关于chrony：
chrony is a versatile implementation of the Network Time Protocol (NTP). It can synchronize 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.
It is designed to perform well in a wide range of conditions, including intermittent network connections, heavily congested networks, changing temperatures (ordinary computer clocks are sensitive to temperature), and systems that do not run continuosly, or run on a virtual machine.
Typical accuracy between two machines synchronised over the Internet is within a few milliseconds; on a LAN, accuracy is typically in tens of microseconds. With hardware timestamping, or a hardware reference clock, sub-microsecond accuracy may be possible.
Two programs are included in chrony, chronyd is a daemon that can be started at boot time and chronyc is a command-line interface program which can be used to monitor chronyd’s performance and to change various operating parameters whilst it is running.
NTP：Network Time Protocol；[root@lamp ~]# yum install chrony
[root@lamp ~]# rpm -ql chrony
程序环境：
配置文件：/etc/chrony.conf
主程序文件：chronyd
工具程序：chronyc
unit file: chronyd.service
配置文件：chrony.conf
server：指明时间服务器地址； 客户端直接配置 NTP server IP , 启动chrony进程即可以进行时间同步
allow NETADD/NETMASK
allow all：允许所有客户端主机；
deny NETADDR/NETMASK
deny all：拒绝所有客户端；
bindcmdaddress：命令管理接口监听的地址；
local stratum 10：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；
服务器端配置
[root@lib ~]# ls -lt /etc/chrony.conf*-rw-r--r-- 1 root root 1106 Aug 7 12:07 /etc/chrony.conf
-rw-r--r-- 1 root root 1108 Apr 13 2018 /etc/chrony.conf.bk.20190807.org
[root@lib ~]# diff /etc/chrony.conf /etc/chrony.conf.bk.20190807.org
26c26
< allow 192.168.0.0/24---
#allow 192.168.0.0/16
38c38
< log measurements statistics tracking#log measurements statistics tracking
[root@lib ~]# grep -v '#' /etc/chrony.conf
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
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
allow 192.168.0.0/24
logdir /var/log/chrony
log measurements statistics tracking
[root@lib ~]#
客户端配置
[root@lamp chrony]# ls -l /etc/chrony.conf*
-rw-r--r-- 1 root root 1139 Aug 7 12:07 /etc/chrony.conf
-rw-r--r-- 1 root root 1108 Apr 13 2018 /etc/chrony.conf.bk.20190807
[root@lamp chrony]# diff /etc/chrony.conf /etc/chrony.conf.bk.20190807
3,7c3,6
< #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 192.168.0.103 iburst---
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
39c38
<log measurements statistics tracking#log measurements statistics tracking
[root@lamp chrony]#
####################
配置
[root@lib ~]# grep -v '#' /etc/chrony.conf
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
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
allow 192.168.0.0/24
local stratum 10
logdir /var/log/chrony
log measurements statistics tracking
[root@lib ~]#
实例
服务器端
[root@lib ~]# date -s 12:30:00
Wed Aug 7 12:30:00 CST 2019
[root@lib ~]#
[root@lib ~]#
[root@lib ~]# date
Wed Aug 7 12:30:01 CST 2019
[root@lib ~]#
客户端
[root@lamp ~]# date
Wed Aug 7 12:53:14 CST 2019
[root@lamp ~]# ntpdate 192.168.0.103
7 Aug 12:30:10 ntpdate[3064]: step time server 192.168.0.103 offset -1407.571506 sec
[root@lamp ~]# date
Wed Aug 7 12:30:13 CST 2019
[root@lamp ~]#
##########################
实例2
服务器端
[root@lib ~]# grep -v '#' /etc/chrony.conf
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
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
allow 192.168.0.0/24
local stratum 10 不建议开启，本身chronyd服务器时间与互联网时间同步有问题，就不允许客户端来同步，开启后就允许
logdir /var/log/chrony
log measurements statistics tracking
[root@lib ~]#
客户端配置
[root@lamp ~]# grep -v '#' /etc/chrony.conf
server 192.168.0.103 iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
logdir /var/log/chrony
log measurements statistics tracking
[root@lamp ~]# systemctl start chronyd
[root@lamp ~]#
[root@lamp ~]# chronyc
chrony version 3.2
Copyright (C) 1997-2003, 2007, 2009-2017 Richard P. Curnow and others
chrony comes with ABSOLUTELY NO WARRANTY. This is free software, and
you are welcome to redistribute it under certain conditions. See the
GNU General Public License version 2 for details.
chronyc> sourcestats
210 Number of sources = 1
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev==============================================================================
www.test.com 4 4 6 -2.316 70.585 -92us 6210ns
chronyc> ?
