# systemctl enable chronyd.service

# systemctl restart chronyd.service

# systemctl status chronyd.service

查看时间同步源：

# 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

||                                                /   xxxx = adjusted offset,

||         Log2(Polling interval) -.             |    yyyy = measured offset,

||                                  \            |    zzzz = estimated error.

||                                   |           |

MS Name/IP address         Stratum Poll Reach LastRx Last sample

===============================================================================

^? ys-ad1.ys.com      3   6     3     1    +12ms[  +12ms] +/-  268ms

查看时间同步源状态：

# 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

==============================================================================

ys-ad1.ys.com    4   3     6   -939.214  56272.109  -4371us  5267us

# 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。一般而言，你想添加多少服务器，就可以添加多少服务器。

server 0.rhel.pool.ntp.org iburst

server 1.rhel.pool.ntp.org iburst

server 2.rhel.pool.ntp.org iburst

server 3.rhel.pool.ntp.org iburst

# Ignore stratum in source selection.

# stratumweight指令设置当chronyd从可用源中选择同步源时，每个层应该添加多少距离到同步距离。默认情况下，设置为0，让chronyd在选择源时忽略源的层级。

stratumweight 0

# Record the rate at which the system clock gains/losses time.

# chronyd程序的主要行为之一，就是根据实际时间计算出计算机增减时间的比率，将它记录到一个文件中是最合理的，它会在重启后为系统时钟作出补偿，甚至可能的话，会从时钟服务器获得较好的估值。

driftfile /var/lib/chrony/drift

# Enable kernel RTC synchronization.

# rtcsync指令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

# In first three updates step the system clock instead of slew

# if the adjustment is larger than 10 seconds.

通常，chronyd将根据需求通过减慢或加速时钟，使得系统逐步纠正所有时间偏差。在某些特定情况下，系统时钟可能会漂移过快，导致该调整过程消耗很长的时间来纠正系统时钟。该指令强制chronyd在调整期大于某个阀值时步进调整系统时钟，但只有在因为chronyd启动时间超过指定限制（可使用负值来禁用限制），没有更多时钟更新时才生效。

makestep 10 3

# Allow NTP client access from local network.

# 这里你可以指定一台主机、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 192.168.56.6

#deny 192.168/16

# Listen for commands only on localhost.

# 该指令允许你限制chronyd监听哪个网络接口的命令包（由chronyc执行）。该指令通过cmddeny机制提供了一个除上述限制以外可用的额外的访问控制等级。

bindcmdaddress 127.0.0.1

bindcmdaddress ::1

# Serve time even if not synchronized to any NTP server.

#local stratum 10

keyfile /etc/chrony.keys

# Specify the key used as password for chronyc.

commandkey 1

# Generate command key if missing.

generatecommandkey

# Disable logging of client accesses.

noclientlog

# Send a message to syslog if a clock adjustment is larger than 0.5 seconds.

logchange 0.5

logdir /var/log/chrony

#log measurements statistics tracking

# cat /etc/chrony.keys

1 MD5 HEX:BD359B2633CD6105AB8820E47A8D8EAB

# cat/etc/chrony.keys

1 xyzzy