Raspberry Pi hardware real-time-clock?

[roger peppe]

Hi,

Not sure if this is the right place to ask this question - apologies if not.

I need a hardware RTC on my Raspberry Pi model B and I have
acquired one of these https://www.abelectronics.co.uk/p/52/RTC-Pi-Plus

I'm running a reasonably recent version of Ubuntu Core with snappy
version 2.18.1.

What's the best way of adding this to my Pi so that it gets the time
on bootstrap and keeps it in sync? The instructions I've found rely
on changing configuration files that are on the read-only filesystem,
such as /etc/init.d/hwclock.sh. I'd be happy to make a new snap
to do this if that's what's needed.

Thanks for any pointers,

  cheers,
     rog.