https://stackoverflow.com/questions/69140522/what-is-wrong-with-trying-to-create-two-instances-of-docker-compose-yml

No-reproduce-session.txt

$ docker --version
Docker version 20.10.8, build 3967b7d

$ docker-compose --version
docker-compose version 1.29.2, build unknown

$ tree -a
.
├── config
│   ├── .env.dev
│   └── .env.dev2
├── docker-compose.yml
└── postgres
    └── Dockerfile

2 directories, 4 files

$ cat config/.env.dev
COMPOSE_PROJECT_NAME=instance1
PORT_NUMBER=5432

$ cat config/.env.dev2 
COMPOSE_PROJECT_NAME=instance2
PORT_NUMBER=5433

$ cat postgres/Dockerfile 
FROM postgres:9.6

$ cat docker-compose.yml 
version: '3.1'

services:
 postgres:
   image: my_postgres
   build:
     context: .
     dockerfile: postgres/Dockerfile
   environment:
     - POSTGRES_PASSWORD=postgres
     - POSTGRES_USER=postgres
   ports:
     - "${PORT_NUMBER}:5432"
     
$ docker-compose --env-file config/.env.dev up -d
Creating network "instance1_default" with the default driver
Building postgres
Sending build context to Docker daemon  6.144kB
Step 1/1 : FROM postgres:9.6
9.6: Pulling from library/postgres
442547fc262c: Pull complete 
99f9b0d37d63: Pull complete 
673a0386621a: Pull complete 
e6d442b05d6a: Pull complete 
e9b9f3eeffa3: Pull complete 
17b8a068ac5a: Pull complete 
2916937b1163: Pull complete 
ddee610c7782: Pull complete 
ce9cbe2e8b78: Pull complete 
eaf59b47e853: Pull complete 
54b66656577d: Pull complete 
a786874f0014: Pull complete 
88cc180e8f2d: Pull complete 
2738829e1ed0: Pull complete 
Digest: sha256:f202bd795dd0896c476960ff3a08e68246c07c0cf83b208a64c893b4ce3bf041
Status: Downloaded newer image for postgres:9.6
 ---> fef432eee5c2
Successfully built fef432eee5c2
Successfully tagged my_postgres:latest
WARNING: Image for service postgres was built because it did not already exist. To rebuild this image you must use `docker-compose build` or `docker-compose up --build`.
Creating instance1_postgres_1 ... done

$ docker-compose --env-file config/.env.dev2 up -d
Creating network "instance2_default" with the default driver
Creating instance2_postgres_1 ... done

$ PGPASSWORD=postgres psql -h localhost -p 5432 -U postgres -c "\\c"
psql (12.8 (Ubuntu 12.8-0ubuntu0.20.04.1), server 9.6.23)
You are now connected to database "postgres" as user "postgres".

$ PGPASSWORD=postgres psql -h localhost -p 5433 -U postgres -c "\\c"
psql (12.8 (Ubuntu 12.8-0ubuntu0.20.04.1), server 9.6.23)
You are now connected to database "postgres" as user "postgres".

# Cleaning up
$ docker-compose --env-file config/.env.dev down -v
Stopping instance1_postgres_1 ... done
Removing instance1_postgres_1 ... done
Removing network instance1_default

$ docker-compose --env-file config/.env.dev2 down -v
Stopping instance2_postgres_1 ... done
Removing instance2_postgres_1 ... done
Removing network instance2_default

$ docker rmi my_postgres:latest postgres:9.6 
Untagged: my_postgres:latest
Untagged: postgres:9.6
Untagged: postgres@sha256:f202bd795dd0896c476960ff3a08e68246c07c0cf83b208a64c893b4ce3bf041
Deleted: sha256:fef432eee5c23eef4d8cba0357f52447068d4064c8dff5cb415f6ac6f15b84a3
Deleted: sha256:5d720b43abfebf60a6cdbe7e810f2a086c2e5974f487fac7d52cf2d9eefc0632
Deleted: sha256:77ede50ea83caea122ef2534b7ac8a3eaf46ab8698f40f39e43c304d83bf087e
Deleted: sha256:027c1a5108a62cf793fb445149a763fa11501c89cecb7469b5a8a8e9d975a13d
Deleted: sha256:8be4a8a705c4b990b636cb5009954bc34f6094bb76b997586780c6e78d991bfe
Deleted: sha256:2d73b541c21c1b1d4220b895e3872664f412189b0f22f9a1c37932b8d54db73b
Deleted: sha256:614953c9de743c537cda5f9ff90f33c8faaca3cdca4d0db8f9ec5ead7014493a
Deleted: sha256:bf980877d73e73cf1264084af2864f140bf1b96a372f44294e7b03ac8ebba91b
Deleted: sha256:7143240d4493544962988245515aa6af5ab535026c20203a172b25282cff074e
Deleted: sha256:b78ea2341f670374fa5625c825c460e60b557a780192b55a78e954ca0da9796e
Deleted: sha256:bae7f382c10e244b2c54b64bee8dfb385e8cf1e156731e88654caa87cbf2cb20
Deleted: sha256:98b09fe0d45aed922354b20227b5cbc34fdd46e26c7327e197973afaa769b0ef
Deleted: sha256:a4206cd6f43a7ada49edc5a323d339e01314f7d66268c2b3887fcc6f299756a3
Deleted: sha256:b17f829fb6211c3acb7f69c1e0e6c72b060832efbb314dab5cce0f5929261150
Deleted: sha256:12ef3c2ef0384e327d25d29edf73902296040ac49b203f95becaea2e59f243cf