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тАО06-03-2008 04:41 AM
тАО06-03-2008 04:41 AM
OS: SLES 9 SP 3/4
I configure the system time manually, as
# yast2 timezone
then in Region, select "Etc"
then in Time Zone, select "GMT +6"
then Hardware Clock set To UTC
then configure the time 17:07
# date
Tue Jun 3 17:07:57 GMT+6 2008
OK,
after manually configuring, I ran the following command
# rcntp stop
# ntpdate clock.nc.fukuoka-u.ac.jp
3 Jun 06:08:36 ntpdate[6693]: step time server 133.100.9.2 offset -39596.070956 sec
# ntpdate clock.nc.fukuoka-u.ac.jp
3 Jun 06:08:43 ntpdate[6694]: adjust time server 133.100.9.2 offset 0.006033 se c
# ntpdate clock.nc.fukuoka-u.ac.jp
3 Jun 06:08:48 ntpdate[6695]: adjust time server 133.100.9.2 offset 0.009886 se c
# ntpdate clock.nc.fukuoka-u.ac.jp
3 Jun 06:08:55 ntpdate[6696]: adjust time server 133.100.9.2 offset -0.008568 s ec
now problem is that after configuring the time via ntp server(clock.nc.fukuoka-u.ac.jp or any other ntp server, in Asia) the time of my machine(sles10 sp 1/2, sles 9 sp 3/4) goes almost 11 hours BACK, i.e
# date
Tue Jun 3 06:08:57 GMT+6 2008
why the time is 06:08 instead of 17:08 ? why system time goes 11 hours back ? please help
Regards
Maaz
Solved! Go to Solution.
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тАО06-03-2008 06:06 AM
тАО06-03-2008 06:06 AM
Re: time changes, when configured as ntp client
├В┬┐Are you sure that your hardware clock is using UTC time?
>> then configure the time 17:07
You don't have to configure the time, you just need to run ntpdate. If the time adjusted by ntpdate does not match the time you need, your timezone is not correct.
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тАО06-03-2008 06:11 AM
тАО06-03-2008 06:11 AM
Re: time changes, when configured as ntp client
The ntpdate command works using UTC time, and that's what all Unix and Linux timekeeping internally uses. So the ntpdate command sets your system clock to correct UTC time (you can verify this by using the "date -u" command) but the mapping from UTC to local time is wrong.
Until now, the wrong mapping has hidden a big error in the UTC time value.
MK
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тАО06-03-2008 10:42 PM
тАО06-03-2008 10:42 PM
Re: time changes, when configured as ntp client
>Are you sure that your hardware clock is using UTC time?
I dont know ;( ... but atleast I enable/select the "Hardware Clock set To UTC" option.
>If the time adjusted by ntpdate does not match the time you need, your timezone is not correct.
ASIA/PAKISTAN/Karachi is +5 GMT(SEP-MAY), and now a days (daylight saving) its +6 GMT till August. The change puts Pakistan six hours ahead of the GMT.
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тАО06-03-2008 11:03 PM
тАО06-03-2008 11:03 PM
Re: time changes, when configured as ntp client
>Note that "GMT+6" specifies a timezone 6 hours _west_ of Greenwich. All >timezones on the eastern hemisphere should have a minus sign in the >timezone identifier.
YES, you are righrt, I just manually configure the system time WED 4 JUNE 12:55 PM -6 GMT, and then
# ntpdate clock.nc.fukuoka-u.ac.jp
4 Jun 12:57:42 ntpdate[4388]: adjust time server 133.100.9.2 offset 0.003521 sec
# date
Wed Jun 4 12:57:43 GMT-6 2008
# hwclock
Wed Jun 4 12:57:45 2008 -0.000486 seconds
Mutti Kurkela can you please share the reference(url/doc etc) for your following statement:
>All timezones on the eastern hemisphere should have a minus sign in the >timezone identifier
and what should I do now ? I mean should I configure my system timezone as -6 GMT ?
Regards
Maaz
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тАО06-03-2008 11:06 PM
тАО06-03-2008 11:06 PM
Re: time changes, when configured as ntp client
>Until now, the wrong mapping has hidden a big error in the UTC time value.
I think I must report this BUG to novell ... should I ?
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тАО06-03-2008 11:38 PM
тАО06-03-2008 11:38 PM
Re: time changes, when configured as ntp client
>> I dont know ;( ... but atleast I enable/select the "Hardware Clock set To UTC" option.
The question is asking you if you have UTC time in your bios instead of local time. If so, select yes.
And probably yes, you should use -6. Sometimes, as said above, the time zone "name" or location does not match the time offset.
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тАО06-04-2008 02:32 AM
тАО06-04-2008 02:32 AM
Re: time changes, when configured as ntp client
>...if you have UTC time in your bios instead of local time.
ooopps again a strange issue ...
