switched to postgres-backup

docker-compose.yml

                     - postgresql.pdns.internal.docker
         volumes:
             - ./data/postgresql/data:/var/lib/postgresql/data
+            - ./data/postgresql/backup:/var/lib/postgresql/backup
         ports:
             - "127.0.0.1:34020:5432"
         env_file:

postgresql/Dockerfile

-FROM postgres:9.6
+FROM robinthoni/postgres-backup:9.6
 
 RUN rm -rf /var/log/*