synchronize the clocks in four Sun690 servers
> (SunOS 4.1.3). Two of the 690s will be on one subnet,
> for example, and the other two will be on another subnet
> that is at the other end of a T1 link (but in the
> same metropolitan area, so the systems are in the same timezone).
> I envision that one of the 690s will function as the time server
> and the other systems would be clients that synchronize their
> clocks with the server.
> Since I am new to Sun system administration, I would appreciate any
> help in this. Some of the questions I have are
> 1) What type of software that is available in SunOS 4.1.3
> that I can use? What would run on the server? What would
> run on the clients?
> 2) If a configuration file(s) is(are) necessary for the server
> and clients, could I get a sample of the file(s)?
> 3) What kind of operational issues could arise?

I received 36 responses that divided into the following three categories:

A) 'rdate' command - 18 votes
B) Network Time Protocol daemon xntpd - 22 votes
C) synclockd/synservd programs from comp.sources - 1 vote

(Votes do not total because some persons made multiple recommendations)

A) 'rdate' command
        This looks like the easiest to implement, so we will be using
        this method at first. We will execute it out of /etc/rc.local
        and have it cron'ed several times a day. Based on the testing
        I did, it appears we should be able to keep the systems
        in sync within plus or minus one second of each other. One
        cautionary note was made in that it could cause the time on the
        client system to make discontinous jumps, especially bad is to
        go back in time (shades of H. G. Wells :-)

B) Network Time Protocol
        I think we will eventually migrate to this since it seems the
        more robust/accurate solution, plus it is also a standards based
        method. Resolution, based on the comments I received, is in
        milliseconds. Software to implement NTP can be found at several
        ftp sites, i.e., (/pub/ntp).

C) synclockd/synservd programs
         I did not purse this method any further.

Once again, to all those who responded thank you very much.

Jim Thompson                     
daytime phone: 703-759-8252    

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