Unrecognized command
chronyc> exit
[root@lamp ~]# date
Wed Aug 7 13:02:42 CST 2019
[root@lamp ~]# chronyc sources
210 Number of sources = 1
MS Name/IP address Stratum Poll Reach LastRx Last sample===============================================================================
^~ www.test.com 3 6 37 16 -1080s[ -1080s] +/- 22ms
[root@lamp ~]# 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===============================================================================
^~ www.test.com 3 6 37 34 -1080s[ -1080s] +/- 22ms
[root@lamp ~]# date
Wed Aug 7 13:04:01 CST 2019
[root@lamp ~]# chronyc sourcestats
210 Number of sources = 1
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev==============================================================================
www.test.com 6 4 135 -10456225 18356178 -1746s 221.3s
[root@lamp ~]# date
Wed Aug 7 13:04:41 CST 2019
[root@lamp ~]#
不会同步服务器时间，有问题
[root@lamp ~]# systemctl status chronyd
● chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor pres et: enabled)
Active: active (running) since Wed 2019-08-07 12:38:08 CST; 28min ago
Docs: man:chronyd(8)
man:chrony.conf(5)
Process: 3086 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exi ted, status=0/SUCCESS)
Process: 3083 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCC ESS)
Main PID: 3085 (chronyd)
CGroup: /system.slice/chronyd.service
└─3085 /usr/sbin/chronyd
Aug 07 12:38:08 lamp systemd[1]: Starting NTP client/server...
Aug 07 12:38:08 lamp chronyd[3085]: chronyd version 3.2 starting (+CMDMON +...G)
Aug 07 12:38:08 lamp chronyd[3085]: Frequency 0.670 +/- 2.937 ppm read from...ft
Aug 07 12:38:08 lamp systemd[1]: Started NTP client/server.
Aug 07 12:38:12 lamp chronyd[3085]: Selected source 192.168.0.103
Aug 07 12:38:12 lamp chronyd[3085]: System clock wrong by 1407.589018 secon...ed
Aug 07 13:01:40 lamp chronyd[3085]: System clock was stepped by 1407.589018...ds
Aug 07 13:02:47 lamp chronyd[3085]: Can't synchronise: no selectable sources
报错
Hint: Some lines were ellipsized, use -l to show in full.
[root@lamp ~]#
可能是时间服务器本身也不对导致
重启服务器chronyd 让其与互联网时间同步
再重启客户端的chronyd ，时间可以同步了
[root@lamp ~]# systemctl restart chronyd
[root@lamp ~]# systemctl status chronyd -l
● chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2019-08-07 12:20:17 CST; 1s ago
Docs: man:chronyd(8)
man:chrony.conf(5)
Process: 3125 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
Process: 3122 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 3124 (chronyd)
CGroup: /system.slice/chronyd.service
└─3124 /usr/sbin/chronyd
Aug 07 12:20:17 lamp systemd[1]: Starting NTP client/server...
Aug 07 12:20:17 lamp chronyd[3124]: chronyd version 3.2 starting (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP +SCFILTER +SECHASH +SIGND +ASYNCDNS +IPV6 +DEBUG)
Aug 07 12:20:17 lamp chronyd[3124]: Frequency 0.658 +/- 3.454 ppm read from /var/lib/chrony/drift
Aug 07 12:20:17 lamp systemd[1]: Started NTP client/server.
[root@lamp ~]# date
Wed Aug 7 13:10:02 CST 2019
[root@lamp ~]# cat /var/lib/chrony/drift
0.658242 3.453812
[root@lamp ~]#