








			 p]wPǽTq

		       @: Ron Bean, rbean@execpc.com

		   Ķ: Da-Wei Chiang, dawei@sinica.edu.tw

		   v, December 1996 ½Ķ: 2-16 July 1998



				   Abstract

     p]wPǽTq.



1.  

ӤHq(ƦܩQu@)DOWҨϥΪ real-time-clock
ǽTOҬҪƱ.  M Linux
@~tδѤF@²檺kӮեoӤǽTq,
ϱoqNOʿ~ծɷ]iHF *۷* ǽTaB.
OGjhƤH٤DoӤk, ]pU:

  1.   b@ ``p]w linux @~t'' 󤤨åzγoӤk,
      ӥBbw˧@~tήɫ۰ʦa]w (OzפWäOi઺,
      pGA@xƾھ).

  2.   YAϥ``man clock''Ӭdݳ]w, Ai|oDw
      clock(3) e.  (յۨϥ``man 8 clock'').

  3.   GjhƤHäbN{bTɨOh.

  4.   ǤּƦbNH|ĥ louie.udel.edu ҴѪ xntpd
      {HKP~ծɷ, ҦpծɦAεLuqH, oPB.

pGU糧zC]wk۷ת,
ڱjPĳUǮɶs<URL:http://www.eecis.udel.edu/~ntp/> ,
oӺۦUAҷP쪺e,Ҧp xntpd TH  NIST P USNO
xWs.  (ڦb᭱] xntpd @Fǳ\².)

      `N
	    pGAbP@xW]hӧ@~t, Aӥu䤤@Өӭs]w
	    CMOS , pפ|ۤvTӾɭPV.
	    ϧA`bP@xW] Linux M Windows Gا@~t,
	    ӷAnM@Ǧ@ɪծɵ{KɥiH Windows @~tΪ
	    (ѦҫeһWs).


2.  ϥ``clock''{

ҦAnDeb clock(8) , ӥNaU짹ӳ]w{.


p]wPǽTq						      1





p]wPǽTq						      2



      `N
	    n``clock''άO䥦|vTtήɶM CMOS {,
	    A֦ root v.

2.1  ˬdA@~t

ˬdA@~tΪ}ɤO_``clock -a'' ``clock -ua''RO.
oөROib /etc/rc.local , /etc/rc.d/rc.sysinit , Ψ䥦a,
onݧAw˪O@M Linux @~t.

pG쪺ROO ``clock -s''  ``clock -us'' , бN ``s'' 令 ``a'' ,
ˬdݬݬO_ /etc/adjtime oɮ, ɮתeu@ݰ_ӹOo:

     0.000000 842214901 0.000000

oǼƦŗǬOե]l (CѰt), W@եɶ ( Jan 1, 1970
}l_⪺), W@եҦ.  pGA䤣oɮ, ХH root
ͦɮ, 䤺eu@ݰ_ӹOo (Os):

     0.0 0 0.0

MzL shell ʰ ``clock -a''  ``clock -ua'' HKsĤGӼƦr
(pGAQ]wհڮɶӤOaɶ Aoϥ ``u''oӰѼ).

2.2  qtv

AoD{b쩳OXI :-).  AaɶiOǽT.
ڳ̳wkOqܨ WWV  (303)499-7111 qܳɥx (oOӥIOq).
pGAPծɦAsWu, A]iHϥ xntpd {ҴѪ ntpdate
{Ӯծ (ϥ -b ﶵHקKtΧ˶ CMOS ).  Ϊ̨ϥ ``date -s
hh:mm:ss'' Hʤ覡]wtή, ר@ؤk᳣̫oϥ ``clock -w''
NtήɶgJ CMOS .  AOo̫@]w,
ҥHAoNӤgUөb|򥢪a.  pGAϥΪO ntpdate {, 
``date +%s'' MgU۱q Jan 1,1970 _ӵ{檺.

MᵥݴXѩδXӬPᤧA^Ӭݬݮ쩳tFh֮ɶ.
pGAHʪ覡]w, ĳܤֱoݤGӬP,
AӭptvNioͪ .1 sec/day G.  XӤ뤧᰾tvӷ|ͪ
.01 sec/day (ǤHźӧǽT, OڭӤHOdA).  pGAϥ ntpdate
{ӳ]wAiणݤӤ[ɶ,
MӤרϥΨؤ覡᳣oǷLժu@.

AiHϥ cron b@wɶP ``clock -a'' HKtήɶP
(եL) CMOSɶ@P.
bAC}ɭԳ|q}ɨӰoөRO,
Mӥun``WoӰʧ@NiHFAǽTɶت.

`NpGtήɶץ@WL@άOɶ^ץ, ǨtΪ clock
{i|Lk.  pGAo譱D, hiHϥ xntpd  ntpdate {
ӳvBaץɶ.

2.3  










p]wPǽTq						      3



2.3.1  ]wɶ

ñJtΨæ root.  qܦ (303)499-7111 (y), Ӳťɪe.
MϥLXUXӦr:

     date -s hh:mm:ss


@ͪ@n׫U enter .  (pGbBϥ ``ntpdate'' {,
hAiHٲqܪʧ@) oӨBJb]w ``tήɶ''.	۰:

     clock -w


oӨBJNtήɶg^ CMOS G̮ɶ@P.  ۰:

     date +%j


(pGbeϥ ``ntpdate'' {Ao ``date +%s'') N檺GOU.

