[CentOS] tzdata, Greenwich zone: URGENT!

Johnny Hughes johnny at centos.org
Tue Jun 3 21:58:18 UTC 2008

Guy Boisvert wrote:
> Anne Wilson wrote:
>> On Tuesday 03 June 2008 14:57:29 Karanbir Singh wrote:
>>> Guy Boisvert wrote:
>>>> Hi!
>>>> It appears that there have been some changes to tzdata recently. We
>>>> run an application that needs the server to stay at GMT. Previously, we
>>>> used the Casablanca timezone but now there seems to be a 1 hour
>>>> difference to GMT. I checked the London zone and they seem to change
>>>> time too.
>>> Looks like you were never on GMT / UTC - but on British Time, Which in
>>> the summer is one hour off GMT
>> Where/how is the system clock set?  My server appears to have the 
>> system clock on GMT/UTC and KDE on British Time.
>> Anne
> Hi!
>     Thanks for all the fast responses!  I didn't know about the 
> internals of the tzdata, the symlinks and the potential problems that 
> Rick reported.  So finally, before the 1st response arrived from the 
> list, i decided to do a "brute force" downgrade.
> I downloaded the previous CentOS tzdata file from:
> http://rpm.pbone.net/index.php3/stat/3/srodzaj/1/search/tzdata
> and did an rpm -ivh --force tzdata-2007k-2.el4.noarch.rpm
>     I rebooted the server and everything went ok!  I didn't have the 
> time to explain my case but for the sake of completeness, here it is:
> 1) Our application is for TV broadcasting.  We have a complete in-house 
> developped automatic broadcasting system.
> 2) We have two players (1 active, 1 standby) that run on Windows 2000 
> Server platform.  There are 3 deamons: Copy service (from the big 
> multi-terabyte library to local "cache" of 200 gigs), Broadcaster 
> (playlist maker) and Player.  The former 2 services read data from 
> PostgreSQL database on CentOS x64 4.6.  As is said, the Broadcaster 
> service read from the database and make the playlist then send it to the 
> player.  Copier make check what it needs locally and act accrodingly. It 
> managed a kind of big local cache.
> 3) The broadcast schedule is entered with a JAVA application that writes 
> the time and date in GMT/UTC time in the database.  The JAVA application 
> knows the local time and the offset and write accordingly, adding the 
> amount of time required (we are in Montreal so it's GMT-4 or GMT-5) to 
> "reach" GMT+0.
> 4) The database servers have always been in Casablanca zone and until 
> today, it seems that it was never changing time.  1st of june, tzdata 
> was updated by a yum update and since then, it was only a question of 
> time before we'de be offset.  Playlists are looked up and made for 36 
> hours so today was panic day!
> 5) Stumbling across the problem, i read many strange things while 
> Googling, related to what Rick said in his post to the list: localtime 
> file, symlinks, etc.  I was kinda lost!
> Practically, as i said, i tried to find the GMT zone doing a 
> system-config-date to no avail... I was shocked!  We shouldn't be the 
> only one to have this need!
> So, as i decode from what i received in response to my initial post, and 
> correct me if i'm wrong, all that does system-config-date is to copy a 
> file from /usr/share/zoneinfo/... into /etc/localtime ? (and maybe set a 
> couple of symlinks?).
> And if i do what Marcelo said:
> cp  /usr/share/zoneinfo/right/Etc/GMT-0 /etc/localtime
> am i cleared from future updates / changes in timezones?  I simply want 
> the server to stay at GMT+0 and never change timezone.
> I'm waiting for advice from experts!
> And would it be possible to include "GMT+0" in system-update-date ? What 
> is strange on top of all that is that the time of the schedule seems to 
> be stored on the database relative to the local time of the server...  
> I'll have that checked by the programmers!

I use UTC

make sure that the file /etc/sysconfig/clock says this:
#---start cut
#---end cut

Copy the file /usr/share/zoneinfo/UTC to /etc/localtime

set the time via an ntp server with the command (if ntp is installed):

ntpdate -s 0.centos.pool.ntp.org

Then you should always be at the correct time.

NOTE:  If you do not have the correct time zone in the 
/etc/sysconfig/clock file then on the next update, you will get the 
reset to the timezone that is there and not the one you manually copied in.

The UTC time zone is also available on install as a selection.

Johnny Hughes

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