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Old 06-03-2008, 02:36 PM
Anne Wilson
 
Default tzdata, Greenwich zone: URGENT!

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
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Old 06-03-2008, 04:03 PM
Guy Boisvert
 
Default tzdata, Greenwich zone: URGENT!

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!



Many thanks to Marcelo, Rick, Karambir & Anne!


Guy Boisvert, ing.
IngTegration inc.
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Old 06-03-2008, 04:06 PM
Karanbir Singh
 
Default tzdata, Greenwich zone: URGENT!

Anne Wilson wrote:

Where/how is the system clock set? My server appears to have the system clock
on GMT/UTC and KDE on British Time.



you can use the 'hwclock' command to set / reset / retrieve the physical
hardware clock timestamp. And you can use what Marcelo already pointed
out to set a timezone if you like ( cp or ln -s a physical zone file
from /usr/share/zoneinfo/ to /etc/localtime on the machine ).


Also, sanity check /etc/sysconfig/clock
_______________________________________________
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Old 06-03-2008, 09:58 PM
Johnny Hughes
 
Default tzdata, Greenwich zone: URGENT!

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
ZONE="UTC"
UTC=true
ARC=false
#---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.

Thanks,
Johnny Hughes

_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 06-04-2008, 09:43 AM
Anne Wilson
 
Default tzdata, Greenwich zone: URGENT!

On Tuesday 03 June 2008 17:06:09 Karanbir Singh wrote:
> Anne Wilson wrote:
> > Where/how is the system clock set? My server appears to have the system
> > clock on GMT/UTC and KDE on British Time.
>
> you can use the 'hwclock' command to set / reset / retrieve the physical
> hardware clock timestamp. And you can use what Marcelo already pointed
> out to set a timezone if you like ( cp or ln -s a physical zone file
> from /usr/share/zoneinfo/ to /etc/localtime on the machine ).
>
> Also, sanity check /etc/sysconfig/clock
>
Yes that did show up a difference, so I copied the GB file to localtime,
rebooted to make absolutely sure that it wasn't working on the old setting,
and hoped that the situation was cured. Unfortunately it isn't.

This is driving me crazy. Now I can make an appointment for 10a.m., and
depending on which computer I use to read the korganizer file it may show up
as 10a.m. or 11a.m., and there's no indication, of course, which computer
originated the entry, so I can't tell which is the correct version.

Anne
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 06-04-2008, 02:49 PM
Guy Boisvert
 
Default tzdata, Greenwich zone: URGENT!

Johnny Hughes wrote:


I use UTC

make sure that the file /etc/sysconfig/clock says this:
#---start cut
ZONE="UTC"
UTC=true
ARC=false
#---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.

Thanks,
Johnny Hughes




Thanks Johnny! Great info.

I edited the /etc/sysconfig/clock file and did what you said. I did
also: cp -p /usr/share/zoneinfo/UTC /etc/localtime. I'll probably
schedule a reboot, just to be sure all is clean. NTPd is already running.


Checking /usr/share/zoneinfo/, i saw GMT, GMT0, GMT-0, GMT+0, UTC &
Greenwich. Does anybody knows the differences between all these or
could provide a link to a reference? I found some infos but nothing
that explains the subtlety.


I made a diff and they are binary different. I just want to understand
better what happened to us and the "time" thing!


Regards,

Guy Boisvert, ing.
IngTegration inc.

_______________________________________________
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CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 06-04-2008, 02:57 PM
"Michael Simpson"
 
Default tzdata, Greenwich zone: URGENT!

> Checking /usr/share/zoneinfo/, i saw GMT, GMT0, GMT-0, GMT+0, UTC &
> Greenwich. Does anybody knows the differences between all these or could
> provide a link to a reference? I found some infos but nothing that explains
> the subtlety.

Basicly it comes down to GMT being based on the rotation of the earth
around its axis and the sun (which isn't completely regular) and UTC
being based on a Cesium atomic clock (which is far more accurate and
regular). UTC is regularly modified with "leap seconds" so that it
matches up to GMT to be the standard for date/time stamps. Also, UTC
is the authoriative measurement for calculations involving duration.

plagarised from

http://people.etango.com/~markm/archives/2004/02/29/gmt_vs_utc.html

not sure about the GMT-0 GMT+0 or GMT0

mike
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Old 06-05-2008, 10:14 AM
Karanbir Singh
 
Default tzdata, Greenwich zone: URGENT!

Anne Wilson wrote:
This is driving me crazy. Now I can make an appointment for 10a.m., and
depending on which computer I use to read the korganizer file it may show up
as 10a.m. or 11a.m., and there's no indication, of course, which computer
originated the entry, so I can't tell which is the correct version.


make sure the Hardware clock on all the machine is correct ( or setup
and run ntpd ) and make sure that they are all on a valid timezone (
just typing 'date' on the command line should tell you ). If that still
does not resolve the issue I'd guess your next action would be to post
on the kde lists about this issue. Perhaps you have different versions
of the same s/w on different machines - and they handle timezone
adjustments differently ( as in, one version does, and another does not )


--
Karanbir Singh : http://www.karan.org/ : 2522219@icq
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Old 06-05-2008, 03:29 PM
Anne Wilson
 
Default tzdata, Greenwich zone: URGENT!

On Thursday 05 June 2008 11:14:16 Karanbir Singh wrote:
> Anne Wilson wrote:
> > This is driving me crazy. Now I can make an appointment for 10a.m., and
> > depending on which computer I use to read the korganizer file it may show
> > up as 10a.m. or 11a.m., and there's no indication, of course, which
> > computer originated the entry, so I can't tell which is the correct
> > version.
>
> make sure the Hardware clock on all the machine is correct ( or setup
> and run ntpd ) and make sure that they are all on a valid timezone (
> just typing 'date' on the command line should tell you ). If that still
> does not resolve the issue I'd guess your next action would be to post
> on the kde lists about this issue. Perhaps you have different versions
> of the same s/w on different machines - and they handle timezone
> adjustments differently ( as in, one version does, and another does not )

I still can't find the difference between the boxes. KDE - it's possible.
I've tried to ask a couple of times, but haven't managed to get the message
clear enough to get an answer. The whole thing is extremely confusing. If I
solve it I'll post the resolution, for the sake of the archives.

Anne
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