Monday, August 31, 2015

Decoding Docker - Part 1

Having worked with multiple Virtualization platforms, I recently got an interesting opportunity to work with its younger sibling containerization . The  platform of choice was obviously Docker. Getting Docker up and run in an OS of your preference is a simple task, you can straightaway get it done using the instructions here . Interesting part is  getting to play around with it

 Getting it up and running:

Docker can be started as a services or at a tcp port. Starting as a service is pretty straight forward

#service docker start

However, the interesting bit is when you want to run it as a deamon listening to a specific port. This is useful in scenarios when you want to manage the docker engine remotely, say using a windows docker client or using one of the open source GUIs available for docker like Shipyard and Mist.io

The command to run docker as a deamon listening to a port is

# /usr/bin/docker  -d -H tcp://0.0.0.0:4243 -H unix:///var/run/docker.sock &

Here docker will listen at all IPs of the machine at port 4243. If you want to connect to this docker engine from a remote docker client, the following command can be used

#docker -H tcp://<docker engine host>:4243 <commands>

For eg: #docker -H tcp://<docker engine host>:4243 ps

One downside of this method is that there is no inherent authentication mechanisms for remote access

Spin up your containers:

Lets start with pulling an image from the Docker hub, which is  a public repository of Docker images