Since the app name has been changed from gyazz to Scrapbox when it was released, the name of the database has also been changed and you can use the following steps to migrate your database.
Cautionary note You can continue without changing the name of your database. Simply follow steps 2 and 3 of this document. In that case, you can continue using your database without changing MONGODB_URL.
1. Renaming the database
Note: You can also rename your database later after completing steps 2 and 3 first
First, after closing your instance, copy (backup) your data to another location
The default location for the database data is the mongo directory in the same location as docker-compose.yml.
Open a new instance and start the mongo shell
$ docker-compose exec mongo mongo
Since mongo can't rename the database, first make a copy
> db.copyDatabase('gyazz', 'scrapbox')
Just in case, delete gyazz
> use gyazz
After exiting the mongo shell,
change the 'MONGODB_URL' in 'docker-compose.yml'.
Restart the instance
$ docker-compose down
$ docker-compose up
and you're finished!
2. Renaming the folder
Change the name of the folder containing docker-compose.yml and the mongo data from gyazz to scrapbox.