Docker 101 – Getting started with Docker

What is Docker

As per Docker’s website
Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications, whether on laptops, data center VMs, or the cloud.”
Docker is basically, based on operating-system-level virtualization
Operating-system-level virtualization is a server-virtualization method where the kernel of an operating system allows for multiple isolated user-space instances, instead of just one. Such instances (sometimes called containerssoftware containers, virtualization engines (VE), virtual private servers (VPS), or jails) may look and feel like a real server from the point of view of its owners and users.”

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Install Ansible on CentOS 7

For an overview of what is Ansible – Getting started with Ansible

For this tutorial we are using 3 VMs, with IPs and hostnames – one Ansible controller/manager (ansible-controller) which will be doing the provisioning on the two remote servers i.e. ansible-node1 and ansible-node2:
192.168.40.192 ansible-controller
192.168.40.193 ansible-node1
192.168.40.194 ansible-node2
ansible-controller‘ is the manger node, the one performing the provisioning on the rest of the hosts i.e. on ansible-controller we’ll be installing and configuring Ansible.

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Getting started with Ansible

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What is Ansible ?

Ansible is an open-source configuration management tool i.e. for automating development or production environment setups, cloud provisioning, change management across multiple nodes. The thing which makes Ansible better then the other popular configuration management tools, like Puppet, Chef, etc is it’s agentless architecture. In the formal (Chef and Puppet) you are required to install the daeman/agent on all the nodes i.e. the controller/master node, as well as the nodes you need to manage (can be 100s or 1000s). In case of Ansible all you need to do is install the Ansible on the controller/master node, and it’ll ssh into all the ‘to be managed’ nodes (may require you to add the keys). This architecture not only makes the setup easy, but also reduces the network overhead, as continuous polling of controller node by the client nodes isn’t required. Ansible was initially supported and sponsored by Ansible, Inc (originally AnsibleWorks, Inc) – in October 2015 it was acquired by Red Hat.

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