$ yum install chrony -y

$ systemctl enable chronyd.service
$ systemctl restart chronyd.service
$ systemctl status chronyd.service

$ cat /etc/chrony.conf

# 该参数可以多次用于添加时钟服务器，必须以"server "格式使用。使用pool.ntp.org项目中的公共服务器。理论上你想添加多少时间服务器都可以。（如果chrony只作为client，只需要修改这一个配置即可）
# 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

# chronyd程序根据实际时间计算出服务器增减时间的比率，然后记录到一个文件中，在系统重启后为系统做出最佳时间补偿调整。
driftfile /var/lib/chrony/drift

#默认情况下，chronyd通过减慢速度或加快速度来逐渐调整时钟。如果时钟距离实际时间太远，则需要很长时间才能纠正错误。maketep指令可用于允许chronyd步进更新时钟。
#“makestep 1.0 3”表示：如果时间偏移量大于1s，则在chronyd启动后的前三次更新时使用步进更新的方式。通常，建议仅在前几次更新中允许步进更新，之后的更新采用逐渐调整的方式。但是有某些情况下，需要每次更新都是用步进更新，例如没有RTC的计算机、在不正确的时间进行暂停和恢复的虚拟机等情况。此时我们可以使用“makestep 1 -1”，-1表示每一次更新都使用步进更新方式。
# Allow the system clock to be stepped in the first three updates
# if its offset is larger than 1 second.
makestep 1.0 3


# 将启用一个内核模式，在该模式中，系统时间每11分钟会拷贝到实时时钟（RTC）。
rtcsync

# Enable hardware timestamping on all interfaces that support it.
# 通过使用hwtimestamp指令在某个接口上启用硬件时间戳
#hwtimestamp eth0
#hwtimestamp eth1
#hwtimestamp *

# 增加调整系统时钟所需的最小可选源数量。
# Increase the minimum number of selectable sources required to adjust
# the system clock.
#minsources 2

# 指定一台主机、子网、或者网络，以允许或拒绝NTP连接到扮演时钟服务器的机器
#allow 192.168.0.0/16
#deny 192.168/16

# Serve time even if not synchronized to a time source.
# 即使自己本身不能与远程ntp源进行时间同步，也允许将本地时间作为标准时间对外提供时间同步服务(授时服务，serve time)
# 大的值10表示时钟距离参考时钟有很多跳，其时间可能不可靠。
local stratum 10

# 指定包含NTP验证密钥的文件。
#keyfile /etc/chrony.keys

# 指定日志文件的目录。
logdir /var/log/chrony

# Select which information is logged.
#log measurements statistics tracking

$ timedatectl
      Local time: Fri 2018-2-29 13:31:04 CST
  Universal time: Fri 2018-2-29 05:31:04 UTC
        RTC time: Fri 2018-2-29 08:17:20
       Time zone: Asia/Shanghai (CST, +0800)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: n/a

如果你当前的时区不正确，请按照以下操作设置。

查看所有可用的时区：
$ timedatectl list-timezones

筛选式查看在亚洲S开的上海可用时区：

$ timedatectl list-timezones |  grep  -E "Asia/S.*"

Asia/Sakhalin
Asia/Samarkand
Asia/Seoul
Asia/Shanghai
Asia/Singapore
Asia/Srednekolymsk

设置当前系统为Asia/Shanghai上海时区：

$ timedatectl set-timezone Asia/Shanghai

设置完时区后，强制同步下系统时钟：

$ chronyc -a makestep
200 OK

查看时间同步源：
root@master01:/# 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
===============================================================================
^? docker.inspur.com             0   6   377     -     +0ns[   +0ns] +/-    0ns


查看时间同步源状态：
root@master01:/# chronyc sourcestats -v
210 Number of sources = 1
                             .- Number of sample points in measurement set.
                            /    .- Number of residual runs with same sign.
                           |    /    .- Length of measurement set (time).
                           |   |    /      .- Est. clock freq error (ppm).
                           |   |   |      /           .- Est. error in freq.
                           |   |   |     |           /         .- Est. offset.
                           |   |   |     |          |          |   On the -.
                           |   |   |     |          |          |   samples. \
                           |   |   |     |          |          |             |
Name/IP Address            NP  NR  Span  Frequency  Freq Skew  Offset  Std Dev
==============================================================================
docker.inspur.com           0   0     0     +0.000   2000.000     +0ns  4000ms


设置硬件时间

硬件时间默认为UTC：

$ timedatectl set-local-rtc 1

启用NTP时间同步：

$ timedatectl set-ntp yes

#显示系统时间信息：
$ chronyc tracking
accheck - 检查NTP访问是否对特定主机可用
activity - 该命令会显示有多少NTP源在线/离线
add server - 手动添加一台新的NTP服务器。
clients - 在客户端报告已访问到服务器
delete - 手动移除NTP服务器或对等服务器
settime - 手动设置守护进程时间
tracking - 显示系统时间信息