2.3.2  s]wɶPˬdtv

XAWgUӤ.  ñJtΨæ root.  M:

     clock -a


oӨBJN CMOS ɶgJtήG̮ɶ@P.  qܦ (303)499-7111 (y),
Ӳťɪe.  ۨϥLXUXӦr:

     date


@ͪ@n׫U enter , OAݪɭ, gUɪe,
åB٤nWq.  oӰʧ@OADثeuɶOXI,
Ӧɬ۹AWɶOXI.  {bϥLXUXӦr:

     date -s hh:mm:00


䤤wҳ]wƦrNOثeɤe *᪺* U@,
@ͪ@n׫U enter  ({biHWqܤF).   hh
hϥξaɰwƦrYi.  oӨBJb]w ``tήɶ''.  M:

     clock -w


Ns (եL) tήɶg^ CMOS .  M:

     date +%j


(άO ``date +%s'' )








p]wPǽTq						      4



A{bWTӼƦr (GӮեΤ@ӥTɶ) OAiH}lpⰾtvF.

2.3.3  pե]l

AbY@ ``date'' {, AaɶOC٬O֩O?  pGO֤F,
ANh@ǬƥHŦXTɶ, ҥHAӼgU@ӭttƭ.
pGOCF,AN[W@ǬƥHŦXTɶ,
ҥHAӼgU@ӥtƭ.

{bNGӮե۴.  pGeAϥΪO ``date +%j'',
hƭȩҥNNq@~ĴX (1-365,  1-366 pGO|~).
pG۱qAW@]w{bgL1 1 AٶnNĤGӮե[ 365 (
366) pGeAϥΪO ``date +%s'' hƭȪ쬰, ANH 86400
HKo.

pGAɮ /etc/adjtime wgե]l, ANewեLƦҼ{i,
pGAեL, oӮե]ltNPAq찾tƭȬۤ;
pGAեhG̥tۦP.  Nªե]lH,
M[Wsot (-- pGG̥tۦP,
ANo@Ӹjtƭ, pGG̥tۤ, ANo@Ӹptƭ).

۱No`tưHƥHKosե]l, MNɮ /etc/adjtime
ªե]lNs.  ̫gUsե (HƩΤƬ)
HKUϥ.

o̬Oڪ /etc/adjtime ɮפe:

     -9.600000 845082716 -0.250655


(`NC 9.6 h@ӤN 5 t!)


3.  xntpd ²

AtιڤWGӮ-- @ӬOt~ϥιqqOpɥ\઺
``real time clock'' (]NOҿת ``CMOS '', ``w'',  ``RTC'')
ӥt@ӬO ``kernel clock'' (ɺ٬ ``n''  ``tή'')
tήʬOHpɾ_HǨæb}ɱqCMOS BJl.
oGӮPɶtv, ҥHGӮWɶ|vaͰt, ӥB]|P
``u''ɶͰt.

b xntpd 󤤩ҭzΪ ``the clock'' NO ``kernel clock''.	A xntpd
 timed { (άOLϥΨ adjtimex tΩIs{) linux
@~tη|wtή CMOS ǽT, ӥB|b}Cj 11 s]w@
CMOS ɶ (@쭫}).  oN ``clock'' {ADW@s]w
CMOS Tɶ, ҥHAiHϥɮ /etc/adjtime ե]l.
AiHb}ɤWϥ ntpdate { HKb즸 xntpd
{ePծɦA.  pGAb}ɭԤ@LksWǽTծɷ,
oi|A{@ǧx-- ڤW xntpd OQ]pӦbرpUϥΪ.

Xntpd ]tF\hLuqXʵ{, åB]iHQ]wb@wPqܦ
NIST qܼqծɪA
(A]wnqܼP̦np@Uqܱb檺O).








p]wPǽTq						      5



bPLծɷhp@qɶoӤ覡]ണѨtή@Ӯե]l.

jLuqjnO $3-4K, LAiHĥθKy ``gadget box'' 
(ڤWO@ 300 baud ƾھ) LQbAqP@xuiLuq
WDզ Canada  CHU ծɵLuqx (Ѩ}
<URL:ftp://ftp.udel.edu/pub/ntp/gadget.tar.Z>).  Heathkit WWV 
(``̷ǽT'') MR (O@ծM), jnO $4-500.  ثeGPS
T̤M]tծɪT, ӥB GPS iHWqC.
b̪񪺥ӳoi|C쪺ѨM.

zפW, @HiHۤvg{Өϥ NIST qܼqծɪAȥHK۰ p
CMOS Ptήtv.  MڤDO_W{Foӥت,
Oj{XӥiHɥΦ xntpd {.

















































p]wPǽTq						      6





































































				   CONTENTS



1.  ..................................................................... 1

2. ϥ``clock''{ ........................................................ 1
   2.1 ˬdA@~t ..................................................... 2
   2.2 qtv ..................................................... 2
   2.3  ................................................................. 2

3. xntpd ² ............................................................... 4












































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