Furthermore, it also displays the currently configured time zone of the system (which is UTC by default in our images). The timedatectl allows displaying the current time, both, the system clock and the hardware clock. Note: To let one of the RTCs retain the time even when no power is applied to the system, put a backup battery in the respective holder on the carrier board. Traditionally, on power off, the system clock will get stored into the hardware clock by a shutdown script. You can display the current time, set a hardware clock to a specified time, set a hardware clock to the system time, and set the system time from the hardware clock. The system clock will not get stored into the hardware clock on shutdown.Īlternatively, there is the tool hwclock for accessing one of the hardware clocks directly.
When using the timedatectl utility, the time will get stored into the hardware clock immediately when setting a new date or time.
Our images use systemd-timedated and the timedatectl command since V2.1 and sytemd-timesyncd since V2.4 to synchronize time with a remote Network Time Protocol (NTP) server. From that point onward the system clock is used to track time. At boot time, the hardware clock is read and used to set the system clock.
The second clock is called the ‘ system clock/tick’ or ' kernel clock' and is maintained by the operating system. This is the battery-backed clock that keeps time even when the system is shut down. Note: To let one of the RTCs retain the time even when no power is applied to the system, put a backup battery in the respective holder on the carrier board. Two clocks are important in Linux: a ‘ hardware clock’, also known as RTC, CMOS or BIOS clock.
#HOWTO SET THE RTC POWER ON TIME HOW TO#
This article describes how to use a Real-Time Clock (RTC) on Embedded Linux. Is this page helpful? Real-Time Clock / RTC (Linux) Purpose
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