Let ntp server not synchronize time from other servers - NTP

This is a discussion on Let ntp server not synchronize time from other servers - NTP ; Hello, experts! Is there any way to configure my NTP server *not* to synchronize time from other servers? I have read the man pages about ntpd and googled a lot, but I didn't find any good solution. Any comments are ...

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  1. Let ntp server not synchronize time from other servers

    Hello, experts!

    Is there any way to configure my NTP server *not* to synchronize time
    from other servers?
    I have read the man pages about ntpd and googled a lot, but I didn't
    find any good solution.

    Any comments are welcome! Thanks!

  2. Re: Let ntp server not synchronize time from other servers

    Hello WANG Cong,

    WANG Cong wrote:
    > Hello, experts!
    >
    > Is there any way to configure my NTP server *not* to synchronize time
    > from other servers?


    Just don't put any server lines into your ntp.conf file ;-)

    If you want some upstream servers to be polled but don't want to synchronize
    to them you can simply append the noselect keyword to the entries, e.g.

    server pool.ntp.org noselect

    Martin
    --
    Martin Burnicki

    Meinberg Funkuhren
    Bad Pyrmont
    Germany

  3. Re: Let ntp server not synchronize time from other servers

    On Aug 28, 11:12 a.m, Martin Burnicki
    wrote:
    > Hello WANG Cong,
    >
    > WANG Cong wrote:
    > > Hello, experts!

    >
    > > Is there any way to configure my NTP server *not* to synchronize time
    > > from other servers?

    >
    > Just don't put any server lines into your ntp.conf file ;-)



    That's what I did. But it can't work, if there's no server lines, I
    _always_ got:

    # /usr/sbin/ntpdate -u -b 192.168.90.41
    28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    found

    (192.168.90.41 is my own NTP server.)

    And if I didn't remove the server lines, I can easily run the above
    command
    successfully. :-)

    Any ideas?

    >
    > If you want some upstream servers to be polled but don't want to synchronize
    > to them you can simply append the noselect keyword to the entries, e.g.
    >
    > server pool.ntp.org noselect
    >


    Thanks, I just need not to synchronize.

  4. Re: Let ntp server not synchronize time from other servers

    "WANG Cong" wrote in message
    news:8d3c2902-93a5-44fc-9e66-0356538955c0@t54g2000hsg.googlegroups.com...

    > [...] if there's no server lines, I _always_ got:
    >
    > # /usr/sbin/ntpdate -u -b 192.168.90.41
    > 28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    > found
    >
    > (192.168.90.41 is my own NTP server.)


    It seems that without servers, you have no synchronisation sources left.
    (Which is probably correct.) So you fake one.

    server 127.127.1.0
    fudge 127.127.1.0 stratum 14

    These two lines will cause your server to believe its own, free-running,
    clock and consider itself synchronised and serve time, while indicating
    that the time served is of quite atrocious quality.

    Is there any particular reason why you won't take the time from anyone?

    Groetjes,
    Maarten Wiltink



  5. Re: Let ntp server not synchronize time from other servers

    WANG Cong wrote:
    > Hello, experts!
    >
    > Is there any way to configure my NTP server *not* to synchronize time
    > from other servers?
    > I have read the man pages about ntpd and googled a lot, but I didn't
    > find any good solution.
    >
    > Any comments are welcome! Thanks!


    What problem are you trying to solve?

    You can equip your system with a "hardware reference clock"; e.g. a GPS
    Timing Receiver, or an atomic clock and you will not need any external
    server(s).

    If you don't really care what time it is and simply want all your
    systems to have the SAME time, I'd suggest something like rdate.

  6. Re: Let ntp server not synchronize time from other servers

    On Aug 28, 12:49 pm, "Maarten Wiltink"
    wrote:
    > "WANG Cong" wrote in message
    >
    > news:8d3c2902-93a5-44fc-9e66-0356538955c0@t54g2000hsg.googlegroups.com...
    >
    > > [...] if there's no server lines, I _always_ got:

    >
    > > # /usr/sbin/ntpdate -u -b 192.168.90.41
    > > 28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    > > found

    >
    > > (192.168.90.41 is my own NTP server.)

