On 10/10/2011 5:04 PM, mcclnx mcc wrote:

We have CENTOS 4.X and 5.X on DELL servers. On Nov. 6, 2:00 A.M. will change to 1:00 A.M.

If I have cron job on 1:20 A.M., will it run twice?

$ man cron

...

Daylight Saving Time and other time changes Local time changes of less than three hours, such as those caused by the start or end of Daylight Saving Time, are handled specially. This only applies to jobs that run at a specific time and jobs that are run with a granularity greater than one hour. Jobs that run more frequently are scheduled normally.

If time has moved forward, those jobs that would have run in the interval that has been skipped will be run immediately. Conversely, if time has moved backward, care is taken to avoid running jobs twice.

Time changes of more than 3 hours are considered to be corrections to the clock or timezone, and the new time is used immediately.