測試作業系統 CentOS 8 x86_64 (虛擬機)
目前 Linux 上的時間是透過 timedatectl 與 chronyd 這兩個服務,下面來看一下用法.
timedatectl
timedatectl 指令是由 systemd 套件提供.
[root@localhost ~]# rpm -qf /usr/bin/timedatectl systemd-239-39.el8.x86_64
之前通常會使用 date 來修改時間,不過在 CentOS 7 / CentOS 8 使用 systemd 的系統,建議使用 timedatectl 來設定與檢視日期時間.
[root@localhost ~]# timedatectl
Local time: Thu 2019-08-08 11:49:20 CST
Universal time: Thu 2019-08-08 03:49:20 UTC
RTC time: Thu 2019-08-08 03:49:20
Time zone: Asia/Taipei (CST, +0800)
NTP enabled: no
NTP synchronized: yes
RTC in local TZ: no
DST active: n/a
設定日期時間.
[root@localhost ~]# timedatectl set-time "2019-08-08 11:50:00"
設定時區 (TimeZone).
[root@localhost ~]# timedatectl list-timezones | grep -i taipei Asia/Taipei
[root@localhost ~]# timedatectl set-timezone "Asia/Taipei"
[root@localhost ~]# timedatectl
Local time: Thu 2019-08-08 11:55:49 CST
Universal time: Thu 2019-08-08 03:55:49 UTC
RTC time: Thu 2019-08-08 03:55:49
Time zone: Asia/Taipei (CST, +0800)
NTP enabled: yes
NTP synchronized: yes
RTC in local TZ: no
DST active: n/a
改時區需把 rsyslog – https://benjr.tw/34103 日誌 log 服務重啟,避免時間與 log 紀錄的時間不相同.
[root@localhost ~]# systemctl restart rsyslog
chronyd
從 RHEL / CentOS 7 之後使用 Chrony 為預設校時服務 (NTP :Network Time Protocol ) ,預設應該都有安裝, chrony 套件如下.
[root@localhost ~]# yum install chrony
timedatectl 可以設定 NTP (Network Time Protocol) 使用網路校時.
[root@localhost ~]# timedatectl set-ntp yes
[root@localhost ~]# timedatectl
Local time: Thu 2019-08-08 11:54:53 CST
Universal time: Thu 2019-08-08 03:54:53 UTC
RTC time: Thu 2019-08-08 03:54:00
Time zone: Asia/Taipei (CST, +0800)
NTP enabled: yes
NTP synchronized: no
RTC in local TZ: no
DST active: n/a
- NTP Client
當我們設定 NTP (Network Time Protocol) 為 Yes 時,會把 chronyd 這個 NTP 服務打開.[root@localhost ~]# cat /var/log/messages Mar 12 19:21:18 localhost dbus-daemon[921]: [system] Activating via systemd: service name='org.freedesktop.timedate1' unit='dbus-org.freedesktop.timedate1.service' requested by ':1.199' (uid=0 pid=2374 comm="timedatectl set-ntp yes ") Mar 12 19:21:18 localhost systemd[1]: Starting System clock and RTC settings service... Mar 12 19:21:18 localhost dbus-daemon[921]: [system] Successfully activated service 'org.freedesktop.timedate1' Mar 12 19:21:18 localhost systemd[1]: Started System clock and RTC settings service. Mar 12 19:21:18 localhost systemd[1]: Starting NTP client/server... Mar 12 19:21:18 localhost systemd[1]: Reloading. Mar 12 19:21:18 localhost chronyd[2400]: chronyd version 3.5 starting (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP +SCFILTER +SIGND +ASYNCDNS +SECHASH +IPV6 +DEBUG) Mar 12 19:21:18 localhost chronyd[2400]: Initial frequency 100000.000 ppm Mar 12 19:21:18 localhost chronyd[2400]: Using right/UTC timezone to obtain leap second data Mar 12 19:21:18 localhost systemd[1]: Started NTP client/server. Mar 12 19:21:24 localhost chronyd[2400]: Selected source 103.122.188.3 Mar 12 11:38:38 localhost chronyd[2400]: System clock TAI offset set to 37 seconds Mar 12 11:38:38 localhost chronyd[2400]: System clock wrong by -27765.715096 seconds, adjustment started Mar 12 11:38:38 localhost chronyd[2400]: System clock was stepped by -27765.715096 seconds Mar 12 11:38:38 localhost rsyslogd[1240]: imjournal: journal reloaded... [v8.37.0-13.el8 try http://www.rsyslog.com/e/0 ] Mar 12 11:38:40 localhost chronyd[2400]: Selected source 183.177.72.202 Mar 12 11:38:49 localhost chronyd[2400]: Source 2406:2000:fc:437::2000 replaced with 106.104.162.193 Mar 12 11:38:59 localhost chronyd[2400]: Selected source 106.104.162.193 Mar 12 11:38:59 localhost chronyd[2400]: System clock wrong by 1.888458 seconds, adjustment started Mar 12 11:38:59 localhost chronyd[2400]: System clock was stepped by 1.888390 seconds
也可以透過 systemctl 來顯示 chronyd.service 的狀態.
