how do i backup a database in docker - postgresql

Question

i'm running my app using docker-compose with the below yml file
postgres:
container_name: postgres
image: postgres:${POSTGRES_VERSION}
volumes:
- postgresdata:/var/lib/postgresql/data
expose:
- "5432"
environment:
- POSTGRES_DB=42EXP
- POSTGRES_USER=${POSTGRES_USER}
- POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
node:
container_name: node
links:
- postgres:postgres
depends_on:
- postgres
volumes:
postgresdata:
As you can see here ,i'm using a named volume to manage postgres state.
According to the official docs, i can backup a volume like the below
docker run --rm --volumes postgresdata:/var/lib/postgresql/data -v $(pwd):/backup ubuntu tar cvf /backup/backup.tar /dbdata
Some other tutorials suggested i use the pg-dump function provided by postgres for backups.
pg_dump -Fc database_name_here > database.bak
I guess i would have to go inside the postgres container to perform this function and mount the backup directory to the host.
Is one approach better/preferable than the other?

Answer 1

To run pg_dump you can use docker exec command:
To backup:
docker exec -u <your_postgres_user> <postgres_container_name> pg_dump -Fc <database_name_here> > db.dump
To drop db (Don't do it on production, for test purpose only!!!):
docker exec -u <your_postgres_user> <postgres_container_name> psql -c 'DROP DATABASE <your_db_name>'
To restore:
docker exec -i -u <your_postgres_user> <postgres_container_name> pg_restore -C -d postgres < db.dump
Also you can use docker-compose analog of exec. In that case you can use short services name (postgres) instead of full container name (composeproject_postgres).
docker exec
docker-compose exec
pg_restore

Answer 2

Since you have
expose:
- "5432"
you can run
pg_dump -U <user> -h localhost -Fc <db_name> > 1.dump
pg_dump connects to 5432 port to make dump since it is listened by postgres in container you will dump db from container

Answer 3

You can also run
docker-compose exec -T postgres sh -c 'pg_dump -cU $POSTGRES_USER $POSTGRES_DB' | gzip > netbox.sql.gz
where netbox.sql.gz is the name of the backup file.
restoring would be
gunzip -c netbox.sql.gz | docker-compose exec -T postgres sh -c 'psql -U $POSTGRES_USER $POSTGRES_DB'