Managing Accurate Date and Time

Avi Alkalay

IBM Linux Impact Team :: ibm.com/linux <http://ibm.com/linux>
Linux, Open Standards consultant :: Senior IT and Software Architect

avi at unix.sh
avi at br.ibm.com

Brad Knowles - pool.ntp.org  NTP stratum 2 J^CT[o̗pɊ
鎦

Kent Borg - ntpdc ̑ ntpq 𗘗pƂ̎

Yura Moron - ntpq  ntpdc ̏Ɋւǂ

앐Y - {

nakano at apm.seikei.ac.jp
 

SHAKI - VA

sha-ki at narod.ru

Copyright (C) 2002,2003 by Avi Alkalay

1.0.6 :: 2004-02-25

Revision History                                                       
Revision 1.0.6           25 Feb 2004         Revised by: avi           
Included credits and link to russian translation.                      
Revision 1.0.5           05 Jul 2003         Revised by: avi           
Changed public time servers list URL. Added pool.ntp.org.              
Revision 1.0.4           21 Dec 2002         Revised by: avi           
Added japanese translation link and credits.                           
Revision 1.0.3           24 Aug 2002         Revised by: avi           
Fixed wrong screen and programlisting widths.                          
Revision 1.0.2           04 Aug 2002         Revised by: avi           
Link to public time servers page.                                      
Revision 1.0.1           07 May 2002         Revised by: avi           
Final XML conversion. Files reorganization.                            
Revision 1.0             28 Apr 2002         Revised by: avi           
Finalized image.                                                       
Revision 0.8             27 Apr 2002         Revised by: avi           
Switched from ntpdc example to ntpq, based on contributions.           
Revision 0.8.1           20 Apr 2002         Revised by: avi           
Improved graphic. Links to other doc locations.                        
Revision 0.8             14 Apr 2002         Revised by: avi           
Beter tunning of NTP graphic.                                          
Revision 0.76            13 Apr 2002         Revised by: avi           
Inclusion of architecture graphic.                                     
Revision 0.75            10 Apr 2002         Revised by: avi           
Spell checked. Using DocBook XSLT 1.50.                                
Revision 0.65            31 Mar 2002         Revised by: avi           
Upgraded to XML 4.1.2 DocBook format                                   
Revision 0.6             29 Mar 2002         Revised by: avi           
Finished timezone mechanism on Linux. Created appendix. Now only       
drawings are needed.                                                   
Revision 0.4             24 Mar 2002         Revised by: avi           
All skeleton defined. All command examples written.                    
Revision 0.2             19 Mar 2002         Revised by: avi           
First DocBook version                                                  

 

Table of Contents
1. Rs[^ɂnł̓tEԂ̈
2. ^C][Ƃ
   
    2.1. T}[^C (Daylight Savings Time, DST)
    2.2. ^C][̗
    2.3. Linux ɂ^C][̎dg
   
3. Linux }V𐳂ݒ肷
   
    3.1. ^C][ݒ
    3.2. n[hEFANbNݒ肷
   
4. mȐEɓ
   
    4.1. NTP: lbg[N^CvgR
    4.2. ȒPȎ\\z
    4.3. NTP ̐ݒ
    4.4. ̊mF
    4.5. NTP u[gɎN悤ݒ肷
   
A. ̕ɂ

1. Rs[^ɂnł̓tEԂ̈

  n̂nɒuꂽRs[^ݎ肷ɂ́A
̏𐳊mɒmKv܂B

 1.  UTC  (OjbWɂ鐢EB GMT ł͂Ȃ)
   
 2. ̒ň݂̃^C][
   
  Rs[^ɂ̓n[hEFANbNtĂA OS ͎̎
ݒ肷ƂɂƂėp܂B

  OS ̓tƎ (ȍ~ł͓t/̂ꂩ݂̂܂) ͋N
ɐݒ肳܂B炩̃XNvgn[hEFANbNǂ݁A܂^
C][vZ OS ɐݒ肵܂ (BIOS ɂ̓^C][̃f[^͕
Ă܂)B̓ȂĈȍ~́ABIOS ̎ OS ̎
͊SɓƗ̂ƂȂ܂Bł炵΂炭oł́A҂
bقȂ邱Ƃ邩܂Bǂ炪̂ł傤H炩
ݒĂȂAǂ͂܂B

  ł́A̗҂n̂ꏊ 100% mɂ@ɂ
ċc_Ă܂B

 

