RTC
Pigeon RB100 has a real-time clock with a backup battery (CR2032). When the system starts, it takes the time from the RTC if system clock update is failed through NTP.
Useful commands
-
Read hardware clock date and time
hwclock
-
Copy system time to hardware time
hwclock -w
-
Copy hardware time to system time
hwclock -s
- Set hardware clock date and time manually
hwclock --set --date "02/20/2016 11:10:00"
Change system time zone
- Run:
raspi-config
- Select Internationalization options
- Select Time Zone
- Select Geographical area
- Select city or region
Network time synchronization
There's a systemd-timesync service running on a default install of Stretch. Systemd-timesyncd is a daemon that has been added for synchronizing the system clock across the network. It implements an SNTP client. Make sure the machine is allowed to query servers over port 123/udp.
To check the service status, use:
timedatectl
You can also watch systemd/clock:
pi@pigeon:~$ stat /var/lib/systemd/clock
File: /var/lib/systemd/clock
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: b302h/45826d Inode: 18931 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 100/systemd-timesync) Gid: ( 103/systemd-timesync)
Access: 2019-01-11 11:40:58.613881976 +0000
Modify: 2019-01-11 11:40:58.613881976 +0000
Change: 2019-01-11 11:40:58.613881976 +0000
Birth: -
The Access/Modify/Change times on this file show when systemd-timesynd last touched it.
Restarting the systemd-timesyncd service force a sync:
systemctl restart systemd-timesyncd
Systemd-timesyncd automatically updates the hardware clock after sync.
If you would like to change NTP servers (for example to a local one) edit file /etc/systemd/timesyncd.conf. The configuration parameters PollIntervalMinSec and PollIntervalMaxSec that can be set in /etc/systemd/timesyncd.conf are not recognized in current Raspbian. Default PollIntervalMaxSec is 2048 seconds.
Network time synchronization is enabled by default. To disable it use:
timedatectl set-ntp false
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