Joel,
The only thing the -x option does is change the step threshold to 600 s,
or ten minutes. I find it mighty curious that you would consider a large
discrepancy like that within acceptable bounds for a any consistent
distributed data system, but that's not my call.
If you really do insist on disabling all steps, put a "tinker step 0"
and "tinker panic 0" in the configuration file. Be advised, should the
correction be many hours or days, the time to amortize the correction
will be months or years. Also, be sure to disable the kernel discipline
if available. In some systems like Solaris which have broken the
original Unix adjtime() model, a large correction becomes unstable and
results in wild swings that can take many hours or days to damp out.
Note that the tinkers disable all steps for any reason, including a step
at startup. If you need that, you will need another program or to start
ntpd in ntpdate mode before launching the daemon.
Dave
Joel Shellman wrote:
Looking at:
http://www.eecis.udel.edu/~mills/ntp/html/ntpd.html
It says:
"As the result of this behavior, once the clock has
been set, it very rarely strays more than 128 ms, even
under extreme cases of network path congestion and
jitter. Sometimes, in particular when ntpd is first
started, the error might exceed 128 ms. This may on
occasion cause the clock to be set backwards if the
local clock time is more than 128 s in the future
relative to the server. In some applications, this
behavior may be unacceptable. If the -x option is
included on the command line, the clock will never be
stepped and only slew corrections will be used."
But then at the bottom, in the discussion of command
line args, it says:
"-x
Normally, the time is slewed if the offset is less
than the step threshold, which is 128 ms by default,
and stepped if above the threshold. This option sets
the threshold to 600 s, which is well within the
accuracy window to set the clock manually. Note: Since
the slew rate of typical Unix kernels is limited to
0.5 ms/s, each second of adjustment requires an
amortization interval of 2000 s. Thus, an adjustment
as much as 600 s will take almost 14 days to complete.
This option can be used with the -g and -q options.
See the tinker command for other options. Note: The
kernel time discipline is disabled with this option."
This seems to imply that if the offset is greater than
600s a step would occur. Is this correct? I understand
that a difference of 1000s would result in ntpd
exiting anyway, but in that space between 600-1000s, a
step could occur even with -x specified? I'm asking
because it's a requirement that we never have the time
stepped (especially not backwards) except at startup.
I know we can run -q -g at startup, but I want to
ensure that it is not possible to step the clock after
startup. I would rather have ntpd exit.
Thank you,
-joel
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