Log into Postgres on a Docker container

docker exec -it <container_name> psql -U <database_username>

Log into a Postgres DB on a Docker container

docker exec -it <container_name> psql -U <database_username> -a <database_name>

Backing up Your Data

docker exec -it <container_name> pg_dump -U <user_name> --column-inserts --data-only <db_name> > backup.sql

eg:

docker exec -it ocs-postgresql pg_dump -U postgres --column-inserts --data-only ocs > backup.sql

Restore data from sql files

docker cp ./backup.sql <container_name>:/data.sql
docker exec -it <container_name> psql -U <user_name> -a <db_name> -f /data.sql

eg:

docker cp ./backup.sql ocs-postgresql:/data.sql
docker exec -it ocs-postgresql psql -U postgres -a ocs -f /data.sql

References