initialize postgres container from docker-compose file

Question

I am trying to start a postgres container form docker-compose file and also initialize it.

docker-compose.yml

version: "3"
  postgres:
  image: "postgres"
  command: bash -c "
   postgres &&
   createuser -l \"auser\"
   "

My goal is: 1) start postgres container 2) create a user

The current implementation fails with the following error

"root" execution of the PostgreSQL server is not permitted.
The server must be started under an unprivileged user ID to prevent
possible system security compromise.  See the documentation for
more information on how to properly start the server.

Answer 1

"root" execution of the PostgreSQL server is not permitted.

You should not run the DB container with root user. better to run postgres user.

one way is to specify the user in the docker-compose.

postgres:
  image: postgres
  container_name: postgres
  user: postgres
  ports:
    - "5432:5432"
  command: 'postgres'

But agains

  command: bash -c "
   postgres &&
   createuser -l \"auser\"
   "

during the create user command, there might be the case that the DB contains is not ready to accept the connection.

So you have two best option.

• Using Environment variables

POSTGRES_USER

This optional environment variable is used in conjunction with POSTGRES_PASSWORD to set a user and its password. This variable will create the specified user with superuser power and a database with the same name. If it is not specified, then the default user of postgres will be used.

postgres:
  image: postgres
  container_name: postgres
  environment:
    POSTGRES_USER: test
    POSTGRES_PASSWORD: password
    POSTGRES_DB: myapp
  user: postgres
  ports:
    - "5432:5432"

The second option

Initialization scripts

If you would like to do additional initialization in an image derived from this one, add one or more *.sql, *.sql.gz, or *.sh scripts under /docker-entrypoint-initdb.d (creating the directory if necessary). After the entrypoint calls initdb to create the default postgres user and database, it will run any *.sql files , run any executable *.sh scripts, and source any non-executable *.sh scripts found in that directory to do further initialization before starting the service.

For example, to add an additional user and database , add the following to /docker-entrypoint-initdb.d/init-user-db.sh :

#!/bin/bash
set -e

psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
    CREATE USER docker;
    CREATE DATABASE docker;
    GRANT ALL PRIVILEGES ON DATABASE docker TO docker;
EOSQL