2. ^C][Ƃ

  ^C][Ƃ́AnnwIɁACMX̃OjbWN_Ƃ
15o Ƃɕ̂łBE̕ʂ̏ꏊł͍Ȃ̂AƂ
킩₷邽߂ɍ܂B

  ߔNł̓^C][́AnwIƂ́AƐIȂ̂ɂ
Ă܂BlX́u߂̐lvƎLꍇ邩ł
B܂ȃGlM[̖ʂAł̓T}[^C (Daylight Savings
Time) pĂA^C][ω܂B

  ^C][͒ʏe̐{V@ւɂĒ`A 3 ܂
4 ŕ\L܂B Section 2.2 ĂB

  E̕ʂ̒nōȂ̂m肽ꍇɂ́A 
timezoneconverter.com <http://www.timezoneconverter.com/>  web TCg
gƂ킩܂B

 

2.1. T}[^C (Daylight Savings Time, DST)

  GlM[ߖ̂߁Ae̐{̓T}[^C݂邱Ƃ܂
B̎v 1 Ԑi߂AɂĒԂȂ悤Ɋ
܂BۂɋNĂ̂́APɃ^C][̕ύXɂ܂B
ƂȂ鎞 (UTC) ͕sςŁAɓłB

  Linux ŃT}[^CIɗLEɂ@ɂẮAق
ĂƂɂ܂B

 

2.2. ^C][̗

  ȏɂ킩₷͂Ȃł傤B

 

Table 1. uW̃^C][ UTC ɑ΂鎞


OƎDST ̖Oꏊ                                        
      Ǝ                                                

BREST   BREDT -1: Fernando de Noronha                         
-2:00   00                                                    

BRST -3:BRDT -2:00So Paulo, Rio, Brasilia, Minas Gerais, North
00                East Region, South Region,etc               

BRWST   BRWDT -3: West Region                                 
-4:00   00                                                    

BRAST   BRADT -4: Acre                                        
-5:00   00                                                    

 

  US ̃^C][ɂāÂ悤ȕ\ǂȂĂ܂
B

 

2.3. Linux ɂ^C][̎dg

  Linux VXe GLIBC ̓Iȃ^C][pĂA /etc/
localtime Ō܂܂B̃t@ĆA][t@Cւ̃
N (܂͂̃Rs[) łB][t@C͒ʏ /usr/share/
zoneinfo fBNgȉɒuĂ܂B

  nwIȊϓ_炢ƁAEɂ 360o/15o=24 ̃^C][
Ηǂ͂łB킩₷邽߁A܂IȕύX (T
}[^CȂ) ɂ킹₷邽߁A /usr/share/zoneinfo ɂ͐S
 zoneinfo t@CuĂ܂Bꂼ͐ÊssE
ȂǂɑΉĂ܂ASȂ̂ł͂܂ (͖ł傤)
B

  ɂĂ (uWł)AT}[^C̊Jnt
ĂȂƂ܂BuWł̓T}[^C͔NƂɌ肳A
Ă 2`3 OɎn܂܂B̏󋵂܂ɂ́Azoneinfo t@C
ŕύXȂ΂Ȃ܂B zoneinfo t@ĆAȉ̂悤
eLXgt@C zic R}hŃRpC邱ƂɂĐ܂
B

Example 1. uW̃][̃eLXgt@C

# Brazil Time Zones                                                           
#                                                                             
# Brazilian Time Zones are:                                                   
# BREST: East of Brasilia. Fernando de Noronha.                               
# BRST:  Brasilia, So Paulo, Rio, Northeast, South etc                        
# BRWST: West of Brasilia. Mato Grosso, Manaus                                
# BRAST: Acre.                                                                
#                                                                             
# In daylight saving time, letter 'S' changes to 'D'.                         
#                                                                             
# To install, make:                                                           
#                                                                             
# # zic Brazil.txt                                                            
#                                                                             
# Zone files will be installed in /usr/share/zoneinfo (depends on your        
# distribution). Then, make a symbolic link from your zone to /etc/localtime: 
#                                                                             
# # ln -sf /usr/share/zoneinfo/Brazil/Brasilia /etc/localtime                 
#                                                                             
#                                                                             
# If you have updates and new standards to this file please send to           
#                                                                             
# Avi Alkalay <avi @ unix.sh>                                                 
#                                                                             
# Last update: 18 Nov 2000                                                    
# This file is available at http://avi.alkalay.net/linux/zoneinfo/            
#                                                                             
                                                                              
