Linux Device Drivers Development

The hwclock utility

The hardware clock (hwclock) is a tool used to access RTC devices. The man hwclock command will probably be much more meaningful than everything else discussed in this section. That said, let's write some commands to set the hwclock RTC from the system clock:

 $ sudo ntpd -q    # make sure system clock is set from network time
 $ sudo hwclock --systohc   # set rtc from the system clock
 $ sudo hwclock --show      # check rtc was set
 Sat May 17 17:36:50 2017  -0.671045 seconds  

The preceding example assumes that the host has a network connection on which it can access an NTP server. It is also possible to set the system time manually:

 $ sudo date -s '2017-08-28 17:14:00' '+%s' #set system clock manually
 $ sudo hwclock --systohc #synchronize ...