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NTP設定メモ

Posted at

RHEL6
ntpdate : ntpdate-4.2.6p5-12.el6.centos.2.x86_64
ntp : ntp-4.2.6p5-12.el6.centos.2.x86_64

で設定したNTPのメモ

デフォルト値の確認

# /etc/init.d/ntpd start
ntpd を起動中:                                             [  OK  ]
# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 x.ns.gin.ntt.ne .INIT.          16 u    -   64    0    0.000    0.000   0.000
 y.ns.gin.ntt.ne 249.224.99.213   2 u    1   64    1    5.086    4.880   0.000
 nipper.paina.ne 131.113.192.40   2 u    -   64    1    0.437    6.861   0.000
 nipper.paina.ne .INIT.          16 u    -   64    0    0.000    0.000   0.000

設定するNTPサーバ

以下の3つのNTPサーバーを設定。

  1. NICT
    http://jjy.nict.go.jp/tsp/PubNtp/index.html
    ntp.nict.jp

  2. インターネットマルチフィード
    http://www.jst.mfeed.ad.jp/about/04.html
    ntp1.jst.mfeed.ad.jp

  3. Google Public NTP
    https://developers.google.com/time/
    time.google.com

/etc/ntp.conf 確認、バックアップ、設定変更

/etc/ntp.confのデフォルトのNTPサーバをコメントアウトする。
上の3サーバを/etc/ntp.confに記載する
参考:iburstの意味
http://d.hatena.ne.jp/incarose86/20110505/1312522379

# ls -l /etc/ntp.conf
-rw-r--r-- 1 root root 1778 12月 18 22:51 2017 /etc/ntp.conf
# cp /etc/ntp.conf /etc/ntp.conf.`date "+%Y%m%d"`
# ls -l /etc/ntp.conf /etc/ntp.conf.20180314 
-rw-r--r-- 1 root root 1878  3月 15 00:02 2018 /etc/ntp.conf
-rw-r--r-- 1 root root 1778  3月 14 23:48 2018 /etc/ntp.conf.20180314
# vi /etc/ntp.conf
# diff /etc/ntp.conf /etc/ntp.conf.20180314 
22,29c22,25
< server ntp.nict.jp iburst
< server ntp1.jst.mfeed.ad.jp iburst
< server time.google.com iburst
< 
< # server 0.centos.pool.ntp.org iburst
< # server 1.centos.pool.ntp.org iburst
< # server 2.centos.pool.ntp.org iburst
< # server 3.centos.pool.ntp.org iburst
---
> server 0.centos.pool.ntp.org iburst
> server 1.centos.pool.ntp.org iburst
> server 2.centos.pool.ntp.org iburst
> server 3.centos.pool.ntp.org iburst

設定の反映

時刻がずれているとntpdが上手く動作しないため(なぜ?)、手動で時刻を合わせてからntpdを再起動する。
参考:手動の時刻合わせの必要性
http://www.turbolinux.co.jp/products/server/11s/user_guide/x6278.html

# /etc/init.d/ntpd stop
ntpd を停止中:                                             [  OK  ]
# ntpdate ntp.nict.jp
15 Mar 00:12:01 ntpdate[14309]: adjust time server 2001:df0:232:eea0::fff3 offset 0.009183 sec
# /etc/init.d/ntpd start
ntpd を起動中:                                             [  OK  ]
# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*ntp-a2.nict.go. .NICT.           1 u    8   64    1    1.421   -7.424   0.183
+ntp1.jst.mfeed. 133.243.236.17   2 u    7   64    1    0.748   -7.689   0.143
+time4.google.co .GOOG.           1 u    6   64    1   53.146  -14.625   2.835
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