The master password must be set in the 5_tempfs.json configuration file. This password is used to encrypt S3 access and secret keys in the database and should be the same for every instance of the Temp File Service that uses this database.
To configure this password, execute the following command from a command line interface, with [path to 5_tempfs.json] replaced with the path to the 5_tempfs.json file and [my_password_here] replaced with the password:
.\TempFileService.Configuration.exe security set-global-scheme --use-master-password-v2 --password "[my_password_here]" --json-config "[path to 5_tempfs.json]"
Note:
Once this command is run, the password is encrypted using the Windows DPAPI.