Docker Container смотреть онлайн

Docker – Container Setup

Docker is a software technology providing containers, promoted by the company Docker, Inc. Docker provides an additional layer of abstraction and automation of operating-system-level virtualization on Linux.
Docker

While VMs in ESX and Oracle Virtual Servers get explicit resources allocated on them, Docker Containers share resource from parent server.

Machinery

My environment setup consists of the following:

Nix OS. (I chose CentOS 6.x) 8 GB RAM (Minimum 4 GB) 100 GB HDD

Installation

This setup assumes that CentOS has already been installed on the server. It is preferred to have a separate partition to house all the containers.

Once the docker package and all the dependencies have been installed, we are good to go setting up docker containers.

Provision Containers

Before we start provisioning containers, we have to start the docker service.

Just as we need ISO image to install any operating system, we need ISO images to provision the containers as well. This can be checked using the following command.

As we can see, there are no ISO images available to start installing containers. Therefore, we need to download the image that we need using pull attribute.

By default, docker downloads images from the default docker.io repository. In the above screenshot, I chose CentOS v6.7. Instead of the version number, we can also give the keyword “latest” which will download the latest version of CentOS available in that repository. Users can setup their own in-house repositories which will be covered in next blog.

Now that we have downloaded the ISO image, we will setup the network & IP for each container. Let us first list the existing network details.

Next, we begin by creating network name along with the required subnet.

Now that the initial network and subnet are configured, we will start provisioning a container, in this case, an Apache container.

Just like NFS, docker gives privilege to share a directory from parent server onto a docker container. For this setup, we will create a directory on the parent server called “apache” with the usual mkdir command. We will share this directory inside our container.

Notice that I am sharing the directory with the container, which I created on the parent server “/container/apache“. I’ve set hostname as “apache“, provisioned an IP to the container from the subnet that I created in the previous step.

Obviously, the default ports used by Apache are 80 and 443. But, in the real-time conditions, we have to assume that these ports are already active on the parent server. So we need to redirect the traffic from a pseudo port on parent server to the real port inside docker container. Docker has a beauty of NATting the traffic from pseudo port to the real port

In this case, traffic from port 8000 (parent server) is being redirected to port 80 (real port) inside the container. Same is the case with other mentioned ports.

Once the container is up and running, we can check the status as follows.

Now that everything has been setup, we can get inside the container using “docker attach CONTAINER-ID/CONTAINER-NAME”. I will choose container-NAME to get inside it as an example.

“docker attach clever_bassi”

Once in, we can install openssh-server RPM and start the service. We can now be able to ssh into the server from any allowed source.

Check out the complete setup which includes installation of MySQL as well.

Visit http://www.nixfury.com for more tutorials.