  The Clock Mini-HOWTO

  Ron Bean, mc864mclink.it <mailto: rbean@execpc.com>

  Dec. 1996
  :    sanghoon_rhee@geocities.com <mailto:
  sanghoon_rhee@geocities.com>

  2000 1

  How to set and keep your computer clock on time.  ǻ ð踦
    ̸  Ȯϰ  ΰ.

  ______________________________________________________________________

  

  1. 1.  Ұ
  2. ``clock'' α׷ 
     2.1 ġ¸ Ȯ
     2.2 ý ð  (drift rate) Ѵ.
     2.3 
        2.3.1 ð ߱
        2.3.2 ð ʱȭ ϰ ð  (drift rate)  ȮѴ.
        2.3.3   (correction factor)  Ѵ.

  3. xntpd ؼ

  ______________________________________________________________________

  1.  1.  Ұ

  ο ǻ  忡 ޷ ִ ǽð ð (Real-time Clock,
  RTC)  Ȯ ϱ  ѵ, ̰  ũ̶̼ ؼ
  ܰ ƴմϴ.  ̷ Ȳ,  Ư
  ϵ ܺο ִ Ÿ     ǻ ð踦
  *ſ* Ȯϰ   ִ Ʈ  մϴ.
  κ     𸣰 ִµ ̰ Ƹ   
  ̶ մϴ:

  1.      ִ `` ġ ''   
      ʰ, ġ     Ȯ ð ߴ  Ʊ
     ̴. ( ̳ Ʈũ ī ޷ ִٸ  Ұ
       ƴմϴ)

  2. ``man clock''  Է   clock(3) شϴ 
     µ, ̰ clock Ŀǵ忡   ƴϴ. (``man 8
     clock'' ̶ ؾ clock Ŀǵ忡   ɴϴ)

  3. 밳  Ȯ ð ״ Ű澲 ʴ´.

  4. Ϻ ű⿡ Ű澲  louie.udel.edu  xntpd Ű
     ͼ Ʈũ Ÿ  (ǥ  ú    ִ)
      ð ϵ ̿ؼ ð .

      mini-HOWTO      ϴ
     Դϴ.  ̷ ڽ ϴ  ƴ϶ ϴ е
     <www.eecis.udel.edu/~ntp/ <http://www.eecis.udel.edu/~ntp/>> 
     湮ؼ Ⱦ ʽÿ.  Ʈ xntpd   
     NIST(1)  USNO(2)  ũ  ̷ο ڷḦ ϰ
     ֽϴ. (   xntpd   ణ   
     ξϴ).

     ϳ̻ ü ϴ 迡,  ü
  ΰ θ ȥŰ   ϳ ü ð
  ߾ մϴ.  迡    Ͽ
  ϴ      ð ȭ α׷
       ֽϴ. (  URL )

  2.  ``clock'' α׷ 

   ʿ  clock(8) Ŵ   ϰ ,
  ⼭  ü   ڽϴ.

     ``clock'' α׷̳ Ÿ Ŀνð質 CMOSð迡  
  α׷ ݵ Ʈ ؾ ȿ ֽϴ.

  2.1.  ġ¸ Ȯ

  ý õ ũƮ ϵ  ``clock -a''  ``clock -ua'' 
   ϴ  ִ Ȯմϴ. ýۿ ġ ǿ 
    /etc/rc.local  ֱ⵵ ϰ /etc/rc.d/rc.sysinit  ٸ
   Ͽ   ֽϴ.

    ϵ鿡 ``clock -s''  ``clock -us''   ִٸ
  ``s'' ``a''  ϰ /etc/adjtime ̶  ִ
  Ȯմϴ.    뷫    ٿ  
  Դϴ:

  0.000000 842214901 0.000000

   ڸ  ڸ, ù° ڴ `' (Ϸ翡  ʾ
  ð谡 Ʋ °), ι° ڴ  ð豳   (1970
  1 1 0  귯 ʸ ϴ), ° ڴ 
  ð豳 ʴ   󸶳  ߴ° ϴ Դϴ. 
  /etc/adjtime ̷  ٸ Ʈ α     
    0  ǰ ؼ  ݴϴ:

  0.0 0 0.0

    ``clock -a''  ``clock -ua''    Էϸ 
  2° ڰ ˴ϴ. ý ð谡 ǥؽ (UTC Ȥ GMT)
  Ѵٸ ``u'' ְ ׷  ׳ ``a'' ɼ ݴϴ.

  2.2.  ý ð  (drift rate) Ѵ.