# Rule  NAME    FROM  TO    TYPE  IN    ON   AT    SAVE   LETTER/S            
Rule    Brazil  1931  1932  -     Oct   3    0:00  1:00   D                   
Rule    Brazil  1932  1933  -     Mar   31   0:00  0      S                   
Rule    Brazil  1949  only  -     Dec   1    0:00  1:00   D                   
Rule    Brazil  1950  only  -     Apr   30   0:00  0      S                   
Rule    Brazil  1950  1952  -     Dec   1    0:00  1:00   D                   
Rule    Brazil  1951  only  -     Apr   16   0:00  0      S                   
Rule    Brazil  1952  only  -     Mar   31   0:00  0      S                   
Rule    Brazil  1953  only  -     Feb   28   0:00  0      S                   
Rule    Brazil  1963  only  -     Oct   23   0:00  1:00   D                   
Rule    Brazil  1964  only  -     Mar   1    0:00  0      S                   
Rule    Brazil  1965  only  -     Jan   31   0:00  1:00   D                   
Rule    Brazil  1965  only  -     Mar   31   0:00  0      S                   
Rule    Brazil  1965  only  -     Dec   1    0:00  1:00   D                   
Rule    Brazil  1966  1968  -     Mar   1    0:00  0      S                   
Rule    Brazil  1966  1967  -     Nov   1    0:00  1:00   D                   
Rule    Brazil  1984  only  -     Nov   2    0:00  1:00   D                   
Rule    Brazil  1985  only  -     Mar   15   0:00  0      S                   
Rule    Brazil  1985  only  -     Nov   2    0:00  1:00   D                   
Rule    Brazil  1986  only  -     Mar   15   0:00  0      S                   
Rule    Brazil  1986  only  -     Oct   25   0:00  1:00   D                   
Rule    Brazil  1987  only  -     Feb   14   0:00  0      S                   
Rule    Brazil  1987  only  -     Oct   25   0:00  1:00   D                   
Rule    Brazil  1988  only  -     Feb   7    0:00  0      S                   
Rule    Brazil  1988  only  -     Oct   16   0:00  1:00   D                   
Rule    Brazil  1989  only  -     Jan   29   0:00  0      S                   
Rule    Brazil  1989  only  -     Oct   15   0:00  1:00   D                   
Rule    Brazil  1990  only  -     Feb   11   0:00  0      S                   
Rule    Brazil  1990  only  -     Oct   21   0:00  1:00   D                   
Rule    Brazil  1991  only  -     Feb   17   0:00  0      S                   
Rule    Brazil  1991  only  -     Oct   20   0:00  1:00   D                   
Rule    Brazil  1992  only  -     Feb   9    0:00  0      S                   
Rule    Brazil  1992  only  -     Oct   25   0:00  1:00   D                   
Rule    Brazil  1993  only  -     Jan   31   0:00  0      S                   
Rule    Brazil  1993  only  -     Oct   17   0:00  1:00   D                   
Rule    Brazil  1994  only  -     Feb   20   0:00  0      S                   
Rule    Brazil  1994  only  -     Oct   16   0:00  1:00   D                   
Rule    Brazil  1995  only  -     Feb   19   0:00  0      S                   
Rule    Brazil  1995  only  -     Oct   15   0:00  1:00   D                   
Rule    Brazil  1996  only  -     Feb   11   0:00  0      S                   
Rule    Brazil  1996  only  -     Oct   06   0:00  1:00   D                   
Rule    Brazil  1997  only  -     Feb   16   0:00  0      S                   
Rule    Brazil  1997  only  -     Oct   06   0:00  1:00   D                   
Rule    Brazil  1998  only  -     Mar   01   0:00  0      S                   
Rule    Brazil  1998  only  -     Oct   11   0:00  1:00   D                   
Rule    Brazil  1999  only  -     Feb   21   0:00  0      S                   
Rule    Brazil  1999  only  -     Oct   03   0:00  1:00   D                   
Rule    Brazil  2000  only  -     Feb   27   0:00  0      S                   
Rule    Brazil  2000  only  -     Oct   8    0:00  1:00   D                   
Rule    Brazil  2001  only  -     Feb   18   0:00  0      S                   
                                                                              
