[root@centos8 ~]#rpm -qi chrony
Name : chrony
Version : 3.5
Release : 2.el8
Architecture: x86_64
Install Date: Sun 13 Jun 2021 12:40:02 PM CST
Group : System Environment/Daemons
Size : 537759
License : GPLv2
Signature : RSA/SHA256, Wed 03 Mar 2021 12:26:24 AM CST, Key ID 05b555b38483c65d
Source RPM : chrony-3.5-2.el8.src.rpm
Build Date : Tue 02 Mar 2021 03:04:32 PM CST
Build Host : x86-01.mbox.centos.org
Relocations : (not relocatable)
Packager : CentOS Buildsys <[email protected]>
Vendor : CentOS
URL : https://chrony.tuxfamily.org
Summary : An NTP client/server
Description :
chrony is a versatile implementation of the Network Time Protocol (NTP).
It can synchronise the system clock with NTP servers, reference clocks
(e.g. GPS receiver), and manual input using wristwatch and keyboard. It
can also operate as an NTPv4 (RFC 5905) server and peer to provide a time
service to other computers in the network.
[root@centos7 ~]#cat /etc/redhat-release
CentOS Linux release 7.2.1511 (Core)
[root@centos7 ~]#uname -r
3.10.0-327.el7.x86_64
[root@centos7 ~]#rpm -qi chrony
Name : chrony
Version : 2.1.1
Release : 1.el7.centos
Architecture: x86_64
Install Date: 2019年11月25日 星期一 20时17分23秒
Group : System Environment/Daemons
Size : 479430
License : GPLv2
Signature : RSA/SHA256, 2015年11月25日 星期三 22时19分35秒, Key ID 24c6a8a7f4a80eb5
Source RPM : chrony-2.1.1-1.el7.centos.src.rpm
Build Date : 2015年11月24日 星期二 05时36分12秒
Build Host : worker1.bsys.centos.org
Relocations : (not relocatable)
Packager : CentOS BuildSystem <http://bugs.centos.org>
Vendor : CentOS
URL : http://chrony.tuxfamily.org
Summary : An NTP client/server
Description :
A client/server for the Network Time Protocol, this program keeps your
computer's clock accurate. It was specially designed to support
systems with intermittent internet connections, but it also works well
in permanently connected environments. It can use also hardware reference
clocks, system real-time clock or manual input as time references.
server configuration
The main configuration file /etc/chrony
focuses on:
allow 0.0.0.0/0
local stratum 10
Simple explanation:
Allow NTP clients to access from the local network.
Even if it cannot be synchronized with a remote server time source, it can continue to provide time synchronization services for other clients.
10 means that the current server is set to the 10th layer. According to the atomic clock as the first layer, several time servers on the Internet are the Nth layer. Layer 10 is enough to represent the local area network where the current host is located
iburst: Parallel synchronization to speed up synchronization
[root@centos8 ~]#vim /etc/chrony.conf
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
pool 2.centos.pool.ntp.org iburst
server ntp.aliyun.com iburst iburst
server ntp.ecslb.sjtu.edu.cn iburst
server time1.cloud.tencent.com 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 192.168.0.0/16
allow 0.0.0.0/0
# Serve time even if not synchronized to a time source.
#local stratum 10
local stratum 10
# 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
restart service
systemctl restart chronyd
Check whether the UDP port 123 that the chrony service listens to by default is open
[root@centos8 ~]#ss -ntlu
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
udp UNCONN 0 0 0.0.0.0:111 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:123 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:39087 0.0.0.0:*
udp UNCONN 0 0 0.0.0.0:5353 0.0.0.0:*
udp UNCONN 0 0 127.0.0.1:323 0.0.0.0:*
udp UNCONN 0 0 [::]:111 [::]:*
udp UNCONN 0 0 [::]:50298 [::]:*
udp UNCONN 0 0 [::]:5353 [::]:*
udp UNCONN 0 0 [::1]:323 [::]:*
tcp LISTEN 0 128 127.0.0.1:6010 0.0.0.0:*
tcp LISTEN 0 128 127.0.0.1:6011 0.0.0.0:*
tcp LISTEN 0 128 127.0.0.1:6012 0.0.0.0:*
tcp LISTEN 0 128 127.0.0.1:6013 0.0.0.0:*
tcp LISTEN 0 128 0.0.0.0:111 0.0.0.0:*
tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:*
tcp LISTEN 0 5 127.0.0.1:631 0.0.0.0:*
tcp LISTEN 0 128 [::1]:6010 [::]:*
tcp LISTEN 0 128 [::1]:6011 [::]:*
tcp LISTEN 0 128 [::1]:6012 [::]:*
tcp LISTEN 0 128 [::1]:6013 [::]:*
tcp LISTEN 0 128 [::]:111 [::]:*
tcp LISTEN 0 128 *:80 *:*
tcp LISTEN 0 128 [::]:22 [::]:*
tcp LISTEN 0 5 [::1]:631 [::]:*
client testing
[root@centos7 ~]#date -s "-1 year"
2020年 08月 27日 星期四 20:09:11 CST
[root@centos7 ~]#date
2020年 08月 27日 星期四 20:09:17 CST
[root@centos7 ~]#ntpdate 10.0.0.5
27 Aug 16:09:37 ntpdate[4935]: step time server 10.0.0.5 offset 31521600.000748 sec
[root@centos7 ~]#date
2021年 08月 27日 星期五 16:09:40 CST
#更改配置文件使客户端时间服务默认指向10.0.0.5
[root@centos7 ~]#vim /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.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
server 10.0.0.5 iburst
restart service
systemctl restart chronyd
test
[root@centos7 ~]#date -s "-1 year"
2020年 08月 27日 星期四 16:17:28 CST
#查看同步详细信息
[root@centos7 ~]#chronyc sources -v
210 Number of sources = 1
.-- 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
===============================================================================
^? 10.0.0.5 3 6 377 17 -8760h[ -8760h] +/- 17ms
#同步成功
[root@centos7 ~]#chronyc sources -v
210 Number of sources = 1
.-- 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
===============================================================================
^* 10.0.0.5 3 6 377 1 +76us[ -8760h] +/- 16ms
Note: It takes a few minutes to wait for the default synchronization. You can use ntpdate 10.0.0.5 or restart the chrony service systemctl restart chronyd for immediate synchronization
Common domestic NTP time server addresses
Tsinghua University
https://tuna.moe/help/ntp/
ntp.tuna.tsinghua.edu.cn
Shanghai Jiaotong University
ntp.sjtu.edu.cn
ntp.ecslb.sjtu.edu.cn
Tencent
time1.cloud.tencent.com
time2.cloud.tencent.com
time3.cloud.tencent.com
time4.cloud.tencent.com
time5.cloud.tencent.com
Microsoft
windows comes with
time.windows.com