安装
bash
yum -y install chrony两台主机：192.168.239.141（服务器）、192.168.239.142（客户端）
修改配置文件（服务器）vim /etc/chrony.conf
bash
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
pool 192.168.239.141 iburst
# Record the rate at which the system clock gains/losses time.
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.
makestep 1.0 3
# Enable kernel synchronization of the real-time clock (RTC).
rtcsync
# Enable hardware timestamping on all interfaces that support it.
#hwtimestamp *
# Increase the minimum number of selectable sources required to adjust
# the system clock.
#minsources 2
# Allow NTP client access from local network.
allow 10.251.149.0/24
# Serve time even if not synchronized to a time source.
local stratum 5
# Specify file containing keys for NTP authentication.
#keyfile /etc/chrony.keys
# Get TAI-UTC offset and leap seconds from the system tz database.
leapsectz right/UTC
# Specify directory for log files.
logdir /var/log/chrony
# Select which information is logged.
#log measurements statistics tracking修改客户端：192.168.239.142
vim /etc/chrony.conf
bash
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
pool 10.251.149.40 iburst
# Record the rate at which the system clock gains/losses time.
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.
makestep 1.0 3
# Enable kernel synchronization of the real-time clock (RTC).
rtcsync
# Enable hardware timestamping on all interfaces that support it.
#hwtimestamp *
# Increase the minimum number of selectable sources required to adjust
# the system clock.
#minsources 2
# Allow NTP client access from local network.
#allow 10.251.149.0/24
# Serve time even if not synchronized to a time source.
#local stratum 5
# Specify file containing keys for NTP authentication.
#keyfile /etc/chrony.keys
# Get TAI-UTC offset and leap seconds from the system tz database.
leapsectz right/UTC
# Specify directory for log files.
logdir /var/log/chrony
# Select which information is logged.
#log measurements statistics tracking配置文件说明
bash
server
可用于时钟服务器，iburst 选项当服务器可达时，发送一个八个数据包而不是通常的一个数据包。 包间隔通常为2秒,可加快初始同步速度，这个可以添加外网服务器或者内网服务器，域名或者IP都可以。
driftfile
根据实际时间计算出计算机增减时间的比率，将它记录到一个文件中，会在重启后为系统时钟作出补偿
stratumweight
stratumweight指令设置当chronyd从可用源中选择同步源时，每个层应该添加多少距离到同步距离。默认情况下，CentOS中设置为0，让chronyd在选择源时忽略源的层级。
rtcsync
启用内核模式，系统时间每11分钟会拷贝到实时时钟（RTC）
allow / deny
指定一台主机、子网，或者网络以允许或拒绝访问本服务器
cmdallow / cmddeny
可以指定哪台主机可以通过chronyd使用控制命令
bindcmdaddress
允许chronyd监听哪个接口来接收由chronyc执行的命令
makestep
通常chronyd将根据需求通过减慢或加速时钟，使得系统逐步纠正所有时间偏差。在某些特定情况下，系统时钟可能会漂移过快，导致该调整过程消耗很长的时间来纠正系统时钟。该指令强制chronyd在调整期大于某个阀值时调整系统时钟
local stratum 10
即使server指令中时间服务器不可用，也允许将本地时间作为标准时间授时给其它客户端chronyc命令启动服务
bash
# 设置开机启动
[root@x~]# systemctl enable chronyd.service
# 重启服务
[root@x~]# systemctl restart chronyd.service
# 查看时间同步状态
[root@x~]# timedatectl status
# 手动强制同步下系统时钟
[root@x~]# chronyc -a makestep
# 查看时间同步源
[root@x~]# chronyc sources -v
# 查看时间同步源状态
[root@x~]# chronyc sourcestats -v
# 硬件时间默认为UTC
[root@x~]# timedatectl set-local-rtc 1