                                                                              
# Zone  NAME                          GMTOFF  RULES/SAVE    FORMAT  [UNTIL]   
Zone    Brazil/DeNoronha              -2:00   Brazil        BRE%sT            
Zone    posix/Brazil/DeNoronha        -2:00   Brazil        BRE%sT            
Zone    right/Brazil/DeNoronha        -2:00   Brazil        BRE%sT            
Zone    Brazil/East                   -2:00   Brazil        BRE%sT            
Zone    posix/Brazil/East             -2:00   Brazil        BRE%sT            
Zone    right/Brazil/East             -2:00   Brazil        BRE%sT            
                                                                              
Zone    America/Sao_Paulo             -3:00   Brazil        BR%sT             
Zone    America/Rio_de_Janeiro        -3:00   Brazil        BR%sT             
Zone    America/Brasilia              -3:00   Brazil        BR%sT             
Zone    posix/America/Sao_Paulo       -3:00   Brazil        BR%sT             
Zone    posix/America/Rio_de_Janeiro  -3:00   Brazil        BR%sT             
Zone    posix/America/Salvador        -3:00   Brazil        BR%sT             
Zone    posix/America/Brasilia        -3:00   Brazil        BR%sT             
Zone    posix/Brazil/Central          -3:00   Brazil        BR%sT             
Zone    posix/Brazil/Brasilia         -3:00   Brazil        BR%sT             
Zone    posix/Brazil/Sao_Paulo        -3:00   Brazil        BR%sT             
Zone    posix/Brazil/Salvador         -3:00   Brazil        BR%sT             
Zone    posix/Brazil/Rio_de_Janeiro   -3:00   Brazil        BR%sT             
Zone    right/America/Sao_Paulo       -3:00   Brazil        BR%sT             
Zone    right/America/Rio_de_Janeiro  -3:00   Brazil        BR%sT             
Zone    right/America/Salvador        -3:00   Brazil        BR%sT             
Zone    right/America/Brasilia        -3:00   Brazil        BR%sT             
Zone    right/Brazil/Central          -3:00   Brazil        BR%sT             
Zone    right/Brazil/Brasilia         -3:00   Brazil        BR%sT             
Zone    right/Brazil/Sao_Paulo        -3:00   Brazil        BR%sT             
Zone    right/Brazil/Salvador         -3:00   Brazil        BR%sT             
Zone    right/Brazil/Rio_de_Janeiro   -3:00   Brazil        BR%sT             
Zone    Brazil/Central                -3:00   Brazil        BR%sT             
Zone    Brazil/Brasilia               -3:00   Brazil        BR%sT             
Zone    Brazil/Sao_Paulo              -3:00   Brazil        BR%sT             
Zone    Brazil/Rio_de_Janeiro         -3:00   Brazil        BR%sT             
Zone    Brazil/Salvador               -3:00   Brazil        BR%sT             
                                                                              
Zone    Brazil/West                   -4:00   Brazil        BRW%sT            
Zone    Brazil/Manaus                 -4:00   Brazil        BRW%sT            
Zone    Brazil/Rondonia               -4:00   Brazil        BRW%sT            
Zone    Brazil/Roraima                -4:00   Brazil        BRW%sT            
Zone    Brazil/Mato_Grosso            -4:00   Brazil        BRW%sT            
Zone    posix/Brazil/Manaus           -4:00   Brazil        BRW%sT            
Zone    posix/Brazil/Mato_Grosso      -4:00   Brazil        BRW%sT            
Zone    right/Brazil/Manaus           -4:00   Brazil        BRW%sT            
Zone    right/Brazil/Mato_Grosso      -4:00   Brazil        BRW%sT            
Zone    posix/America/Manaus          -4:00   Brazil        BRW%sT            
Zone    right/America/Manaus          -4:00   Brazil        BRW%sT            
                                                                              
Zone    Brazil/Acre                   -5:00   Brazil        BRA%sT            
                                                                              

  Rule ubN̓^C][ύXtƎ`Ă܂B
Zone ubNł́Ã][Ǘ Rule QƂĂ܂B

  ̃t@C̃Rgł́A][RpCł zic gĂ
̃^C][CXg[@Ă܂ (ɃCX
g[ς݂ɂȂĂƎv܂)BCXg[̂Lɂ
́Ã][t@C /etc/localtime t@C烊N (邢
̓Rs[) 邾 OK łBfBXgr[VɂẮA荂
x (Ă炭]܂) ^C][̐ݒ@݂܂B
 Section 3.1 Ő܂B

