Basic Setup

Being distributed version control, It seems that it is difficult to set up. But believe me its not. We need to install git softwares on all the machines where we need to use version control. First of all we need to maintain one central repository, which could be on different server or one of the developer machines by using below command

ssh user@host git init –bare /path/to/repo.git

In above command we need to provide the user,host,path and repo as per our needs. The bare options doesnt allow this to be working directory which we want for our central directory.

Cloning

Now foo and bar will clone this central repo to their machine which will create local repositories in their respective machines using below command. Cloning will also add a shortcut called origin which points to the remote central repositories

git clone ssh://user@host/path/to/repo.git

Edit/Stage/Commit Process

Now both foo and bar have their respective repository which is local copy of the central repository. They can work on their respective task with whatever IDEs they are using by opening local repo copy on their machine. They can use edit/stage/commit model of Git, which means add it and commit it. The above steps will ensure that your changes are being tracked in your local repositories regardless what other developer is working on. Below commands are used to see the status of our local repo which will tell us about the modified file which we can then add to staging area and commit to our local copy.

git status # View the state of the repo

_git add # Stage a file_

git commit # Commit a file</some-file>

Why use Docker?

Due to different operating systems ,system packages, application supporting packages in the various environments of software development lifecycle, sometimes our application doesn’t run as expected. We need something that ensures that our application, related packges are same in every environment.

What is Docker?

Docker as the name suggests, are kind of containers that wrap a piece of software in a complete filesystem that contains everything needed to run: code, runtime, system tools, system libraries – anything that can be installed on a server. This guarantees that the software will always run the same, regardless of its environment.

Installing Docker is super-easy and one can follow the steps at docker site for the installation and quick startup guide. I am using windows and you will see these application installed after the installer exits.

You can open Docker Quickstart Terminal and can play with it by running basic commands(shown below).

docker –version shows the version related information

docker –help shows the varios docker related commands

docker images shows the various images in your docker machine

docker ps shows the various containers in your docker machine

Lets dive deeper.

What is an image?

Docker is based on concept of images which could be base OS or some other minimal image. Over this base image we can create more images by adding softwares, system packages, third party applications as required in development cycle. So the various changes made to the base image are saved in layes forming different images. The base image we can create ourselves by using dockerfile or downloading some image from docker hub.

Below is the screenshot from my machine and you can see base image is ubuntu and with additional changes I create new images that is similar to version control where we have differnt versions of source code but in docker we are maining incremental images upon commiting.

What is a container?

Now whats the purpose of images if we dont run it and use it. Whenever we start an image of our interest, docker create containers which are kind of instance of that image. we can run multiple conatiners of an image. In the screenshot below I started an image in my docker with bash shell or I can run it in background. I can see the list of running containers with the command docker ps

Accessing our container from host network or some other containers?

There are basically 3 approaches for this

1. Exposing ports
2. Port Binding
3. Linking Containers

More about this in my next post. Let me know for any questions/corrections.