    >
    > It seems that without servers, you have no synchronisation sources left.
    > (Which is probably correct.) So you fake one.
    >
    > server 127.127.1.0
    > fudge 127.127.1.0 stratum 14



    Cool! It works! 8-)
    But there's a little problem, when I changed my ntp.conf, I have to
    wait
    for several minutes until it works well, if not, I got:

    192.168.90.41: Server dropped: strata too high

    I googled a bit, and someone said this is due to the time of the
    server is far from correct, but it is not. See below:

    # /usr/sbin/ntpdate -u pool.ntp.org
    28 Aug 14:23:38 ntpdate[18923]: adjust time server 194.117.9.136
    offset -0.174164 sec
    # LC_ALL=en_US-UTF8 date
    Thu Aug 28 14:23:42 WEST 2008

    At the same time, I ran this on the server:
    > date

    Thu Aug 28 14:23:47 BST 2008

    Now:
    # /usr/sbin/ntpdate -u 192.168.90.41
    28 Aug 14:24:02 ntpdate[18942]: no server suitable for synchronization
    found

    So the time on the server was nearly correct. Right?

    Any idea to solve this?

    >
    > These two lines will cause your server to believe its own, free-running,
    > clock and consider itself synchronised and serve time, while indicating
    > that the time served is of quite atrocious quality.
    >
    > Is there any particular reason why you won't take the time from anyone?


    Yes, because we want:

    1. Configure the time of the server manually, no matter how wrong it
    is.
    So in this situation, we don't want synchronization, but still need to
    provide
    the time service to other PCs.

    2. Synchronize the time from other servers and provide service. This
    is
    very easy and works well.

    Thanks.

  7. Re: Let ntp server not synchronize time from other servers

    On Aug 28, 12:49 pm, "Richard B. Gilbert"
    wrote:
    > WANG Cong wrote:
    > > Hello, experts!

    >
    > > Is there any way to configure my NTP server *not* to synchronize time
    > > from other servers?
    > > I have read the man pages about ntpd and googled a lot, but I didn't
    > > find any good solution.

    >
    > > Any comments are welcome! Thanks!

    >
    > What problem are you trying to solve?



    Can you have a look at my another reply in this thread?
    I just explained. :-)

    >
    > You can equip your system with a "hardware reference clock"; e.g. a GPS
    > Timing Receiver, or an atomic clock and you will not need any external
    > server(s).



    Unfortunately, we don't have this.

    >
    > If you don't really care what time it is and simply want all your
    > systems to have the SAME time, I'd suggest something like rdate.


    Yes, but I still need a server to provide time service, right?
    That's the problem. :-)


  8. Re: Let ntp server not synchronize time from other servers

    "WANG Cong" wrote in message
    news:cd532c88-96c6-42c2-91fe-cce8a72b4487@b1g2000hsg.googlegroups.com...
    > On Aug 28, 12:49 pm, "Maarten Wiltink"
    > wrote:


    >> server 127.127.1.0
    >> fudge 127.127.1.0 stratum 14

    >
    > Cool! It works! 8-)
    > But there's a little problem, when I changed my ntp.conf, I have to
    > wait for several minutes until it works well, if not, I got:
    >
    > 192.168.90.41: Server dropped: strata too high


    NTP really solves a different problem than yours. It's slower than
    it might be as a result. Nothing you can fix. Live with it.


    > I googled a bit, and someone said this is due to the time of the
    > server is far from correct, but it is not. See below:
    >
    > # /usr/sbin/ntpdate -u pool.ntp.org
    > 28 Aug 14:23:38 ntpdate[18923]: adjust time server 194.117.9.136
    > offset -0.174164 sec
    > # LC_ALL=en_US-UTF8 date
    > Thu Aug 28 14:23:42 WEST 2008
    >
    > At the same time, I ran this on the server:
    > > date

    > Thu Aug 28 14:23:47 BST 2008


    That's not the same time. There's a five second difference! Please
    realise that you are dealing with a product, and a crowd, to whom
    128ms time difference is enough to go to emergency measures, and
    500PPM speed difference is enough to stop trying permanently.


    [...]
    >> Is there any particular reason why you won't take the time from anyone?

    >
    > Yes, because we want:
    >
    > 1. Configure the time of the server manually, no matter how wrong it
    > is.


    I've been in that boat. It can be a right pain to test expiration dates
    with a clock that won't stay in 2099 or more than a few seconds.

    Groetjes,
    Maarten Wiltink



  9. Re: Let ntp server not synchronize time from other servers

    On 2008-08-28, WANG Cong wrote:

    > On Aug 28, 12:49 pm, "Richard B. Gilbert"
    >
    >> If you don't really care what time it is and simply want all your
    >> systems to have the SAME time, I'd suggest something like rdate.

