How you ever wondered how docker volumes work? Let's jump into it real quick.

• A special type of storage in docker.
• Designed to persist data independent of the container lifecycle.
  • The idea is that when a container stops, crashes, or is deleted, the data stored in the volume remains intact as long as the volume itself is not deleted.
• Gives you data isolation.
• Bind mount:
  • Directly maps a host (your local system filesystem) directory, into a docker volume.
• Volume:
  • Is managed by docker and stored in docker's storage directory (e.g., /var/lib/docker/volumes on Linux).

• E.g. in this compose file we Map a named volume (i.e. postgres) to the container path /var/lib/postgresql/data/pgdata.

  That is where PostgreSQL stores its data files by default (ref). This ensures PostgreSQL's database files are written to the volume.

• To test it:

  1. Run this python script.
  2. docker compose down. Do NOT pass -v flag since it will delete the volume along side the data.
  3. docker compose up -d.
  4. Check your database to see if everything is there.