centos 7 系统默认已安装chronyd时间同步服务&已开启（ntpd服务默认是关闭的）
[BEGIN] 2024/6/4 20:14:16
[tang@localhost ~]$ chronyc sources
210 Number of sources = 4
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^- ntp7.flashdance.cx 2 6 7 43 -14ms[ -14ms] +/- 94ms
^* ntp1.flashdance.cx 2 6 177 107 -699us[+2836us] +/- 106ms
^- makaki.miuku.net 3 6 177 42 +174ms[ +174ms] +/- 313ms
^- 139.199.214.202 2 6 265 102 +165ms[ +165ms] +/- 248ms
[tang@localhost ~]$ systemctl status chronyd
● chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
Active: active (running) since Tue 2024-06-04 05:10:12 PDT; 5min ago
Docs: man:chronyd(8)
man:chrony.conf(5)
Process: 753 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
Process: 677 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 694 (chronyd)
Tasks: 1
CGroup: /system.slice/chronyd.service
└─694 /usr/sbin/chronyd
[tang@localhost ~]$ chronyc sources -v
210 Number of sources = 4
.-- 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
===============================================================================
^+ ntp7.flashdance.cx 2 6 377 4 +50ms[ +50ms] +/- 152ms
^+ ntp1.flashdance.cx 2 6 377 7 +128ms[ +128ms] +/- 237ms
^+ makaki.miuku.net 3 7 337 6 +95ms[ +95ms] +/- 193ms
^* 139.199.214.202 2 6 377 132 +2911us[-6360us] +/- 53ms
[tang@localhost ~]$ date
Tue Jun 4 05:26:59 PDT 2024
[tang@localhost ~]$ timedatectl list-timezones
Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
Africa/Algiers
Africa/Asmara
Africa/Bamako
Africa/Bangui
Africa/Banjul
Africa/Bissau
Africa/Blantyre
Africa/Brazzaville
Africa/Bujumbura
Africa/Cairo
Africa/Casablanca
.....
[root@localhost ~]# sudo timedatectl set-timezone Asia/Shanghai
[root@localhost ~]# timedatectl
Local time: Tue 2024-06-04 20:29:09 CST
Universal time: Tue 2024-06-04 12:29:09 UTC
RTC time: Tue 2024-06-04 12:29:09
Time zone: Asia/Shanghai (CST, +0800)
NTP enabled: yes
NTP synchronized: yes
RTC in local TZ: no
DST active: n/a
[root@localhost ~]# date
Tue Jun 4 20:29:19 CST 2024
[root@localhost ~]# cat /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
# 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
# Serve time even if not synchronized to a time source.
#local stratum 10
# Specify file containing keys for NTP authentication.
#keyfile /etc/chrony.keys
# Specify directory for log files.
logdir /var/log/chrony
# Select which information is logged.
#log measurements statistics tracking
[root@localhost ~]# chronyc tracking
Reference ID : 8BC7D6CA (139.199.214.202)
Stratum : 3
Ref time (UTC) : Tue Jun 04 12:31:00 2024
System time : 0.000245490 seconds fast of NTP time
Last offset : +0.002240096 seconds
RMS offset : 0.017738925 seconds
Frequency : 7.964 ppm slow
Residual freq : +0.520 ppm
Skew : 18.742 ppm
Root delay : 0.087588310 seconds
Root dispersion : 0.026381345 seconds
Update interval : 64.2 seconds
Leap status : Normal
[root@localhost ~]# vim /etc/chrony.conf
[root@localhost ~]# systemctl restart chrony
[root@localhost ~]# chronyc tracking
Reference ID : 00000000 ()
Stratum : 0
Ref time (UTC) : Thu Jan 01 00:00:00 1970
System time : 0.000000000 seconds slow of NTP time
Last offset : +0.000000000 seconds
RMS offset : 0.000000000 seconds
Frequency : 2.040 ppm slow
Residual freq : +0.000 ppm
Skew : 0.000 ppm
Root delay : 1.000000000 seconds
Root dispersion : 1.000000000 seconds
Update interval : 0.0 seconds
Leap status : Not synchronised
server ntp1.aliyun.com
server ntp.tencent.com
[root@localhost ~]# chronyc tracking
Reference ID : 00000000 ()
Stratum : 0
Ref time (UTC) : Thu Jan 01 00:00:00 1970
System time : 0.000000000 seconds slow of NTP time
Last offset : +0.000000000 seconds
RMS offset : 0.000000000 seconds
Frequency : 2.040 ppm slow
Residual freq : +0.000 ppm
Skew : 0.000 ppm
Root delay : 1.000000000 seconds
Root dispersion : 1.000000000 seconds
Update interval : 0.0 seconds
Leap status : Not synchronised
[root@localhost ~]# 如果System time和Last offset的值为0，表示时间同步成功。
bash: 如果System: command not found...
