Now that I am runing Radicale on my own Linux server (to manage calendars and contacts), I am trying to figure out how to backup Addressbooks via a bash script (which I could then cron or manually launch).
The exporting part is not going to be so difficult thanks to Duplicity.
But where the ... is located the Addressbook ? There is no *.vcf related to Radicale anywhere on my system.
I've found it. It is in located in the personal directory : ~/.config/radicale/collections/contact/AddressBook.vcf
In ~/.config/radicale/collections/contact you there are as well the calendars.
Hum. This seems to me to be (remotly) a programing question, since its answer is program for who want to program its own bash backup script.