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Fri Sep 7 14:54:47 2001 UTC (22 years, 9 months ago) by harris41
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CVS tags: version_1_0_3, version_1_0_2, version_1_0_1, version_1_0_0, version_0_99_5, version_0_99_4, version_0_99_3, version_0_99_2, version_0_99_1, version_0_99_0, version_0_6_2, version_0_6, version_0_5_1, version_0_5, version_0_4, stable_2002_spring, stable_2002_july, stable_2002_april, stable_2001_fall, conference_2003, STABLE, HEAD
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    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>
   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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