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ntpd on SCO OpenServer system machines supports a special pseudo-clock used for backup or when no other clock source is available (for example, Internet access is not available). The address of this clock should be set as follows in the ntp.conf file:
127.127.1.u - Local synchronization clock driverThis driver doesn't support an actual clock, but rather allows the server to synchronize to its own clock, in essence to run without its stratum increasing to infinity. This can be used to run an isolated NTP synchronization network, where no standard time source is available, by allowing a free running clock to appear as if it has external synchronization to other servers.
By running the local clock at an elevated stratum, it can also be used to prevent a server's stratum from rising above a fixed value, thus allowing a synchronization subnet to synchronize to a single local server for periods when connectivity to the primary servers is lost.
The unit number of the clock (the least significant octet in the address) must lie in the range of 0 through 15 inclusive and is used as the stratum the local clock will run at. Note that the server, when synchronized to the local clock, will advertise a stratum one greater than the clock peer's stratum. More than one local clock may be configured (indeed all 16 units may be active at once), though this hardly seems useful.
It is recommended that the local clock be configured at a large stratum number, for example, 10. This will minimize problems if it is being used as a backup, or if Internet connectivity is acquired later. Since the local clock is not connected to a reliable time source such as GPS or radio signals, configuring it at an elevated stratum will cause other systems to avoid it if a more accurate source is available.