How to configure time zone and NTP on RHEL7/CentOS7

Tue, 29 Sep 2020 11:41:43 +0800

How to configure time zone and NTP on RHEL7/CentOS7

chrony includes two programs: chronyd is a daemon that starts on boot, and chronyc is a command-line client that can monitor chronyd and change runtime parameters.

Use either ntpd or chronyd, not both.

Configure time zone

~# timedatectl set-timezone Asia/Taipei
~# timedatectl
 Local time: Tue 2018-03-27 14:13:38 CST
 Universal time: Tue 2018-03-27 06:13:38 UTC
 RTC time: Tue 2018-03-27 06:13:40
 Time zone: Asia/Taipei (CST, +0800)
 NTP enabled: no
NTP synchronized: no
 RTC in local TZ: no
 DST active: n/a

Configure chronyd

# Install
~# yum install -y chrony

# Config file
~# cat /etc/chrony.conf
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 0.tw.pool.ntp.org iburst --->改成本地的伺服器
server 1.tw.pool.ntp.org iburst --->改成本地的伺服器
server 2.tw.pool.ntp.org iburst --->改成本地的伺服器
server 3.tw.pool.ntp.org iburst --->改成本地的伺服器

# Start service and enable on boot
~# systemctl enable chronyd
~# systemctl start chronyd

tracking parameters show system time performance

~# chronyc tracking
Reference ID : 3DD8996B (61-216-153-107.hinet-ip.hinet.net) --->表示現在同步的時間伺服器，如果沒有id表示沒有同步
Stratum : 4 --->表示計算機有多少"跳hop" 表示本地的是第四層
Ref time (UTC) : Tue Mar 27 06:03:38 2018 --->最後一次測量的時間
System time : 0.000040356 seconds fast of NTP time --->調整系統時間
Last offset : +0.000163738 seconds
RMS offset : 0.000163738 seconds
Frequency : 21.384 ppm fast
Residual freq : +0.000 ppm
Skew : 675.319 ppm
Root delay : 0.008527911 seconds
Root dispersion : 0.066466033 seconds
Update interval : 2.0 seconds
Leap status : Normal --->Normal要顯示此值, Insert second, Delete second or Not synchronised.

~# chronyc sources -v
210 Number of sources = 4

 .-- Source mode '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| / '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \  | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^* 59-124-29-241.hinet-ip.h> 3 6 37 24 -1462us[-2363us] +/- 49ms
^+ 61-216-153-107.hinet-ip.> 3 6 37 23 -556us[ -556us] +/- 64ms
^? 59-125-122-217.hinet-ip.> 0 7 0 - +0ns[ +0ns] +/- 0ns
^- 61-216-153-105.hinet-ip.> 3 6 37 23 -280us[ -280us] +/- 64ms

View sync source info

~# chronyc sourcestats -v
210 Number of sources = 4
 .- Number of sample points in measurement set.
 / .- Number of residual runs with same sign.
 | / .- Length of measurement set (time).
 | | / .- Est. clock freq error (ppm).
 | | | / .- Est. error in freq.
 | | | | / .- Est. offset.
 | | | | | | On the -.
 | | | | | | samples. \
 | | | | | | |
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================
59-124-29-241.hinet-ip.h> 6 5 135 -0.454 4.553 -784us 66us
61-216-153-107.hinet-ip.> 6 6 135 +4.455 19.761 +622us 247us
59-125-122-217.hinet-ip.> 0 0 0 +0.000 2000.000 +0ns 4000ms
61-216-153-105.hinet-ip.> 6 4 136 +8.965 42.440 +1250us 495us

Write system time to hardware clock