[root@localhost ~]# systemctl status chronyd.service ● chronyd.service - NTP client/server Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled) Active: active (running) since Thu 2020-03-12 19:21:18 CST; 7h left Docs: man:chronyd(8) man:chrony.conf(5) Process: 2406 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS) Process: 2379 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS) Main PID: 2400 (chronyd) Tasks: 1 Memory: 1.9M CGroup: /system.slice/chronyd.service └─2400 /usr/sbin/chronyd設定檔位於 /etc/chrony.conf ,或是透過下面指令來檢視其狀態.
- tracking : The tracking command displays parameters about the system’s clock performance.
[root@localhost ~]# chronyc tracking Reference ID : B7B148CA (t2.time.tw1.yahoo.com) Stratum : 3 Ref time (UTC) : Thu Mar 12 03:43:18 2020 System time : 0.118893698 seconds slow of NTP time Last offset : +0.091888450 seconds RMS offset : 1.505703568 seconds Frequency : 100000.000 ppm fast Residual freq : -17442.777 ppm Skew : 1000000.000 ppm Root delay : 0.048257317 seconds Root dispersion : 19.612304688 seconds Update interval : 68.3 seconds Leap status : Normal
- sources : This command displays information about the current time sources that chronyd is accessing.
[root@localhost ~]# chronyc sources 210 Number of sources = 4 MS Name/IP address Stratum Poll Reach LastRx Last sample =============================================================================== ^* t2.time.tw1.yahoo.com 2 6 377 40 +98ms[ +190ms] +/- 35ms ^- zimbra.alqualonde.org 3 6 377 40 +102ms[ +102ms] +/- 155ms ^- 103.122.188.3 2 6 377 40 +99ms[ +99ms] +/- 51ms ^- 106-104-162-193.adsl.sta> 2 6 375 45 +95ms[ +95ms] +/- 84ms
- tracking : The tracking command displays parameters about the system’s clock performance.
- NTP Server (IP: 192.168.31.132)
當 chronyd.service 服務啟動後,其他電腦就可以把這一台當作 NTP(Network Time Protocol) 伺服器,需調整 chrony.conf 設定檔(須設定哪些網段可以使用).[root@localhost ~]# cat /etc/chrony.conf # Allow NTP client access from local network. allow 192.168.0.0/16
這一行設定允許特定網段的使用者把你當做時間伺服器.
如果你的 Chrony (NTP Server) 是在內部無法對外,這樣還能當 NTP Server 嗎? 找了一下資料 https://serverfault.com/questions/995101/how-to-synchronize-clocks-on-servers-with-no-internet-access 設定如下.
[root@localhost ~]# cat /etc/chrony.conf # Record the rate at which the system clock gains/losses time. driftfile /var/lib/chrony/drift # Serve time even if not synchronized to a time source. local stratum 10 manual
說明:
- driftfile /var/lib/chrony/drift
儲存本地端主機與上層 NTP Server 的誤差 (單位 : PPM – Parts Per Million , 1 PPM (Part Per Million) -> 1 microsecond per second -> 1*60*60/1000 (m) = 3.6ms per hour -> 3.6ms*24= 86.4ms per day) - local stratum 8
NTP是階層架構 (stratum) ,把服務設定在 local 階層架構 (stratum) 8 . - manual
?
- driftfile /var/lib/chrony/drift
- NTP Client (Internal chronyd)
要使用剛剛設定好的 NTP Server (chronyd IP: 192.168.31.132 ), Client 須把設定檔 /etc/chrony.conf 指定為這一台 IP.[root@localhost ~]# vi /etc/chrony.conf # Use public servers from the pool.ntp.org project. # Please consider joining the pool (http://www.pool.ntp.org/join.html). # pool 2.centos.pool.ntp.org iburst server 192.168.31.132 iburst [root@localhost ~]# systemctl restart chronyd
測試一下.
[root@localhost ~]# chronyc -a makestep 200 OK
測試時 Source state 必須為 ‘*’ ( current best )
[root@localhost ~]# chronyc sources -v .-- Source mode '^' = server, '=' = peer, '#' = local clock. / .- Source state '*' = current best, '+' = combined, '-' = not combined, | / 'x' = may be in error, '~' = too variable, '?' = unusable. || .- 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 =============================================================================== ^* 192.168.31.132 3 6 377 52 +132us[ +143us] +/- 36ms
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