How to handle the DST changes for 2008(RHEL)

[skt_skt]

I am trying to collect information "Patch requierment/apply to handle the DST changes for 2008(both mar and Nov)"

I am looking for a dicussion covering all RHEL version (2.1 to 4); what are the precaution to take for the pathcing; Any need of appl/db bouncing etc..

I hope this is going to be intersing since it is a very good Topic for LINUX admins.

[Matti_Kurkela]

If your country has not changed its DST rules since last year, you probably won't need to do anything. The patches are not for DST changes themselves: they are for updating the rules for calculating *when* the change is supposed to happen.

You can use "zdump -v " to verify any past and future DST change times the system currently knows.

For example, I could do this:
# zdump -v Europe/Helsinki |grep 2008
Europe/Helsinki Sun Mar 30 00:59:59 2008 UTC = Sun Mar 30 02:59:59 2008 EET isdst=0 gmtoff=7200
Europe/Helsinki Sun Mar 30 01:00:00 2008 UTC = Sun Mar 30 04:00:00 2008 EEST isdst=1 gmtoff=10800
Europe/Helsinki Sun Oct 26 00:59:59 2008 UTC = Sun Oct 26 03:59:59 2008 EEST isdst=1 gmtoff=10800
Europe/Helsinki Sun Oct 26 01:00:00 2008 UTC = Sun Oct 26 03:00:00 2008 EET isdst=0 gmtoff=7200

I know my country will change to DST on last Sunday of March, at 01:00 UTC, just like it's been done since year 1981. The time to switch back to standard time changed from the last Sunday of September to the last Sunday of October back in 1996, to harmonize the transition time within EU. At that time, we needed to patch all our computers to use the new DST rules... but since then, the computers have done it automatically!

I can see that zdump indicates the correct dates and times to switch between the DST & standard time, so I know I won't need to do anything.

Some unfortunate countries don't have a standard DST transition rule in place, but instead decide the transition dates separately for each year. In these countries, the admins should be prepared to write their own timezone definitions and install them as soon as the DST transition dates for the current year are published. The system vendors *may* provide official patches, but the necessary changes aren't really that hard to do manually.

If there is enough time between the publication of new DST transition times and the actual transition, this might even be accomplished as part of a standard, scheduled maintenance break.

If your server is used e.g. to handle the scheduling of a multi-national organization, you might wish to be sure you have the correct DST rules for _all_ countries... but for most servers, the correct rules for the server's home country are probably sufficient.

MK

[skt_skt]

DST change for Brazil happend today.. All was transparent with tzdata-2007k.

# zdump -v /etc/localtime|grep 2008
/etc/localtime Sun Feb 17 01:59:59 2008 UTC = Sat Feb 16 23:59:59 2008 BRST isdst=1 gmtoff=-7200
/etc/localtime Sun Feb 17 02:00:00 2008 UTC = Sat Feb 16 23:00:00 2008 BRT isdst=0 gmtoff=-10800