[root@k8s-master01 ~]# chronyc help
System clock:               
tracking                    Display system time information
makestep                    Correct clock by stepping immediately
makestep <threshold> <updates>
                            Configure automatic clock stepping
maxupdateskew <skew>        Modify maximum valid skew to update frequency
waitsync [<max-tries> [<max-correction> [<max-skew> [<interval>]]]]
                            Wait until synchronised in specified limits
                            
Time sources:               
sources [-v]                Display information about current sources
sourcestats [-v]            Display statistics about collected measurements
reselect                    Force reselecting synchronisation source
reselectdist <dist>         Modify reselection distance
                            
NTP sources:                
activity                    Check how many NTP sources are online/offline
ntpdata [<address>]         Display information about last valid measurement
add server <address> [options]
                            Add new NTP server
add peer <address> [options]
                            Add new NTP peer
delete <address>            Remove server or peer
burst <n-good>/<n-max> [<mask>/<address>]
                            Start rapid set of measurements
maxdelay <address> <delay>  Modify maximum valid sample delay
maxdelayratio <address> <ratio>
                            Modify maximum valid delay/minimum ratio
maxdelaydevratio <address> <ratio>
                            Modify maximum valid delay/deviation ratio
minpoll <address> <poll>    Modify minimum polling interval
maxpoll <address> <poll>    Modify maximum polling interval
minstratum <address> <stratum>
                            Modify minimum stratum
offline [<mask>/<address>]  Set sources in subnet to offline status
online [<mask>/<address>]   Set sources in subnet to online status
polltarget <address> <target>
                            Modify poll target
refresh                     Refresh IP addresses
                            
Manual time input:          
manual off|on|reset         Disable/enable/reset settime command
manual list                 Show previous settime entries
manual delete <index>       Delete previous settime entry
settime <time>              Set daemon time
                            (e.g. Sep 25, 2015 16:30:05 or 16:30:05)
                            
NTP access:                 
accheck <address>           Check whether address is allowed
clients                     Report on clients that have accessed the server
serverstats                 Display statistics of the server
allow [<subnet>]            Allow access to subnet as a default
allow all [<subnet>]        Allow access to subnet and all children
deny [<subnet>]             Deny access to subnet as a default
deny all [<subnet>]         Deny access to subnet and all children
local [options]             Serve time even when not synchronised
local off                   Don't serve time when not synchronised
smoothtime reset|activate   Reset/activate time smoothing
smoothing                   Display current time smoothing state
                            
Monitoring access:          
cmdaccheck <address>        Check whether address is allowed
cmdallow [<subnet>]         Allow access to subnet as a default
cmdallow all [<subnet>]     Allow access to subnet and all children
cmddeny [<subnet>]          Deny access to subnet as a default
cmddeny all [<subnet>]      Deny access to subnet and all children
                            
Real-time clock:            
rtcdata                     Print current RTC performance parameters
trimrtc                     Correct RTC relative to system clock
writertc                    Save RTC performance parameters to file
                            
Other daemon commands:      
cyclelogs                   Close and re-open log files
dump                        Dump all measurements to save files
rekey                       Re-read keys from key file
                            
Client commands:            
dns -n|+n                   Disable/enable resolving IP addresses to hostnames
dns -4|-6|-46               Resolve hostnames only to IPv4/IPv6/both addresses
timeout <milliseconds>      Set initial response timeout
retries <retries>           Set maximum number of retries
keygen [<id> [<type> [<bits>]]]
                            Generate key for key file
exit|quit                   Leave the program
help                        Generate this help

yum install -y chrony

sed -i '2a server ntp1.aliyun.com iburst' /etc/chrony.conf
systemctl restart chronyd
systemctl enable chronyd

root@mgt01:~# systemctl cat chrony
# /etc/systemd/system/chrony.service
[Unit]
Description=Network Time Service
Wants=docker.socket
After=docker.service

[Service]
User=root
ExecStart=/usr/bin/docker run \
  --restart=on-failure:5 \
  --net=host \
  --privileged=true \
  -v /etc/chrony.conf:/etc/chrony/chrony.conf \
  -v /var/run:/var/run \
  --name=chrony-container \
  docker.inspur.com:5000/library/cke/ntpd/chrony:v3.0.2-2 \
  /bin/bash -c 'rm -rf /var/run/chronyd.pid && rm -rf /var/run/chrony && /usr/sbin/chronyd -d -s'
ExecStartPre=-/usr/bin/docker rm -f chrony-container
ExecStop=/usr/bin/docker stop chrony-container
Restart=always
RestartSec=15s
TimeoutStartSec=30s

[Install]
WantedBy=multi-user.target