====== NTPサーバー ======

===== パッケージインストール =====
<code>
$ sudo dnf install ntp ntpdate
</code>
===== NTPサーバーの設定 =====
設定ファイルのバックアップ。
<code>
$ sudo cp /etc/ntp.conf /etc/ntp.conf.org
</code>

設定ファイルの修正。
<code>
$ sudo vi /etc/ntp.conf
</code>
<code>
# Hosts on local network are less restricted.
#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
#pool 2.fedora.pool.ntp.org iburst
pool ntp.jst.mfeed.ad.jp iburst      # MFEED
pool ntp.nict.jp iburst              # NICT
server s2csntp.miz.nao.ac.jp iburst  # NAO
pool ntp.ring.gr.jp iburst           # Ring Server
pool time.google.com iburst          # Google
</code>
===== ファイヤーウォールの設定 =====
<code>
$ sudo firewall-cmd --permanent --add-service=ntp
$ sudo firewall-cmd --reload
</code>

===== サービス自動起動設定 =====
<code>
$ sudo systemctl enable ntpd.service
</code>

===== 時刻の手動同期 =====
サービスを起動する前に手動で同期しておく。
<code>
$ sudo ntpdate ntp.nict.jp
</code>

===== サービス起動 =====
<code>
$ sudo systemctl start ntpd.service
</code>

===== 動作確認 =====
<code>
$ sudo ntpdate -d timeserver
10 Jan 01:42:07 ntpdate[2809]: ntpdate 4.2.8p12@1.3728-o Wed Aug 15 08:39:42 UTC 2018 (1)
Looking for host timeserver and service ntp
192.168.1.10 reversed to timeserver.tomoyan.local
host found : black-dc.tomoyan.local
transmit(192.168.1.10)
transmit(192.168.1.10)
receive(192.168.1.10)
receive: pkt.org and peer.xmt differ
receive(192.168.1.10)
transmit(192.168.1.10)
transmit(192.168.1.10)
receive(192.168.1.10)
receive: pkt.org and peer.xmt differ
receive(192.168.1.10)

server 192.168.1.10, port 123
stratum 2, precision -24, leap 00, trust 000
refid [133.243.238.163], root delay 0.034470, root dispersion 0.097672
transmitted 4, in filter 4
reference time:    dfe02435.fe2f13ad  Wed, Jan  9 2019 16:41:41.992
originate timestamp: dfe02455.9f9c7ecd  Wed, Jan  9 2019 16:42:13.623
transmit timestamp:  dfe0a2e5.fc372597  Thu, Jan 10 2019  1:42:13.985
filter delay:  0.00000  0.66539  0.00000  2.24023
         0.00000  0.00000  0.00000  0.00000
filter offset: 0.000000 -32400.8 0.000000 -32401.4
         0.000000 0.000000 0.000000 0.000000
delay 0.66539, dispersion 24.32080
offset -32400.827489

10 Jan 01:42:16 ntpdate[2809]: step time server 192.168.1.10 offset -32400.827489 sec
</code>
<code>
$ sudo ntpdate timeserver
 9 Jan 16:55:00 ntpdate[8074]: adjust time server 192.168.1.10 offset -0.003202 sec
</code>