Ntpdate (mini) HOWTO

Ntpdate (mini) HOWTO

- Author: zartik <zartik@spot.org>
- Date: January 28, 2000
- File Information: This text document may be copied, deleted, and
published as
                    desired provided credit is given to the author. If any 
                    alterations are made, each and every change must be
                    commented as change to the original document, thank
you.
- Purpose: Shory and simple explanation of how to make your system's clock
	   as acurate as possible.

Part One:
---------
    Before we start, you should select servers which are closest to you in
order to update your system's clock. A complete list of primary servers
can be retrieved from: http://www.eecis.udel.edu/~mills/ntp/clock1.htm.
Considering most people are lazy I list a few of what I find to be the
popular ones here:

    * bonehed.lcs.mit.edu (18.26.4.105)
    * navobs1.usnogps.navy.mil (204.34.198.40) CNAME:
tick.usnogps.navy.mil
    * ntp.nasa.gov (143.232.55.5)

    I do urge you to look at the complete list and find sites in your
area; it helps the net run smoother, and will give you better results.

Part Two:
---------
    Now that we have our personalized list of servers, let's take a look
at how to update our system's clock from the command line. If you aren't
already, login as root, because for practical reasons, it is the only user
allowed to modify the system's clock. We will be using multiple servers in
our example because it will provide better overall performance. It is very
simple to just use the defaults in ntpdate, just type:

    [zartik@spot]:~$ ntpdate bonehed.lcs.mit.edu ntp.nasa.gov
navobs1.usnog
                     ps.navy.mil
    28 Jan 20:28:30 ntpdate: bind() fails: Permission denied
    [zartik@spot]:~$ 

    As you can see we we not successful and recieved an error. But alas, I
was just a peon little user w/o the permissions of mighty old root. So
after su'ing into root, here are my results:

    [root@spot]:/usr/home/zartik# ntpdate bonehed.lcs.mit.edu ntp.nasa.gov
                                  navobs1.usnogps.navy.mil
    28 Jan 20:28:45 ntpdate: step time server 18.26.4.105 offset 0.003293
    [root@spot]:/usr/home/zartik# 

    If you desire to see how ntpdate is working, before listing the
servers, add a -d option in there and it will print to the screen it's
behind the scenes workings.

Part Three:
-----------
    Now that we have the command line down, it is generally common
practice to both crontab this procedure as well as adding it to your
/etc/rc.local startup file.
    To avoid annoying test from suddenly popping up, we will be tossing in
the -s option to send output to the syslog rather then console. To run
ntpdate on boot, add the following line to your /etc/rc.local file:

    echo 'Updating system's clock from an atomic clock site....'
    ntpdate -s bonehed.lcs.mit.edu ntp.nasa.gov navobs1.usnogps.navy.mil

    Great, now on startup our clock will be accurate, but what about when
we have those amazing 100 day uptime and we want to avoid our clock from
drifting too far? Just add that same line from the rc.local file to ROOT's
crontab file. If you do not know how to use crontab file, get a howto on
it.

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