    >
    > Yes, but I still need a server to provide time service, right? That's
    > the problem. :-)


    rdate retrieves the time from inetd.

    --
    Steve Kostecke
    NTP Public Services Project - http://support.ntp.org/

  10. Re: Let ntp server not synchronize time from other servers

    On 2008-08-28, WANG Cong wrote:

    > On Aug 28, 12:49 pm, "Maarten Wiltink" wrote:
    >
    >> server 127.127.1.0
    >> fudge 127.127.1.0 stratum 14

    >
    > Cool! It works! 8-) But there's a little problem, when I changed my
    > ntp.conf, I have to wait for several minutes until it works well, if
    > not, I got:
    >
    > 192.168.90.41: Server dropped: strata too high
    >
    > I googled a bit, and someone said this is due to the time of the
    > server is far from correct, but it is not. See below:


    No. That's not the problem.

    Your server needs to be "synced" before ntpdate will consider it
    acceptable. The issue here is that with the configuration suggested
    above the current stable release of ntpd will take almost 3.5 minutes
    before it decides that it is "synced". This is because the default poll
    interval is 64 seconds and ntpd requires 3 poll periods before it
    accepts the Undiciplined Local Clock.

    You may speed this process up by reducing the minpoll to 4. This sets
    the minumum poll to 16 seconds and reduces the "sync" time to ~ 50
    seconds.

    If that is not fast enough try the current ntp-dev snap shot which,
    IIRC, accepts the Undiciplined Local Clock after the first poll.

    You may also want to try Orphan mode instead of the Undisciplined Local
    Clock on your "server". Enable orphan mode like this:

    tos orphan N

    Where 'N' is the stratum that you want your server to operate at. It is
    considered good practice to use a large number (e.g. 10, or so) to
    prevent problems when your time-island is connected to other networks.

    >> Is there any particular reason why you won't take the time from
    >> anyone?

    >
    > Yes, because we want:
    >
    > 1. Configure the time of the server manually, no matter how wrong it
    > is. So in this situation, we don't want synchronization, but still
    > need to provide the time service to other PCs.


    Why do you need to do this?

    Please keep in mind that NTP is designed to synchronize computers to
    a common time-base. UTC (via WAN, LAN, or directly attached reference
    clock) is ubiquitous time-base because, but other time-bases may be
    used. NTP is not a magic black box which can produce stable clocks with
    out some sort of stable (usually external) reference.

    > 2. Synchronize the time from other servers and provide service. This
    > is very easy and works well.


    That is what NTP is designed for.

    --
    Steve Kostecke
    NTP Public Services Project - http://support.ntp.org/

  11. Re: Let ntp server not synchronize time from other servers

    On Aug 28, 3:10 pm, "Maarten Wiltink"
    wrote:
    > "WANG Cong" wrote in message
    >
    > news:cd532c88-96c6-42c2-91fe-cce8a72b4487@b1g2000hsg.googlegroups.com...
    >
    > > On Aug 28, 12:49 pm, "Maarten Wiltink"
    > > wrote:
    > >> server 127.127.1.0
    > >> fudge 127.127.1.0 stratum 14

    >
    > > Cool! It works! 8-)
    > > But there's a little problem, when I changed my ntp.conf, I have to
    > > wait for several minutes until it works well, if not, I got:

    >
    > > 192.168.90.41: Server dropped: strata too high

    >
    > NTP really solves a different problem than yours. It's slower than
    > it might be as a result. Nothing you can fix. Live with it.
    >


    Thanks, Maarten and others!

  12. Re: Let ntp server not synchronize time fromother servers


    [demime 1.01d removed an attachment of type multipart/signed]

  13. Re: Let ntp server not synchronize time from other servers

    WANG Cong writes:

    >Hello, experts!


    >Is there any way to configure my NTP server *not* to synchronize time
    >from other servers?
    >I have read the man pages about ntpd and googled a lot, but I didn't
    >find any good solution.


    Sure. switch it off. What is the problem you are trying to solve?


  14. Re: Let ntp server not synchronize time from other servers

    WANG Cong writes:

    >On Aug 28, 11:12 a.m, Martin Burnicki
    >wrote:
    >> Hello WANG Cong,
    >>
    >> WANG Cong wrote:
    >> > Hello, experts!

    >>
    >> > Is there any way to configure my NTP server *not* to synchronize time
    >> > from other servers?