  /etc/localtime  zoneinfo t@Cw悤ɂAɂ
̃Rs[^͂̃][̋Kɏ]ĂAT}[^C̕ύX
Iɍs܂B蓮ŕύXKv͂܂B

  ɎÃR}h́A Linux ̃^C][Ɋւ郁JjY̓
̂łBׂ͂ 1 ȓɎsꂽ̂łB

bash$ ls -al /etc/localtime                                                                   
lrwxrwxrwx  1 root root 35 May 22  2001 /etc/localtime -> /usr/share/zoneinfo/Brazil/Brasilia 
bash$ date                                                                                    
Fri Mar 29 20:13:38 BRST 2002                                                                 
bash# ln -sf /usr/share/zoneinfo/GMT /etc/localtime                                           
bash$ date                                                                                    
Fri Mar 29 23:13:47 GMT 2002                                                                  
bash# ln -sf /usr/share/zoneinfo/Brazil/Brasilia /etc/localtime                               
bash$ date                                                                                    
Fri Mar 29 20:14:03 BRST 2002                                                                 

  20:13 ɁÃ͎ftHgłuW̃^C][ (BRST) 
܂BŎ͎̃VXe GMT ɕύXAƎ̃VXe
 23:13 ɂȂ܂! ȂÂ^C][T}[^C
ɕςƂɁAľۂ邱ƂɂȂ܂ [: {ł͖
ł :-)]B̋Kׂ͂ă^C][̓ɂ̂ł
(/etc/localtime ̃N̗̂悤ɕς킯ł͂܂)B

  ̃}Vœ삵ĂAvP[V (ANZXO𐶐 web
T[oȂ) ́A̕ύXF܂B Section 1 ŏqׂƂ
ASȈӖł̎Ƃ݂͌̎vX݂̃^C][łA
𗝉邱Ƃ́AJ҂ɂƂĔɏdvłB

  ŌɎ́A̐^C][ɖ߂܂B

 

3. Linux }V𐳂ݒ肷

  ǂ OS CXg[ɂÃ݂^C][Ɋւ
K{łB͓ssEBEȂǂŕ\܂B BIOS ǂݒ肷
邩߂ĂȂ΂Ȃ܂񂪁Aɂ͎̕jɏ]̂
傤B

Linux ̃}V
   
      ̏ꍇ BIOS  UTC ɂĂ̂ł傤BT}[^C
    ̕ύX^C][ݒɂēIɊǗ܂B
   
Linux  MS Windows ̃fAu[g}V
   
      Windows ́ALinux ɔׁAnIɈ܂B Windows ł
    BIOS ɒn (localtime) ɓAăT}[^C
    ɂẮAn[hEFANbNڕύXƂA傫
    ω邱ƂɂȂ܂B Linux  Windows u[gɂ̓n[h
    EFA玞擾Đݒ肷̂ŁA҂Ƃɂ
    Linux łŎȂ΂Ȃ܂B BIOS
    ̒nɍ킹Ȃ΂Ȃ܂B
   
 

3.1. ^C][ݒ

  Red Hat Linux т̔hVXeł́An[hEFANbN̐ݒ
jƃ^C][Ƃ timeconfig R}hŐݒł܂B̃R}h
̓[U[th[ȃ_CAO\Ă܂B܂ΘbIɎg
Ƃł܂B

Example 2. ݒc[

bash# timeconfig "Brasil/East"   # set HC to localtime, and TZ to "Brazil/East" 
bash# timeconfig --utc "Brasil/East"   # set HC to UTC, and TZ to "Brazil/East" 

  ̕@łAtimeconfig ͋Nɓǂݍ܂ /etc/sysconfig/
clock t@CύX܂B̃t@CŕҏW邱Ƃł܂B
̂悤ȓeɂȂĂ͂łB

Example 3. /etc/sysconfig/clock t@C

ZONE="Brazil/East"                                                     
UTC=true                                                               
ARC=false                                                              

 

3.2. n[hEFANbNݒ肷

  n[hEFANbN̐ݒŝ́A̎擾@𗝉
ɂ邱Ƃ߂Ă܂B̂ Section 4 Ő
B

  hwclock ̓n[hEFANbN (HC) ǂݏR}hŁA
݂IvVɉē삵܂ (IvVɂĂ man y[W
ɋLqĂ܂)Bŋ߂ Linux fBXgr[Vg
Ȃ΁A hwclock gKv͂܂B HC ƃ^C][̕j
߂A荂x̃R}hł setclock g HC 𐳂
ł܂B setclock ɂ̓p[^nKv͂ȂÃR}h̓C
eWFg hwclock ĂсA݂ OS ̓tEɊÂ BIOS
ݒ肵܂BāA setclock g悤ɂ܂傤B

  n[h[NDȃ~j}Xg̐lɁA hwclock 
ɋĂ܂傤B

Example 4. setclock  hwclock ̎g

bash# setclock                                  # The easy way to set HC                                 
bash# hwclock                                   # reads HC                                               
bash# hwclock --systohc --utc                   # set HC with UTC time based on OS current time          
bash# hwclock --systohc                         # set HC with local time based on OS current time        
bash# hwclock --set --date "22 Mar 2002 13:17"  # set HC with time specified on string                   

