If you update from a version prior 1.8.0 to 1.8.0 you need to do a backup as described in the docs of <1.8.0: go Here
You can make a backup to the local host. There is a backup-script which will make a copy of all necessary folders and does complete DB-dumps.
Make sure the server is running (launched by ./install.sh). Then run:
This will create a new folder inside the home-folder of the pi-server-docker installation called backup. Inside this folder it will create a new directory for each backup. In that directory you will find the DB-dumps of the postgres-server and the two mongo-db's. Additionally the piplanning.cfg config file will be copied over.