Shammerism

2018-08-28 Does NTP work correctly with enabled Tokyo Daylight Saving Time?

Does NTP work correctly with enabled Tokyo Daylight Saving Time?

I have heard that there is a possibility to start summer time, Daylight Saving Time, at Tokyo within years, around Tokyo Olympic. So I investigated if ntpd would work under daylight saving time at Tokyo.

The ntpd module of almost Linux distributions are referring /etc/localtime, which is a timezone file itself or symbolic link of any timezone files.

root@server:~# file /etc/localtime 
/etc/localtime: timezone data, version 2, 3 gmt time flags, 3 std time flags, no leap seconds, 9 transition times, 3 abbreviation chars
root@server:~#  cat /etc/issue
Debian GNU/Linux 8 \n \l

#

And all zone files are saved at /usr/share/zoneinfo.

root@server:/usr/share/zoneinfo# ls
Africa	    Atlantic   Canada  EST5EDT	Factory  GMT-0	    Iceland  Japan	MST7MDT  PRC	   ROC	      UCT	 WET		    posix
America     Australia  Chile   Egypt	GB	 GMT0	    Indian   Kwajalein	Mexico	 PST8PDT   ROK	      US	 Zulu		    posixrules
Antarctica  Brazil     Cuba    Eire	GB-Eire  Greenwich  Iran     Libya	NZ	 Pacific   Singapore  UTC	 iso3166.tab	    right
Arctic	    CET        EET     Etc	GMT	 HST	    Israel   MET	NZ-CHAT  Poland    SystemV    Universal  leap-seconds.list  zone.tab
Asia	    CST6CDT    EST     Europe	GMT+0	 Hongkong   Jamaica  MST	Navajo	 Portugal  Turkey     W-SU	 localtime
root@server:/usr/share/zoneinfo# 

Some of zone has 2 files, for example, EST and EST5EDT. One is DST timezone file, and the other is not DST timezone file. Those of them are binary file and I'm not sure how to read it. But, Tokyo zone file is only one.

root@server:/usr/share/zoneinfo# ls Asia/
Aden	   Baghdad  Calcutta	Dhaka	     Hong_Kong	Kamchatka    Kuala_Lumpur  Muscat	 Pyongyang  Seoul	   Tel_Aviv	  Urumqi
Almaty	   Bahrain  Chita	Dili	     Hovd	Karachi      Kuching	   Nicosia	 Qatar	    Shanghai	   Thimbu	  Ust-Nera
Amman	   Baku     Choibalsan	Dubai	     Irkutsk	Kashgar      Kuwait	   Novokuznetsk  Qyzylorda  Singapore	   Thimphu	  Vientiane
Anadyr	   Bangkok  Chongqing	Dushanbe     Istanbul	Kathmandu    Macao	   Novosibirsk	 Rangoon    Srednekolymsk  Tokyo	  Vladivostok
Aqtau	   Barnaul  Chungking	Gaza	     Jakarta	Katmandu     Macau	   Omsk		 Riyadh     Taipei	   Tomsk	  Yakutsk
Aqtobe	   Beirut   Colombo	Harbin	     Jayapura	Khandyga     Magadan	   Oral		 Saigon     Tashkent	   Ujung_Pandang  Yangon
Ashgabat   Bishkek  Dacca	Hebron	     Jerusalem	Kolkata      Makassar	   Phnom_Penh	 Sakhalin   Tbilisi	   Ulaanbaatar	  Yekaterinburg
Ashkhabad  Brunei   Damascus	Ho_Chi_Minh  Kabul	Krasnoyarsk  Manila	   Pontianak	 Samarkand  Tehran	   Ulan_Bator	  Yerevan
root@server:/usr/share/zoneinfo# 

So, at the current release, there is no way to enable DST in Tokyo on the ntpd, I believe.

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トラックバック - http://d.hatena.ne.jp/shammer/20180828/p1