  OS ̎̓n[hEFANbNƂ͓ƗĂ邽߁A BIOS ύX
AɃu[g܂ł̕ύX͔f܂B

   HC ̐ݒ@ƂẮAċNăRs[^ BIOS 
ɓ܂B IBM e-server zSeries <http://ibm.com/servers/
eserver/zseries/os/linux/> ł́A z/VM xōsKv܂
B Linux ͂ł z/VM ɍꂽz}Vœ삵Ă邩ł
B

 

4. mȐEɓ

  ǗĂ邷ׂẴ}V̎𐳊mɕۂƂ́A肵lb
g[NZLeB̕j𗧂Ă (ut@CAEH[uv
Ɛ̃x) ̂Ɠ炢dvȂƂłBVXe@\I
SɁAǗĂŁA͎̓vȗvf̂ЂƂƌ܂
BɕU^̃AvP[V web T[rXA邢͕U^̃ZL
eBĎc[Ǘꍇɂ́AmȎ͕KvsłB

 

4.1. NTP: lbg[N^CvgR

  ł̓vgRɂĂ͐G܂񂪁Â΂炵ƃC^
[lbg̕yƂAɂǂ̂悤ɖ𗧂Ă邩͐܂傤
B NTP Ɋւڂ www.ntp.org <http://www.ntp.org/> 
ł傤B

  xVXeݒ肷ƁA NTP  (삵ĂAvP[Vɂ͉e
yڂȂ悤) ɏȏCsȂA̐mȎ
悤Ƃ܂B

  qɊ܂܂dq̐UTCNg𗘗pn[hEFAp
ƁAɐmȎ擾ł܂B܂ GPS (Global Positioning
System) p@܂BO҂̂ق萳młA҂[
DĂ܂B҂ƂōȑuKvƂ܂Ȃu
L (Ăw) ́ȂuRs[^ɐڑA
Rs[^ NTP f[𑖂点AC^[lbgɂȂAX
ŃANZX邱ƂĂĂ̂łBĉX́Ag
Ď̃VXe̎悤Ƃ킯łB

 

4.2. ȒPȎ\\z

  KvȂ̂:

 1.   ڂ܂͊Ԑ (t@CAEH[oR) ̃C^[lbgڑB
   
 2.   NTP T[oI܂BJT[oł pool.ntp.org <http://
    www.fortytwo.ch/time/> 𗘗p邱Ƃł܂A NTP  web TC
    gɂ stratum 2 J^CT[o <http://www.eecis.udel.edu/
    ~mills/ntp/clock2a.html> IԂƂł܂BC^[lbg֐
    ĂȂꍇ́AȂ WAN ̊Ǘ҂K؂ȓAhX
    Ăł傤 (r̂Ǘ҂ȂAł)B
   
 3.   VXeׂĂ NTP pbP[WCXg[邱
    B̎gĂ Linux fBXgr[V CD  RPM 
    ł傤AȂ rpmfind.net <http://rpmfind.net/> Ō
    <http://rpmfind.net/linux/rpm2html/search.php?query=ntp> Ă݂܂
    傤B
   
  ǂ\̗Ɏ܂B

Figure 1. NTP ̃[J[T[o

[ntp]

  }VꍇA炷ׂĂI[g
NTP T[oɐڑĂ͂܂B̊ǗĂT[o 2 
IсA[g NTP T[oփANZX}V͂ 2 Ɍ
̂łBđ̃}V́A 2 ɑ΂ē̂łB 2
̂ƂAȍ~ł̓[T[oƌĂԂƂɂ܂傤B

  [T[o̓lbg[NɂȂĂ}V̂ǂł܂܂
B NTP ̎g CPU ͂킸łAp̃}VpӂK
v͂܂B

    Tip: ̃[Jȃ[T[oɂ́Antp1.my.com  ntp2.my.com
    ̂悤ɁAzXg̃GCAXĂƂł傤B
    ΁A NTP ̋@\ (IP AhXƃzXg̈Ⴄ) ʂ̃[T[
    oɈړĂANCAgł͕ύXs킸ɂ݂܂B DNS ̊Ǘ
    ҂ɁÃGCAX쐬悤ł݂܂傤B
   
