Table of Contents

• Introduction
• Changelog
• Contributing
• Reporting Issues
• Installation
• Quick Start
• Creating User and Database at Launch
• Creating a Snapshot or Slave Database
• Configuration
  • Data Store
• Shell Access
• Upgrading
• Host UID / GID Mapping

Introduction

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

Contributing

If you find this image useful here's how you can help:

• Send a Pull Request with your awesome new features and bug fixes
• Help new users with Issues they may encounter
• Send me a tip via Bitcoin or using Gratipay

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:9.4

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:9.4

The simplest way to login to the postgresql container as the administrative postgres user is to use the docker exec command to attach a new process to the running container and connect to the postgresql server over the unix socket.

docker exec -it postgresql sudo -u postgres psql

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:9.4

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:9.4

You may also specify a comma separated list of database names in the DB_NAME variable. The following command creates two new databases named dbname1 and dbname2 (p.s. this feature is only available in releases greater than 9.4)

docker run --name postgresql -d \
-e 'DB_NAME=dbname1,dbname2' sameersbn/postgresql:latest

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

For example,

docker run --name postgresql -d \
  -e 'DB_USER=dbuser' -e 'DB_PASS=dbpass' -e 'DB_NAME=dbname' \
  sameersbn/postgresql:9.4

, 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.

The PSQL_TRUST_LOCALNET environment variable can be used to configure postgres to trust connections on the same network. This is handy for other containers to connect without authentication. To enable this behavior, set PSQL_TRUST_LOCALNET to true.

For example,

docker run --name postgresql -d \
  -e 'PSQL_TRUST_LOCALNET=true' \
  sameersbn/postgresql:9.4

This has the effect of adding the following to the pg_hba.conf file:

host    all             all             samenet                 trust

Creating a Snapshot or Slave Database

You may use the PSQL_MODE variable along with REPLICATION_HOST, REPLICATION_PORT, REPLICATION_USER and REPLICATION_PASS to create a snapshot of an existing database and enable stream replication.

Your master database must support replication or super-user access for the credentials you specify. The PSQL_MODE variable should be set to "master" for replication on your master node and "slave" or "snapshot" for streaming replication or a point-in-time snapshot of a running database.

Create a new master instance:

docker run --name postgresql-master 5432:5432 -d \
  -e 'PSQL_TRUST_LOCALNET=true' \
  -e 'PSQL_MODE=master' \
  -e 'DB_NAME=dbname' \
  -e 'DB_USER=dbuser' -e 'DB_PASS=dbpass' \
  -e 'REPLICATION_USER=replicator'  -e 'REPLICATION_PASS=replicatorpass' \
  sameersbn/postgresql:9.4

Create a slave instance with streaming replication:

docker run --name postgresql-slave -p 5433:5432 -d \
  -e 'PSQL_TRUST_LOCALNET=true' \
  -e 'PSQL_MODE=slave' \
  -e 'REPLICATION_HOST=localhost' -e 'REPLICATION_PORT=5432' \
  -e 'REPLICATION_USER=replicator' -e 'REPLICATION_PASS=replicatorpass' \
  sameersbn/postgresql:9.4

Create a snapshot downloaded from a master instance:

docker run --name postgresql-slave -p 5433:5432 -d \
  -e 'PSQL_TRUST_LOCALNET=true' \
  -e 'PSQL_MODE=snapshot' \
  -e 'REPLICATION_HOST=localhost' -e 'REPLICATION_PORT=5432' \
  -e 'REPLICATION_USER=replicator' -e 'REPLICATION_PASS=replicatorpass' \
  sameersbn/postgresql:9.4

You may use docker links and interactive shells when testing this module:

mkdir -p /tmp/postgresql-master
mkdir -p /tmp/postgresql-slave
# master
docker run --name='postgresql-master' -it --rm \
  --volume=/tmp/postgresql-master:/var/lib/postgresql \
  -e 'PSQL_TRUST_LOCALNET=true' \
  -e 'PSQL_MODE=master' \
  -e 'REPLICATION_USER=replicator'  -e 'REPLICATION_PASS=replicatorpass' \
  sameersbn/postgresql:latest

# slave
docker run --link postgresql-master:psql --name='postgresql-slave' -it --rm \
  --volume=/tmp/postgresql-slave:/var/lib/postgresql \
  -e 'PSQL_TRUST_LOCALNET=true' \
  -e 'PSQL_MODE=slave' \
  -e 'REPLICATION_HOST=psql' -e 'REPLICATION_USER=replicator' -e 'REPLICATION_PASS=replicatorpass' \
  sameersbn/postgresql:latest

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:9.4

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

Enable Unaccent (Search plain text with accent)

Unaccent is a text search dictionary that removes accents (diacritic signs) from lexemes. It's a filtering dictionary, which means its output is always passed to the next dictionary (if any), unlike the normal behavior of dictionaries. This allows accent-insensitive processing for full text search.

By default unaccent is configure to false

docker run --name postgresql -d \
  -e 'DB_UNACCENT=true' \
  sameersbn/postgresql:9.4

Shell Access

For debugging and maintenance purposes you may want access the containers shell. If you are using docker version 1.3.0 or higher you can access a running containers shell using docker exec command.

docker exec -it postgresql bash

If you are using an older version of docker, 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 nsenter execute the following command on your host,

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

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:9.4

• Step 3: Start the image

docker run --name postgresql -d [OPTIONS] sameersbn/postgresql:9.4

Host UID / GID Mapping

Per default the container is configured to run postgres as user and group postgres with some unknown uid and gid. The host possibly uses these ids for different purposes leading to unfavorable effects. From the host it appears as if the mounted data volumes are owned by the host's user/group [whatever id postgres has in the image].

Also the container processes seem to be executed as the host's user/group [whatever id postgres has in the image]. The container can be configured to map the uid and gid of postgres to different ids on host by passing the environment variables USERMAP_UID and USERMAP_GID. The following command maps the ids to user and group postgres on the host.

docker run --name=postgresql -it --rm [options] \
  --env="USERMAP_UID=$(id -u postgres)" --env="USERMAP_GID=$(id -g postgres)" \
  sameersbn/postgresql:9.4