debian stretchにntpdを導入する。

■debian stretchにntpdを導入する。

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux 9.1 (stretch)
Release:	9.1
Codename:	stretch

$ sudo apt-get install -y ntp

■デフォルトの時刻同期参照先を無効化

$ sudo sed -i -e 's/^pool/# &/' /etc/ntp.conf
$ grep "^# pool" /etc/ntp.conf 
# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pool: <http://www.pool.ntp.org/join.html>
# pool 0.debian.pool.ntp.org iburst
# pool 1.debian.pool.ntp.org iburst
# pool 2.debian.pool.ntp.org iburst
# pool 3.debian.pool.ntp.org iburst

■自ネットワークの時刻同期参照先を設定
　iburstによる同期高速化を指定する。

$ grep ^server /etc/ntp.conf 
server -4 172.31.31.252 iburst

■ntpデーモンの再起動、階層(stratum)3で、
　正常に同期(leap=00)していることを確認。

$ sudo systemctl restart ntp.service

$ watch -d -n 1 'ntpq -pn -c rv'
Every 1.0s: ntpq -pn -c rv                vm-stretch: Tue Aug  1 22:01:11 2017

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*172.31.31.252   78.73.67.84      2 u    5   64    1    0.471   -0.015   0.424
associd=0 status=0614 leap_none, sync_ntp, 1 event, freq_mode,
version="ntpd 4.2.8p10@1.3728-o Sun May  7 22:26:51 UTC 2017 (1)",
processor="x86_64", system="Linux/4.9.0-3-amd64", leap=00, stratum=3,
precision=-24, rootdelay=39.762, rootdisp=209.193, refid=172.31.31.252,
reftime=dd2afa12.e621a54f  Tue, Aug  1 2017 22:01:06.898,
clock=dd2afa17.56606af9  Tue, Aug  1 2017 22:01:11.337, peer=31741, tc=6,
mintc=3, offset=0.418392, frequency=0.000, sys_jitter=0.000000,
clk_jitter=0.207, clk_wander=0.000

$ sudo tail -f /var/log/syslog | grep --color ntp
Aug  1 22:07:09 vm-stretch ntp[19630]: Starting NTP server: ntpd.
Aug  1 22:07:09 vm-stretch ntpd[19641]: proto: precision = 0.063 usec (-24)
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listen and drop on 0 v6wildcard [::]:123
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listen and drop on 1 v4wildcard 0.0.0.0:123
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listen normally on 2 lo 127.0.0.1:123
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listen normally on 3 ens192 172.31.31.70:123
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listen normally on 4 lo [::1]:123
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listen normally on 5 ens192 [fe80::20c:29ff:fe45:ba0f%2]:123
Aug  1 22:07:09 vm-stretch ntpd[19641]: Listening on routing socket on fd #22 for interface updates

■統計ログを有効にする。

$ grep log /etc/ntp.conf 
# Enable this if you want statistics to be logged.
#statsdir /var/log/ntpstats/
$ grep drift /etc/ntp.conf 
driftfile /var/lib/ntp/ntp.drift

$ sudo sed -i -e 's/^#\(statsdir\)/\1/' /etc/ntp.conf 

$ sudo systemctl restart ntp.service

$ ls /var/lib/ntp/ /var/log/ntpstats/
/var/lib/ntp/:
ntp.drift

/var/log/ntpstats/:
loopstats  loopstats.20170801  peerstats  peerstats.20170801