 

4.3. NTP ̐ݒ

[T[oł
   
      /etc/ntp.conf ҏWāAI[gT[oǉ܂B
   
    Example 5. [T[o /etc/ntp.conf
   
    .                                                                     
    .                                                                     
    server  otherntp.server.org     # A stratum 1 server at server.org    
    server  ntp.research.gov        # A stratum 2 server at research.gov  
    .                                                                     
    .                                                                     
   
      Oɂqׂ܂AJT[o pool.ntp.org <http://
    www.fortytwo.ch/time/> g܂A NTP  web TCgJ^C
    T[o <http://www.eecis.udel.edu/~mills/ntp/clock2a.html> ̃X
    g񂹂邱Ƃł܂B
   
NCAgł
   
      /etc/ntp.conf ҏWāA[T[o (NTP T[oł邱Ƃ
    Ӗ) zXgǉ܂B
   
    Example 6. NCAg}V /etc/ntp.conf
   
    .                                                                  
    .                                                                  
    server  ntp1.my.com             # My first local relay             
    server  ntp2.my.com             # My second local relay            
    .                                                                  
    .                                                                  
   
  }V UTC  NTP T[oɑ΂ĐȏジĂƁA NTP
͓삵܂B]čŏɊS (full sync) sȂ΂Ȃ܂
 (VXeŎdsĂȂԑтIт܂傤)B̍Ƃ NTP
̏ݒsKvƂ܂Bȍ~͑SsvłB

Example 7. ŏ̓

bash# ntpdate otherntp.research.gov     (1)                                          
24 Mar 18:16:36 ntpdate[10254]: step time server 200.100.20.10 offset -15.266188 sec 
bash# ntpdate otherntp.research.gov     (2)                                          
24 Mar 18:16:43 ntpdate[10255]: adjust time server 200.100.20.10 offset -0.000267 sec

(1)   ŏ̊Sł́AX̃VXe 15 bxĂ܂B
(2)   xڂ̊ŚAPɊmF̂߂ɍs܂BقƂǂ̓[
    ŁA OK łB

  ŏIiḰAe}Vł NTP f[̋N (܂͍ċN) łB

bash# service ntpd restart                                             

 

4.4. ̊mF

  ȏŐݒׂ͂ďIłB NTP ͂ƂȂ̃}V̎𓯊
ĂĂ͂łB̗lq́ANTP Query R}h (ntpq) Ō
邱Ƃł܂B

Example 8. ̏

bash# ntpq -p                                                                  
     remote           refid      st t when poll reach   delay   offset  jitter 
============================================================================== 
-jj.cs.umb.edu   gandalf.sigmaso  3 u   95 1024  377   31.681  -18.549   1.572 
 milo.mcs.anl.go ntp0.mcs.anl.go  2 u  818 1024  125   41.993  -15.264   1.392 
-mailer1.psc.edu ntp1.usno.navy.  2 u  972 1024  377   38.206   19.589  28.028 
-dr-zaius.cs.wis ben.cs.wisc.edu  2 u  502 1024  357   55.098    3.979   0.333 
+taylor.cs.wisc. ben.cs.wisc.edu  2 u  454 1024  347   54.127    3.379   0.047 
-ntp0.cis.strath harris.cc.strat  3 u  507 1024  377  115.274   -5.025   1.642 
*clock.via.net   .GPS.            1 u  426 1024  377  107.424   -3.018   2.534 
 ntp1.conectiv.c 0.0.0.0         16 u    - 1024    0    0.000    0.000 4000.00 
+bonehed.lcs.mit .GPS.            1 u  984 1024  377   25.126    0.131  30.939 
-world.std.com   204.34.198.40    2 u  119 1024  377   24.229   -6.884   0.421 

