http://www.timeanddate.com/worldclock/city.html?n=204

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Chris Hoogendyk

-
  O__  ---- Systems Administrator
 c/ /'_ --- Biology & Geology Departments
(*) \(*) -- 140 Morrill Science Center

<hoogendyk AT bio.umass DOT edu>

Erdös 4




donald.ritchey AT exeloncorp DOT com wrote:

Actually, the time period to avoid is Sunday morning from 0100 to 0300, since you will get hit as described below, except that the period of Fall danger is from 0100 to 0200 (all of these entries will get run twice). Fall DST causes the clocks to reset at 0200 back to 0100, so that period gets a "double dose"

of whatever goodness is scheduled for that period.

In the spring, the danger is that jobs scheduled between 0200 and 0300 will not get run at all.

After 20+ years of UNIX admin experience, nothing critical gets scheduled between the hours of 0100 and 0300 on any Sunday. I even put comments in the crontab files to ensure that the follow-on person (the one who picks up after me) knows why that "gap" in processing exists and doesn't improve efficiency by scheduling something in that interval.

Remember, in System Administration, paranoia is not a disability...
        It is a job requirement.

Don Ritchey
IT ED RTS Tech Services, Senior IT Analyst (UNIX)
Exelon Corporation


-----Original Message-----
From: owner-amanda-users AT amanda DOT org [mailto:owner-amanda-users AT amanda 
DOT org] On Behalf Of Chris Hoogendyk
Sent: Tuesday, October 30, 2007 11:22 AM
To: AMANDA users
Subject: Backups and Daylight Savings Time

On another backup list I monitor, there was an instance of someone who had their system change time on October 28th. Two issues came out of this. One is that they may have failed to patch their system for the 2007 statutory changes in daylight savings time (it should change on Nov. 4th for many). Two is that they had a backup job scheduled for 2:05am that Sunday. It launched at 2:05, and then 2:05 rolled around again an hour later, whereupon it launched again, waited for the first to complete and then repeated the whole backup.

So, I thought I would pass this along to the Amanda users list just in case it is a useful memory nudge for anyone.

Daylight Savings time laws changed affective Spring 2007 in the U.S. and Australia. I don't know what the situation is for other countries. There were patches to be applied according to your operating system. I applied Solaris 9 patches. Mac OS X and Windows systems got theirs by automatic updates. One of our labs had an older Sun OS 5.6 system for which there were no patches. After messing with it for a while, they finally punted and said it didn't really matter.

If you have a server that was not patched this year, and you are in a jurisdiction where it matters, now is the time to check into it. It will bite you twice a year until you patch it.

On the second item, my backups start at 12:45am, so no problem. However, I'm going to be checking all my crontabs to make sure I don't have anything between 2 and 3am that might be affected. In the Spring they might be skipped, and in the Fall they might be run twice.

My apologies to those who find this too obvious. ;-)


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Chris Hoogendyk

-
   O__  ---- Systems Administrator
  c/ /'_ --- Biology & Geology Departments
 (*) \(*) -- 140 Morrill Science Center

~~~~~~~~~~ - University of Massachusetts, Amherst

<hoogendyk AT bio.umass DOT edu>

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Erdös 4