--- title: 使用Systemd Timesyncd服务来同步Linux时间 abbrlink: c4366641 categories: - 基础运维 tags: - Linux - time - NTP - Systemd date: 2022-04-05 10:53:50 --- 现代Linux发行版都采用systemd管理系统，systemd体系也提供了基础的 `timesyncd` 服务来实现SNTP客户端，可以替代传统的 `ntpd` 来实现主机NTP同步(客户端)。虽然不能作为NTP服务器，但是精简的 `systemd-timesyncd` 可以实现非常轻量级的时钟同步功能。 `systemd-timesyncd` 是通过网络提供系统时钟同步的服务，实现了SNTP client。和NTP实现chrony ntp服务不同， `systemd-timesyncd` 只实现客户端功能，而不是实现完整的NTP，聚焦于从远程服务器查询时间并同步到本地时钟。除非你需要需要为网络中其他NTP客户端提供服务或者需要连接本地硬件时钟，否则一个简单的NTP客户端，例如 `systemd-timesyncd` ，往往是最好的解决方案。这个时钟同步客户端运行只需要最小的权限。每次新的NTP同步请求发起，`timesyncd` 服务就把当前时钟保存到磁盘，并使用它来矫正启动时的系统时钟，这样就适合用于缺少RTC的设备，例如 `Raspberry Pi`或者嵌入设备，可以确保这些系统时钟正确。需要注意，在安装`Systemd进程管理器`时候需要确保创建一个名为 `systemd-timesync` 的用户和组。 ## 配置 - 安装: ```bash yum install systemd-timesyncd ``` - 激活: ```bash systemctl enable systemd-timesyncd.service systemctl start systemd-timesyncd.service ``` 当 `systemd-timesyncd` 启动时会读取 `/etc/systemd/timesyncd.conf` 配置，所以如果要修订配置，例如更改时钟服务器，则类似: ```text [Time] NTP=0.arch.pool.ntp.org 1.arch.pool.ntp.org 2.arch.pool.ntp.org 3.arch.pool.ntp.org FallbackNTP=0.pool.ntp.org 1.pool.ntp.org 0.fr.pool.ntp.org ``` - 要验证配置，执行: ```bash timedatectl show-timesync --all ``` 显示类似: ```text LinkNTPServers= SystemNTPServers= FallbackNTPServers=0.rhel.pool.ntp.org 1.rhel.pool.ntp.org 2.rhel.pool.ntp.org 3.rhel.pool.ntp.org ServerName=0.rhel.pool.ntp.org ServerAddress=124.108.20.1 RootDistanceMaxUSec=5s PollIntervalMinUSec=32s PollIntervalMaxUSec=34min 8s PollIntervalUSec=32s NTPMessage={ Leap=0, Version=4, Mode=4, Stratum=2, Precision=-25, RootDelay=19.866ms, RootDispersion=1.800ms, Reference=D8DAC0CA, OriginateTimestamp=Fri 2021-05-28 16:23:26 CST, ReceiveTimestamp=Fri 2021-05-28 16:23:34 CST, TransmitTimestamp=Fri 2021-05-28 16:23:34 CST, DestinationTimestamp=Fri 2021-05-28 16:23:26 CST, Ignored=no PacketCount=1, Jitter=0 } Frequency=0 ``` ## timedatectl和timesyncd - 使用 `timedatectl status` 可以检查时钟状况: ```bash timedatectl status ``` 输出显示: ```text Local time: Tue 2018-05-01 21:54:24 CST Universal time: Tue 2018-05-01 13:54:24 UTC RTC time: Tue 2018-05-01 13:54:24 Time zone: Asia/Shanghai (CST, +0800) Network time on: yes NTP synchronized: yes RTC in local TZ: no ``` 如果上述显示输出中: ```text Local time: Fri 2021-05-28 16:24:59 CST Universal time: Fri 2021-05-28 08:24:59 UTC RTC time: Fri 2021-05-28 16:24:57 Time zone: Asia/Shanghai (CST, +0800) System clock synchronized: yes NTP service: inactive RTC in local TZ: yes Warning: The system is configured to read the RTC time in the local time zone. This mode cannot be fully supported. It will create various problems with time zone changes and daylight saving time adjustments. The RTC time is never updated, it relies on external facilities to maintain it. If at all possible, use RTC in UTC by calling 'timedatectl set-local-rtc 0'. ``` 可以看到: ```bash NTP service: inactive ``` 实际上没有激活，所以我们通过以下命令激活: ```bash timedatectl set-ntp true ``` 然后再次检查 `timedatectl status` 可以看到: ```text ... NTP service: active ... ``` 此外，按照提示，关闭从本地时区读取RTC时间: ```bash timedatectl set-local-rtc 0 ``` 完成后再次检查 `timedatectl status` 可以看到: ```text Local time: Fri 2021-05-28 