Ivan I found that when I check the system BIOS, BIOS always shows the time almost 6 hours ahead.
i.e when system shows
# date && hwclock --show
Wed Jun 4 16:20:46 GMT-6 2008
Wed Jun 4 16:20:46 2008 -0.000461 seconds
then init 6
The BIOS shows the time Wed Jun 04 22 23 03
now again just after login
# date && hwclock --show
Wed Jun 4 16:27:20 GMT-6 2008
Wed Jun 4 16:27:21 2008 -0.000450 seconds
you can see the BIOS time is almost 6 hours in advance/ahead.
but the hwclock and date shows the same time
>the time zone "name" or location does not match the time offset.
is there any workaround ? how can i fix it ? for our environment this is very important.
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тАО06-04-2008 03:17 AM
тАО06-04-2008 03:17 AM
SolutionAfter running ntpdate, you should run "hwclock --systohc --utc" to update the BIOS clock to the correct UTC value. The "--utc" option is important here. The /etc/adjtime file tells the system whether the BIOS clock is supposed to be in local time or UTC time: if this file is wrong, the "--utc" option corrects it automatically.
Unfortunately, some distributions store the information "BIOS clock is running in local/UTC time" in some other location too; you should make sure that both /etc/adjtime and that other location are in agreement, otherwise strange things may happen.
In Linux, the system clock (visible using "date" or "date -u") is created by the OS. It's completely separate from the hardware-based BIOS clock that keeps time when the system is shut down.
Very early in the Linux boot process, the system clock gets its time from tha BIOS clock. If you run ntpd, it will automatically synchronize the BIOS clock to the (NTP-corrected) system clock. If you just use ntpdate, you must synchronize the BIOS clock manually (using the hwclock command) whenever you change the system time.
If your timezone is 6 hours ahead of the GMT time, you should specify it in all Unix systems as GMT-6, not as GMT+6.
You can check the timezone conversion rules using the "zdump" command. It prints time values in UTC and the matching times in the local time of the timezone you specify.
For example:
# zdump -v Etc/GMT+6
Etc/GMT+6 Fri Dec 13 20:45:52 1901 UTC = Fri Dec 13 14:45:52 1901 GMT+6 isdst=0 gmtoff=-21600
Etc/GMT+6 Sat Dec 14 20:45:52 1901 UTC = Sat Dec 14 14:45:52 1901 GMT+6 isdst=0 gmtoff=-21600
Etc/GMT+6 Mon Jan 18 03:14:07 2038 UTC = Sun Jan 17 21:14:07 2038 GMT+6 isdst=0 gmtoff=-21600
Etc/GMT+6 Tue Jan 19 03:14:07 2038 UTC = Mon Jan 18 21:14:07 2038 GMT+6 isdst=0 gmtoff=-21600
As there are no DST rules in the generic "GMT+6" specification, the command displays the times from the beginning of the known DST data (December 13 1901) to the end of the traditional Unix time_t epoch (Jan 19 2038).
As you can see, "GMT+6" means that the time is 6 hours _behind_ of UTC/GMT, not 6 hours _ahead_.
If you're located in a timezone 6 hours _east_ of Greenwich, you should configure your timezone settings to "GMT-6". This is just how the POSIX timezone designation works: the signed number is what you must add to your local time to get the GMT time, not vice versa.
Reference:
http://www.twinsun.com/tz/tz-link.htm
(see the end of the paragraph "Time Notation")
MK
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тАО06-04-2008 11:22 PM
тАО06-04-2008 11:22 PM
Re: time changes, when configured as ntp client
>After running ntpdate, you should run "hwclock --systohc --utc" to update the >BIOS clock to the correct UTC value.
I ran the ntpdate, then "hwclock --systohc --utc", but still BIOS shows the wrong time.
date and hwclock always shows the same time.
# date && hwclock
Thu Jun 5 13:12:39 GMT-6 2008
Thu Jun 5 13:12:39 2008 -0.000485 seconds
---
# cat /etc/adjtime
0.000000 1212649604 0.000000
1212649604
UTC
>If your timezone is 6 hours ahead of the GMT time, you should specify it in all >Unix systems as GMT-6, not as GMT+6
I think these Unix peoples don't have Bosses[ atleast My boss doesn't agree on -6 GMT :( ].
>If you're located in a timezone 6 hours _east_ of Greenwich, you should >configure your timezone settings to "GMT-6"
OK, it means if i am located 6 hours behind of GMT, then only I can use GMT+6.
here is output of
# zdump -v GMT-6
GMT-6 Fri Dec 13 20:45:52 1901 UTC = Sat Dec 14 02:45:52 1901 GMT isdst=0 gmtoff=21600
GMT-6 Sat Dec 14 20:45:52 1901 UTC = Sun Dec 15 02:45:52 1901 GMT isdst=0 gmtoff=21600
GMT-6 Mon Jan 18 03:14:07 2038 UTC = Mon Jan 18 09:14:07 2038 GMT isdst=0 gmtoff=21600
GMT-6 Tue Jan 19 03:14:07 2038 UTC = Tue Jan 19 09:14:07 2038 GMT isdst=0 gmtoff=21600
Regards
Maaz