Exploring the Functionality and Significance of RTC in Linux Systems（linuxrtc）
Real-Time Clock (RTC) is an essential component of Linux systems that is often taken for granted. While its main job is to provide accurate time and date information, RTCs also act as a source for other system functions, such as setting the system time and providing a time reference for timed events. This article takes a look at what RTCs are and how they work in the Linux operating system.
RTCs are used to keep track of time between reboots of the operating system and power cycles of the system. The clock is set using a small battery connected to the system. This battery allows the data to persist even when the power is off. This is useful in applications such as scheduling tasks, where the system needs to record events that have been scheduled without having to depend on a time server.
RTCs typically have a separate time zone and day-light savings setting that is unique to each system. It is important to ensure the operating system is set for the correct time zone and daylight savings setting if the system is used over multiple geographic areas. This can be set through the RTC settings in the operating system.
RTCs also play an important role in synchronizing the various threads running in the Linux operating system. This involves two tasks: 1) synchronizing the system time with the RTC, and 2) synchronizing the various threads with each other. The first task is often done by the operating system itself by setting the system time with the data stored in the RTC. The second task is done by using the RTC as the reference against which all the systems threads can be synchronized.
RTCs are an essential component of the Linux operating system, without which it would be impossible to keep accurate time. RTCs allow the operating system to accurately set the time, record events and synchronize the various threads running in the OS. Setting the correct time and time zone is essential as incorrect time settings can cause inconsistency in the system.
Below is a sample code to set RTC time in Linux:
# include
# include
/* Set the RTC time from the given struct tm */
int set_rtc_time(struct tm *t)
{
int rtc_fd;
rtc_fd = open(“/dev/rtc”, O_RDWR);
if (rtc_fd == -1) {
perror(“Failed to open RTC, exiting”);
close(rtc_fd);
return -1;
}
struct rtc_time r;
/* Fill rtc_time structure */
r.tm_sec = t->tm_sec;
r.tm_min = t->tm_min;
r.tm_hour = t->tm_hour;
r.tm_mday = t->tm_mday;
r.tm_mon = t->tm_mon;
r.tm_year = t->tm_year;
/* Set the rtc time on the RTC */
int res = ioctl(rtc_fd, RTC_SET_TIME, &r);
if (res == -1) {
perror(“Failed to set RTC time, exiting”);
close(rtc_fd);
return -1;
}
close(rtc_fd);
return 0;
}
In conclusion, RTCs are an essential part of Linux systems and plays a crucial role in keeping accurate time. For the system to function correctly, the time and time zone must be correctly configured. RTCs provide a reliable source for system time as well as for synchronization of the various threads within the operating system. Developers and system administrators should pay close attention to setting up and maintaining RTCs in their Linux systems.