  , ð ؼ    ʿ䰡 ְ :-) ? 츮 
  ľϰ ִ  ð Ȯ  ְ Ȯ  
  ֽϴ.  ڴ (303)499-7111  ȭ ؼ WWV (3)  
  ȳ ̿ϴ  մϴ ( ȣ Ÿ ȭԴϴ).
  Ʈũ Ÿ    ִٸ xntpd Ű ԵǾ ִ
  ntpdate α׷ ϸ մϴ. (ntpdate   -b
  ɼ   Ŀ CMOS ð踦 ߸ ǵ帱  ֽϴ).

  ƴϸ ``date -s hh:mm:ss''   Էؼ Ŀ ð踦  
  ִµ ̷ ϰ  ``clock -w''  ָ Ŀ ð踦 
  CMOS ð踦 ߰ ˴ϴ.  ð ٲ   
   ξ ϴ ٲٰ  ٷ ð Ȯؼ  Ӵϴ.
  ntpdate   ``date +%s''  ؼ  ڸ
   Ӵϴ. (  1970 1 1 0  귯 Դϴ)

  ׷   ̳  ֵ ذ ٰ ٽ ƿͼ ð
  󸶳 Ʋ Ȯմϴ. ntpdate  ʰ ۾
  ð ٸ ּ 2  ̻   Ȯϴ  ϴ.
     0.1  ݿø ؼ ϴ.    
    Ѵٸ  0.01  Ȯϰ   ֽϴ.
  (  ̰ͺ    ŷ  ִٰ մϴٸ, ణ
   ϴ  ).  ntpdate ϴ 
  ׷  ٸ ʿ ,   ߰   ð
  ڿ ѹ  ð ϴ   ʿմϴ.

  cron ̿ϸ ``clock -a'' ֱ ؼ Ŀ ð踦
  CMOSð迡 ġ Ű   ֽϴ.    õ ũƮ
  򰡿  ֱ    ý     ˴ϴ.
     Ѵٸ װ ε CMOS ð Ŀ ð踦 
    ġ Ű ȿ   ֽϴ.  (  ϴ
   ?)

   α׷ Ŀ ð谡 ѹ 1 ̻ ǰų Ŀ ð谡
  ڷ   ޽ ⵵ մϴ. ̷    xntpd
  ntpdateα׷ ؼ, Ŀνð谡   CMOS ð
  ġ ǰ    ֽϴ.

  2.3.  

  2.3.1.  ð ߱

  , Ʈ α մϴ. (303)499-7111 (3) ȭ ɾ ú
  ȳ ϴ. ׸   Էϰ (Ű̸ ġ 
  ä) ٸϴ:

  date -s hh:mm:ss

  úȳ ''Ҹ  Ű̸ ϴ. (⼭ ``date''
  ƴ϶ ``ntpdate'' ϴ  ȭɰ '' Ҹ ٸ
  ϴ     ʿ䰡 ϴ).  ̷ ϸ ``Ŀ ð''
  ο  ˴ϴ.     Էմϴ;

  clock -w

  ̷ ϸ CMOS ð踦 Ŀ ð迡 ϴ.    
  Էմϴ:

  date +%j

  ׸ µǴ ڸ   ؼ   Ӵϴ.  (
  ``date'' ``ntpdate'' ߴ ̶ ``date +%s''
  մϴ)

  2.3.2.  ð ʱȭ ϰ ð  (drift rate)  ȮѴ.

     ¥ Ȯմϴ.   Ʈ α ؼ 
   Էմϴ:

  clock -a ȭ ɾ ú ȳ 鼭,   ԷѴ:
  ̷ ϸ Ŀνð踦  CMOS ð迡 ϴ.  (303)499-7111 (3)
   ȭ ɾ ú ȳ 鼭,   Էմϴ (
  Ű̸  ʽϴ):

   date

  `' Ҹ ٸ  ú  ˷ִ ð  
  Ӵϴ. ׸ `' Ҹ  ͸ Ĩϴ. ,  ȭ
   ȵ˴ϴ. ̷ ؼ ð (ú `' Ҹ  )
  Ŀ ð (date   µ ð) 󸶳 ̰  Ȯ
    ֽϴ.  ,    Էմϴ:

   date hh:mm:00

      ú   ִ ں 1  
     ʽÿ.  ٲ  `' Ҹ  Ű
  Ĩϴ. (  ȭ  ˴ϴ). hhκп ø
  ϴ.   ``Ŀ ð'' ߴ Դϴ.   
   Էմϴ:
   clock -w ̷ ϸ ο ( Ȯ) Ŀ ð谪 CMOS ð踦
  ϴ.  

  date +%j

   Էմϴ. (  ``date +%s''  ٸ ⼭ 
    ϴ).

  ̷ ϸ  (drift rate) ϱ  ʿ 3 ġ
  ( ¥ 2  ʴ )  Ȯ  ˴ϴ.

