Ubuntu NTP 校時

timedatectl 時間管理工具

• 顯示目前的設定狀態

  # 顯示目前狀態
  timedatectl
  

               Local time: 三 2023-04-26 11:00:22 CST
           Universal time: 三 2023-04-26 03:00:22 UTC
                 RTC time: 三 2023-04-26 03:00:22    
                Time zone: Asia/Taipei (CST, +0800)  
System clock synchronized: yes                       
              NTP service: active                    
          RTC in local TZ: no  

• 啟動網路校時 輸入下面指令後，就會打開網路校時功能

  # 啟用 NTP 校時
  timedatectl set-ntp yes
  

  Ubuntu使用的是systemd-timesyncd，因此等一下要設定systemd-timesyncd

• 檢查systemd-timesyncd服務狀態

  # 檢查 systemd-timesyncd 服務狀態
  systemctl status systemd-timesyncd
  

● systemd-timesyncd.service - Network Time Synchronization
     Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2023-04-26 10:58:34 CST; 1min 19s ago
       Docs: man:systemd-timesyncd.service(8)
   Main PID: 221565 (systemd-timesyn)
     Status: "Synchronized to time server 91.189.89.198:123 (ntp.ubuntu.com)."
      Tasks: 2 (limit: 38317)
     Memory: 1.2M
     CGroup: /system.slice/systemd-timesyncd.service
             └─221565 /lib/systemd/systemd-timesyncd

• 設定校時伺服器 要設定校時伺服器可以用root權限編輯以下檔案/etc/systemd/timesyncd.conf

[Time]
# NTP 伺服器（以空白分隔多個伺服器）
NTP=tw.pool.ntp.org jp.pool.ntp.org

# 備用 NTP 伺服器（以空白分隔多個伺服器）
FallbackNTP=sg.pool.ntp.org ntp.ubuntu.com

• 重新啟動systemd-timesyncd服務 重啟服務讓更改生效

  # 重新啟動 systemd-timesyncd 服務
  systemctl restart systemd-timesyncd
  

• 檢查一下是不是有跟NTP校時了 用指令systemctl status systemd-timesyncd看一下目前服務狀態，如果有更新成功會顯示出來

錯誤排除

• 出現Server has too large root distance. Disconnecting.訊息 表示機器跟ntp server之間回應的時間太久，因此可以去修改/etc/systemd/timesyncd.conf並加入RootDistanceMaxSec=，通常30秒已經很夠用了

  # See timesyncd.conf(5) for details.
  [Time]
  NTP=10.10.1.30
  #FallbackNTP=
  RootDistanceMaxSec=30
  #PollIntervalMinSec=32
  #PollIntervalMaxSec=2048
  

  詳細說明如下 https://unix.stackexchange.com/a/655489

參考:
https://www.cnblogs.com/pipci/p/12833228.html
https://officeguide.cc/ubuntu-linux-timedatectl-time-synchronization-tutorial/
https://www.digitalocean.com/community/tutorials/how-to-set-up-time-synchronization-on-ubuntu-20-04
https://www.tenable.com/audits/items/CIS_Ubuntu_18.04_LTS_Server_v2.1.0_L1.audit:26286d27c59292cfdb9c7b04593edbed
https://serverfault.com/questions/1024770/ubuntu-20-04-time-sync-problems-and-possibly-incorrect-status-information