Chrony time synchronization

1. chrony brief introduction ：

   Realization NTP Free software of the protocol . The system clock can be synchronized with NTP The server , Reference clock （ for example GPS Receiver ） And the use of watches Synchronize with manual input from the keyboard . adopt Internet The typical accuracy between two synchronous machines is within a few milliseconds , stay LAN On , The precision is usually tens of microseconds . Use hard Piece timestamp or hardware reference clock , It can achieve sub microsecond precision .

2. chrony Install and use

2.1. chrony install

host	IP
node01	192.168.80.131
node02	192.168.80.132
node03	192.168.80.133

Each node is installed chrony

yum install chrony -y
systemctl enable chronyd.service
systemctl restart chronyd.service
systemctl status chronyd.service

Release within the firewall , because NTP Use 123/UDP Port agreement , So allow NTP The service can be .（ Ignore if the firewall is closed ）

firewall-cmd --add-service=ntp --permanent
firewall-cmd --reload

2.2 modify node01 The configuration file

Change the synchronization server in the configuration file to a domestic time server （ Recommend Alibaba and Tencent ）

vim /etc/chrony.conf

server ntp.aliyun.com iburst
server ntp1.aliyun.com iburst
server ntp2.aliyun.com iburst

restart

systemctl restart chronyd.service
systemctl status chronyd.service

 Force synchronization of the system clock ：
# chronyc -a makestep

 View time synchronization source status ：
# chronyc sourcestats

 Check the time synchronization source ：
# chronyc sources -v

2.3 node Node configuration chrony

stay /etc/chrony.conf Comment out the previous IP, newly added node01 The host IP The address will do （ Remember to restart chrony）

2.4 Configuration file details

#  Use pool.ntp.org The public server in the project . With server open , In theory you can add as many servers as you want .
# 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

#  Calculate the ratio of server time to actual time , It is then recorded in a file , Make the best time compensation adjustment for the system after system restart .
driftfile /var/lib/chrony/drift

# chronyd Adjust the time to slow down or speed up according to the demand ,
#  In some cases the system clock may drift too fast , Cause the time adjustment to take too long .
#  The instruction enforces chronyd Adjust the period , Stepwise adjustment of the system clock when greater than a certain threshold .
#  Only for chronyd When the startup time exceeds the specified limit （ Negative values can be used to disable restrictions ） No more clock updates to take effect .
makestep 1.0 3

#  A kernel mode is enabled , In this mode , System time per 11 Minutes are copied to the real-time clock （RTC）.
rtcsync

# Enable hardware timestamping on all interfaces that support it.
#  By using hwtimestamp The directive enables the hardware timestamp 
#hwtimestamp eth0
#hwtimestamp eth1
#hwtimestamp *

# Increase the minimum number of selectable sources required to adjust
# the system clock.
#minsources 2

#  Specify a host 、 subnet , Or network to allow or deny NTP Connect to the machine that ACTS as the clock server 
#allow 192.168.0.0/16
#deny 192.168/16

# Serve time even if not synchronized to a time source.
local stratum 10

#  The specified contains NTP The file that verifies the key .
#keyfile /etc/chrony.keys

#  Specifies the directory for the log files .
logdir /var/log/chrony

# Select which information is logged.
#log measurements statistics tracking
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 The copyright belongs to the author ： come from 51CTO The original work of blogger Nangong Chengfeng , Please contact the author for permission to reprint , Otherwise, the legal liability will be investigated 
Centos7 Cluster time synchronization （Chrony）
https://blog.51cto.com/heian99/3220521