一、简介
chrony 是NTP（Network Time Protocol ，网络时间协议）的另一种实现方式，相比ntpd,可以更快更准确地同步系统时钟，最大程度地减少时间和频率误差
chrony包括两个核心程序：chronyd是一个守护进程，用于调整内核中运行的系统时钟与NTP服务器同步；chronyc是一个命令行界面程序，用于监视chronyd的性能以及进行各项配置。
二、安装与配置
[root@host240 ~]# yum -y install chrony
配置文件 vim /etc/chrony.conf
Custom source
# Use public servers from the pool.ntp.org project.
# 添加的时钟同步服务器
server ha-vip iburst
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
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
# Record the rate at which the system clock gains/losses time.
# 根据实际时间计算出服务器增减时间的比率，然后记录到一个文件中，方便在系统重启后为系统做出最佳的时间补偿调整
driftfile /var/lib/chrony/drift
# Allow the system clock to be stepped in the first three updates
# if its offset is larger than 1 second.
# 如果系统时钟的误差小于1秒，则通过逐渐增大或减慢时钟来进行调整
# 如果系统时钟的偏移量超过1秒，则允许系统时钟在前三次更新时允许步进时间（时间跳变）
makestep 1.0 3
# Enable kernel synchronization of the real-time clock (RTC).
# 启动硬件时钟RTC的内核同步
rtcsync
# Enable hardware timestamping on all interfaces that support it.
# 通过使用hwtimestamp指令启用硬件时间戳
#hwtimestamp *
# Increase the minimum number of selectable sources required to adjust
# the system clock.
#minsources 2
# 指定允许NTP客户端的地址范围，以允许或拒绝连接到时钟源的机器
# Allow NTP client access from local network.
#allow 192.168.0.0/16
allow all #允许所有客户端
# 即使自己未能通过网络时间服务器同步到时间，也允许将本地时间作为标准时间授时给其它客户端
# Serve time even if not synchronized to a time source.
local stratum 10
# Specify file containing keys for NTP authentication.
# 指定包含NTP身份验证的文件
#keyfile /etc/chrony.keys
# Specify directory for log files.
# 日志文件的目录
logdir /var/log/chrony
# 选择日志要记录的信息
# Select which information is logged.
#log measurements statistics tracking
# 拒绝的客户端
deny host216
三、使用方式
服务端修改配置文件
allow all #指定允许访问的客户端地址范围
客户端修改配置文件
server 服务端地址 iburst
服务端和客户端重启服务
systemctl restart chronyd.service
四、常用命令
# 查看时钟源
[root@host216 ~]# chronyc sources -v
210 Number of sources = 5
.-- 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
===============================================================================
^? 10.46.157.240 10 6 1 20 +68us[ +68us] +/- 353us
# 查看日期时间、时区及 NTP 状态
[root@host216 ~]# timedatectl
Local time: Thu 2020-06-11 18:41:39 CST
Universal time: Thu 2020-06-11 10:41:39 UTC
RTC time: Thu 2020-06-11 10:41:38
Time zone: Asia/Shanghai (CST, +0800)
NTP enabled: yes
NTP synchronized: yes
RTC in local TZ: no
DST active: n/a
#查看时钟源状态
[root@host216 ~]# chronyc sourcestats -v
210 Number of sources = 5
.- 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
==============================================================================
10.46.157.240 2 0 65 +0.000 2000.000 -5528ns 4000ms
# 查看时钟源是否在线
[root@host216 ~]# chronyc activity -v
200 OK
# 查看 ntp 详细信息
[root@host216 ~]# chronyc tracking -v
Reference ID : 0A2E9DF0 (10.46.157.240)
Stratum : 11
Ref time (UTC) : Thu Jun 11 09:40:56 2020
System time : 0.000014615 seconds fast of NTP time
Last offset : +0.000018921 seconds
RMS offset : 0.000018921 seconds
Frequency : 68.835 ppm fast
Residual freq : -0.480 ppm
Skew : 0.092 ppm
Root delay : 0.000887929 seconds
Root dispersion : 0.000064294 seconds
Update interval : 64.5 seconds
Leap status : Normal
#查看时区列表
[root@host216 ~]# timedatectl list-timezones
Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
Africa/Algiers
... ...
Asia/Shanghai
# 修改时区
timedatectl set-timezone Asia/Shanghai