Recently I need to change the clocksource on Ubuntu 22.04 running on RISC-V LicheeRV Dock to something else, since the default timer was unreliable. The question is, how to make a change to /sys/devices permanent?

At first, I thought to use sysctl and modify one of /etc/sysctl.conf or /etc/sysctl.d but that actually only works for /proc/sys and not /sys sysfs.

Alternative was to use sysfsutils but the documentation is totally lacking.

How about the good old /etc/rc.local? The systemctl way looks quite complicated though.

Cron offers the @reboot directive, so it’s quite easy to do sudo crontab -e then add the following line:

@reboot echo riscv_clocksource > /sys/devices/system/clocksource/clocksource0/current_clocksource

Verify that cron is enabled:

sudo systemctl status cron

And reboot.