16:29:18 CST Universal time: Fri 2021-05-28 08:29:18 UTC RTC time: Fri 2021-05-28 08:29:18 Time zone: Asia/Shanghai (CST, +0800) System clock synchronized: yes NTP service: active RTC in local TZ: no ``` - 检查服务详细信息: ```bash timedatectl timesync-status ``` 可以看到类似输出: ```text Server: 124.108.20.1 (0.rhel.pool.ntp.org) Poll interval: 1min 4s (min: 32s; max 34min 8s) Leap: normal Version: 4 Stratum: 2 Reference: D8DAC0CA Precision: 1us (-25) Root distance: 11.275ms (max: 5s) Offset: -14.956ms Delay: 186.719ms Jitter: 0 Packet count: 1 Frequency: +28.703ppm ``` - 检查时钟同步情况: ```bash systemctl status systemd-timesyncd ``` 显示输出: ```text ● systemd-timesyncd.service - Network Time Synchronization Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled) Drop-In: /lib/systemd/system/systemd-timesyncd.service.d └─disable-with-time-daemon.conf Active: active (running) since Mon 2018-04-16 10:33:42 CST; 2 weeks 1 days ago Docs: man:systemd-timesyncd.service(8) Main PID: 910 (systemd-timesyn) Status: "Synchronized to time server 91.189.91.157:123 (ntp.ubuntu.com)." Tasks: 2 Memory: 2.2M CPU: 2.710s CGroup: /system.slice/systemd-timesyncd.service └─910 /lib/systemd/systemd-timesyncd Apr 29 07:30:24 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.91.157:123 (ntp.ubuntu.com). Apr 29 07:30:24 devstack systemd-timesyncd[910]: Synchronized to time server 91.189.94.4:123 (ntp.ubuntu.com). Apr 29 09:14:36 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.94.4:123 (ntp.ubuntu.com). Apr 29 09:14:46 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.89.198:123 (ntp.ubuntu.com). Apr 29 09:14:56 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.89.199:123 (ntp.ubuntu.com). Apr 29 09:49:06 devstack systemd-timesyncd[910]: Synchronized to time server 91.189.89.199:123 (ntp.ubuntu.com). Apr 29 13:52:01 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.89.199:123 (ntp.ubuntu.com). Apr 29 13:52:11 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.89.198:123 (ntp.ubuntu.com). Apr 29 13:52:21 devstack systemd-timesyncd[910]: Timed out waiting for reply from 91.189.94.4:123 (ntp.ubuntu.com). Apr 29 13:52:22 devstack systemd-timesyncd[910]: Synchronized to time server 91.189.91.157:123 (ntp.ubuntu.com). ``` - 在 `/etc/systemd/timesyncd.conf` 设置 `timedatectl` 和 `timesyncd` 获取时钟值的服务器，并且详细配置可以在 `/etc/systemd/timesyncd.conf.d/` 目录下找到 - 在 `/etc/systemd/timesyncd.conf` 中配置了 `timedatectl` 访问的服务器，这里配置局域网中自建的 [部署NTP服务(集群)](https://cloud-atlas.readthedocs.io/zh_CN/latest/linux/redhat_linux/systemd/../../../infra_service/ntp/deploy_ntp.html#deploy-ntp) ```ini [Time] NTP=192.168.6.11 ``` - 重启 `systemd-timesyncd` 服务: ```bash sudo systemctl restart systemd-timesyncd ``` - 检查和指定NTP服务器同步时间: ```bash systemctl status systemd-timesyncd ``` 可以看到同步过程: ```text ... May 01 22:38:36 pi1 systemd[1]: Starting Network Time Synchronization... May 01 22:38:37 pi1 systemd[1]: Started Network Time Synchronization. May 01 22:38:37 pi1 systemd-timesyncd[23922]: Synchronized to time server 192.168.6.11:123 (192.168.6.11). ``` ## 参考 - [systemd-timesyncd](https://wiki.archlinux.org/title/systemd-timesyncd)