    >>
    >> Just don't put any server lines into your ntp.conf file ;-)



    >That's what I did. But it can't work, if there's no server lines, I
    >_always_ got:


    ># /usr/sbin/ntpdate -u -b 192.168.90.41
    >28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    >found


    Sure. That was what you asked for. It is unusual, but it is what you
    wanted. What is the problem?



    >(192.168.90.41 is my own NTP server.)


    >And if I didn't remove the server lines, I can easily run the above
    >command
    >successfully. :-)


    >Any ideas?


    >>
    >> If you want some upstream servers to be polled but don't want to synchronize
    >> to them you can simply append the noselect keyword to the entries, e.g.
    >>
    >> server pool.ntp.org noselect
    >>


    >Thanks, I just need not to synchronize.


  15. Re: Let ntp server not synchronize time from other servers

    On Aug 28, 4:25 pm, Steve Kostecke wrote:
    > On 2008-08-28, WANG Cong wrote:
    >
    > > On Aug 28, 12:49 pm, "Maarten Wiltink" wrote:

    >
    > >> server 127.127.1.0
    > >> fudge 127.127.1.0 stratum 14

    >
    > > Cool! It works! 8-) But there's a little problem, when I changed my
    > > ntp.conf, I have to wait for several minutes until it works well, if
    > > not, I got:

    >
    > > 192.168.90.41: Server dropped: strata too high

    >
    > > I googled a bit, and someone said this is due to the time of the
    > > server is far from correct, but it is not. See below:

    >
    > No. That's not the problem.
    >
    > Your server needs to be "synced" before ntpdate will consider it
    > acceptable. The issue here is that with the configuration suggested
    > above the current stable release of ntpd will take almost 3.5 minutes
    > before it decides that it is "synced". This is because the default poll
    > interval is 64 seconds and ntpd requires 3 poll periods before it
    > accepts the Undiciplined Local Clock.
    >
    > You may speed this process up by reducing the minpoll to 4. This sets
    > the minumum poll to 16 seconds and reduces the "sync" time to ~ 50
    > seconds.
    >
    > If that is not fast enough try the current ntp-dev snap shot which,
    > IIRC, accepts the Undiciplined Local Clock after the first poll.
    >
    > You may also want to try Orphan mode instead of the Undisciplined Local
    > Clock on your "server". Enable orphan mode like this:
    >
    > * * * * tos orphan N
    >
    > Where 'N' is the stratum that you want your server to operate at. It is
    > considered good practice to use a large number (e.g. 10, or so) to
    > prevent problems when your time-island is connected to other networks.



    Excellent! Thank you.

    >
    > >> Is there any particular reason why you won't take the time from
    > >> anyone?

    >
    > > Yes, because we want:

    >
    > > 1. Configure the time of the server manually, no matter how wrong it
    > > is. So in this situation, we don't want synchronization, but still
    > > need to provide the time service to other PCs.

    >
    > Why do you need to do this?
    >
    > Please keep in mind that NTP is designed to synchronize computers to
    > a common time-base. UTC (via WAN, LAN, or directly attached reference
    > clock) is ubiquitous time-base because, but other time-bases may be
    > used. NTP is not a magic black box which can produce stable clocks with
    > out some sort of stable (usually external) reference.
    >


    NTP is always provide correct time, we give the power of being wrong
    to
    the users, although we know this is bad. :^) Forgive me.

    Thanks for your care.


  16. Re: Let ntp server not synchronize time from other servers

    On Aug 28, 7:07 pm, Unruh wrote:
    > WANG Cong writes:
    > >On Aug 28, 11:12 a.m, Martin Burnicki
    > >wrote:
    > >> Hello WANG Cong,

    >
    > >> WANG Cong wrote:
    > >> > Hello, experts!

    >
    > >> > Is there any way to configure my NTP server *not* to synchronize time
    > >> > from other servers?

