See OrphanModeDev for discussion of this topic.
6.2. Orphan mode
Orphan Mode is the stated replacement
for the UndisciplinedLocalClock
. It was added to ntp-4.2.2.
Orphan Mode allows a group of
processes to automonously select a leader in the event that all real time sources become unreachable (i.e. are inaccessible).
Orphan Mode is enabled by adding the line
tos orphan N
specifies the stratum at which this
will switch to Orphan Mode. For example, an
tos orphan 6
will not switch to Orphan Mode as long as a time source of strata 1 through 5 is reachable. The recommended value for
is 2 less than the worst-case externally-reachable source of time.
In addition to the
line all members of the Orphan Mode group must be configured in a mesh
(i.e. they must all be clients / peers of each other). Any NTP association mode may be used to set up this mesh.
NTP versions prior to 4.2.4p5 and 4.2.5p101 will not start up properly in Orphan Mode unless at least one time source is configured in
. If no time sources are specified the
continually increases. This makes these versions unsuitable for use as stand-alone Orphan Mode servers in a time island.
NTP versions including and after 4.2.5p101 will start up correctly in pure Orphan Mode.
Related Topics: Distribution Documentation: Orphan Mode