Rolling back time Post: 18241

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Top Forums UNIX for Dummies Questions & Answers Rolling back time Post 18241 by Perderabo on Tuesday 26th of March 2002 08:31:31 AM

03-26-2002

Administrator Emeritus

Ideally, you want to set your system time to Zulu Time and then set your timezone variable so that your local software handles everything right for your locale. I would try hard for that solution. But in this thread we saw that peter.herlihy had a problem with an unusual timezone too. Most modern variants of unix now have very programmable timezone software. But some older versions only really support US timezones well.

It may be that if you use ntp to sync your clocks that you are left with no way to display the correct local time. If so, you may be forced to misalign your system clock. This is unfortunate, but it's what I would do if I were forced into it. If this is the case, you do do not want ntp.

When one of my system clocks is very far off for some odd reason, I do not patiently wait for ntp to correct the situation. I want instant gratification.

So to answer your original question, kill cron, then change the time, then restart cron. If cron sees the time change, it will catch up or stop running until it thinks it resyncs. Also be sure that no one is using "make". It's best to do this at a time when no one is using the system. If that's not possible, let the users know.

Perderabo

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rtc

rtc(1M) 						  System Administration Commands						   rtc(1M)

NAME

       rtc - provide all real-time clock and GMT-lag management

SYNOPSIS

       /usr/sbin/rtc [-c] [-z zone-name]

DESCRIPTION

       On x86 systems, the rtc command reconciles the difference in the way that time is established between UNIX and MS-DOS systems. UNIX systems
       utilize Greenwich Mean Time (GMT), while MS-DOS systems utilize local time.

       Without arguments, rtc displays the currently configured time zone string. The currently configured time zone string is based on  what  was
       last recorded by rtc-z zone-name.

       The  rtc  command  is  not normally run from a shell prompt; it is generally invoked by the system. Commands such as date(1) and rdate(1M),
       which are used to set the time on a system, invoke /usr/sbin/rtc -c to ensure that daylight savings time (DST) is corrected for properly.

OPTIONS

       -c	       This option checks for DST and makes corrections if necessary. It is normally run once a day by a cron job.

		       If there is no RTC time zone or /etc/rtc_config file, this option will do nothing.

       -z zone-name    This option, which is normally run by the system at software installation time, is used to specify the time zone  in  which
		       the  RTC is to be maintained. It updates the configuration file /etc/rtc_config with the name of the specified zone and the
		       current GMT lag for that zone. If there is an existing rtc_config file, this command will update it. If not,  this  command
		       will create it.

FILES

       /etc/rtc_config	  The data file used to record the time zone and GMT lag. This file is completely managed by /usr/sbin/rtc, and it is read
			  by the kernel.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Architecture		     |x86			   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       date(1), rdate(1M), attributes(5)

SunOS 5.11							    3 Oct 2003								   rtc(1M)