How to customize the configuration file of the official PostgreSQL Docker image?

Question

I\'m using the official Postgres Docker image trying to customize its configuration. For this purpose, I use the command sed to change max_connections

Answer 1

A fairly low-tech solution to this problem seems to be to declare the service (I'm using swarm on AWS and a yaml file) with your database files mounted to a persisted volume (here AWS EFS as denoted by the cloudstor:aws driver specification).

  version: '3.3'
  services:
    database:
      image: postgres:latest
      volumes:
        - postgresql:/var/lib/postgresql
        - postgresql_data:/var/lib/postgresql/data
    volumes:
       postgresql:
         driver: "cloudstor:aws" 
       postgresql_data:
         driver: "cloudstor:aws"

1. The db comes up as initialized with the image default settings.
2. You edit the conf settings inside the container, e.g if you want to increase the maximum number of concurrent connections that requires a restart
3. stop the running container (or scale the service down to zero and then back to one)
4. the swarm spawns a new container, which this time around picks up your persisted configuration settings and merrily applies them.

A pleasant side-effect of persisting your configuration is that it also persists your databases (or was it the other way around) ;-)