PostgreSQL with docker on OS-X

Background

• Docker using light weigh virtualization system provide by linux kernal which introduced as container
• More info - Linux containers
• Since docker using linux kernal features the docker host machine should runs on linux
• In order to run docker in OS-X, we have to use linux virtual machine
• We are using boot2docker light weight linux VM in here
• Following diagram briefly explains how docker works in OS-X

• Docker server runs on boot2docker VM(docker host)
• Docker client runs on OS-X host machine
• We can interact with docker through boot2docker VM

Install boot2docker

• First install VirtualBox
• Then install boot2docker and other packages, I'm using Homebrew to install all the packages

brew update

## install boot2docker
brew install boot2docker

## install docker client
brew install docker

## up boot2docker 
boot2docker init
boot2docker up

• Execute following commands to view docker information

## docker info
docker info

## boot2docker info
boot2docker info
boot2docker status
boot2docker ip

## docker host
echo $DOCKER_HOST

Docker and postgres

Search for postgres

• You can get the latest version of postgres image from docker-registry
• If you have your own private docker registry you can get postgres from it as well
• More info - using private docker registry
• For an example use following command to search postgres from docker-registry

docker search "postgres"

• Following is the output of search

Install postgres

• You can install postgres via docker run command

docker run -p 5432:5432 \
--name postgres-db \
-d postgres:latest

• Few things to notice

  1. -p 5432:5432 defines port forwarding, it means forward docker container port 5432 to the docker host post 5432
  2. --name postgres-db defines name of the container
  3. -d allows to run container as a demon
  4. postgres:latest defines the container name and tag in docker-registry

• If you download postgres from your own registry(private registry), you have to specifies the registry details with docker run command

docker run -p 5432:5432 \
--name postgres-db \
-d 10.2.4.201/postgres:2.48

• Few things to notice

  1. 10.2.4.201 defines private registry host
  2. postgres:2.48 defines postgres container name and tag in the registry

• Now we have successfully installed postgres with docker(on docker container)

Run postgres

• We have to start newly created postgres container

## docker start <container-name>
docker start postgres-db

• Issue docker ps command to verify the status of the containers

docker ps -a

• Output would be like below(it will list container details)

Connect to postgres

• Now you can connect to postgres service from pgAdmin(or any other postgres client)
• Following are my connection parameters on pgAdmin3

• Few things to notice,

  1. I'm trying to connect postgres service via localhost
  2. This will gives an error Failed connect to localhost:5432; Connection refused

• Reason to this error is, we trying to connect localhost:5432 of our host OS-X machine

• But our port forwarding rules defines to forward docker container port 5432 to docker host post 5432(in boot2docker VM)

• Its NOT for host OS-X port 5432

• To simply solve this issue we can connect to boot2docker VM(docker host)

• Use following command to get boot2docker IP

boot2docker ip

## output 192.168.59.103

• My latest working connection parameters are below

More on boot2docker and port forwarding

docker and docker-host

• As I mentions earlier docker forward posts to docker host
• In our scenario boot2docker is the docker host(not our OS-X machine)

Port forward to OS-X localhost

• If you want to access postgres via localhost, you have to forward the 5432 port from boot2docker to OS-X 5432 port
• Following diagram shows the overview of the port forwarding layers

Define port forwarding rules

• VirtaulBox provides a package VBoxManage to which can use to define/modify virtual box configuration
• We can use VBoxManage to specify the port forwarding rules (form boot2docker to OS-X host)
• Execute following commands from OS-X

## first need to down boot2docker
boot2docker down

## define port forwarding rules
VBoxManage modifyvm "boot2docker-vm" --natpf1 "postgres-port,tcp,127.0.0.1,5432,,5432"

## up boot2docker 
boot2docker up

## start postgres 
docker start postgres-db

• Few things to notice,

  1. postgres-port - name of the modification
  2. 127.0.0.1 - localhost
  3. 5432,,5432 - VM machine(boot2docker) post and host machine(OS-X machine) port

• Now you can connect to postgres via localhost(without boot2docker ip - 192.168.59.103)

• If you want to delete the previously defined port forwarding rule, use following command

## first need to down boot2docker
boot2docker down

## delete port forwarding rule
VBoxManage modifyvm "boot2docker-vm" --natpf1 delete "postgres-port"

## up boot2docker 
boot2docker up

• More info - VBoxManage port forwarding

Reference

• http://www.alexecollins.com/first-steps-with-docker/
• http://learningdocker.com/wp-content/plugins/really-static/static/running-postgresql-service-docker-container/
• http://blog.dahanne.net/2015/01/19/stop-installing-postgres-on-your-laptop-use-docker-instead/