hwclock - settings that affect the behaviour of the hwclock init script
The /etc/default/hwclock file contains settings in POSIX format:
VAR=VAL
Only one assignment is allowed per line. Comments (starting with '#') are also allowed.
The following settings can be set.
The hardware clock device you want to use. Defaults to rtc0. It should probably match the CONFIG_RTC_HCTOSYS_DEVICE kernel config option.
If you change this, you also need to install a custom udev rule, mirroring /usr/lib/udev/rules.d/85-hwclock.rules. Otherwise, the hardware clock device will be ignored during boot.
On almost all systems, this should not be changed.
On systems using systemd as init, the hwclock init script is ignored.
hwclock(8), systemd-timesyncd.service(8)