No PostgreSQL clusters exist; see "man pg_createcluster" ... (warning).

[gayanath]

I am using Docker for Mac (Version 1.12.0-rc4-beta20 (build: 10404))

After creating a container, I couldn't connect to Postgres. Following is what I did to reproduce the issue, and get it working.

docker run --name postgres-1 -e POSTGRES_PASSWORD=postgres -d postgres:9.5.3
docker exec -it postgres-1 /bin/bash
root@ee38e70bca23:/# /etc/init.d/postgresql start

Above /etc/init.d/postgresql start command gave the following error.

No PostgreSQL clusters exist; see "man pg_createcluster" ... (warning).

After googling I found http://dba.stackexchange.com/questions/50906/why-wont-postgresql-9-3-start-on-ubuntu

Ran following commands, and after that Postgres was running.

root@ee38e70bca23:/# dpkg-reconfigure locales
root@ee38e70bca23:/# pg_createcluster 9.5 main --start
root@ee38e70bca23:/# /etc/init.d/postgresql start

Running dpkg-reconfigure locales prompted me to choose a locale, and I chose en_US.utf8. How can I extend this image, and use RUN commands in a Dockerfile to avoid prompting to choose the locale?

Is this something that can be fixed in postgres image?

[yosifkit]

You definitely shouldn't be running the init.d scripts in the container, since there is no init process in the container. Postgres itself is PID 1 within the container. Your first docker run command starts postgres and only postgres. docker exec is a neat trick to get an interactive shell in the same namespaces as the container so that we can inspect things.

$ docker run --name postgres-1 -e POSTGRES_PASSWORD=postgres -d postgres:9.5.3992fd0e32d3e673f2c88c43a72b4ad43e5369d7974ae9d10dec789b6d4f45029
$ docker run -it --rm postgres psql -U postgres -h ip-of-postgres-container
Password for user postgres: 
psql (9.5.3)
Type "help" for help.

postgres=# 

As for changing the locale, that is in the docs under how-to-extend-this-image. This is the source for the docs on the Docker Hub.

[gayanath]

@yosifkit Thanks a lot for the explanation. For some reason, the first few times I tried the container, I couldn't connect to it from localhost even with port mapping. That's why I tried getting it working as above. Now I can connect from localhost with a command like below.

docker run --name postgres953 -e POSTGRES_PASSWORD=postgres -p 5432:5432

[waiting-for-dev]

Just in case it is useful for somebody, in my case I got that error because I was running the container with another process within it (because of a helper shell function that I didn't realize it was not right in this case). So, I was running something like:

docker run --name postgres-1 -e POSTGRES_PASSWORD=postgres -d postgres:9.5.3 tail -f /dev/null