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Old 10-21-2013, 12:49 PM   #1
techux
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Daylight saving Eastern Time end


Hi guys.

We have some linux servers, when I got the job, the servers were already configured. Florida.

The servers are using NTP, but how can I be sure that on November 3 (when Daylight Saving Time ends) every servers is gonna update the time correctly?

my /etc/sysconfig/clock shows:

ZONE="America/New_York"
UTC=false
ARC=false


date: Mon Oct 21 12:46:02 EDT 2013

On november 3rd at 2am the clocks are turned backward 1


Thanks
 
Old 10-21-2013, 01:09 PM   #2
AlucardZero
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Make sure you have the latest tzdata package available for whatever distro you are running.

Then check with
Code:
zdump -v America/New_York | grep 2013
http://chrisjean.com/2009/03/10/upda...time-on-linux/
 
Old 10-21-2013, 01:31 PM   #3
suicidaleggroll
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You could also use date

Code:
$ date
Mon Oct 21 11:31:01 MDT 2013
$ date -d "12 days"
Sat Nov  2 11:31:04 MDT 2013
$ date -d "13 days"
Sun Nov  3 10:31:07 MST 2013

Last edited by suicidaleggroll; 10-21-2013 at 01:34 PM.
 
3 members found this post helpful.
Old 10-21-2013, 01:59 PM   #4
michaelk
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FYI
UTC=false just means the hardware clock is set to local time
arc=false means that the system is using the standard Unix epoch i.e. 00:00:00 1 Jan 1970.

ntp uses UTC and so the time displayed on your servers is based upon the configured timezone. If your servers are kept updated then they should have the current time zone data which can be verified as stated above.

The timezone file being used is /etc/localtime which should be a copy of the America/New_York in your case.

Last edited by michaelk; 10-21-2013 at 02:03 PM.
 
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Old 10-22-2013, 10:15 AM   #5
techux
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If I run zdump it is what I get, I guess with this the server should update/change the time automatically on November 3, right?

or should I do something else.

Regarding the NTP configuration, is there anything that should be changed?

Quote:
[root@localhost ~]# zdump -v America/New_York |grep 2013
America/New_York Sun Mar 10 06:59:59 2013 UTC = Sun Mar 10 01:59:59 2013 EST isdst=0 gmtoff=-18000
America/New_York Sun Mar 10 07:00:00 2013 UTC = Sun Mar 10 03:00:00 2013 EDT isdst=1 gmtoff=-14400
America/New_York Sun Nov 3 05:59:59 2013 UTC = Sun Nov 3 01:59:59 2013 EDT isdst=1 gmtoff=-14400
America/New_York Sun Nov 3 06:00:00 2013 UTC = Sun Nov 3 01:00:00 2013 EST isdst=0 gmtoff=-18000
 
Old 10-28-2013, 10:09 AM   #6
techux
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the date is close, do you guys think I need to configure something else or it should be change automatically on Nov 3?

thanks
 
Old 10-28-2013, 10:47 AM   #7
michaelk
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Nope, It should change automatically.
 
Old 10-28-2013, 10:51 AM   #8
suicidaleggroll
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Quote:
Originally Posted by techux View Post
I guess with this the server should update/change the time automatically on November 3, right?
Quote:
Originally Posted by techux View Post
should be change automatically on Nov 3?
Why don't you just try it and see for yourself?
Quote:
Originally Posted by suicidaleggroll View Post
You could also use date

Code:
$ date
Mon Oct 21 11:31:01 MDT 2013
$ date -d "12 days"
Sat Nov  2 11:31:04 MDT 2013
$ date -d "13 days"
Sun Nov  3 10:31:07 MST 2013
 
Old 10-29-2013, 09:25 AM   #9
techux
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thank you so much. that helped me.
 
Old 10-29-2013, 09:55 PM   #10
Spect73
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Quote:
Originally Posted by suicidaleggroll View Post
You could also use date

Code:
$ date
Mon Oct 21 11:31:01 MDT 2013
$ date -d "12 days"
Sat Nov  2 11:31:04 MDT 2013
$ date -d "13 days"
Sun Nov  3 10:31:07 MST 2013
Neat. I never realized that 'date' could do that. I guess 'man date' is indeed my friend

Coordially
 
Old 10-31-2013, 07:37 PM   #11
sundialsvcs
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Excellent suggestion there, "eggroll." (Love the nick.)

Here's the bottom-line on this:
  • The NTP daemons will retrieve and calculate a time-value, and set it into the hardware clock. The hardware-clock can be set to GMT, or not. It's up to you, just make sure that all of your systems (esp. in a network) are consistent with one another. (Most applications do not query the hardware directly, anyway.)
  • The time-zone information file includes cutoff-dates for daylight time. Just be sure (as "eggroll" showed) that your files are up-to-date on this. This will ensure that "what time is it, here and now?" will be returned correctly.

Last edited by sundialsvcs; 10-31-2013 at 07:38 PM.
 
Old 10-31-2013, 08:05 PM   #12
michaelk
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Actually NTP sets the system clock but the kernel if configured will keep the hardware clock updated every 11 minutes. I believe this is still an accurate statement...


http://www.ntp.org/ntpfaq/NTP-s-trbl-spec.htm
 
  


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