≡ Menu

How to: FreeBSD Setup Time / Clock Synchronization with NTP server and ntpdate command

FreeBSD use the Network Time Protocol (NTP) for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. NTP uses UDP port 123. If you have one computer or single server then you can easily synchronization time with other NTP servers. All you need is ntp client called ntpdate. It is use to set the date and time via NTP servers.

FreeBSD: Install NTP Client

Use any one of the following command to install NTP:

# pkg_add -rv  ntp


# cd /usr/ports/net/ntp
# make; make install

Pick appropriate NTP Servers

Visit public ntp timeserver list to pick up your NTP server.

Open UDP port 123 at firewall

If you are running FreeBSD ipfilter firewall, you need to open the UDP port 123. Just add following rule to your firewall script:

pass out quick on lnc0 proto udp from YOUR-SERVER to any port = 123
keep state


pass out quick on lnc0 proto udp from YOUR-SERVER to
TIME-SERVER-IP port = 123 keep state

For example, my FreeBSD workstation IP is and is IP of NTP server then my rule is in ipf.conf file as follows:

pass out quick on lnc0 proto udp from
to port = 123 keep state

FreeBSD test clock synchronization

Just run ntpdate command as follows to see you can set date and clock via NTP:
Set wrong date (Mon Dec 13 4:27 pm):

# date 0412131627

Now set correct date with ntp client:

# ntpdate -v -b in.pool.ntp.org

13 Dec 16:27:50 ntpdate[997]: ntpdate 4.2.0-a Thu Nov 3 07:34:22 UTC 2005 (1)
25 Jan 12:35:47 ntpdate[997]: step time server offset 35237275.965726 sec

You can verify that correct data is setup:

# date


Wed Jan 25 12:36:21 IST 2006

Enable date and time/ clock Synchronization at boot time

You need to set ntpdate via /etc/rc.local file.

# vi /etc/rc.conf

Append following line to it:

Save and close the file. Make sure you have correct ntpdate_hosts server entry.

See also:

Updated for accuracy.

Share this on:

{ 6 comments… add one }

  • fink October 26, 2006, 6:32 pm

    how can i tell what date the tutorial was written, or what version of of software was used?

  • nixCraft October 26, 2006, 6:46 pm

    This is one is written on FreeBSD 6.0 but it should work on any version. This entry was written on Jan-25-2006.

    Hope this helps.

  • batso December 19, 2007, 11:43 am

    i have problem. i can’t configuration & check NTP server.
    Help Me. My config:
    install /usr/ports/net/ntp
    make install
    install finish
    my server ip address:
    server 0.asia.pool.ntp.org
    server 1.asia.pool.ntp.org
    server 2.asia.pool.ntp.org
    server 3.asia.pool.ntp.org
    driftfile /var/db/ntp.drift
    logfile /var/log/ntp.log

  • JB June 18, 2008, 3:22 am

    Are you sure this is correct?

    # vi /etc/rc.local

    and that it’s not rc.conf instead?

  • nixCraft June 18, 2008, 9:49 am

    Are you sure this is correct?
    No, it was a typo and the post has been updated to fix this issue. Thanks for the heads up.

  • SIFE October 4, 2009, 1:45 pm

    Salamo Alikom
    is there any way to prevent gnome changing sys clock ?

Leave a Comment

   Tagged with: , , , , , , , , , , , , , , , ,