It usually takes xntpd a day or so after it is started to compute a good estimate of the frequency error. The current value of the frequency error may be stored in a driftfile.
The driftfile allows a restarted xntpd to reinitialize itself to the estimate stored in the driftfile, saving about a day's worth of time in recomputing a good frequency estimate. You specify the path and name of the driftfile. Run ntpdate Make sure xntpd is stopped before issuing the command ntpdate 3.
This file is not reliable. It usually takes some time to have got updated with entries. Thanks to everybody who cleared my doubts. Using two NTP sources is considered to be the worst choice as the NTP application, ntpd in this case, cannot decided which is more stable. Have you configured the host system to act as an NTP server to the guests?
If you search the Knowledgebase you will find many articles and solutions that may help. Comments 4. Is it running? Also what is the general rule for having the hardware clock match the system time?
Many things about NTP are elusive. At the casual user, there are a lot of things to understand: broacast, unicast, multicast, tally codes, servers, peers, stratum, delay, offset, jitter and so much more. Unless you setup your own NTP server, with the intent of providing accurate time keeping for clients, many of those terms can be discarded. However, one term you may want to be familiar with is "drift".
Clock drift is when clocks are either too fast or too slow compared to a reference clock. NTP version 4 has the ability to keep clocks accurate within picoseconds called "resolution". Of course, to have this sort of accuracy, you need exceptionally low latency networks with specialized hardware.
High volume stock exchanges might keep time accuracy at this level. Generally speaking, for the average NTP server and client on the Internet, comparing time in milliseconds is usually sufficient. The frequency offset is stored in parts-per-million PPM. The file is updated by the NTP service every hour.
It is considered good practice to specify a drift file, since it allows NTP to synchronize the local clock faster on start up. A drift file is specified as follows:. You can use the statsdir command in the configuration file to specify a directory where statistics files will be stored.
Statistics files are useful to view local clock synchronization performance. As a minimum a configuration file needs to specify a server that should be used for synchronization along with a drift file to store local clock frequency.
However, a more complete configuration file will include multiple servers, drift file and a statics directory:. The command provides a list of configured peers and their associated synchronization performance characteristics.
The first character in the peer list is a tally code that indicates the status of synchronization. This indicates that the local system clock is synchronized to the peer. The peer may be used in the event of the system peer being discarded.
Other characters generally indicate that the clock has been discarded by the selection algorithm. Refid — indicates the synchronization source of the peer. However, it may also be an address if the peer is a lower stratum in the NTP hierarchy. Stratum 1 is the highest level, 15 the lowest.
Type — the peer type — local, unicast, multicast or broadcast. Most peers are accessed in unicast mode.
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