Scott Harrison
Last updated: 02/07/2001
This file describes issues associated with LON-CAPA and time synchronization.
Since LON-CAPA machines are involved with the submission of homework, quizzes, and exams to the instructor, it is important that the time of the server be kept accurately and precisely.
Accuracy involves
I will explain the components of ntp and how they interrelate on a LON-CAPA system There are three relevant components here: 1. a correct /etc/ntp/step-tickers, 2. a correct /etc/ntp.conf 3. enabling xntpd for boot up Without /etc/ntp.conf, /etc/rc.d/init.d/xntpd won't do anything. With /etc/ntp.conf but without /etc/ntp/step-tickers, Gerd is correct when he says: > What I do know is that if the clock in the CMOS is off by too much,the normal > ntp will not work. Instead, the clock has to be forced to synch initially,and > from then on can be automatically adjusted. The unix commands for Gerd's manual approach are: /etc/rc.d/init.d/xntpd stop /usr/sbin/ntpdate ntp.msu.edu (or whatever your ntp server is) /etc/rc.d/init.d/xntpd start To force xntpd to avoid the offset problem, defining /etc/ntp/step-tickers does the trick. With /etc/ntp.conf and /etc/ntp/step-tickers, xntp still may not work (depending on whether the last instruction was followed for the LON-CAPA installation, see http://install.lon-capa.org/docs/3.1/instructions_with_cd.html) Making sure xntp starts up upon boot time should simply be a matter of: /sbin/chkconfig xntpd on Finally, the correct settings for /etc/ntp.conf and /etc/ntp/step-tickers are: 1 line with the ip address of your ntp server For instance: echo "whistler.sfu.ca" > /etc/ntp/step-tickers echo "whistler.sfu.ca" > /etc/ntp.conf Everyone is currently setting these and other LON-CAPA conf files manually after cvs upgrades, because there were several parties who were * doing different things * in different ways * for different reasons * for different institutions * for their machine-specific configurations I was not able to make everyone happy with "make configinstall". For the future, we (Guy and I) do think we've come up with a new way to do everything for everyone for updating configuration files as the CVS source repository changes. -Scott