ëӖ

remote
   
      [g NTP T[o̖OłB -n XCb`pƁAzXg
    ̑ IP AhX\܂B
   
refid
   
      eT[o݂ǂ玞擾Ă邩܂BT[õz
    Xg .GPS. ̂悤Ȃ̂\܂B҂ Global
    Positioning System 玞擾Ă邱Ƃ܂B
   
st
   
      Stratum  1  16 ܂ł̐lŁA[gT[o̐m
    (precision) Ă܂B 1 ͍łmŁA16 ̓T[oɐڑł
    ȂƂӖ܂BȂ̃}V Stratum ́Ałmȃ[
    gT[o Stratum  1 ̂ɂȂ܂B [: GPS v
    ǂ̎}Vɑ΂uڑivƍlƂ悢Ǝv
    ܂B]
   
poll
   
      |[OsԊԊubPʂŕ\̂łBl͋Ă
    ŏlEől̊ԂɂȂ܂B͍ɓł悤A
    l͏ȂĂ܂BvԂɂȂA|[Ol͂
    񂾂񒷂ȂĂAlbg[N̒ʐMʂAlĈ time T[
    oׂ̕炷悤ɂȂĂ܂B
   
reach
   
      8 rbg̃rbg 8 iŕ\̂ŁA[J̃}V
    T[oւ̐ڑ݂AŌ 8 񕪂̌ʂĂ܂BT[o
    Bꍇ̓rbg܂B [: ]đSĂ
    377 ƂȂ܂B]
   
delay
   
      u܉?vvɑ΂ԓԂ܂łɕKvƂꂽ (b
    P) łB
   
offset
   
      łdvȒlłB[J}Vƃ[gT[o̎̈Ⴂł
    BĂŒ́Aoffset ͏ȂĂ܂B܂胍[J
    ̃}V̎񂾂񐳊mɂȂĂ킯łB
   
jitter
   
      U (dispersion) Ƃh炬 (jitter) ƌĂ΂̂́A񂩗v
    Esۂ́AItZbgl̓vIȗh炬^̂ł
    B̒l͒ႢD܂łBlႢAmȎ\
    ɂȂ܂B
   
T[õzXg̑Oɒu镄̈Ӗ

-
   
      [J NTP T[rX͂̃T[o܂DłȂ
   
+
   
      [J NTP T[rX͂̃T[oDŗpĂ
   
x
   
      sǃzXg
   
*
   
      ݗpĂ
   
 

4.5. NTP u[gɎN悤ݒ肷

  NTP ͂Ɠ삳ĂƂł傤B}VċN
ꍇłłˁBe}Vňȉ̍Ƃs܂傤B

bash# chkconfig --level 2345 ntpd on                                   

  ŎNmɂȂ܂B

  }VċNȂ܂ܒ (N) ƁA{
młȂn[hEFANbNƁA(ɐmƂȂ) VXe
Ƃ̊Ԃɂ́A傫Ȃꂪł傤Bŋ߂ Linux fBXgr[
Vł́AVXeVbg_EۂɁA setclock R}hɎ
dg݂g OS  HC ɃRs[܂B̂悤ɂāA OS
NۂɂAVbg_E̎Ƃ炢Aقڐmȓ
tƎ悤ɂȂĂ̂łB

 

A. ̕ɂ

Copyright 2002, Avi Alkalay.

This document must be distributed under the terms of GNU Free
Documentation License <http://www.gnu.org/copyleft/fdl.html>.

  Ql: ̍̕ĔzzɂẮA GNU Free Documentation License
<http://www.gnu.org/copyleft/fdl.html> ɏ]Ȃ΂Ȃ܂B

  ͈̕ȉŔzzĂ܂B

 E Official site <http://avi.alkalay.net/linux/docs/TimePrecision/> [
    XML (DocBook) \[X <http://avi.alkalay.net/linux/docs/
    TimePrecision/timeprecision.tar.gz>]
   
 E LinuxDoc  HOWTO Ƃēo^ <http://en.tldp.org/HOWTO/
    TimePrecision-HOWTO/> [1 y[W` <http://www.ibiblio.org/pub/
    Linux/docs/HOWTO/other-formats/html_single/
    TimePrecision-HOWTO.html>] [PDF <http://www.ibiblio.org/pub/Linux/
    docs/HOWTO/other-formats/pdf/TimePrecision-HOWTO.pdf>]
   
 E 앐Y <nakano at apm.seikei.ac.jp> ɂ{ <http://
    www.linux.or.jp/JF/JFdocs/TimePrecision-HOWTO/> [eLXg <http:/
    /www.linux.or.jp/JF/JFdocs/TimePrecision-HOWTO.txt>]
   
 E SHAKI <sha-ki at narod.ru> ɂ郍VA <http://
    computerlib.narod.ru/html/linuxtime.htm>
   
  |͒앐Ys܂BĔzz GFDL (Invariant Section 
AFront-Cover Text ȂABack-Cover Text Ȃ) ɏ]܂B

