How to use volume in docker compose for postgres?

Question

Here is the image I am using.

I named it posgres_test

If I run the image individually

docker run -i -t -v="test_volume:/var/lib/postgresql" -p 5432:5432 posgres_test

I can access it with

psql -h 192.168.99.100 -p 5432 -U pguser -W pgdb

Or I can access it with my golang app

// host is set to postgres
db, err := sql.Open("postgres", "postgres://pguser:pguser@postgres:5432/pgdb")
// table test_db is manually created.
rows, err := db.Query("SELECT name FROM test_db WHERE)

However if I use docker compose

docker-compose.yml

version: "2"
services:
  postgres:
    image: my_image/postgresql:9.3
    volumes:
      - test_volume:/var/lib/postgresql
    ports:
      - "5432:5432"
  web:
    image: my-golang-app4
    ports:
      - "8080:8080"
volumes:
  test_volume: {}

I get the following

pguser@pgdb ERROR:  relation "test_db" does not exist at character 15

I know for sure test_db exist in test_volume since

docker run -i -t -v="test_volume:/var/lib/postgresql" -p 5432:5432 posgres_test
psql -h 192.168.99.100 -p 5432 -U pguser -W pgdb

\dt

will show the table I created

But it seems like my app in docker compose cannot find it

Can someone help me out?

Alexis Wilke · Accepted Answer · 2022-08-04 00:22:43Z

36

About your docker-compose file

First, I thought it's because you don't use the 'links' option to link your postgres container to the web container - it's good practice if you don't expand ports - but you expand postgres port.
If you want to use inheritance from the image you posted

Instead of using this line:

my_image/postgresql:9.3

use:
```
docker/postgres
```
and create path docker/postgres and there place Dockerfile with inheritance from the container you want.
I always use shared volumes in docker-compose.yml like this:
```
.:/var/www/html
```
where . is my project path where I place my code files.

Image I created to test this case

I don't have all your docker files structure to reproduce this error and fix it, so I created a docker-compose, which should match your needs or help to fix your issue:

version: '2'
services:
  web:
    build: docker/web
    ports:
      - "8080:8080"
    links:
      - dbpostgres 
    volumes:
      - .:/var/www/html   # I will share my code so I map this path
  dbpostgres:
    image: postgres
    volumes:
      - /private/var/lib/postgresql:/var/lib/postgresql
    ports:
      - "5432:5432"
    environment:
      POSTGRES_USER: pguser
      POSTGRES_PASSWORD: pguser
      POSTGRES_DB: pgdb

Notes:

I will recommend use official postgres image
I left comments next to the lines.

How I made connection:

host=dbpostgres port=5432 dbname=pgdb user=pguser password=pguser

Because my web container knows host dbpostgres (image name and domain name) now - I link them using links.

If you need database from existing container

If you need the database from your existing container just use the docker option cp to copy database locally:

docker cp posgres_test:/var/lib/postgresql /private/var/lib/postgresql

where /private/var/lib/postgresql is a path on your localhost. You also need to change credentials to db in docker-compose to your old credentials. You have to do it before running docker-compose because if db doesn't exist, it will be created.

Any questions, let me know.

edited Aug 4, 2022 at 0:22

Alexis Wilke

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answered Feb 11, 2017 at 18:20

Arkowsky

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2 Comments

Alex Pavlov Over a year ago

Could you please explain why do we need this environtment vars in docker-compose?

Arkowsky Over a year ago

You can just omit it. We just need it when we want to set up database user, password and database name created at the starting container.

Marko K · Accepted Answer · 2021-06-16 22:52:46Z

11

If the volume is external and already existing before the use of docker-compose you should declare it external, or else docker compose will create a new volume with the project name as prefix.

volumes:
  test_volume:
   external: true

Docs for external using compose v3 (mostly similar to v2): https://docs.docker.com/compose/compose-file/compose-file-v3/#external

edited Jun 16, 2021 at 22:52

Marko K

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answered Feb 13, 2017 at 0:46

gprivitera

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Comments

Thibault · Accepted Answer · 2022-02-17 13:36:32Z

1

I think it sould be something like this for you.

docker run -itd -p 5432:5432 --name postgres_test -v /path/in/your/host :/path/in/your/container postgres_test psql -h 192.168.99.100 -p 5432 -U pguser -W pgdb

Read Docker docs(https://docs.docker.com/engine/tutorials/dockervolumes/), watch tutorials (there is a Docker Youtube channel whith great tutorials).

edited Feb 17, 2022 at 13:36

answered Feb 8, 2017 at 13:08

Thibault

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3 Comments

Kevin Over a year ago

I am already able to to access volume when I run docker container individually, (eg. docker run -i -t -v="test_volume:/var/lib/postgresql" -p 5432:5432 posgres_test) the problem arises when I use docker compose

Thibault Over a year ago

Nevermind, I missunderstood yesterday ^^' But I saw that in your post your docker-compose.yml don't have version: 'x' into it, and if I remember well by default docker-compose take version 1 in this case and volume configuration doesn't work... Try to put version: '2'. I hope it will work :)

Thibault Over a year ago

Hmmm... Did you tried without volumes: test_volume: {} in your compose file and putting the complete path or just /var/lib/postgresql ? I've never used it until now so I don't really know how it's meant to be used... And if it doesn't help you I can't help you to fix this... :/

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