  2.3.3.    (correction factor)  Ѵ.

  ``date'' ؼ ð  , ý ð ?
  ƴϸ  ? ð ٸ    󸶰 
  ־ ϹǷ   ˴ϴ. ð  ִٸ  
   󸶰   ־ ϹǷ   ˴ϴ.

  տ  2 ¥  մϴ. ``date +%j''  
     ׳ 1   ° ̾° ϴ  ˷ ݴϴ.
  (  1   365      1   366 
   ɴϴ).  ð    1 1 ̾ٸ 
  ° ¥ ( ¥) 365 366 ؼ  ؾմϴ.

  ``date +%s''    1970  ؼ  
  Ƿ ׳       86400  ָ 
    ̿ 귯 ¥ ڿ ɴϴ.

  /etc/adjtime ̹   ִ    
     մϴ.  ( ġ) ʹ Ǵٸ 
          ȣ ٸ Դϴ.
  ׷ ʴٸ  ȣ ǰ.     
  ϰ,   ʴ    մϴ. (  ȣ 
   ʽÿ. ȣ  ٸ      ۾
  մϴ.  ׷ ʴٸ     ū  )

  ̷  ' '    ο 
  ɴϴ.   /etc/adjtime ڱ ڸ  ֽϴ. ο
  ¥ () (   )  ξ  
  մϴ.

   ý /etc/adjtime   ϴ:

  -9.600000 845082716 -0.250655

  (Ϸ翡 9.6ʶ  Ѵ̸  5  ǹմϴ!)

  3.  xntpd ؼ

  ǻͿ δ 2 ð谡 ֽϴ. ϳ  Ǵ
  ``ǽð ð(real time clock)'' ̶ ε ý   
   ư鼭 ð ϰ ֽϴ. (ٸ δ ``CMOS ð'',
  ``ϵ ð'', ``RTC''  մϴ) ι° ``Ŀ ð'' ε
  ̰ ó  ÿ CMOS ð迡 ؼ    Ÿ̸
  ͷƮ ؼ ŵ˴ϴ. (̰ ``Ʈ ð'' Ǵ
  ``ý ð''  մϴ).      ݾ,  ٸ
   Ʋ  ð     Ȯ ð ̰ Ŀ
   Ӹ ƴ϶       ̰ Ŀ ˴ϴ.

  xntp  ``ð (the clock)'' ̶    ``Ŀ ð''
  ǹϰ ֽϴ. xntp timed (Ǵ adjtimex() ý  ϴ
  ٸ α׷)  ϴ , Ŀ ð谡 CMOS ð  
  Ȯϴٰ ϰ  11  CMOS ð踦 ٽ ϴ. (ý
   ϱ   ˴ϴ). ٽ ؼ ``clock''   
  CMOS ð谡   Ǿ   , /etc/adjtime  
       ȴٴ Դϴ.
  Xntpd  ϵ ` ð (radio clock)' ġ 
  ϹǷ, ֱ NIST  ϴ ú 񽺿 ȭ Ͽ
  ð   ְ Ǿ ֽϴ. (ȭ Ŵ ð  
   ȭ ݿ Ű ʽÿ.) ̰ (xntpd)   ð
  ̻ (NIST ) ܺ ú     Ȳ 
    ̿ؼ Ŀ ð踦    ְ Ǿ ֽϴ.

  밳 ` ð' ġ 3000 4000 ޷  , 
  ``ġ (gadget box)'' (δ 300 baud )  ý۰
  ĳ CHU ú ̾     ؼ 
    ֽϴ. (<ftp://ftp.udel.edu/pub/ntp/gadget.tar.Z> 
  Ͻʽÿ). Heathkit WWV ű (`` Ȯ ð''   ϴ
  ǰ)    ִµ ̰  400 500 ޷  մϴ.  GPS
  ȣ ð  ϰ հ  GPS ű ǻ 
  Ʈ   ְ Ǿ ֽϴ.  巡 ̷ GPS ű⸦
   ݿ   ְ   𸨴ϴ.

  ̷д ڸ, NIST ȭ ú 񽺿 ڵ ؼ
   ڵ ϰ CMOS ð Ŀ ð踦 ڵ  
  ִ α׷  ͵ մϴ.  ̷  
  α׷  ,   Ѵٸ xntpd ҽ 
  ص κ      Դϴ.

  1) NIST : National Institutes of Standards and Technology, ̱
  ǥر

  2) USNO : U.S. Naval Observatory  ر 

  3) WWV : NBS (̱ ǥر) ϴ, ǥ ú ۱ ȭ
   ú ȳ 񽺵 ϰ ֽ. ѱ  116 ȭɸ
  ú ȳ ɴϴ.

  --̻--

