Update Database Containers and Others Reliably

Containers that don't have a built in script

Stop the application (docker-compose down)
Start just the database (docker-compose up -d db)
Export all databases on the server into plaintext (pg_dumpall -U username > data.sql)
Stop the database (docker-compose down)
Remove the contents of the database directory, wherever you’ve mounted in /var/lib/postgres
Update the tag you are using, and pull the new container (postgres:12-alpine → postgres:14-alpine)
Start just the database (docker-compose up -d db). This will recreate a fresh database, using the credentials from the environment.
Import the data into the new database (psql -U username < data.sql)
Stop the database container (docker-compose down)
Start everything (docker-compose up -d)