    >
    > >> Just don't put any server lines into your ntp.conf file ;-)

    > >That's what I did. But it can't work, if there's no server lines, I
    > >_always_ got:
    > ># /usr/sbin/ntpdate -u -b 192.168.90.41
    > >28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    > >found

    >
    > Sure. That was what you asked for. It is unusual, but it is what you
    > wanted. What is the problem?
    >


    If so, that means the clients can't update their time. I don't want
    sync,
    but I stilll need to provide the time service to clients. :-)


  17. Re: Let ntp server not synchronize time from other servers

    WANG Cong wrote:
    > On Aug 28, 7:07 pm, Unruh wrote:
    >> WANG Cong writes:
    >>> On Aug 28, 11:12 a.m, Martin Burnicki
    >>> wrote:
    >>>> Hello WANG Cong,
    >>>> WANG Cong wrote:
    >>>>> Hello, experts!
    >>>>> Is there any way to configure my NTP server *not* to synchronize time
    >>>>> from other servers?
    >>>> Just don't put any server lines into your ntp.conf file ;-)
    >>> That's what I did. But it can't work, if there's no server lines, I
    >>> _always_ got:
    >>> # /usr/sbin/ntpdate -u -b 192.168.90.41
    >>> 28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    >>> found

    >> Sure. That was what you asked for. It is unusual, but it is what you
    >> wanted. What is the problem?
    >>

    >
    > If so, that means the clients can't update their time. I don't want
    > sync,
    > but I stilll need to provide the time service to clients. :-)
    >


    Perhaps you are using the wrong tool for the job. NTP is all about
    getting and keeping the CORRECT time.

    Your requirements seem sufficiently odd that you may need to write your
    own software!

  18. Re: Let ntp server not synchronize time from other servers

    Richard B. Gilbert wrote:
    > WANG Cong wrote:
    >> On Aug 28, 7:07 pm, Unruh wrote:
    >>> WANG Cong writes:
    >>>> On Aug 28, 11:12 a.m, Martin Burnicki
    >>>> wrote:
    >>>>> Hello WANG Cong,
    >>>>> WANG Cong wrote:
    >>>>>> Hello, experts!
    >>>>>> Is there any way to configure my NTP server *not* to synchronize time
    >>>>>> from other servers?
    >>>>> Just don't put any server lines into your ntp.conf file ;-)
    >>>> That's what I did. But it can't work, if there's no server lines, I
    >>>> _always_ got:
    >>>> # /usr/sbin/ntpdate -u -b 192.168.90.41
    >>>> 28 Aug 11:21:35 ntpdate[10515]: no server suitable for synchronization
    >>>> found
    >>> Sure. That was what you asked for. It is unusual, but it is what you
    >>> wanted. What is the problem?
    >>>

    >>
    >> If so, that means the clients can't update their time. I don't want
    >> sync,
    >> but I stilll need to provide the time service to clients. :-)
    >>

    >
    > Perhaps you are using the wrong tool for the job. NTP is all about
    > getting and keeping the CORRECT time.
    >
    > Your requirements seem sufficiently odd that you may need to write your
    > own software!


    Why should it he write his own software? NTP can do this very well.

    If this is run in a closed network where it it sufficient that all nodes
    just have the *same* time then this is absolutely OK.

    For example, we have some customers who need to run their machines on TAI
    rather than UTC. If they synchronize their top level NTP server to TAI then
    using NTP to synchronize all the clients to TAI works like a charme.

    Of course those folks must take care not to intermix NTP servers with UTC or
    TAI or whatever, and they must not make those servers publicly accessible.

    Martin
    --
    Martin Burnicki

    Meinberg Funkuhren
    Bad Pyrmont
    Germany

  19. Re: Let ntp server not synchronize time from other servers

    >>> In article <8d3c2902-93a5-44fc-9e66-0356538955c0@t54g2000hsg.googlegroups.com>, WANG Cong writes:

    > On Aug 28, 11:12 a.m, Martin Burnicki
    >> Just don't put any server lines into your ntp.conf file ;-)


    WANG> That's what I did. But it can't work, if there's no server lines, I
    WANG> _always_ got:

    WANG> # /usr/sbin/ntpdate -u -b 192.168.90.41 28 Aug 11:21:35
    WANG> ntpdate[10515]: no server suitable for synchronization found

    ntpdate does not use the ntp.conf file.

    I suspect that either .41 is not sync'd or you have firewall problems or a
    'restrict' line in .41's ntp.conf file.

    --
    Harlan Stenn
    http://ntpforum.isc.org - be a member!

  20. Re: Let ntp server not synchronize time from other servers

    WANG Cong writes:

    > Hello, experts!
    >
    > Is there any way to configure my NTP server *not* to synchronize time
    > from other servers?


    Maybe see how NTP works: you NEED a reference clock! So maybe explain in
    detail what you really want.

    > I have read the man pages about ntpd and googled a lot, but I didn't
    > find any good solution.
    >
    > Any comments are welcome! Thanks!


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