gem-hunter

A Dockerfile that produces a container that will run PostgreSQL.

This example creates the image with the tag paintedfox/postgresql, but you can change this to use your own username.

$ docker build -t="paintedfox/postgresql" .

Alternately, you can run the following if you have make installed...

$ make

You can also specify a custom docker username like so:

$ make DOCKER_USER=paintedfox

The PostgreSQL server is configured to store data in /data inside the container. You can map the container's /data volume to a volume on the host so the data becomes independant of the running container. There is also an additional volume at /var/log/postgresql which exposes PostgreSQL's logs.

This example uses /tmp/postgresql to store the PostgreSQL data, but you can modify this to your needs.

When the container runs, it creates a superuser with a random password. You can set the username and password for the superuser by setting the container's environment variables. This lets you discover the username and password of the superuser from within a linked container or from the output of docker inspect postgresql.

If you set DB=database_name, when the container runs it will create a new database with the USER having full ownership of it.

$ mkdir -p /tmp/postgresql
$ docker run -d --name="postgresql" \
             -p 127.0.0.1:5432:5432 \
             -v /tmp/postgresql:/data \
             -e USER="super" \
             -e DB="database_name" \
             -e PASS="$(pwgen -s -1 16)" \
             paintedfox/postgresql

Alternately, you can run the following if you have make installed...

$ make run

You can also specify a custom port to bind to on the host, a custom data directory, and the superuser username and password on the host like so:

$ sudo mkdir -p /srv/docker/postgresql
$ make run PORT=127.0.0.1:5432 \
           DATA_DIR=/srv/docker/postgresql \
           USER=super \
           PASS=$(pwgen -s -1 16)

To connect to the PostgreSQL server, you will need to make sure you have a client. You can install the postgresql-client on your host machine by running the following (Ubuntu 12.04LTS):

$ sudo apt-get install postgresql-client

As part of the startup for PostgreSQL, the container will generate a random password for the superuser. To view the login in run docker logs <container_name> like so:

$ docker logs postgresql
POSTGRES_USER=super
POSTGRES_PASS=b2rXEpToTRoK8PBx
POSTGRES_DATA_DIR=/data
Starting PostgreSQL...
Creating the superuser: super
2014-02-07 03:30:55 UTC LOG:  database system was interrupted; last known up at 2014-02-01 07:06:21 UTC
2014-02-07 03:30:55 UTC LOG:  database system was not properly shut down; automatic recovery in progress
2014-02-07 03:30:55 UTC LOG:  record with zero length at 0/17859E8
2014-02-07 03:30:55 UTC LOG:  redo is not required
2014-02-07 03:30:55 UTC LOG:  database system is ready to accept connections
2014-02-07 03:30:55 UTC LOG:  autovacuum launcher started

Then you can connect to the PostgreSQL server from the host with the following command:

$ psql -h 127.0.0.1 -U super template1

Then enter the password from the docker logs command when prompted.

You can link a container to the database container. You may want to do this to keep web application processes that need to connect to the database in a separate container.

To demonstrate this, we can spin up a new container like so:

$ docker run -t -i --link postgresql:db ubuntu bash

This assumes you're already running the database container with the name postgresql. The --link postgresql:db will give the linked container the alias db inside of the new container.

From the new container you can connect to the database by running the following commands:

$ apt-get install -y postgresql-client
$ psql -U "$DB_ENV_USER" \
       -h "$DB_PORT_5432_TCP_ADDR" \
       -p "$DB_PORT_5432_TCP_PORT"

If you ran the postgresql container with the flags -e USER=<user> and -e PASS=<pass>, then the linked container should have these variables available in its environment. Since we aliased the database container with the name db, the environment variables from the database container are copied into the linked container with the prefix DB_ENV_.