Overview
Timing Good system time of day quality is needed on LOIS computers in order to
- Communicate effectively with the UI (Loui)- this will fail if the time offset with the LOUI computer is more than about 5 seconds.
- Have good time for the FITS headers- especially important for occultations and transits- time offset from reality should be much less than 1 sec.
To maintain quality of service for time, (QoS), ntpd is used. The computers themselves have poor clock/calendar h/w- at the level of a very cheap watch- so you would need to check and reset time several times in the night if relying on a manual operation. Ntpd should start automatically when the computer is restarted, and remain up. The timecheck and st scripts will inform you if ntpd is not running. The timefix script, run as super user, will allow you to stop, start, or restart ntpd if you need to do that. There is also an operation called ntpdate which will access a remote timeserver and do a good time correction on a one time basis; this can be invoked with timefix also.
If ntpd is running, a system utility called ntpq is available to give you a table of the ntp protocol status with all of the remote ntp servers that are in the mix. The interesting numbers in this table are reach (up to 377 for complete synchronization) and offset (in msec, gives time displacement with the given server from this host). The timecheck script will summarize this information in a single line.
The st script is available on all lois computers, as are ntpd, ntpdate and ntpq. Timecheck and timefix are currently on deveny only.