普遍使用Chrony

现在Linux的发行版已经普遍使用chrony来代替ntpd进行时间同步管理了。
使用以下命令查看你的系统上chrony启动状态：

  1. systemctl status chronyd

如果你的系统没有chronyd，可以使用以下命令进行安装。

  1. yum install chrony -y

一般情况下，chrony只要启动了很快就会从默认的配置中完成时间的同步，所以只需要重启chrony就可以同步时间。

  1. #启动应用
  2. systemctl enable --now chronyd
  4. #重新启动应用
  5. systemctl restart chronyd

Chrony包含两个部分，chronyd是提供时间同步服务的守护进程，chronyc是用来控制chrony的命令行工具。

Chronyc

与ntpd还有一个不同之处就是Chrony自带了一个命令行工具。

  1. System clock:               
  2. tracking                    Display system time information
  3. makestep                    Correct clock by stepping immediately
  4. makestep <threshold> <updates>
  5. Configure automatic clock stepping
  6. maxupdateskew <skew>        Modify maximum valid skew to update frequency
  7. waitsync [<max-tries> [<max-correction> [<max-skew> [<interval>]]]]
  8. Wait until synchronised in specified limits
  10. Time sources:               
  11. sources [-v]                Display information about current sources
  12. sourcestats [-v]            Display statistics about collected measurements
  13. reselect                    Force reselecting synchronisation source
  14. reselectdist <dist>         Modify reselection distance
  16. NTP sources:                
  17. activity                    Check how many NTP sources are online/offline
  18. ntpdata [<address>]         Display information about last valid measurement
  19. add server <address> [options]
  20. Add new NTP server
  21. add peer <address> [options]
  22. Add new NTP peer
  23. delete <address>            Remove server or peer
  24. burst <n-good>/<n-max> [<mask>/<address>]
  25. Start rapid set of measurements
  26. maxdelay <address> <delay>  Modify maximum valid sample delay
  27. maxdelayratio <address> <ratio>
  28. Modify maximum valid delay/minimum ratio
  29. maxdelaydevratio <address> <ratio>
  30. Modify maximum valid delay/deviation ratio
  31. minpoll <address> <poll>    Modify minimum polling interval
  32. maxpoll <address> <poll>    Modify maximum polling interval
  33. minstratum <address> <stratum>
  34. Modify minimum stratum
  35. offline [<mask>/<address>]  Set sources in subnet to offline status
  36. online [<mask>/<address>]   Set sources in subnet to online status
  37. onoffline                   Set all sources to online or offline status
  38. according to network configuration
  39. polltarget <address> <target>
  40. Modify poll target
  41. refresh                     Refresh IP addresses
  43. Manual time input:          
  44. manual off|on|reset         Disable/enable/reset settime command
  45. manual list                 Show previous settime entries
  46. manual delete <index>       Delete previous settime entry
  47. settime <time>              Set daemon time
  48. (e.g. Sep 25, 2015 16:30:05 or 16:30:05)
  50. NTP access:                 
  51. accheck <address>           Check whether address is allowed
  52. clients                     Report on clients that have accessed the server
  53. serverstats                 Display statistics of the server
  54. allow [<subnet>]            Allow access to subnet as a default
  55. allow all [<subnet>]        Allow access to subnet and all children
  56. deny [<subnet>]             Deny access to subnet as a default
  57. deny all [<subnet>]         Deny access to subnet and all children
  58. local [options]             Serve time even when not synchronised
  59. local off                   Don't serve time when not synchronised
  60. smoothtime reset|activate   Reset/activate time smoothing
  61. smoothing                   Display current time smoothing state
  63. Monitoring access:          
  64. cmdaccheck <address>        Check whether address is allowed
  65. cmdallow [<subnet>]         Allow access to subnet as a default
  66. cmdallow all [<subnet>]     Allow access to subnet and all children
  67. cmddeny [<subnet>]          Deny access to subnet as a default
  68. cmddeny all [<subnet>]      Deny access to subnet and all children
  70. Real-time clock:            
  71. rtcdata                     Print current RTC performance parameters
  72. trimrtc                     Correct RTC relative to system clock
  73. writertc                    Save RTC performance parameters to file
  75. Other daemon commands:      
  76. cyclelogs                   Close and re-open log files
  77. dump                        Dump all measurements to save files
  78. rekey                       Re-read keys from key file
  79. shutdown                    Stop daemon
  81. Client commands:            
  82. dns -n|+n                   Disable/enable resolving IP addresses to hostnames
  83. dns -4|-6|-46               Resolve hostnames only to IPv4/IPv6/both addresses
  84. timeout <milliseconds>      Set initial response timeout
  85. retries <retries>           Set maximum number of retries
  86. keygen [<id> [<type> [<bits>]]]
  87. Generate key for key file
  88. exit|quit                   Leave the program
  89. help                        Generate this help

因为chrony在启动的时候会立刻进行时间同步，所以chronyc的主要用途除了进行配置之外，就是查看当前的状态信息。

配置文件

  1. # Use public servers from the pool.ntp.org project.
  2. # Please consider joining the pool (http://www.pool.ntp.org/join.html).
  3. # 从下列服务器获取时间
  4. server 0.centos.pool.ntp.org iburst
  5. server 1.centos.pool.ntp.org iburst
  6. server 2.centos.pool.ntp.org iburst
  7. server 3.centos.pool.ntp.org iburst
  9. # Record the rate at which the system clock gains/losses time.
  10. driftfile /var/lib/chrony/drift
  12. # Allow the system clock to be stepped in the first three updates
  13. # if its offset is larger than 1 second.
  14. makestep 1.0 3
  16. # Enable kernel synchronization of the real-time clock (RTC).
  17. rtcsync
  19. # Enable hardware timestamping on all interfaces that support it.
  20. #hwtimestamp *
  22. # Increase the minimum number of selectable sources required to adjust
  23. # the system clock.
  24. #minsources 2
  26. # Allow NTP client access from local network.
  27. # 允许以下网段的设备访问此服务器的时间同步服务
  28. #allow 192.168.0.0/16
  30. # Serve time even if not synchronized to a time source.
  31. #local stratum 10
  33. # Specify file containing keys for NTP authentication.
  34. #keyfile /etc/chrony.keys
  36. # Specify directory for log files.
  37. logdir /var/log/chrony
  39. # Select which information is logged.
  40. #log measurements statistics tracking