[root@localhost ~]# ntpdate ntp.tencent.com
4 Jun 20:42:17 ntpdate[2590]: adjust time server 106.55.184.199 offset -0.040531 sec
[root@localhost ~]# ntpdate ntp.tencent.com
4 Jun 20:42:30 ntpdate[2599]: adjust time server 106.55.184.199 offset -0.000609 sec
[root@localhost ~]# chronyc tracking
Reference ID : 6A37B8C7 (106.55.184.199)
Stratum : 3
Ref time (UTC) : Tue Jun 04 12:42:29 2024
System time : 0.000001776 seconds slow of NTP time
Last offset : +0.151495337 seconds
RMS offset : 0.151495337 seconds
Frequency : 2.040 ppm slow
Residual freq : +963.269 ppm
Skew : 12.738 ppm
Root delay : 0.403705478 seconds
Root dispersion : 0.034737572 seconds
Update interval : 0.0 seconds
Leap status : Normal
[root@localhost ~]# systemctl restart chronyd
[root@localhost ~]# chronyc tracking
Reference ID : 00000000 ()
Stratum : 0
Ref time (UTC) : Thu Jan 01 00:00:00 1970
System time : 0.000000000 seconds slow of NTP time
Last offset : +0.000000000 seconds
RMS offset : 0.000000000 seconds
Frequency : 2.040 ppm slow
Residual freq : +0.000 ppm
Skew : 0.000 ppm
Root delay : 1.000000000 seconds
Root dispersion : 1.000000000 seconds
Update interval : 0.0 seconds
Leap status : Not synchronised
[root@localhost ~]# systemctl is-enabled ntpd
disabled
[END] 2024/6/4 20:48:31
如果要配置为时间服务器
chrony.conf 修改两处
allow 192.168.143.0/24 #容许访问的网段
local stratum 10
设置开机启动，重启服务
systemctl enable chronyd
systemctl restart chronyd
客户端主机查看时间同步状态
vim /etc/chrony.conf
server 192.168.143.111
systemctl restart chronyd
#timedatectl status
开启网络时间同步
timedatectl set-ntp true
chronyc 命令
查看 ntp_servers
chronyc sources -v
查看 ntp_servers 状态
chronyc sourcestats -v
查看 ntp_servers 是否在线
chronyc activity -v
查看 ntp 详细信息
chronyc tracking -v
强制同步下系统时钟
chronyc -a makestep
常见时区
（1）UTC 整个地球分为二十四时区，每个时区都有自己的本地时间。在国际无线电通信场合，为了统一起见，使用一个统一的时间，称为通用协调时(UTC, Universal Time Coordinated)。
（2）GMT 格林威治标准时间 (Greenwich Mean Time)指位于英国伦敦郊区的×××格林尼治天文台的标准时间，因为本初子午线被定义在通过那里的经线。(UTC与GMT时间基本相同，本文中不做区分)
（3）CST 中国标准时间 (China Standard Time)
GMT + 8 = UTC + 8 = CST
（4）DST夏令时(Daylight Saving Time) 指在夏天太阳升起的比较早时，将时间拨快一小时，以提早日光的使用。（中国不使用）
chronyc sources 输出结果解析
M
这表示信号源的模式。^表示服务器，=表示对等方，＃表示本地连接的参考时钟。
S
此列指示源的状态。
• * 表示chronyd当前同步到的源。
• + 表示可接受的信号源，与选定的信号源组合在一起。
• - 表示被合并算法排除的可接受源。
• ？ 指示已失去连接性或其数据包未通过所有测试的源。它也显示在启动时，直到从中至少收集了3个样本为止。
• x 表示chronyd认为是虚假行情的时钟（即，其时间与大多数其他来源不一致）。
• 〜 表示时间似乎具有太多可变性的来源。
Name/IP address
这显示了源的名称或IP地址，或参考时钟的参考ID。
Stratum
这显示了来源的层，如其最近收到的样本中所报告的那样。层1表示一台具有本地连接的参考时钟的计算机。与第1层计算机同步的计算机位于第2层。与第2层计算机同步的计算机位于第3层，依此类推。
Poll
这显示轮询源的速率，以秒为单位的时间间隔的以2为底的对数。因此，值为6表示每64秒进行一次测量。chronyd会根据当前情况自动更改轮询速率。
Reach
这显示了源的可达性寄存器以八进制数字打印。寄存器有8位，并在每个从源接收或丢失的数据包上更新。值377表示从最后八次传输中收到了对所有用户的有效答复。
LastRx
此列显示多长时间前从来源接收到了最后一个好的样本（在下一列中显示）。未通过某些测试的测量将被忽略。通常以秒为单位。字母m，h，d或y表示分钟，小时，天或年。
Last sample
此列显示上次测量时本地时钟与源之间的偏移。方括号中的数字表示实际测得的偏移量。可以用ns（表示纳秒），us （表示微秒），ms（表示毫秒）或s（表示秒）作为后缀。方括号左侧的数字表示原始测量值，已调整为允许此后施加于本地时钟的任何摆度。
+/-指示器后面的数字表示测量中的误差范围。正偏移表示本地时钟位于源时钟之前。
[[email protected] ~]# chronyc add server 10.210.57.78
200 OK
[[email protected] ~]# 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
^- ntp1.ams1.nl.leaseweb.net 3 10 377 651 -4572us[-4572us] +/- 227ms
^- 119.29.13.98 2 9 377 17 +2553us[+2553us] +/- 26ms
^* 203.107.6.88 2 10 377 656 -1432us[-1106us] +/- 19ms
^- tock.ntp.infomaniak.ch 1 9 377 52m -16ms[ -16ms] +/- 103ms
^? 10.211.57.78 3 6 1 10 +1089us[+1089us] +/- 34ms
[[email protected] ~]# 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
^- ntp1.ams1.nl.leaseweb.net 3 10 377 843 -4572us[-4572us] +/- 227ms
^- 119.29.13.98 2 9 377 208 +2553us[+2553us] +/- 26ms
^* 203.107.6.88 2 10 377 847 -1432us[-1106us] +/- 19ms
^- tock.ntp.infomaniak.ch 1 9 377 56m -16ms[ -16ms] +/- 103ms
^- 10.211.57.78 3 6 17 6 +1225us[+1225us] +/- 37ms
上面示例中刚加入的NTP部分显示是 ？即不可达的，过了两分钟再查看状态变成了 -
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