[ntp:questions] Correcting a large time difference

unruh unruh at wormhole.physics.ubc.ca
Sat Jul 31 15:51:53 UTC 2010

On 2010-07-31, David Woolley <david at ex.djwhome.demon.invalid> wrote:
> Richard Heritage wrote:
>> I've inherited a RHEL 5 server that isn't running ntp and whose clock
> is about 30 minutes fast. What I would like to do is start ntpd & have
> it gradually correct the clock. I don't care how long it takes--it's
> been running this way for months. The server runs an email application
> that may be sensitive to a large backward jump in the clock, and leaving
> the server down for a half hour isn't a good option.
> Do not run ntpd. Use ntptime to set the tickadj value to give the 
> highest acceptable slew rate (granularity is typically 100ppm).  Reset 
> it to normal as you approach the zero crossing.  Measure the residual 
> frequency error and calculate the ntp.drift value for it.  Set that 
> value in ntp.drift and start ntpd.
> ntptime goes by other names on some systems.

adjtimex on Linux systems. 

> PS Please don't write your paragraphs all on one line.  There are proper 
> ways of representing wrapped text in MIME email.

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