Table of Contents

• Introduction
• Changelog
• Reporting Issues
• Installation
• Quick Start
• Creating User and Database at Launch
• Configuration
  • Data Store
  • Securing the server
• Shell Access
• Upgrading

Introduction

Dockerfile to build a PostgreSQL container image which can be linked to other containers.

Reporting Issues

Docker is a relatively new project and is active being developed and tested by a thriving community of developers and testers and every release of docker features many enhancements and bugfixes.

Given the nature of the development and release cycle it is very important that you have the latest version of docker installed because any issue that you encounter might have already been fixed with a newer docker release.

For ubuntu users I suggest installing docker using docker's own package repository since the version of docker packaged in the ubuntu repositories are a little dated.

Here is the shortform of the installation of an updated version of docker on ubuntu.

sudo apt-get purge docker.io
curl -s https://get.docker.io/ubuntu/ | sudo sh
sudo apt-get update
sudo apt-get install lxc-docker

Fedora and RHEL/CentOS users should try disabling selinux with setenforce 0 and check if resolves the issue. If it does than there is not much that I can help you with. You can either stick with selinux disabled (not recommended by redhat) or switch to using ubuntu.

If using the latest docker version and/or disabling selinux does not fix the issue then please file a issue request on the issues page.

In your issue report please make sure you provide the following information:

• The host ditribution and release version.
• Output of the docker version command
• Output of the docker info command
• The docker run command you used to run the image (mask out the sensitive bits).

Installation

Pull the latest version of the image from the docker index. This is the recommended method of installation as it is easier to update image in the future. These builds are performed by the Docker Trusted Build service.

docker pull sameersbn/postgresql:9.1-1

Alternately you can build the image yourself.

git clone https://github.com/sameersbn/docker-postgresql.git
cd docker-postgresql
docker build -t="$USER/postgresql" .

Quick Start

Run the postgresql image

docker run --name postgresql -d sameersbn/postgresql:9.1-1

The simplest way to login to the postgresql container as the administrative postgres user is to use the --volumes-from docker option to connect to the postgresql server over the unix socket.

docker run -it --rm --volumes-from=postgresql \
  sameersbn/postgresql sudo -u postgres -H psql

Alternately you can fetch the password set for the postgres user from the container logs.

docker logs postgresql

In the output you will notice the following lines with the password:

|------------------------------------------------------------------|
| PostgreSQL User: postgres, Password: xxxxxxxxxxxxxx              |
|                                                                  |
| To remove the PostgreSQL login credentials from the logs, please |
| make a note of password and then delete the file pwfile          |
| from the data store.                                             |
|------------------------------------------------------------------|

To test if the postgresql server is working properly, try connecting to the server.

psql -U postgres -h $(docker inspect --format {{.NetworkSettings.IPAddress}} postgresql)

Creating User and Database at Launch

The image allows you to create a user and database at launch time.

To create a new user you should specify the DB_USER and DB_PASS variables. The following command will create a new user dbuser with the password dbpass.

docker run --name postgresql -d \
  -e 'DB_USER=dbuser' -e 'DB_PASS=dbpass' \
  sameersbn/postgresql:9.1-1

NOTE

• If the password is not specified the user will not be created
• If the user user already exists no changes will be made

Similarly, you can also create a new database by specifying the database name in the DB_NAME variable.

docker run --name postgresql -d \
  -e 'DB_NAME=dbname' sameersbn/postgresql:9.1-1

If the DB_USER and DB_PASS variables are also specified while creating the database, then the user is granted access to the database.

For example,

docker run --name postgresql -d \
  -e 'DB_USER=dbuser' -e 'DB_PASS=dbpass' -e 'DB_NAME=dbname' \
  sameersbn/postgresql:9.1-1

, will create a user dbuser with the password dbpass. It will also create a database named dbname and the dbuser user will have full access to the dbname database.

Configuration

Data Store

For data persistence a volume should be mounted at /var/lib/postgresql.

SELinux users are also required to change the security context of the mount point so that it plays nicely with selinux.

mkdir -p /opt/postgresql/data
sudo chcon -Rt svirt_sandbox_file_t /opt/postgresql/data

The updated run command looks like this.

docker run --name postgresql -d \
  -v /opt/postgresql/data:/var/lib/postgresql sameersbn/postgresql:9.1-1

This will make sure that the data stored in the database is not lost when the image is stopped and started again.

Securing the server

By default a randomly generated password is assigned for the postgres user. The password is stored in a file named pwpass in the data store and is printed in the logs.

If you dont want this password to be displayed in the logs, then please note down the password listed in /opt/postgresql/data/pwpass and then delete the file.

cat /opt/postgresql/data/pwfile
rm /opt/postgresql/data/pwfile

Alternately, you can change the password of the postgres user

psql -U postgres -h $(docker inspect --format {{.NetworkSettings.IPAddress}} postgresql)
\password postgres

Shell Access

For debugging and maintenance purposes you may want access the container shell. Since the container does not allow interactive login over the SSH protocol, you can use the nsenter linux tool (part of the util-linux package) to access the container shell.

Some linux distros (e.g. ubuntu) use older versions of the util-linux which do not include the nsenter tool. To get around this @jpetazzo has created a nice docker image that allows you to install the nsenter utility and a helper script named docker-enter on these distros.

To install the nsenter tool on your host execute the following command.

docker run --rm -v /usr/local/bin:/target jpetazzo/nsenter

Now you can access the container shell using the command

sudo docker-enter postgresql

For more information refer https://github.com/jpetazzo/nsenter

Another tool named nsinit can also be used for the same purpose. Please refer https://jpetazzo.github.io/2014/03/23/lxc-attach-nsinit-nsenter-docker-0-9/ for more information.

Upgrading

To upgrade to newer releases, simply follow this 3 step upgrade procedure.

• Step 1: Stop the currently running image

docker stop postgresql

• Step 2: Update the docker image.

docker pull sameersbn/postgresql:9.1-1

• Step 3: Start the image

docker run --name postgresql -d [OPTIONS] sameersbn/postgresql:9.1-1