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1.1       harris41    1: <HTML>
                      2: <HEAD>
                      3: <TITLE>LON-CAPA Time Synchronization</TITLE>
                      4: </HEAD>
                      5: <BODY>
                      6: <H1>LON-CAPA Time Synchronization</H1>
                      7: <P>
                      8: Scott Harrison
                      9: </P>
                     10: <P>
                     11: Last updated: 02/07/2001
                     12: </P>
                     13: <P>
                     14: This file describes issues associated with LON-CAPA
                     15: and time synchronization.
                     16: </P>
                     17: <H3>Importance</H3>
                     18: <P>
                     19: Since LON-CAPA machines are involved with
                     20: the submission of homework, quizzes, and
                     21: exams to the instructor, it is important that
                     22: the time of the server be kept accurately and precisely.
                     23: </P>
                     24: <P>
                     25: Accuracy involves 
                     26: </P>
1.2     ! harris41   27: <pre>
        !            28: I will explain the components of ntp and how they
        !            29: interrelate on a LON-CAPA system
        !            30: 
        !            31: There are three relevant components here:
        !            32: 1. a correct /etc/ntp/step-tickers,
        !            33: 2. a correct /etc/ntp.conf
        !            34: 3. enabling xntpd for boot up
        !            35: 
        !            36: Without /etc/ntp.conf, /etc/rc.d/init.d/xntpd won't do anything.
        !            37: With /etc/ntp.conf but without /etc/ntp/step-tickers, Gerd is correct
        !            38: when he says:
        !            39: 
        !            40: > What I do know is that if the clock in the CMOS is off by too much,the normal
        !            41: > ntp will not work. Instead, the clock has to be forced to synch initially,and
        !            42: > from then on can be automatically adjusted.
        !            43: 
        !            44: The unix commands for Gerd's manual approach are:
        !            45: /etc/rc.d/init.d/xntpd stop
        !            46: /usr/sbin/ntpdate ntp.msu.edu (or whatever your ntp server is)
        !            47: /etc/rc.d/init.d/xntpd start
        !            48: 
        !            49: To force xntpd to avoid the offset problem, defining
        !            50: /etc/ntp/step-tickers does the trick.
        !            51: 
        !            52: With /etc/ntp.conf and /etc/ntp/step-tickers, xntp still may not
        !            53: work (depending on whether the last instruction was followed
        !            54: for the LON-CAPA installation, see
        !            55: http://install.lon-capa.org/docs/3.1/instructions_with_cd.html)
        !            56: 
        !            57: Making sure xntp starts up upon boot time should simply
        !            58: be a matter of:
        !            59: 
        !            60: /sbin/chkconfig xntpd on
        !            61: 
        !            62: Finally, the correct settings for /etc/ntp.conf
        !            63: and /etc/ntp/step-tickers are:
        !            64: 
        !            65: 1 line with the ip address of your ntp server
        !            66: 
        !            67: For instance:
        !            68: 
        !            69: echo "whistler.sfu.ca" > /etc/ntp/step-tickers
        !            70: echo "whistler.sfu.ca" > /etc/ntp.conf
        !            71: 
        !            72: Everyone is currently setting these and other LON-CAPA conf
        !            73: files manually after cvs upgrades, because
        !            74: there were several parties who were
        !            75: 
        !            76: * doing different things
        !            77: * in different ways
        !            78: * for different reasons
        !            79: * for different institutions
        !            80: * for their machine-specific configurations
        !            81: 
        !            82: I was not able to make everyone happy with
        !            83: "make configinstall".  For the future, we (Guy and I) do think
        !            84: we've come up with a new way to do everything
        !            85: for everyone for updating configuration files
        !            86: as the CVS source repository changes.
        !            87: 
        !            88: -Scott
        !            89: </pre>
        !            90: </body>
        !            91: </html>
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